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06-16-2021 Hearing Examiner Agenda
HEARING EXAMINER June 16, 2021 5:30 p.m. The Auburn City Hearing Examiner Meeting scheduled for Wednesday, June 16, 2021 at 5:30 p.m. will be held virtually and telephonically. To attend the meeting virtually please click the below link, enter the meeting ID into the Zoom app, or call into the meeting at the phone number listed below. Per Governor Inslee's Emergency Proclamation 20-05 and 20-28 et. seq. and Stay Safe-Stay Healthy, the City of Auburn is holding public meetings virtually at this time. City of Auburn Resolution No. 5581, designates City of Auburn meeting locations for all Regular, Special and Study Session Meetings of the City Council and of the Committees, Boards and Commissions of the City as Virtual Locations. The link to the Virtual Meeting or Phone Number to listen to the Hearing Examiner is: Join Zoom Meeting https://zoom.us/j/96943444864 Meeting ID: 969 4344 4864 One tap mobile (253) 215-8782 I. Case No: SHL20-0001 & SHL20-0002 Shoreline Conditional Use Permit Shoreline Substantial Shoreline Variance Applicant(s): Lance Goulet 3226 S 198th St SeaTac, WA 98188 Bruce Goulet 3722 S. 198th St SeaTac, WA 98188 Applicant Representative: Amy Donlan Encompass Engineering & Surveying 165 NE Juniper St, Suite 201 Issaquah, WA 98027 Page 2 Request: Request for Shoreline Conditional Use Permit, Shoreline Substantial Development Permit, and Shoreline Variance to allow for the future site preparation and construction of a three new single-family residences each on adjacent existing lot within the ‘Urban Conservancy’ Shoreline Environment Designation. Project Location: The site is located along the right bank of the Green River, between river mile 31 and 32, directly to the north of 32149 104th Pl SE; The King County parcel numbers are 3341000090, 3341000095, & 3341000100. II. Case No: SHL21-0002 Shoreline Conditional Use Permit Applicant: Tom Bloxton King County River and Floodplain Management 201 S. Jackson St Suite 5600 Seattle, WA 98104 Request: Request for Shoreline Conditional Use Permit to allow for the removal of rock located at the remnant upstream end of the TransCanada Levee. The project is located at River Mile 9.3, along the left bank of the White River. The site has as a ‘Natural’ Shoreline Environment Designation. Location: The site is located along the left bank of the White River, at river mile 9.3, King County parcel number 2821059007. AGENDA BILL APPROVAL FORM HEARING EXAMINER Agenda Subject/Title: SHL20-0001 & SHL20-0002 Shoreline Conditional Use Permit Shoreline Substantial Dev. Permit Shoreline Variance Date: June 3, 2021 Department: Community Development DESCRIPTION: Request for Shoreline Conditional Use Permit, Shoreline Substantial Development Permit, and Shoreline Variance to allow for the future site preparation and construction of a three new single-family residences each on adjacent existing lot within the ‘Urban Conservancy’ Shoreline Environment Designation. ADMINISTRATIVE RECOMMENDATION: Hearing Examiner to conduct a public hearing and approve the Shoreline Conditional Use Permit, Shoreline Substantial Development Permit, and Shoreline Variance . PROJECT SUMMARY: The applicant seeks to construct three new single-family residences on three separate vacant parcels located along the right bank of the Green River within the City’s ‘Urban Conservancy’ Shoreline Environment Designation. The site has a zoning designation of R-5 Residential Zone, Five Dwelling Units Per Acre. The variance is requested for two lots, as one residence will be setback 94.5 feet and one residence will be setback 89.5 feet from the Ordinary High Water Mark (OHWM) of the Green River, even though the minimum setback requirement from the OHWM is 100 feet. With the exception of the reduced setbacks from the OHWM of the Green River, the residences will be designed to meet all of the setback and development requirements of the Urban Conservancy Shoreline Designation and the R-5 Zone. LOCATION: The site is located along the right bank of the Green River, between river mile 31 and 32, directly to the north of 32149 104th Pl SE; The King County parcel numbers are 3341000090, 3341000095, & 3341000100. APPLICANT & PROPERTY OWNER: Launce Goulet & Bruce Goulet, 3226 S 198th St & 3722 S 198th St, SeaTac, WA 98188 APPLICANT’S REPRESENTATIVE: Amy Donlan, Encompass Engineering & Surveying, 165 NE Juniper St, Suite 201, Issaquah, WA 98027 3 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 2 of 26 2019 Aerial Vicinity Map: Subject Site 104th Pl SE 4 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 3 of 26 The Comprehensive Plan designation, Shoreline environment designation, zoning classification and current land uses of the site and surrounding properties are: Location Comprehensive Plan Designation Zoning Classification Shoreline Environment Designation Current Land Use Subject Site “Single Family” R-5 Residential, 5 du per acre Urban Conservancy Vacant North “Single Family” R-5 Residential, 5 du per acre Urban Conservancy Vacant South “Single Family” R-5 Residential, 5 du per acre Urban Conservancy Single family residential East “Single Family” R-5 Residential, 5 du per acre N/A Public Road West “Open Space” Open Space Urban Conservancy Green River Excerpted Comprehensive Plan Designation Map: Subject Site Open Space Single-Family Single-Family 104th Pl SE Multiple-Family 5 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 4 of 26 Excerpted Zoning Classification Map: Excerpted Shoreline Environment Designations Urban Conservancy Green River Subject Site Subject Site Open Space R-5 Residential Zone, 5 dwelling units per acre R-20 Residential Zone, 20 dwelling units per acre 104th Pl SE 104th Pl SE 6 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 5 of 26 SEPA STATUS: A Determination of Non-Significance (DNS) was issued under City File No. SEP20-0009 on February 5, 2021. The comment period ended February 22, 2021 and the appeal period ended March 6, 2021. No appeal of the SEPA decision was received. Additional information regarding the comments received in response to the DNS are included within the below Findings of Fact section. A copy of the SEPA Environmental Checklist, prepared by Encompass Engineering & Surveying, dated November, 2020 and the DNS issued by the City of Auburn are included as Exhibits 12 and 13, respectively. FINDINGS OF FACT: Proposal Description 1. Launce Goulet & Bruce Goulet, applied on May 14, 2020 for a Shoreline Conditional Use Permit (SCUP), Shoreline Substantial Development Permit (SSDP), and two shoreline variance applications for two of the lots to allow for the site preparation and construction of three new single-family residences within the Urban Conservancy Shoreline Environment Designation. The three adjacent sites are directly to the north of 32149 104th Pl SE; King County parcel numbers 334100-0090, -0095, & -0100. A copy of the Civil Sheets, prepared by Encompass Engineering & Surveying, dated May 21, 2021 is included as Exhibit 7. 2. Because the proposal involves the construction of three single-family dwellings that will be constructed by a future builder within the Urban Conservancy Shoreline Environment Designation, a Shoreline Conditional Use Permit (SCUP) is required per the City of Auburn’s Shoreline Master Program, Section 4.5. Additionally, a Shoreline Substantial Development Permit (SSDP) is required per WAC 173-27-040(2)(g), as the construction of single-family residences within the Urban Conservancy designation are not considered an exempt activity from having to obtain a SSDP unless the future residences are for the enjoyment of the owner, purchaser for their own use, or the use of their family. 3. The Shoreline Variance would allow for the construction of the single-family residence on Lot B to provide a 94.5 foot setback and the single-family residence on Lot C to provide a 89.5 foot setback from the Ordinary High Water Mark (OHWM) of the Green River, a Type S Stream. The City of Auburn’s Shoreline Master Program (SMP), Section 4.5, Table 1, requires all development within the Urban Conservancy designation provide a 100-foot setback from the OHWM. The variance approval is necessary to authorize relief from this shoreline setback standard. 4. While it is unknown if the applicant proposes to construct two-story residences, the Applicant has prepared an analysis of the ”proposed developable area” of each lot and the likely “conceptual building footprint' within the developable area, taking into account lot encumbrances and zoning development standards. Lot A is proposed to have a maximum building footprint of 2,097 square feet, Lot B to have a maximum building footprint of 1,675 square feet, and Lot C to have a maximum building footprint of 1,756 square feet. The residence proposed for Lot A will be setback 100 feet from the Green 7 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 6 of 26 River OHWM, while the residences on Lot B and C will be located 94.5 feet and 89.5 feet, respectively, from the Green River OHWM. See Exhibit 7. 5. The proposed residences will be constructed to meet the development standards of the R-5, Residential Zone, five dwelling units per acre, as specified in Auburn City Code (ACC) 18.07.030. With the exception of the setback reductions sought as part of the shoreline variances, the proposed residences will be constructed to meet the residential development standards outlined within the City’s Shoreline Master Program (SMP) 4.7.8. 6. In addition to the Shoreline program requirements, the lots border the Green River, a Type S Stream and are subject to the city’s critical area regulations (ACC 16.10). A minimum 100-foot buffer is required for Type S streams (river). As part of the proposal, 400 square feet of stream buffer area from Lot B and 874 square feet of stream buffer area from Lot C will be lost due to the development of the future residences. Additionally, six significant trees, located more than 100 feet outside of the OHWM, but within the Urban Conservancy shoreline Environment designation, will be removed from the project site. 7. The applicant provided a Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated April 10, 2020, revised May 14, 2021, confirming that the project will have “no net loss” in shoreline functions. This includes Hydrologic, Vegetation, Hyporheic, and Habitat functions. The Critical Area Report is included as Exhibit 8. 8. To offset the loss of the minimum 100-foot stream buffer area that will be impacted on Lots B and C and the loss of the trees removed outside of the 100 foot buffer area, the applicant has provided a detailed stream buffer enhancement plan prepared by a registered, Professional Wetland Scientist. The plan incorporates habitat features, such as downed logs, and a dense mix of trees and shrubs native to the Puget Sound Region. Further, all invasive vegetation, such as the thick Himalayan Blackberry that currently dominates the site, will be removed. A copy of the Shoreline Buffer Mitigation Plan, prepared by Evergreen Aquatic Resource Consultants, LLC, dated May 14, 2021, is included as Exhibit 9. 9. In order to demonstrate that the existing three lots will be able to be developed with single-family residences and associated features while demonstrating compliance with the City’s Surface Water Management Manual, a Preliminary Storm Drainage Report, prepared by Encompass Engineering & Surveying, dated April 17, 2020, was provided as part of the review of the applications. The preliminary report confirms that dispersion trenches and deep rock pads for concentrated flow will be installed on Lots A and B to collect stormwater and disperse it into the native vegetation areas to the west (toward the River). Lot C is wide enough and will have a small enough footprint to allow for stormwater to be managed through two separate deep rock pads for concentrated flow (one for the driveway and one for the roof area of the future dwelling) located to the north side of the building footprint. A copy of the Preliminary Storm Drainage Report is included as Exhibit 11. 10. The applicant provided multiple written narratives and responses that demonstrate consistency with the various SSDP, SCUP, and Shoreline Variance criteria established 8 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 7 of 26 in the City’s Shoreline Master Program and to demonstrate consistency with Washington Administrative Code (WAC) 173-27-140, -150, -160, & -170. A copy of the Written Statement, prepared by Encompass Engineering & Surveying, dated April, 2020 and revised May 15, 2020, is included as Exhibit 6. Site Characteristics (General) 11. The project site is comprised of three vacant parcels that abut the “local” classified street of 104th Pl SE. The parcels have a combined area of 41,250 square feet. The site is located along the right bank of the Green River. Because the Green River abuts the site, the entire site is located within 200 feet of the Green River Ordinary High Water Mark and shoreline jurisdiction and is within the ‘Urban Conservancy’ shoreline environment designation. The site gently slopes to the west towards the Green River and is vegetated with a mix of Himalayan blackberry and mature trees. 12. The subject parcels were originally part of the C.D. Hillman’s Green River Addition, Division No.1, King County, 1908. Specifically, the project involves a portion of Lot 20, 21, and 22 from the original plat. In addition, the current parcels include land that was combined from the right bank of the Green River, which occurred after the 1908 platting date but before the applicant acquired the properties. 13. King County Assessor records indicate that parcel 3341000090 and 3341000095 were purchased by the applicant on June 25th, 1985. There is no sales history readily available for parcel 3341000100. Based on the current assessed value of each lot, the platting history associated with each lot, as well as the sale price in 1985 to acquire two out of the three lots, City staff are of the belief that the three subject parcels are legal lots of record that were in existence prior to the establishment of the Shoreline Master Program and Critical Areas Ordinance. 14. The site contains a public sewer line that crosses the eastern (landward) portion of each lot. City Public Works staff have indicated there is a minimum 10-foot wide setback requirement between any residential structure and the sewer line. An easement associated with this utility line is also located on the eastern portion of all three lots. Structures cannot be built on top of this easement. See Exhibit 7 for a copy of the Civil Sheets showing the easement location in relation to the site. Site Characteristics (Critical Areas & Shoreline Areas) 15. The Green River, which abuts the site directly to the west, is a mapped floodway. No portion of the floodway extends onto any portion of the site proposed for development. A small portion of the special flood hazard area (SFHA) extends onto the site. Additionally, this portion of the Green River has a mapped Channel Migration Zone, meaning that this is an area susceptible to river changing its course long term and diverge into this mapped area. Because of the proximity of the Green River, a small portion of the site is also located within a Riparian Buffer Zone (RBZ), a type of regulatory floodplain area per Chapter 15.68 ACC, “Floodplain Development Management”. In this instance, the vegetation within the RBZ is predominately Himalayan blackberry. For this reason, the limits of the RBZ ends at the edge of the SFHA. See Exhibit 3 for a Copy of the City’s Critical Area Inventory map. 9 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 8 of 26 16. In addition to being a Shoreline of the State, the Green River is also classified by the City as regulated “Critical Area” and more specifically as a Type S Stream per ACC 16.10.080, “Classification and rating of critical areas”. As outlined in SMP 4.5, Table 1, Type S Streams within the Urban Conservancy Shoreline Designation have a-100 foot setback from the OHWM. While defined as a setback within the SMP, the setback effectively acts as a 100 foot buffer. 17. The site is located in Wildlife Habitat Area, as defined in ACC 16.10.080(D). This is due to the forested riverine habitat provided along this portion of the Green River. See Exhibit 3 for a Copy of the City’s Critical Area Inventory map. 18. The site is located within an Aquifer Recharge Area known as Groundwater Protection Zone 2, as defined in ACC 16.10.080(F). These areas have a critical recharging effect on aquifers used for potable water. Best management practices (BMP) will be required for any future development of the site. 19. The applicant provided a Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated April 10, 2020, revised May 14, 2021, in order to identify all wetlands, streams, and any associated buffers affecting the site. Further, the report provides more detail regarding the mitigation proposed resulting from the reductions to the Type S stream buffer. The Report concluded that there are no wetlands or associated buffers on the site and that the Green River, a Type S stream is located along the western portion of the site. See Exhibit 8 for a Copy of the Critical Area Report. 20. The applicant provided an Arborist Report, prepared by Layton Tree Consulting, LLC, dated May 12, 2021, identifying the existing trees on the site. The report notes that 11 trees located outside of the 100-foot stream buffer will need to be removed. Further, of the 11 trees, six meet the definition of ‘significant tree’, per ACC 18.50.045(A). Due to a combination of factors, including the poor health of the trees and the difficulties the trees present with future site development, removal of such trees is necessary. See Exhibit 17 for a copy of the Arborist Report. 21. While not explicitly addressed within the Critical Area Report, the sites location along a Type S Stream also results in the site being within a Wildlife Habitat Area and within a Riparian Buffer Zone. These areas contain habitat that may be used by federal or state listed threatened or endangered Fish species. As noted previously, due to the small reductions in stream buffer area on Lots B and C, the applicant has elected to enhance the remaining stream buffer area by providing a dense mix of trees and shrubs, removing invasive vegetation, and adding woody debris. Further, no trees will be removed within the 100 foot Type S Stream buffer area. No native vegetation within the Protected Area, as defined in ACC 15.68.100(OO), would be removed. See Exhibit 8 for a copy of the Report and a copy of Exhibit 9 for the Shoreline Buffer Mitigation Plan. 22. The property is located within a mapped Landslide Hazard area due to its location at the bottom of a steeply sloped hill, directly across 104th Pl SE to the east. These areas are regulated under the City’s Critical Areas Ordinance, ACC 16.10. See Exhibit 3 for a copy of the City’s Critical Area Inventory map. 10 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 9 of 26 23. The applicant provided a Geotechnical Study, prepared by Bergquist Engineering Services, dated November 4, 2020, addressing the mapped Erosion Prone and Landslide Hazard area on the site and directly to the east. The report noted that the project will be meeting the recommended setbacks from the bottom of the slope containing a mapped landslide area to the east. Further, the report noted that additional geotechnical services will be necessary as part of the foundation designs for each of the future residences. See Exhibit 10 for a copy of the Geotechnical Study. 24. The area within 200 feet of the Ordinary High Water Mark (OHWM) along the Green River is within the “Urban Conservancy” designation and thus, is within the jurisdiction of the Auburn Shoreline Master Program (Auburn SMP, Section 4.2.A). Unless otherwise exempt, the construction of a new single-family residence in the ‘Shoreline Conservancy’ designation will requires a Shoreline Substantial Development Permit (SSDP) and Shoreline Conditional Use Permit (SCUP). The language of this Section provides: “4.2 Applicability. 1. The provisions of this chapter shall apply to all shorelines, shorelands and associated wetland areas covered by the Shoreline Management Act of 1971 as follows: 1. All rivers and streams and their associated wetlands downstream from a point where the mean annual flow is 20 cubic feet per second or greater. 2. All lakes and their associated wetlands which are 20 surface acres in size or larger. 3. Shorelands and associated uplands extending 200 feet in all directions as measured on a horizontal plane from the ordinary high water mark; floodways and contiguous floodplain areas landward two hundred feet from such floodways; and all wetlands and river deltas associated with their streams, lakes, and tidal waters subject to the provisions of Chapter 90.58 RCW.” Characteristics of the Surrounding Area 25. The project and adjacent properties are located within the jurisdiction of the City of Auburn. All proposed work will occur above the OHWM and on private property. No in- water work is proposed. 26. The surrounding areas have Comprehensive Plan designations of: “Single Family” and “Open Space”. The surrounding zoning designations include “R-5” Residential Zone and “OS” Open Space. 27. The existing land use surrounding the site includes single-family residences and open space. 28. The residences directly across from Lots B and C, as well as the residences that are located along 104 Pl SE have an average building footprint size of 2,542 square feet and an average building square footage of 3,063. Please see Exhibit 15, response 11 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 10 of 26 comments provided by the applicant, for a table containing the square footage and building footprint sizes of residences in the immediate area. Comprehensive Plan 29. The following City of Auburn Comprehensive Policies are relevant to the project: Volume 1, Land Use Element: Policy LU-17. Provide a variety of housing typologies to suit the needs of various potential residents. Volume 8, Historic Preservation Element: Policy HP-1. The City shall encourage the protection, preservation, recovery and rehabilitation of significant archaeological resources and historic sites. City staff should be adequately trained to recognize significant resources or should have ready access to professionals who do. Shoreline Management Program 30. The City of Auburn currently uses its 2020 City of Auburn Shoreline Master Program (SMP) to regulate development and management of the City’s shoreline. Under the Shoreline Management Act, all development occurring within the shoreline jurisdiction area must be consistent with policies and regulations of the local Shoreline Management Program (SMP), as well as with the policies of the State Shoreline Management Act. While some policies, goals, and development regulations may be referenced as findings within this staff report, additional policies, goals, and development regulations of the SMP not explicitly referenced may be found by review of the City’s 2020 SMP document. 31. Because the project requires a Shoreline Substantial Development Permit, Shoreline Conditional Use Permit, and Shoreline Variances, the Project must be found consistent with the criteria established in WAC 173-27-150, WAC 173-27-160, WAC 173-27-170, and City of Auburn SMP 6.1.7, SMP 6.1.8, and SMP 6.1.9. 32. The City’s rules and procedures for shoreline permits are contained in the SMP; more specifically Section 6.0. The section provides the following general purpose and intent: “6.1.1 Chapter purpose and intent. It is the intention of the city council that the provisions of this chapter will promulgate and adopt a program for the administration and enforcement of a permit system that shall implement by reference the State Shoreline Management Act of 1971, Chapter 90.58 RCW; the State Department of Ecology regulations and guidelines adopted as Chapters 173-26 and 173-27 WAC; the Auburn shoreline master program attached to the ordinance codified in this chapter, together with amendments and/or additions thereto, and to provide for the implementation of the policy and standards as set forth in the aforesaid laws and 12 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 11 of 26 regulations which are by reference made a part of this chapter with the force and effect as though set out in full in this chapter.” 33. Pursuant ACC 6.1.12, the Hearing Examiner shall hold at least one public hearing on the Shoreline Substantial Development Permit, Shoreline Conditional Use Permit, and Shoreline Variance in accordance with the following: “6.1.12 Application – Hearing – Required. A. The hearing examiner shall hold at least one public hearing on each application for a shoreline substantial development permit, shoreline conditional use permit, or shoreline variance on shorelines within the city. The public hearing shall be held not less than 30 days following the final publication of the notice required by ACC 16.08.050. B. The notice and conduct of the public hearing shall be in accordance with Chapter 2.46 ACC.” 34. The City’s rules provide the following requirements for public notice: “6.1.6 Application – Notices. The director shall give notice of the application in accordance with the applicable provisions of ACC 14.07.040, no less than 30 days prior to permit issuance. The notices shall include a statement that any person desiring to present his view to the director with regard to the application may do so in writing to the director, and any person interested in the hearing examiner's action on an application for a permit may submit his views or notify the director of his interest within 30 days of the last date of publication of the notice. Such notification or submission of views to the director shall entitle said persons to a copy of the action taken on the application.” 35. The City’s SMP contains the following information regarding the “Urban Conservancy” shoreline environment: “3.3 Urban Conservancy 3.3.1 Purpose: The purpose of the “Urban Conservancy” environment is to protect and restore ecological functions of open space, floodplain and other sensitive lands where they exist in urban and developed settings, while allowing a variety of compatible uses consistent with the Comprehensive Plan. 3.3.2 Designation Criteria: The Urban Conservancy environment designation is appropriate for those areas planned for development that is compatible with maintaining or restoring of the ecological functions of the area, and that are not generally suitable for intensive water-dependent uses. 3.3.3 Management Policies: The following management policies should apply to all shorelines in the Urban Conservancy Environment: 13 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 12 of 26 1. Primary allowed uses and their associated development standards should preserve the natural character of the area or promote preservation of open space, floodplain or sensitive lands where they exist in urban and developed settings, either directly or over the long term. Uses that result in restoration of ecological functions should be allowed if the use is otherwise compatible with the purpose of the environment and the setting. 2. Standards should be established for shoreline stabilization measures, vegetation conservation, water quality, and shoreline modifications within the "urban conservancy" designation. These standards should ensure that new development does not result in a net loss of shoreline ecological functions or further degrade other shoreline values. 3. Public access and public recreation objectives should be implemented whenever feasible and significant ecological impacts can be mitigated. 4. Water-oriented uses should be given priority over nonwater-oriented uses. For shoreline areas with commercial development or adjacent to commercially navigable waters, water-dependent uses should be given highest priority. 5. Existing mining and related activities may be an appropriate use within the urban conservancy environment when conducted in a manner consistent with the environment policies and the provisions of WAC 173-26-241(3)(h) and when located consistent with mineral resource lands designation criteria pursuant to RCW 36.70A.170 and WAC 365-190-070. No new mining uses or expansion of existing mines should be permitted within the shoreline jurisdiction.” 36. The City’s SMP contains the following goals related to Shoreline Use: “2.5.1 Goals 1. Promote the best possible pattern of land and water uses that will be most beneficial to the natural and human environments. 2. Designated Shorelines of Statewide Significance are of value to the entire State and shall be managed consistent with this recognition. In order of preference the priorities are to: a. Recognize and protect the Statewide interest over local interest; b. Preserve the natural character of the shoreline; c. Result in long term over short term benefit; d. Protect the resources and ecology of the shoreline; and, e. Increase public access to publicly owned areas of the shorelines.” 37. City City’s SMP contains the following goals related to Flood Prevention/Critical Areas: “2.8.1 Goals 1. Continue to participate in a regional approach to flood protection issues, coordinating with the State of Washington, King County, Pierce County and other entities interested in reducing flood hazards on both the White and Green Rivers. 14 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 13 of 26 2. Continue to protect wetlands, streams, wildlife habitat, and groundwater and minimize geologic hazards in the shoreline environment in accordance with the Critical Areas Ordinance.” 38. The City’s SMP contains the following policies related to Shoreline Vegetation Conservation: “4.4.2 Shoreline Vegetation Conservation 1. Developments and activities in the City’s shoreline should be planned and designed to retain native vegetation or replace shoreline vegetation with native species to achieve no net loss of the ecological functions and ecosystem-wide processes performed by vegetation. 2. Woody debris should be left in the river corridors to enhance wildlife habitat and shoreline ecological functions, except where it threatens personal safety or critical infrastructure, such as bridge pilings. In such cases where debris poses a threat, it should be dislodged, but should not be removed from the river.” 39. The City’s SMP contains the following policies related to Residential Development: “4.7.8 Residential Development 1. New over-water residences, including floating homes, are not a preferred use and should be prohibited. 2. New multi-family residential development and land subdivisions for more than four parcels should provide community and/or public access in conformance to the City’s public access planning and this Shoreline Master Program. Adjoining access shall be considered in making this determination. 3. Accessory development (to either multi-family or single-family) should be designed and located to blend into the site as much as possible. 4. New residential developments and land divisions should avoid the need for new shoreline stabilization or flood hazard reduction measures that would cause significant impacts to other properties or public improvements or a net loss of shoreline ecological functions.” Public Notice, Comments and Procedures 40. The City issued a combined Determination of Non-Significance (DNS) and Notice of Application (NOA) on February 5, 2021 with an associated 15-day comment period (File #SEP20-0009). The notice was mailed to property owners within 300 feet of the project site, published in the newspaper and posted on site (See Exhibit 13). 41. Two public comments were received in response to the DNS and NOA: Comment 1 – Dennis Wardlaw, State of Washington Department of Archaeology & Historic Preservation (DAHP), Feb. 12, 2021. 15 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 14 of 26 Mr. Wardlaw provided comments indicating that the project area has a very high sensitivity for archaeological resources. This determination was made based on review of data available with the Washington State DAHP. As a result, Mr. Wardlaw recommends that a professional archaeological survey of the project area be conducted prior to any ground disturbing activities. Comment 2 – Railin Santiago, Washington State Department of Ecology, Feb. 24, 2021. Ms. Santiago provided comments and questions regarding the need for a variance on Lot C, that the appropriate Washington Administrative Code criteria be addressed, that the need for a bulkhead should not be requested, and to make the recommendations of the geotechnical report conditions of approval for the permit. While Ms. Santiago’s comments were provided after the comment period for the initial DNS and NOA, nothing prevents said comments from being incorporated into the record, as the comment period for the associated SSDP, SCUP, and Shoreline Variance remain open until the close of the Public Hearing. The comments provided from Mr. Wardlaw, DAHP and Ms. Santiago, Ecology are marked as Exhibit 14. 42. City staff provided the applicant with the comments from DAHP and Ecology. City staff noted that regarding DAHP’s comments, it was likely that an archaeological survey will be made a condition of the associated shoreline permits for the project, as such is typical for this type of project along the Green River. Regarding the comments from Ecology, the applicant provided a detailed response noting that the Washington Administrative Code (WAC) criteria for approval of the requested shoreline permits was addressed as part of the initial submittal, that Lot B and C are not the same size and it would not be practical to have a smaller building footprint on Lot B, that the proposed residences are in similar size and scale as the other residences constructed along 104th Pl SE, that the applicant is in agreement with the geotechnical report conditions, and that the applicant is in disagreement with the condition prohibiting a bulkhead from ever being constructed on the site, as this places too much of a burden on future property owners and thus, should not be a condition of approval. The response comments from the applicant are included as Exhibit 15. 43. In addition to the public comments, City staff, including representatives with expertise in Utilities, Transportation, Building, Development Review, as well as the Valley Regional Fire Authority (VRFA) had an opportunity to review the proposal and provide comments. Based on the initial review of the project applications and support materials, none of the City staff or VRFA staff raised objections to the proposal. It should be noted that compliance with various City, state, and federal requirements, as well as securing other permit approvals, will be required in the future should the applicant seek to develop the site. 44. The City issued the Notice of Hearing (NOH) on March 15, 2021. The notice was provided 30 days prior to the hearing date as required by SMP 6.1.6, “Application – Notices”. The notice was mailed to property owners within 300 feet of the project site, published in the newspaper, and posted on site (See Exhibit 13). At the time of the preparation of this report, no comments have been received in response to the NOH. 16 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 15 of 26 45. The contents of the case file for this project (SHL20–0001, SHL20-0002 & SEP20-0009) are hereby incorporated by reference and made part of the record of this hearing. 46. The decision on SSDP, SCUP, and Shoreline Variance shall be final with the Hearing Examiner and subject to the Washington State Dept. of Ecology review period as required by the following code section: “SMP 6.1.18 Grant or denial decision – Notifications. The director shall notify the following persons in writing of the hearing examiner’s final approval, disapproval or conditional approval of a substantial development permit, shoreline conditional use permit, or shoreline variance application within eight days of its final decision: A. The applicant; B. The State Department of Ecology; C. The State Attorney General; D. Any person who has submitted to the director written comments on the application; E. Any person who has written the director requesting notification.” CONCLUSIONS: What follows is the criteria for decision-making provided in italics, followed by an analysis by staff of the project’s consistency with the criteria (in bold). Shoreline Substantial Development Permit 1. The Shoreline Master Program (SMP) provides the following review criteria for Shoreline Substantial Development Permits: “6.1.7 Application – Shoreline substantial development permit – Review criteria. A. A substantial development permit shall be granted by the director only when the development proposed is consistent with the following: “1. Goals, objectives, policies and use regulations of the Auburn SMP; The project has been reviewed for consistency with the goals, objectives, policies, and use regulations of the Auburn SMP. Specifically: • No net loss in shoreline functions will occur; • Three existing lots will be developed with single-family residences. As such, subdivision of existing lots will not occur; • No in-water work is proposed • No flood control systems are proposed for the project • With the exception of the two variances requested (which will be analyzed under a separate set of criteria), the project meets the development requirements of the Urban Conservancy Shoreline Designation and the R-5 Residential Zone. 2. Auburn Comprehensive Plan and Municipal Code; and 17 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 16 of 26 The project involves the construction of three single-family dwellings within a zoning district (R-5 Residential Zone) that allows for such. Additionally, various City staff experts and the VRFA have reviewed the proposal and have raised no objections. Further, outside reviewers from the WA State Department of Ecology and the Department of Archaeology and Historic Preservation have provided comments and recommended mitigation measures for the project. It should be noted that future permit approvals will be required to meet various City, State, and Federal regulations. Through meeting the Auburn City Code requirements and mitigation measures recommended by other agencies, the proposed SSDP will be meeting the policies of the Comprehensive Plan. 3. The policies, guidelines, and regulations of the SMA (Chapter 90.58 RCW; Chapters 173-26 and 173-27 WAC). By meeting the criteria established within the City of Auburn’s SMP, which was most recently approved by the Washington State Department of Ecology on May 7, 2020, the project will be consistent with the state SMA. B. The director may attach conditions to the approval of permits as necessary to assure consistency of the proposal with the above criteria.” Staff finds that the proposal is consistent with the above criteria for a Shoreline Substantial Development Permit and the criteria outlined in WAC 173-27-150 Shoreline Conditional Use Permit 2. The Shoreline Master Program (SMP) provides the following review criteria for Shoreline Conditional Use Permits: “6.1.8 Application – Shoreline conditional use permit – Review criteria. A. Pursuant to WAC 173-27-210, the criteria below shall constitute the minimum criteria for review and approval of a shoreline conditional use permit. Uses classified as conditional uses, and not uses prohibited by the regulations of this SMP, may be authorized; provided, that the applicant can demonstrate all of the following:” “1. That the proposed use will be consistent with the policies of RCW 90.58.020, the policies of this SMP, the City of Auburn comprehensive plan and other applicable plans, programs and/or regulations; The project is found to be consistent with policies and provisions of both the Shoreline Management Act and the local SMP. The application has demonstrated compliance with the applicable requirements of the City’s Shoreline Master Program. The new residences are a conditionally permitted use within the “Urban Conservancy” environment designations. 2. That the proposed use will not interfere with the normal public use or access to public shorelines; The project will not adversely affect the scenic quality of the shoreline environment since the work is being completed on private property and that the 18 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 17 of 26 western portion of the site directly abutting the Green River will generally remain undisturbed. The future dwellings will be constructed at a similar size, scale, and character as the single-family residences near and abutting the project site. 3. That the proposed use of the site and design of the project will be compatible with other permitted uses within the area and with uses planned for the area under the comprehensive plan and shoreline master program; The project involves the construction of three new single-family residences. Such use is compatible with the surrounding area, as the right bank of the Green River along 104th Pl SE is primarily developed with single-family residences. 4. That the proposed use will cause no unreasonably adverse effects to the shoreline, will not result in a net loss of ecological functions, and will not be incompatible with the environment designation or zoning classification in which it is to be located; No net loss in ecological function is anticipated from the project, as confirmed through a detailed critical area analysis prepared by a critical area consultant. No in-water work is proposed. While 11 trees will be removed outside of the 100 foot buffer area, new trees and habitat enhancements will be incorporated into the project. The new trees, plantings, and habitat features will help contribute to shade coverage and add woody debris along the Green River, thereby adding habitat value. With the exception of the tree removals and areas that will need to be cleared to allow for the future residential construction, the only vegetation removal proposed would be invasive species such as Himalayan blackberry. With the project being developed with three single-family homes within the R-5 Residential Zone, the project will be compatible with the zoning classification. Further, the Urban Conservancy shoreline designation supports the construction of single-family residences, provided the subject SCUP is granted. 5. That the public interest suffers no substantial detrimental effect; It is not anticipated that the public interest will suffer a detrimental effect. Public access to the shoreline will remain consistent with how it is today, visual impacts will be similar to what is currently present along 104 Pl SE, and no adverse ecological impacts are anticipated. Further, the project will be developed outside of the special flood hazard area and channel migration zone that both extend landward from the Green River, as well as setback from the bottom of the landslide hazard area directly to the east. 6. That the proposed use is in the best interest of the public health, safety, morals or welfare; and The proposal involves the construction of three new single-family residences in an area that is zoned for such uses. The proposal has been designed to meet various local, state, and federal regulations, including those pertaining to landslide hazardous, floodplain management, and vehicular access. Provided that the proposal is conditioned accordingly, it is in the best interest of the public health, safety, morals, and welfare. 19 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 18 of 26 7. That consideration of cumulative impacts resultant from the proposed use has occurred and has demonstrated that no substantial cumulative impacts are anticipated, consistent with WAC 173-27-160(2). Nothing in the record indicates that any substantial cumulative impacts would occur. While the proposal involves three new residences, no in-water work is proposed. Further, while a portion of a 100-foot Type S stream buffer will be impacted, there will be no net loss of shoreline functions as a result of future site development. This is due to the existing buffer area being enhanced from its current condition, in which invasive vegetation dominates the site, to a condition that will feature a dense mix of native vegetation plantings and woody debris. B. The director may attach conditions to the approval of permits as necessary to assure consistency of the proposal with the above criteria. C. The decision of the hearing examiner shall be the final decision of the city. The Department of Ecology shall be the final authority authorizing a shoreline conditional use permit consistent with WAC 173-27-200.” Staff finds that the proposal is consistent with the above criteria for a Shoreline Conditional Use Permit and the criteria outlined in WAC 173-27-160. Shoreline Variances 3. The Shoreline Master Program (SMP) provides the following review criteria for Shoreline Variances: “6.1.9 Application – Shoreline Variance – Review criteria. A. The purpose of a variance permit is strictly limited to granting relief from specific bulk, dimensional or performance standards set forth in this SMP, and where there are extraordinary or unique circumstances relating to the physical character or configuration of property such that the strict implementation of the SMP would impose unnecessary hardships on the applicant or thwart the SMA policies as stated in RCW 90.58.020. Requests for allowing uses different than those specifically identified as allowed in the shoreline environment cannot be considered in the variance process, but shall be considered through the conditional use process in ACC 16.08.080. B. Pursuant to WAC 173-27-210, the criteria below shall constitute the minimum criteria for review and approval of a Shoreline Variance permit. Variance permits for development that will be located landward of the ordinary high water mark (per RCW 90.58.030(2)(b) definition), except those areas designated as marshes, bogs or swamps pursuant to Chapter 173-22 WAC, may be authorized, provided the applicant can demonstrate all of the following: 4. That the strict requirements of the bulk, dimensional or performance standards set forth in the master program precludes or significantly interferes with a reasonable use of the property not otherwise prohibited by this SMP; Strict application of the 100-foot Type S Stream buffer requirement for Lots B and C significantly interferes with a reasonable use of the property. Specifically, the 20 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 19 of 26 100-foot buffer setback required for Lots B and C would result in a smaller building footprint than what is present throughout the area. Further, meeting the 100-foot buffer setback would result in the garages for each dwelling to be reduced in depth to where they may not be usable for vehicular parking. Moving the proposed residences further to the east is also impractical, as there is a sewer line located along each property’s frontage that has a 10-foot setback. While a smaller home may be possible on Lot B outside of the 100-foot stream buffer, such would be at a size that may not be supported by the market based on review of comparable residences within the area, in addition to the garage not being large enough to accommodate a parked vehicle. 5. That the hardship described above is specifically related to the property, and is the result of unique conditions such as irregular lot shape, size, or natural features and not, for example, from deed restrictions or the applicant’s own actions; The above described hardship is a direct result of the City’s SMP requiring a 100- foot buffer from the OWHM of the Green River impacting three legal lots of record. Further, the public utility easement along the property frontages, which has reduced the applicant’s ability to move the future dwellings further to the east outside of the stream buffer area, was put in place by the City of Auburn in order to allow for sewer service to nearby residents. While there is buildable area available to construct a new residence on Lot B and C, there are multiple critical area related encumbrances that severely reduce the amount of buildable area for each lot. 6. That the design of the project will be compatible with other permitted activities within the area and with uses planned for the area under the comprehensive plan and shoreline master program and will not cause adverse impacts to the shoreline environment; The applicant provided a table showing the building footprints, total square footages, and construction dates of all residences that abut the Green River along 104th Pl SE. The average footprint of 2,542 square feet exceeds the footprints proposed on Lots B and C. As such, the proposed building footprints for Lots B and C are both smaller (greater than 20% smaller) than what is currently within the area. The project involves the construction of single-family residences, which is a permitted land use within the sites R-5 zoning designation. As confirmed within the critical area report and mitigation plan provided by the applicant, the proposal will have no net less on shoreline functions. 7. That the variance authorized does not constitute a grant of special privilege not enjoyed by other properties in the area, and will be the minimum necessary to afford relief; and With the site having multiple critical area related encumbrances, as well as each property being a legal lot of record, other properties in the area could expect similar relief. As demonstrated by the applicant, with the need to keep the homes at a similar and smaller scale with what is present in the surrounding area, as well as having the minimum building footprint necessary to accommodate a two car attached garage, the requested variances are the minimum necessary. 21 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 20 of 26 8. That the public interest will suffer no substantial detrimental effect; The applicant will be developing three lots with three single-family residences meeting the requirements of the R-5 zone and other City requirements related to providing adequate utilities, safe access, and public services. Further, with the exception of the two variances sought to allow for the encroachment of two residences into the 100-foot Type S Stream buffer, the project is consistent with the City of Auburn’s SMP. It is recognized that the Green River, a Shoreline of the State, is of significant value to the public for various reasons. While the applicant will be reducing the 100-foot stream buffer to a width of 94.5 feet on Lot B and 89.5 feet on Lot C, the remaining buffer areas encompassing the entire project will be enhanced and improved significantly from its current condition through the use of native plantings and addition of habitat features such as woody debris. Further, with the project being comprised of three legal lots of record, it is within the public’s interest to add three new housing units within an urban growth area already equipped with utilities and public services to serve such development. Provided that the project is developed in accordance with the mitigation plan and civil drawings submitted with the application, the public interest will suffer no substantial detrimental effect. 9. Variance permits for development that will be located either waterward of the ordinary high water mark or within marshes, bogs or swamps as designated in Chapter 173-22 WAC, may be authorized, provided the applicant can demonstrate all the criteria stated above as well as the following: a. That the strict application of the bulk, dimensional or performance standards set forth in this SMP precludes all reasonable use of the property not otherwise prohibited by this SMP; and b. That the public rights of navigation and use of the shorelines will not be adversely affected by the granting of the variance. Not applicable. The development activities resulting in the need for variances are landward of the OHWM and do not involve development of areas designated as marshes, bogs, or swamps. C. In the granting of all variance permits, consideration shall be given to the cumulative impact of additional requests for like actions in the area. For example, if variances were granted to other developments in the area where similar circumstances exist, the total of the variances should also remain consistent with the policies of Chapter 90.58 RCW and should not produce substantial adverse effects to the shoreline environment or result in a net loss of ecological functions. D. The decision of the hearing examiner shall be the final decision of the city. The Department of Ecology shall be the final authority authorizing a Shoreline Variance consistent with WAC 173-27-200.” Staff finds that the proposal is consistent with the above criteria for two Shoreline Variances and the criteria outlined in WAC 173-27-170 Consistency with SMA & Local SMP 22 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 21 of 26 4. The Shoreline Management rules (WAC 173-27-140) set forth the following two criteria for all developments within the shoreline jurisdiction. “(A) No authorization to undertake use or development on shorelines of the state shall be granted by the local government unless upon review the use or development is determined to be consistent with the policy and provisions of the Shoreline Management Act and the master program.” “(B) No permit shall be issued for any new or expanded building or structure of more than thirty-five feet above average grade level on shorelines of the state that will obstruct the view of a substantial number of residences on areas adjoining such shorelines except where a master program does not prohibit the same and then only when overriding considerations of the public interest will be served.” The proposed project is consistent with the Shoreline Management Act and the City’s Shoreline Management Program (SMP). The City's program identifies the project area to be the “Urban Conservancy” shoreline environment designations. The project will be consistent with the designation by allowing new residences that will have minimal impact on the surrounding properties. Public access to the shorelines will not be impacted or reduced. While there may be a visual impact due to the construction of new residences, such impact will be minimal due to a portion of existing mature trees being retained and the incorporation of new tree plantings and habitat features. Further, the proposed residences will be constructed to meet the 35- foot height requirement. The proposed project is consistent with the SMP policies applicable to residential uses. No in- or overwater work is proposed. The proposal involves three single family residences on three existing lots of record. No accessory development is proposed\, such as shoreline stabilization, or flood hazard reduction measures that would cause impacts to other properties or public improvements are proposed. The proposed dwellings will meet the zoning development standards of the R-5 Residential zone, including meeting the minimum setbacks, height limit, lot coverage, and parking requirements. Removal and disturbance of vegetation near the shoreline will be limited to the removal of invasive vegetation and 11 trees outside of the 100 foot Type S Stream buffer area. While the residences will be located near an area mapped as a landslide hazard area per the City’s critical area inventory, the project will meet the recommendations provided within a Geotechnical Report that will ensure the life, safety, and welfare of the future residential inhabitants is protected. No development will occur within the floodway, Special Flood Hazard Area, or Channel Migration Zone. City of Auburn staff believe the project is consistent with the criteria established in WAC 173-27-140. 23 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 22 of 26 5. The Shoreline Management rules in WAC 173-27-150 set forth the following criteria that must be met for approval of a Shoreline Substantial Development Permit. The project must be consistent with: (1) A substantial development permit shall be granted only when the development proposed is consistent with: (a) The policies and procedures of the act; (b) The provisions of this regulation; and (c) The applicable master program adopted or approved for the area. Provided, that where no master program has been approved for an area, the development shall be reviewed for consistency with the provisions of chapter 173-26 WAC, and to the extent feasible, any draft or approved master program which can be reasonably ascertained as representing the policy of the local government. (2) Local government may attach conditions to the approval of permits as necessary to assure consistency of the project with the act and the local master program. As noted previously within the above analysis outlined within Conclusion 1, City of Auburn staff believe the project is consistent with the criteria established in WAC 173-27-150. 6. The Shoreline Management rules in WAC 173-27-160 set forth the following criteria that must be met for approval of a Shoreline conditional use permit. The project must be consistent with: The purpose of a conditional use permit is to provide a system within the master program which allows flexibility in the application of use regulations in a manner consistent with the policies of RCW 90.58.020. In authorizing a conditional use, special conditions may be attached to the permit by local government or the department to prevent undesirable effects of the proposed use and/or to assure consistency of the project with the act and the local master program. (1) Uses which are classified or set forth in the applicable master program as conditional uses may be authorized provided that the applicant demonstrates all of the following: (a) That the proposed use is consistent with the policies of RCW 90.58.020 and the master program; (b) That the proposed use will not interfere with the normal public use of public shorelines; (c) That the proposed use of the site and design of the project is compatible with other authorized uses within the area and with uses planned for the area under the comprehensive plan and shoreline master program; (d) That the proposed use will cause no significant adverse effects to the shoreline environment in which it is to be located; and (e) That the public interest suffers no substantial detrimental effect. (2) In the granting of all conditional use permits, consideration shall be given to the cumulative impact of additional requests for like actions in the area. For example, if conditional use permits were granted for other developments in the area where similar circumstances exist, the total of the conditional uses shall also remain consistent with 24 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 23 of 26 the policies of RCW 90.58.020 and shall not produce substantial adverse effects to the shoreline environment. (3) Other uses which are not classified or set forth in the applicable master program may be authorized as conditional uses provided the applicant can demonstrate consistency with the requirements of this section and the requirements for conditional uses contained in the master program. (4) Uses which are specifically prohibited by the master program may not be authorized pursuant to either subsection (1) or (2) of this section. As noted previously within the above analysis outlined within Conclusion 2, City of Auburn staff believe that the project is consistent with the criteria established in WAC 173-27-160. 7. The Shoreline Management rules in WAC 173-27-170 set forth the following criteria that must be met for approval of Shoreline Variances. The project must be consistent with: The purpose of a variance permit is strictly limited to granting relief from specific bulk, dimensional or performance standards set forth in the applicable master program where there are extraordinary circumstances relating to the physical character or configuration of property such that the strict implementation of the master program will impose unnecessary hardships on the applicant or thwart the policies set forth in RCW 90.58.020. (1) Variance permits should be granted in circumstances where denial of the permit would result in a thwarting of the policy enumerated in RCW 90.58.020. In all instances the applicant must demonstrate that extraordinary circumstances shall be shown and the public interest shall suffer no substantial detrimental effect. (2) Variance permits for development and/or uses that will be located landward of the ordinary high water mark (OHWM), as defined in RCW 90.58.030 (2)(c), and/or landward of any wetland as defined in RCW 90.58.030 (2)(h), may be authorized provided the applicant can demonstrate all of the following: (a) That the strict application of the bulk, dimensional or performance standards set forth in the applicable master program precludes, or significantly interferes with, reasonable use of the property; (b) That the hardship described in (a) of this subsection is specifically related to the property, and is the result of unique conditions such as irregular lot shape, size, or natural features and the application of the master program, and not, for example, from deed restrictions or the applicant's own actions; (c) That the design of the project is compatible with other authorized uses within the area and with uses planned for the area under the comprehensive plan and shoreline master program and will not cause adverse impacts to the shoreline environment; (d) That the variance will not constitute a grant of special privilege not enjoyed by the other properties in the area; (e) That the variance requested is the minimum necessary to afford relief; and (f) That the public interest will suffer no substantial detrimental effect. (3) Variance permits for development and/or uses that will be located waterward of the ordinary high water mark (OHWM), as defined in RCW 90.58.030 (2)(c), or within any 25 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 24 of 26 wetland as defined in RCW 90.58.030 (2)(h), may be authorized provided the applicant can demonstrate all of the following: (a) That the strict application of the bulk, dimensional or performance standards set forth in the applicable master program precludes all reasonable use of the property; (b) That the proposal is consistent with the criteria established under subsection (2)(b) through (f) of this section; and (c) That the public rights of navigation and use of the shorelines will not be adversely affected. (4) In the granting of all variance permits, consideration shall be given to the cumulative impact of additional requests for like actions in the area. For example if variances were granted to other developments and/or uses in the area where similar circumstances exist the total of the variances shall also remain consistent with the policies of RCW 90.58.020 and shall not cause substantial adverse effects to the shoreline environment. (5) Variances from the use regulations of the master program are prohibited. As noted previously within the above analysis outlined within Conclusion 3, City of Auburn staff believe that the project is consistent with the criteria established in WAC 173-27-170. STAFF RECOMMENDATION Based on the application, findings, and conclusions of the Staff report, Staff recommends that the Hearing Examiner APPROVE the Shoreline Substantial Development Permit, Shoreline Conditional Use Permit, and Shoreline Variance for Lot B and C to be located 94.5 feet and 89.5 feet, respectively, subject to the following conditions: 1. The future development of the site associated with the subject Shoreline Substantial Development Permit, Shoreline Conditional Use Permit, and Shoreline Variances shall be completed within two years from the effective date of the decision from the Department of Ecology, as specified in WAC 173-27-090. 2. The future residences shall be developed to be substantially consistent with the Civil Sheets, prepared by Encompass Engineering & Surveying, dated May 21, 2021 (Exhibit 7). 3. The project shall be developed to be substantially consistent with the Shoreline Buffer Mitigation Plan, prepared by Evergreen Aquatic Resource Consultants, LLC, dated May 14, 2021 (Exhibit 9). The mitigation plan shall be developed and installed as part of the grading or civil review for the project. Further, the mitigation will be required to be installed for the entire project site prior to the issuance of building permits for each respective lot. 4. The future residences shall be developed in accordance with the recommendations from the Geotechnical Study, prepared by Bergquist Engineering Services, dated November 4, 2020 (Exhibit 10). This includes additional future investigation work that will need to be performed to confirm the optimal foundation design for the future dwellings. 26 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 25 of 26 5. The applicant shall secure the necessary floodplain development permit approval(s) from the City of Auburn, if applicable. 6. A professional archaeological survey of the project area, meeting the requirements of the Washington State Department of Archaeology and Historic Preservation (DAHP), shall be conducted prior to any ground disturbing activities on the site. The study, including any recommendations from it, shall be provided to and reviewed by the DAHP prior to any land clearing, grading or building permit for the first lot. 7. The construction of a bulkhead along the western edge of each lot along the right bank of the Green River shall be prohibited. 8. With the exception of the trees identified for removal on the Arborist Report, prepared by Layton Tree Consulting, LLC, dated May 12, 2021, no significant tree removal will be allowed from the site. Should the applicant need to remove any additional significant trees from the site, an updated report prepared by a certified arborist confirming the trees pose a hazard or are unhealthy, shall be provided to the City for review. Additionally, new tree plantings to off-set the loss of such trees may be required either within the mitigation area along the western portion of the site or any remaining areas along the eastern portion of the site. In addition to an arborist report, the applicant shall provide an analysis confirming that the loss of such significant trees will not result in any conflicts with the requirements of ACC 15.68, Article VII, Standards for Habitat Protection. 9. Consistent with ACC 16.10.110(D)(1)(b), the Type S Stream buffer or as modified by the variance, shall be encumbered by a conservation easement prior to final inspection of each home. Staff reserves the right to supplement the record of the case to respond to matters and information raised subsequent to the writing of this report. EXHIBIT LIST Exhibit 1 Staff Report Exhibit 2 Vicinity Map Exhibit 3 City of Auburn Critical Area Inventory Map Exhibit 4 Completed City of Auburn Land Use Application Forms, Received May 15, 2020 Exhibit 5 Joint Aquatic Resources Permit Application (JARPA) form, Encompass Engineering & Surveying, April 10, 2021 Exhibit 6 Written Statement, Encompass Engineering & Surveying, dated April, 2020, and revised May 15, 2020 Exhibit 7 Civil Sheets, Encompass Engineering & Surveying, May 21, 2021 Exhibit 8 Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated April 10, 2020, revised May 14, 2021 Exhibit 9 Shoreline Buffer Mitigation Plan, prepared by Evergreen Aquatic Resource Consultants, LLC, dated May 14, 2021 Exhibit 10 Geotechnical Study, prepared by Bergquist Engineering Services, dated November 4, 2020 27 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 26 of 26 Exhibit 11 Preliminary Storm Drainage Report, prepared by Encompass Engineering & Surveying, dated April 17, 2020 Exhibit 12 SEPA Environmental Checklist, prepared by Encompass Engineering & Surveying, dated November, 2020 Exhibit 13 Notice of Application (NOA) and Determination of Non-Significance (DNS), issued February 5th, 2021 & Notice of Public Hearing (NOH), issued March 15th, 2021 Exhibit 14 Public Comments Received, DAHP & Ecology, February 12, 2021 & February 24, 2021 Exhibit 15 Response Comments, Encompass Engineering & Surveying, dated April 3, 2021 Exhibit 16 Public Notice Affidavits and Confirmation of Postings Exhibit 17 Arborist Report, prepared by Layton Tree Consulting, LLC, dated May 12, 2021 28 of 721 666.7 NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet Feet666.7 Notes Type any additional notes- delete text to leave blank Legend 333.30 1:4,000 Vicinity Map 1in =333 ft 4/3/2021Printed Date: Map Created by City of Auburn eGIS Imagery Date: May 2015 Information shown is for general reference purposes only and does not necessarily represent exact geographic or cartographic data as mapped. The City of Auburn makes no warranty as to its accuracy. Public Streets Alley Highways Local Minor Arterial Non Residential Collector Principal Arterial Residential Collector Rural Collector 29 of 721 166.7 NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet Feet166.7 Notes Legend 83.30 1:1,000 City of Auburn Critical Area Map 1in =83 ft 3/31/2021Printed Date: Map Created by City of Auburn eGIS Imagery Date: May 2015 Information shown is for general reference purposes only and does not necessarily represent exact geographic or cartographic data as mapped. The City of Auburn makes no warranty as to its accuracy. City of Auburn Channel Migration Zone Delineation Riparian Habitat Zones (RHZ) 2020 FIRM Floodway 2020 FIRM Special Flood Hazard Area (SFHA) Wetlands Priority Habitats and Species Elk Riparian Zones Roosevelt Elk Urban Natural Open Space Waterfowl Concentrations Wetlands Streams Landslide Hazard Parcel Boundaries 30 of 721 31 of 721 32 of 721 33 of 721 ORIA-16-011 Page 1 of 14 WASHINGTON STATE Joint Aquatic Resources Permit Application (JARPA) Form1,2 [help] USE BLACK OR BLUE INK TO ENTER ANSWERS IN THE WHITE SPACES BELOW. Part 1–Project Identification 1. Project Name (A name for your project that you create. Examples: Smith’s Dock or Seabrook Lane Development) [help] Goulet Single Family Residences Part 2–Applicant The person and/or organization responsible for the project. [help] 2a. Name (Last, First, Middle) Goulet, Lance P & Goulet, Bruce 2b. Organization (If applicable) 2c. Mailing Address (Street or PO Box) 3226 S 196th Street 2d. City, State, Zip SeaTac, Washington 98188 2e. Phone (1) 2f. Phone (2) 2g. Fax 2h. E-mail 206-948-2009 425-444-0461 laonthelake@centurylink.net 1Additional forms may be required for the following permits: • If your project may qualify for Department of the Army authorization through a Regional General Permit (RGP), contact the U.S. Army Corps of Engineers for application information (206) 764-3495. • Not all cities and counties accept the JARPA for their local Shoreline permits. If you need a Shoreline permit, contact the appropriate city or county government to make sure they accept the JARPA. 2To access an online JARPA form with [help] screens, go to http://www.epermitting.wa.gov/site/alias__resourcecenter/jarpa_jarpa_form/9984/jarpa_form.aspx . For other help, contact the Governor’s Office for Regulatory Innovation and Assistance at (800) 917-0043 or help@oria.wa.gov. AGENCY USE ONLY Date received: Agency reference #: Tax Parcel #(s): 34 of 721 ORIA-16-011 Page 2 of 14 Part 3–Authorized Agent or Contact Person authorized to represent the applicant about the project. (Note: Authorized agent(s) must sign 11b of this application.) [help] 3a. Name (Last, First, Middle) Gill, Mariah 3b. Organization (If applicable) Encompass Engineering & Surveying 3c. Mailing Address (Street or PO Box) 165 NE Juniper Street, Suite 201 3d. City, State, Zip Issaquah, Washington 98027 3e. Phone (1) 3f. Phone (2) 3g. Fax 3h. E-mail 425-961-2203 mgill@encompasses.net Part 4–Property Owner(s) Contact information for people or organizations owning the property(ies) where the project will occur. Consider both upland and aquatic ownership because the upland owners may not own the adjacent aquatic land. [help] ☒ Same as applicant. (Skip to Part 5.) ☐ Repair or maintenance activities on existing rights-of-way or easements. (Skip to Part 5.) ☐ There are multiple upland property owners. Complete the section below and fill out JARPA Attachment A for each additional property owner. ☐ Your project is on Department of Natural Resources (DNR)-managed aquatic lands. If you don’t know, contact the DNR at (360) 902-1100 to determine aquatic land ownership. If yes, complete JARPA Attachment E to apply for the Aquatic Use Authorization. 4a. Name (Last, First, Middle) Same as applicant 4b. Organization (If applicable) Same as applicant 4c. Mailing Address (Street or PO Box) Same as applicant 4d. City, State, Zip Same as applicant 4e. Phone (1) 4f. Phone (2) 4g. Fax 4h. E-mail Same as applicant Same as applicant Same as applicant Same as applicant 35 of 721 ORIA-16-011 Page 3 of 14 Part 5–Project Location(s) Identifying information about the property or properties where the project will occur. [help] ☐ There are multiple project locations (e.g. linear projects). Complete the section below and use JARPA Attachment B for each additional project location. 5a. Indicate the type of ownership of the property. (Check all that apply.) [help] ☒ Private ☐ Federal ☐ Publicly owned (state, county, city, special districts like schools, ports, etc.) ☐ Tribal ☐ Department of Natural Resources (DNR) – managed aquatic lands (Complete JARPA Attachment E) 5b. Street Address (Cannot be a PO Box. If there is no address, provide other location information in 5p.) [help] Approximately ±32XXX 104th Place SE 5c. City, State, Zip (If the project is not in a city or town, provide the name of the nearest city or town.) [help] Auburn, Washington 98092 5d. County [help] King County 5e. Provide the section, township, and range for the project location. [help] ¼ Section Section Township Range NW 17 21 North 5 East 5f. Provide the latitude and longitude of the project location. [help] • Example: 47.03922 N lat. / -122.89142 W long. (Use decimal degrees - NAD 83) 47.31423 N lat / -122.20452 W long. (NAD 83) 5g. List the tax parcel number(s) for the project location. [help] • The local county assessor’s office can provide this information. 334100-0090; 334100-0095; 334100-0100 5h. Contact information for all adjoining property owners. (If you need more space, use JARPA Attachment C.) [help] Name Mailing Address Tax Parcel # (if known) City of Auburn 25 West Main Street 334100-0088 Auburn, Washington 98001-4998 Anh N Pham & Dand Huy 32149 104th Place SE 334100-0125 Auburn. Washington 98092 36 of 721 ORIA-16-011 Page 4 of 14 5i. List all wetlands on or adjacent to the project location. [help] No wetlands present. 5j. List all waterbodies (other than wetlands) on or adjacent to the project location. [help] Green River 5k. Is any part of the project area within a 100-year floodplain? [help] ☒ Yes ☐ No ☐ Don’t know 5l. Briefly describe the vegetation and habitat conditions on the property. [help] Each lot is undeveloped and includes dense shrub vegetation with occasional scattered trees. Plant species richness is low and dominant plant species are non-native species. No significant habitat features or considerable vegetation structure is present. Dominant plant species is dense Himalayan blackberry. Scattered bigleaf maple, black cottonwood, Douglas-fir, and black locust and occasional western swordfern, salmonberry, and common snowberry are also present. Trees are primarily limited to portions of the site located along 104th Place SE or along the river bank. Each lot maintains frontage on the Green River and includes a portion of the 100 year floodplain and channel migration zone. 5m. Describe how the property is currently used. [help] The property is currently vacant undeveloped land. 5n. Describe how the adjacent properties are currently used. [help] Adjacent properties are generally residential in nature. The property located immediately north of the project site is a small undeveloped City of Auburn owned residentially zoned lot. A single family residence exists on the property immediately south of the site. 104th Place SE is located east of the site and the Green River is located west of the site. 5o. Describe the structures (above and below ground) on the property, including their purpose(s) and current condition. [help] None present. Historically the site was used for agriculture, but since at least 1957, the site has remained vacant, undeveloped land. 5p. Provide driving directions from the closest highway to the project location, and attach a map. [help] The project site can be accessed from SR 167 by taking the 15th Street NW exit and heading east for 1.1 miles. 15th Street NW turns into Harvey Road NE at its intersection with Auburn Way N. Continue southeast on Harvey Road NE for approximately 0.5 miles, then turn left onto 8th Street NE. Travel east on 8th Street NE for approximately 0.5 miles and then turn right onto 104th Place SE. The project site is located on the west side of 104th Place SE approximately 450 feet south of 8th Street NE. Part 6–Project Description 6a. Briefly summarize the overall project. You can provide more detail in 6b. [help] The proposed project includes the construction of a 55 foot wide by 28.5 foot deep single-family residence on Lot A and 55 foot wide by 30 foot deep single-family residences on both Lot B and Lot C. Each residence will be constructed in the eastern portion of the respective lot and will comprise a multi-story design with attached garage. The proposed project includes compact building footprints, minimum width driveways, and minimum property line and easement setbacks. 37 of 721 ORIA-16-011 Page 5 of 14 6b. Describe the purpose of the project and why you want or need to perform it. [help] The purpose of the proposed project is to develop each existing undeveloped residential lot for single-family residential use as allowed by the underlying R-5 zoning designation. The project goal is to construct a single- family residence on each lot that has all the essential components of a modern residence. The project provides needed residential housing within the local area. As proposed, the project achieves the desired purpose and need while at the same time complements the character of the existing development within the local area and enhances stream buffer and shoreline ecological functioning. 6c. Indicate the project category. (Check all that apply) [help] ☐ Commercial ☒ Residential ☐ Institutional ☐ Transportation ☐ Recreational ☐ Maintenance ☐ Environmental Enhancement 6d. Indicate the major elements of your project. (Check all that apply) [help] ☐ Aquaculture ☐ Bank Stabilization ☐ Boat House ☐ Boat Launch ☐ Boat Lift ☐ Bridge ☐ Bulkhead ☐ Buoy ☐ Channel Modification ☐ Culvert ☐ Dam / Weir ☐ Dike / Levee / Jetty ☐ Ditch ☐ Dock / Pier ☐ Dredging ☐ Fence ☐ Ferry Terminal ☐ Fishway ☐ Float ☐ Floating Home ☐ Geotechnical Survey ☐ Land Clearing ☐ Marina / Moorage ☐ Mining ☐ Outfall Structure ☐ Piling/Dolphin ☐ Raft ☐ Retaining Wall (upland) ☐ Road ☐ Scientific Measurement Device ☐ Stairs ☐ Stormwater facility ☐ Swimming Pool ☐ Utility Line ☒ Other: Residential development. The proposed project is a residential development project located within the 200 foot shoreline management zone associated with the Green River. No in-water work is proposed. Residential development will not occur within the 100 year floodplain and/or channel migration hazard area. 38 of 721 ORIA-16-011 Page 6 of 14 6e. Describe how you plan to construct each project element checked in 6d. Include specific construction methods and equipment to be used. [help] • Identify where each element will occur in relation to the nearest waterbody. • Indicate which activities are within the 100-year floodplain. Construction of the proposed project will include the following processes and methods: • Construction Access Construction access to each building site will be directly from 104th Place SE. No specialized to temporary access points or routes are proposed. Access will be established at the start of construction and will be maintained through the duration of construction. • Clearing and Grading Vegetation within each building site will be removed and minimal grading will be necessary to level and prepare each building site for construction. Vegetation removal is limited to primarily Himalayan blackberry. Only one significant tree will be removed. No grading or filling is proposed within the Green River, associated flood hazard areas, or reduced buffer areas. • Stormwater Management Temporary erosion and sediment control (TESC) measures will be installed prior to the start of construction and will be properly maintained during the entire construction period. TESC measures will conform to City of Auburn standards and will include, at a minimum, filter fabric (silt) fencing, temporary cover, and rock construction entrance best management practices (BMP’s). Permanent stormwater management for the completed project will conform to City of Auburn standards and will include the collection of stormwater runoff from impervious surfaces and dispersion via a gravel lined trench or similar BMP. Stormwater infiltration will occur between the developed portion of each lot and the Green River. • Utility Installation Power, telephone, cable, sewer, and water connections to each lot will be from existing utilities located in 104th Place SE. • Building Construction Proposed building construction includes conventional framing construction methods. Foundation design and construction methods will depend on the results of future geotechnical analysis; however, it is anticipated that foundation design could include one or more of the following: conventional spread footings, driven pipe piles, and/or drilled augercast piles. • Critical Area Protection and Enhancement During construction, the required shoreline buffer limits will be marked using hi-visibility plastic orange construction fencing. No construction staging or material stockpiling will occur within the reduced shoreline buffer. Following construction, a permanent cedar split rail fence will be installed along the reduced shoreline buffer and the shoreline buffer will be enhanced per a City of Auburn approved mitigation plan. 6f. What are the anticipated start and end dates for project construction? (Month/Year) [help] • If the project will be constructed in phases or stages, use JARPA Attachment D to list the start and end dates of each phase or stage. Start Date: upon approval End Date: ASAP ☐ See JARPA Attachment D 6g. Fair market value of the project, including materials, labor, machine rentals, etc. [help] XXX 39 of 721 ORIA-16-011 Page 7 of 14 6h. Will any portion of the project receive federal funding? [help] • If yes, list each agency providing funds. ☐ Yes ☒ No ☐ Don’t know Part 7–Wetlands: Impacts and Mitigation ☐ Check here if there are wetlands or wetland buffers on or adjacent to the project area. (If there are none, skip to Part 8.) [help] 7a. Describe how the project has been designed to avoid and minimize adverse impacts to wetlands. [help] ☒ Not applicable 7b. Will the project impact wetlands? [help] ☐ Yes ☒ No ☐ Don’t know 7c. Will the project impact wetland buffers? [help] ☐ Yes ☒ No ☐ Don’t know 7d. Has a wetland delineation report been prepared? [help] • If Yes, submit the report, including data sheets, with the JARPA package. ☒ Yes ☐ No - See Critical Area Report 7e. Have the wetlands been rated using the Western Washington or Eastern Washington Wetland Rating System? [help] • If Yes, submit the wetland rating forms and figures with the JARPA package. ☐ Yes ☐ No ☐ Don’t know Not applicable 7f. Have you prepared a mitigation plan to compensate for any adverse impacts to wetlands? [help] • If Yes, submit the plan with the JARPA package and answer 7g. • If No, or Not applicable, explain below why a mitigation plan should not be required. ☐ Yes ☐ No ☐ Don’t know Not applicable Not applicable. 7g. Summarize what the mitigation plan is meant to accomplish, and describe how a watershed approach was used to design the plan. [help] Not applicable. 40 of 721 ORIA-16-011 Page 8 of 14 7h. Use the table below to list the type and rating of each wetland impacted, the extent and duration of the impact, and the type and amount of mitigation proposed. Or if you are submitting a mitigation plan with a similar table, you can state (below) where we can find this information in the plan. [help] Activity (fill, drain, excavate, flood, etc.) Wetland Name1 Wetland type and rating category2 Impact area (sq. ft. or Acres) Duration of impact3 Proposed mitigation type4 Wetland mitigation area (sq. ft. or acres) Not applicable. 1 If no official name for the wetland exists, create a unique name (such as “Wetland 1”). The name should be consistent with other project documents, such as a wetland delineation report. 2 Ecology wetland category based on current Western Washington or Eastern Washington Wetland Rating System. Provide the wetland rating forms with the JARPA package. 3 Indicate the days, months or years the wetland will be measurably impacted by the activity. Enter “permanent” if applicable. 4 Creation (C), Re-establishment/Rehabilitation (R), Enhancement (E), Preservation (P), Mitigation Bank/In-lieu fee (B) Page number(s) for similar information in the mitigation plan, if available: Not applicable. 7i. For all filling activities identified in 7h, describe the source and nature of the fill material, the amount in cubic yards that will be used, and how and where it will be placed into the wetland. [help] Not applicable. 7j. For all excavating activities identified in 7h, describe the excavation method, type and amount of material in cubic yards you will remove, and where the material will be disposed. [help] Not applicable. Part 8–Waterbodies (other than wetlands): Impacts and Mitigation In Part 8, “waterbodies” refers to non-wetland waterbodies. (See Part 7 for information related to wetlands.) [help] ☒ Check here if there are waterbodies on or adjacent to the project area. (If there are none, skip to Part 9.) 8a. Describe how the project is designed to avoid and minimize adverse impacts to the aquatic environment. [help] ☐ Not applicable As a general overview, the project has employed the following environmental protection and conservation measures: • Limiting the amount, type, and location of development within the project site; • The use of protective buffers from designated critical areas; • The use of appropriate construction practices; • The use of site-specific stormwater management practices during and after construction; and • On-site shoreline buffer enhancements. The proposed project does not include in-water water work, structure placement in the river bank, or grading or filling within the 100 year floodplain or mapped channel migration zone. Development within each lot will be consolidated in the extreme eastern portion of each lot at the outer limits of the standard width 100 foot stream buffer and within the 200 foot shoreline management zone associated with the Green River. Project impacts 41 of 721 ORIA-16-011 Page 9 of 14 are further minimized by utilizing minimum length driveways and maintaining minimum setbacks from 104th Place NE. 8b. Will your project impact a waterbody or the area around a waterbody? [help] ☐ Yes ☒ No 8c. Have you prepared a mitigation plan to compensate for the project’s adverse impacts to non-wetland waterbodies? [help] • If Yes, submit the plan with the JARPA package and answer 8d. • If No, or Not applicable, explain below why a mitigation plan should not be required. ☒ Yes ☐ No ☐ Don’t know The proposed project includes buffer enhancement on each lot as compensatory mitigation. The proposed mitigation is detailed on the plan entitled “Shoreline Buffer Mitigation Plan: Proposed Goulet Single Family Residences”, dated April 10, 2020. The mitigation will occur on-site and will comprise enhancement of degraded shoreline buffer areas. The proposed mitigation will be completed as a single phase at the landowner’s expense and will completed prior to the issuance of certificate of occupancy for each proposed residence. Specific components of the mitigation include the following: • Intensive noxious weed control. • Habitat structure installation – logs with and without rootwads. • Dense native plantings – effective plant spacing will be 9 feet on-center for trees and 4 feet on-center for shrubs. • Application of dense mulch throughout all planting areas. • Critical area fencing and signage. • Two years of temporary irrigation. • Five years of maintenance and monitoring. • Permanent preservation using a long-term protection notice on title. 8d. Summarize what the mitigation plan is meant to accomplish. Describe how a watershed approach was used to design the plan. • If you already completed 7g you do not need to restate your answer here. [help] The broad goal and objective of the mitigation is to provide for a “no-net loss” in shoreline ecological functioning. This will be achieved by: 1) removing noxious weeds; 2) installing site appropriate enhancements; and 3) permanently protecting the enhanced buffer. Specific mitigation goals, objectives, and performance standards are detailed on the mitigation plan. The proposed mitigation utilizes best management practices (BMP’s) in design to ensure a diverse assemblage of native plants, high native plant coverage, a significant reduction in non-native plant species, and an appropriate mitigation monitoring program. It is expected that over time, the buffer enhancements will develop into a forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973). Based on the proposed planting densities, the distribution and abundance of native plantings within each site will increase and/or will provide opportunities for structural habitat diversity, shade, and LWD production that currently either does not exist or is otherwise limited within the project site. 8e. Summarize impact(s) to each waterbody in the table below. [help] Activity (clear, dredge, fill, pile drive, etc.) Waterbody name1 Impact location2 Duration of impact3 Amount of material (cubic yards) to be placed in or removed from waterbody Area (sq. ft. or linear ft.) of waterbody directly affected 42 of 721 ORIA-16-011 Page 10 of 14 Residential development Green River No in-water work is proposed. Work will occur in the outer portion of 100 ft buffer and setback. No in-water work is proposed. No in-water work is proposed. No in-water work is proposed. Site maintains approximately 300 lf of frontage along the right (east) bank of river. 1 If no official name for the waterbody exists, create a unique name (such as “Stream 1”) The name should be consistent with other documents provided. 2 Indicate whether the impact will occur in or adjacent to the waterbody. If adjacent, provide the distance between the impact and the waterbody and indicate whether the impact will occur within the 100-year flood plain. 3 Indicate the days, months or years the waterbody will be measurably impacted by the work. Enter “permanent” if applicable. 8f. For all activities identified in 8e, describe the source and nature of the fill material, amount (in cubic yards) you will use, and how and where it will be placed into the waterbody. [help] No in-water work is proposed. All work will occur at the limits of the 100 ft buffer. Fill that will be imported to the site will be minimal and may include crushed rock and suitable foundation support materials. Fill will only be placed in building sites. 8g. For all excavating or dredging activities identified in 8e, describe the method for excavating or dredging, type and amount of material you will remove, and where the material will be disposed. [help] No in-water work is proposed. Any dirt removed from the site will be disposed of at a legal upland location. Part 9–Additional Information Any additional information you can provide helps the reviewer(s) understand your project. Complete as much of this section as you can. It is ok if you cannot answer a question. 9a. If you have already worked with any government agencies on this project, list them below. [help] Agency Name Contact Name Phone Most Recent Date of Contact City of Auburn Steve Sturza, Engineer 253-876-1969 City of Auburn Dustin Lawence, Planner 253-931-3092 9b. Are any of the wetlands or waterbodies identified in Part 7 or Part 8 of this JARPA on the Washington Department of Ecology’s 303(d) List? [help] • If Yes, list the parameter(s) below. • If you don’t know, use Washington Department of Ecology’s Water Quality Assessment tools at: https://ecology.wa.gov/Water- Shorelines/Water-quality/Water-improvement/Assessment-of-state-waters-303d. 43 of 721 ORIA-16-011 Page 11 of 14 ☒ Yes ☐ No The segment of the Green River located adjacent to the site is not 303d listed; however, the Green River is 303d listed for dissolved oxygen approximately two miles downstream of the site and approximately 1.5 miles upstream of the site (Ecology 2020). The Green River currently has Environmental Protection Agency (EPA) approved total maximum daily load (TMDL) water quality improvement projects for temperature, dissolved oxygen, and ammonia-n 9c. What U.S. Geological Survey Hydrological Unit Code (HUC) is the project in? [help] • Go to http://cfpub.epa.gov/surf/locate/index.cfm to help identify the HUC. 17110013 9d. What Water Resource Inventory Area Number (WRIA #) is the project in? [help] • Go to https://ecology.wa.gov/Water-Shorelines/Water-supply/Water-availability/Watershed-look-up to find the WRIA #. 9 – Green/Duwamish 9e. Will the in-water construction work comply with the State of Washington water quality standards for turbidity? [help] • Go to https://ecology.wa.gov/Water-Shorelines/Water-quality/Freshwater/Surface-water-quality-standards/Criteria for the standards. ☐ Yes ☐ No ☒ Not applicable 9f. If the project is within the jurisdiction of the Shoreline Management Act, what is the local shoreline environment designation? [help] • If you don’t know, contact the local planning department. • For more information, go to: https://ecology.wa.gov/Water-Shorelines/Shoreline-coastal-management/Shoreline-coastal- planning/Shoreline-laws-rules-and-cases. ☐ Urban ☐ Natural ☐ Aquatic ☐ Conservancy ☒ Other: Urban Conservancy 9g. What is the Washington Department of Natural Resources Water Type? [help] • Go to http://www.dnr.wa.gov/forest-practices-water-typing for the Forest Practices Water Typing System. ☒ Shoreline ☐ Fish ☐ Non-Fish Perennial ☐ Non-Fish Seasonal 9h. Will this project be designed to meet the Washington Department of Ecology’s most current stormwater manual? [help] • If No, provide the name of the manual your project is designed to meet. ☒ Yes ☐ No Name of manual: 2014 Stormwater Management Manual for Western Washington with supplemental requirements specific to the City of Auburn. 9i. Does the project site have known contaminated sediment? [help] • If Yes, please describe below. ☐ Yes ☒ No None known. 9j. If you know what the property was used for in the past, describe below. [help] 44 of 721 ORIA-16-011 Page 12 of 14 Prior to 1936, the project site was cleared of native vegetation and used as farmland. By 1957, intensive agricultural use had ended. Since that time, the project site has remained vacant unused land. 9k. Has a cultural resource (archaeological) survey been performed on the project area? [help] • If Yes, attach it to your JARPA package. ☐ Yes ☒ No 9l. Name each species listed under the federal Endangered Species Act that occurs in the vicinity of the project area or might be affected by the proposed work. [help] The segment of the Green River located adjacent to Lot A is known to support or exist with the home range of the following species that are federally listed as “threatened” under the Endangered Species Act: • Chinook Salmon Puget Sound (Oncorhynchus tshawytscha) • Steelhead Puget Sound (Oncorhynchus mykiss) • Bull Trout (Salvelinus confluentus) 9m. Name each species or habitat on the Washington Department of Fish and Wildlife’s Priority Habitats and Species List that might be affected by the proposed work. [help] The WDFW maps the segment of the Green River located adjacent to the project site is as an occurrence, migration, and breeding area for numerous native salmonid species. No in-water work is proposed. A large biodiversity area and corridor is also mapped east of the project site; however, no work is proposed east of 104th Place SE. Part 10–SEPA Compliance and Permits Use the resources and checklist below to identify the permits you are applying for. • Online Project Questionnaire at http://apps.oria.wa.gov/opas/. • Governor’s Office for Regulatory Innovation and Assistance at (800) 917-0043 or help@oria.wa.gov. • For a list of addresses to send your JARPA to, click on agency addresses for completed JARPA. 10a. Compliance with the State Environmental Policy Act (SEPA). (Check all that apply.) [help] • For more information about SEPA, go to https://ecology.wa.gov/regulations-permits/SEPA-environmental-review. ☐ A copy of the SEPA determination or letter of exemption is included with this application. ☒ A SEPA determination is pending with The City of Auburn (lead agency). The expected decision date is included with application - TBD . ☐ I am applying for a Fish Habitat Enhancement Exemption. (Check the box below in 10b.) [help] ☐ This project is exempt (choose type of exemption below). ☐ Categorical Exemption. Under what section of the SEPA administrative code (WAC) is it exempt? ☐ Other: 45 of 721 ORIA-16-011 Page 13 of 14 ☐ SEPA is pre-empted by federal law. 10b. Indicate the permits you are applying for. (Check all that apply.) [help] LOCAL GOVERNMENT Local Government Shoreline permits: ☐ Substantial Development ☒ Conditional Use ☒ Variance ☐ Shoreline Exemption Type (explain): Other City/County permits: ☐ Floodplain Development Permit ☐ Critical Areas Ordinance STATE GOVERNMENT Washington Department of Fish and Wildlife: ☐ Hydraulic Project Approval (HPA) ☐ Fish Habitat Enhancement Exemption – Attach Exemption Form Washington Department of Natural Resources: ☐ Aquatic Use Authorization Complete JARPA Attachment E and submit a check for $25 payable to the Washington Department of Natural Resources. Do not send cash. Washington Department of Ecology: ☐ Section 401 Water Quality Certification FEDERAL AND TRIBAL GOVERNMENT United States Department of the Army (U.S. Army Corps of Engineers): ☐ Section 404 (discharges into waters of the U.S.) ☐ Section 10 (work in navigable waters) United States Coast Guard: ☐ General Bridge Act Permit ☐ Private Aids to Navigation (for non-bridge projects) United States Environmental Protection Agency: ☐ Section 401 Water Quality Certification (discharges into waters of the U.S.) on tribal lands where tribes do not have treatment as a state (TAS) Tribal Permits: (Check with the tribe to see if there are other tribal permits, e.g., Tribal Environmental Pro tection Act, Shoreline Permits, Hydraulic Project Permits, or other in addition to CWA Section 401 WQC) ☐ Section 401 Water Quality Certification (discharges into waters of the U.S.) where the tribe has treatment as a state (TAS). 46 of 721 ORIA-16-011 Page 14 of 14 Part 11–Authorizing Signatures Signatures are required before submitting the JARPA package. The JARPA package includes the JARPA form, project plans, photos, etc. [help] 11a. Applicant Signature (required) [help] I certify that to the best of my knowledge and belief, the information provided in this application is true, complete, and accurate. I also certify that I have the authority to carry out the proposed activities, and I agree to start work only after I have received all necessary permits. I hereby authorize the agent named in Part 3 of this application to act on my behalf in matters related to this application. _________ (initial) By initialing here, I state that I have the authority to grant access to the property. I also give my consent to the permitting agencies entering the property where the project is located to inspect the project site or any work related to the project. _________ (initial) Applicant Printed Name Applicant Signature Date 11b. Authorized Agent Signature [help] I certify that to the best of my knowledge and belief, the information provided in this application is true, complete, and accurate. I also certify that I have the authority to carry out the proposed activities and I agree to start work only after all necessary permits have been issued. Authorized Agent Printed Name Authorized Agent Signature Date 11c. Property Owner Signature (if not applicant) [help] Not required if project is on existing rights-of-way or easements (provide copy of easement with JARPA). I consent to the permitting agencies entering the property where the project is located to inspect the project site or any work. These inspections shall occur at reasonable times and, if practical, with prior notice to the landowner. Property Owner Printed Name Property Owner Signature Date 18 U.S.C §1001 provides that: Whoever, in any manner within the jurisdiction of any department or agency of the United States knowingly falsifies, conceals, or covers up by any trick, scheme, or device a material fact or makes any false, fictitious, or fraudulent statements or representations or makes or uses any false writing or document knowing same to contain any false, fictitious, or fraudulent s tatement or entry, shall be fined not more than $10,000 or imprisoned n ot more than 5 years or both. If you require this document in another format, contact the Governor’s Office for Regulatory Innovation and Assistance (ORIA) at (800) 917-0043. People with hearing loss can call 711 for Washington Relay Service. People with a speech disability can call (877) 833- 6341. ORIA publication number: ORIA-16-011 rev. 09/2018 47 of 721 Gree n R i v e r Road S E 104th Ave SELea Hill Rd SE8th ST NE 4th ST NE East Main ST West Mai n S T 14th ST NE 22nd ST NE Auburn Way NE ST NEM ST NERivervi e w DR NE I ST NED ST NEC ST NWA ST NWB ST NW15th ST NE 15th ST NW 12th ST NE H a r v e y R d N E West Valley Hwy167 18Auburn Way N2nd ST NW M ST NE4th ST NE K ST NEJ ST NER ST SET ST SEV ST SEL ST SE4th ST SE Cros s ST SE 112th PL SE105th PL SE PROJECT SITE PROPOSED PROJECT: GOULET SINGLE FAMILY RESIDENCES IN: SHORELINES NEAR/AT: CITY OF AUBURN COUNTY: KING STATE: WASHINGTON REFERENCE: APPLICANT: LAUNCE P. GOULET & BRUCE GOULET LOCATION: 32XXX 104TH PLACE SE AUBURN, WASHINGTON SHEET 1 OF 6 DATE: 04/08/2019 VICINITY MAP SITE ADDRESS: 3 RESIDENTIAL LOTS AT LATITUDE: 47.31444 SECTION/TOWNSHIP/RANGE: NW 17-21-5 32XXX 104TH PLACE SE LONGITUDE: -122.20469 AUBURN, WASHINGTON 98092 KING COUNTY TAX PARCEL 334100-0090, 334100-0095, 334100-0100 LOT A - TAX PARCEL NUMBER 334100-0090 THAT PORTION OF LOT 20, C.D. HILLMAN'S GREEN RIVER ADDITION, DIVISION No. 1, ACCORDING TO THE PLAT RECORDED IN VOLUME 17 OF PLATS, PAGE 67, IN KING COUNTY, WASHINGTON, AND UNPLATTED PORTION OF GOVERNMENT LOT 2, IN SECTION 17, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, DESCRIBED AS A WHOLE AS FOLLOWS: BEGINNING AT A POINT ON THE EASTERLY LINE OF SAID LOT 20, DISTANT THEREON, SOUTH 17°00' EAST 9.002 FEET FROM THE NORTHEASTERLY CORNER OF SAID LOT 20; THENCE SOUTH 17°00' EAST ALONG THE NORTHEASTERLY LINE OF SAID LOT 20, A DISTANCE OF 60.00 FEET; THENCE SOUTH 73° 00' WEST 125.00 FEET, MORE OR LESS TO THE EASTERLY BANK OF THE GREEN RIVER; THENCE NORTHERLY ALONG SAID BANK TO A POINT WHICH BEARS NORTH 89°41'07" WEST FROM THE POINT OF BEGINNING; THENCE SOUTH 89°41'07" EAST 155.00 FEET, MORE OR LESS TO THE POINT OF BEGINNING. LOT B - TAX PARCEL NUMBER 334100-0095 THOSE PORTIONS OF LOTS 20 AND 21, C.D. HILLMAN'S GREEN RIVER ADDITION, DIVISION No. 1, ACCORDING TO THE PLAT RECORDED IN VOLUME 17 OF PLATS, PAGE 67, IN KING COUNTY, WASHINGTON, AND UNPLATTED PORTION OF GOVERNMENT LOT 2, IN SECTION 17, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, DESCRIBED AS A WHOLE AS FOLLOWS: BEGINNING AT A POINT ON THE EASTERLY LINE OF SAID LOT 20, DISTANT THEREON, SOUTH 17°00' EAST 69.002 FEET FROM THE NORTHEASTERLY CORNER OF SAID LOT 20; THENCE SOUTH 17°00' EAST ALONG THE NORTHEASTERLY LINE OF SAID LOT 20, A DISTANCE OF 28.656 FEET TO THE NORTHEASTERLY CORNER OF LOT 21; THENCE SOUTH 31°03' EAST ALONG THE NORTHEASTERLY LINE OF SAID LOT 21, A DISTANCE OF 40.00 FEET; THENCE SOUTH 58°57' WEST 135.00 FEET, MORE OR LESS TO THE EASTERLY BANK OF THE GREEN RIVER; THENCE NORTHERLY ALONG SAID BANK TO A POINT WHICH BEARS SOUTH 73°00' WEST FROM THE POINT OF BEGINNING; THENCE NORTH 73°00' EAST 125.00 FEET, MORE OR LESS TO THE POINT OF BEGINNING. LOT C - - TAX PARCEL NUMBER 334100-0100 THOSE PORTIONS OF LOTS 21 AND 22, C.D. HILLMAN'S GREEN RIVER ADDITION, DIVISION No. 1, ACCORDING TO THE PLAT RECORDED IN VOLUME 17 OF PLATS, PAGE 67, IN KING COUNTY, WASHINGTON, AND UNPLATTED PORTION OF GOVERNMENT LOT 2, IN SECTION 17, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, DESCRIBED AS A WHOLE AS FOLLOWS: BEGINNING AT A POINT ON THE EASTERLY LINE OF SAID LOT 20, DISTANT THEREON, SOUTH 17°00' EAST 97.658 FEET FROM THE NORTHEASTERLY CORNER OF SAID LOT 20 OF C.D. HILLMAN'S GREEN RIVER ADDITION; THENCE SOUTH 31°03' EAST ALONG THE NORTHEASTERLY LINES OF SAID LOT 21 AND 22, A DISTANCE OF 90.00 FEET; THENCE SOUTH 58°57' WEST 135.00 FEET, MORE OR LESS TO THE EASTERLY BANK OF THE GREEN RIVER: THENCE NORTHERLY ALONG SAID BANK TO A POINT WHICH BEARS SOUTH 58°57' WEST FROM THE TRUE POINT OF BEGINNING; THENCE NORTH 58°57' EAST 135.00 FEET TO THE TRUE POINT OF BEGINNING. PROJECT SITE THE PROJECT SITE CAN BE ACCESSED FROM SR 167 BY TAKING THE 15TH STREET NW EXIT AND HEADING EAST FOR 1.1 MILES. 15TH STREET NW TURNS INTO HARVEY ROAD NE AT ITS INTERSECTION WITH AUBURN WAY N. CONTINUE SOUTHEAST ON HARVEY ROAD NE FOR APPROXIMATELY 0.5 MILES, THEN TURN LEFT ONTO 8TH STREET NE. TRAVEL EAST ON 8TH STREET NE FOR APPROXIMATELY 0.5 MILES AND THEN TURN RIGHT ONTO 104TH PLACE SE. THE PROJECT SITE IS LOCATED ON THE WEST SIDE OF 104TH PLACE SE APPROXIMATELY 450 FEET SOUTH OF 8TH STREET NE. 48 of 721 REFERENCE: APPLICANT: LAUNCE P. GOULET & BRUCE GOULET LOCATION: 32XXX 104TH PLACE SE AUBURN, WASHINGTON SHEET 2 OF 6 DATE: 04/08/2019 AERIAL PHOTOGRAPH SHOWING PROJECT SITE LOT A TPN 334100-0090 (14,628 SF - 0.33 ACRES ) LOT B TPN 334100-0095 (13,601 SF - 0.31 ACRES) LOT C TPN 334100-0100 (13,021 SF - 0.30 ACRES) N SCALE: 1" = 40' PROPOSED PROJECT: GOULET SINGLE FAMILY RESIDENCES IN: SHORELINES NEAR/AT: CITY OF AUBURN COUNTY: KING STATE: WASHINGTON PHOTOGRAPH REFERENCE: KING COUNTY IMAP, DATE OF PHOTO 2017 Green River 49 of 721 REFERENCE: APPLICANT: LAUNCE P. GOULET & BRUCE GOULET LOCATION: 32XXX 104TH PLACE SE AUBURN, WASHINGTON SHEET 3 OF 6 DATE: 04/08/2019 PHOTOGRAPH SHOWING GENERAL CONDITIONS WITHIN PROJECT SITE PROPOSED PROJECT: GOULET SINGLE FAMILY RESIDENCES IN: SHORELINES NEAR/AT: CITY OF AUBURN COUNTY: KING STATE: WASHINGTON DATE OF PHOTOGRAPH: OCTOBER 4, 2019 50 of 721 REFERENCE: APPLICANT: LAUNCE P. GOULET & BRUCE GOULET LOCATION: 32XXX 104TH PLACE SE AUBURN, WASHINGTON SHEET 4 OF 6 DATE: 04/08/2019 PHOTOGRAPH SHOWING GENERAL CONDITIONS ALONG OHWM OF GREEN RIVER DATE OF PHOTOGRAPH: OCTOBER 4, 2019 PROPOSED PROJECT: GOULET SINGLE FAMILY RESIDENCES IN: SHORELINES NEAR/AT: CITY OF AUBURN COUNTY: KING STATE: WASHINGTON 51 of 721 MODERATE CHANNEL MIGRATION ZONE 50' CHANNEL MIGRATION ZONE BUFFER 100 YEAR FLOODPLAIN (HATCHED AREA)66' 6 4 '62'60' 7 2 '70'6 8 '66'64' 7 4 ' 68'60'62' 7 0 ' 7 4 ' 68'68'BASE FLOOD ELEVATION = 66.80' 7 2 ' 100' SHORELINE BUFFER BASE FLOOD ELEVATION = 67.00' BASE FLOOD ELEVATION = 66.90' REFERENCE: APPLICANT: LAUNCE P. GOULET & BRUCE GOULET LOCATION: 32XXX 104TH PLACE SE AUBURN, WASHINGTON SHEET 5 OF 6 DATE: 04/08/2019 PROPOSED SITE PLAN N PROPOSED PROJECT: GOULET SINGLE FAMILY RESIDENCES IN: SHORELINES NEAR/AT: CITY OF AUBURN COUNTY: KING STATE: WASHINGTON SCALE: 1" = 40' HORIZONTAL DATUM: NAD 83/91 VERTICAL DATUM: NAVD 88 LEGEND: OHWM PROPOSED STREAM BUFFER REDUCTION CHANNEL MIGRATION HAZARD AND BUFFER 100 YEAR FLOODPLAIN 52 of 721 REFERENCE: APPLICANT: LAUNCE P. GOULET & BRUCE GOULET LOCATION: 32XXX 104TH PLACE SE AUBURN, WASHINGTON SHEET 6 OF 6 DATE: 04/07/2019 PROPOSED MITIGATION PLANT SCHEDULE: COMMON NAME SCIENTIFIC NAME QUANTITY BIGLEAF MAPLE ACER MACROPHYLLUM 73 BLACK COTTONWOOD POPULUS BALSAMIFERA 47 DOUGLAS-FIR PSEUDOTSUGA MENIESII 27 WESTERN REDCEDAR THUJA PLICATA 76 VINE MAPLE ACER CIRCINATUM 47 REDOSIER DOGWOOD CORNUS SERICEA 40 INDIAN PLUM OEMLERIA CERASFORMIS 102 REDFLOWER CURRANT RIBIS SANGUINEUM 60 SALMONBERRY RUBUS SPECTABILIS 177 SITKA WILLOW SALIX SITCHENSIS 110 SNOWBERRY SYMPHORICARPOS ALBUS 168 LEGEND: PLANTING AREA - FLAT BUFFER (16,733 SF) PLANTING AREA - RIVER BANK (9,124 SF) LOG WITH ROOTS (QTY = 6) LOG (QTY = 6) CRITICAL AREA FENCE (260 LF) CRITICAL AREA SIGN (QTY = 3) REFER TO FINAL MITIGATION PLAN FOR MORE DETAIL. N SCALE: 1" = 40' HORIZONTAL DATUM: NAD 83/91 VERTICAL DATUM: NAVD 88 PROPOSED PROJECT: GOULET SINGLE FAMILY RESIDENCES IN: SHORELINES NEAR/AT: CITY OF AUBURN COUNTY: KING STATE: WASHINGTON 53 of 721 Western Washington Division Eastern Washington Division 165 NE Juniper St., Ste 201, Issaquah, WA 98027 108 East 2nd Street, Cle Elum, WA 98922 Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419 www.EncompassES.net SHORELINE CONDITIONAL USE PERMIT: WRITTEN STATEMENT 1. The shoreline designation according to the Shoreline Master Program: Urban Conservancy 2. The name of the shoreline (water body) that the site of the proposal is associated with: Green River 3. A specific description of the proposed project, including the proposed use(s) and the activities necessary to accomplish the project: No development is proposed below the base flood elevation of each lot, within the floodplain, or within the “Channel Migration Moderate Hazard” area of each property. The proposal includes the construction of a 55’ wide by 28.5’ deep single-family residence on Lot A and 55’ by 30’ single family residence on both Lot B and Lot C. Each residence will be construction in the eastern portion of the respective lot and will comprise a multi-story design with attached garage. Lot development requires unavoidable shoreline buffer impacts on Lot B and Lot C but no buffer impacts are proposed for Lot A. As such the stream ’s 100’ standard buffer will be reduced by 17’ to 26.8’ on Lots B & C but maintained at 100’ on Lot A. Restoration involving invasive plant species removal, native plantings, and habitat enhancements are proposed to mitigate the unavoidable impacts to the stream buffer. Basic dispersion trenches with native vegetated flow paths are proposed to mitigate stormwater runoff as a result of the development. 4. A general description of the property’s existing physical characteristics, improvements, and structures: The lots are located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. The site is within NW 17-21-05, W.M, King County, Washington. The three lots are currently undeveloped vacant land that is moderately forested. The parcels are vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry. Fine silty SAND describes the majority of the parcel’s underlying soil type. Topography within the project site is characterized by a moderately steep to near vertical riverbank that transitions to nearly flat or gently sloping land throughout the central portion of the site to a short-inclined transition along 104th PL SE. There are no wetlands within or immediately adjacent to the site. The green River, a Type S water exists along the western limits of the site. 5. A general description of adjacent (within 1,000 feet in all directions) use, structures, improvements, intensity of development, and physical characteristics: Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Residential development along the west side of 104th PL SE extends back to the early 1900’s and existing development generally includes one or two story single family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th ST, most residence are of a conventional on-site stick-built construction averaging 2,510 SF (dwelling unit + accessory structures) in footprint. Most residences are setback from the Green River and are located close to 104th PL SE. See Figure 1 land uses within 1000’ of the project site. Residential uses surround the project site of varying densities. 54 of 721 King County Assessor's Office, King County GIS Center, King County, Kingcounty Assessor's Office, King County GIS Center Date: 4/23/2020 ±The information included on this map has been compiled by King County staff from a variety of sources and issubject to change without notice. King County makes no representations or warranties, express or implied,as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intendedfor use as a survey product. King County shall not be liable for any general, special, indirect, incidental, orconsequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuseof the information contained on this map. Any sale of this map or information on this map is prohibited except bywritten permission of King County. King County 55 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 2 CRITERIA COMPLIANCE REPORT FOR SHORELINE CONDITIONAL USE PERMIT 1. The proposed use will be consistent with the policies of RCW 90.58.020, the policies of the City of Auburn Shoreline Master Program (SMP), the City of Auburn comprehensive plan, and the other applicable plans, programs, and/or regulations. • The proposed use is consistent with the following policies of RCW 90.58.0320: 2. Preserve the natural character of the shoreline The proposal involves the restoration of the three subject properties’ buffer area along the Green River. The area is currently overgrown with the invasive Himalayan Blackberry. The proposal includes removal of all invasive species and the replanting with native riparian shoreline species. The buffer area will be enhanced and protected resulting in a “no net loss” of shoreline buffer ecological functions (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, April 2020). 4. Protect the resources and ecology of the shoreline The proposed project balances the landowner’s reasonable use of the three legal and existing residential lots and the environmental protection necessary to ensure no net loss of the shoreline resources and ecology. Consolidated building sites along 104th Place SE ensures that the disturbance generally associated with residential development is limited to a small portion of each lot and that the disturbance is located as far from the Green River as feasible within the private properties. During construction, the proposed shoreline buffer limits will be marked using hi- visibility plastic orange construction fencing. No construction staging or material stockpiling will occur within the shoreline buffer. Following construction, a permanent cedar split rail fence will be installed along the reduced shoreline buffer and the shoreline buffer will be enhanced per a City of Auburn approved mitigation plan. Because the project includes three contiguous lots, the project presents a unique opportunity to enhance a substantial stretch of river shoreline area from its current degraded Himalayan Blackberry dominated landscape to one that will ultimately resemble a forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, April 2020) and will increase and/or provide opportunities for structural habitat diversity, shade, and large woody debris production that currently either does not exist or is limited within the project site. • The proposed use is consistent with all the Management Polices of the Urban Conservancy lands (see below) as well as the following policies of City of Auburn Shoreline Master Program: SMP 3.3.3 Urban Conservancy Management Policies: 1. Primary allowed uses and their associated development standards should preserve the natural character of the area or promote preservation of open space, floodplain, or sensitive lands where they exist in urban and developed settings, either directly or over the long term. Uses that result in restoration of ecological functions should be allowed if the use is otherwise compatible with the purpose of the environment and the setting. 56 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 3 No disturbance is proposed within the floodplain. The proposed stream and shoreline buffer areas on each of the three lots will be restored from the generally degraded state and protected in the short and long terms. During construction, the proposed shoreline buffer limits will be marked using hi-visibility plastic orange construction fencing. No construction staging or material stockpiling will occur within the shoreline buffer. Following construction, a permanent cedar split rail fence and signage will be installed along the reduced shoreline buffer boundary and a notice will be placed on title to protect this area permanently. Mitigation for the disturbance proposed to allow for reasonable and consolidated residential use of the properties outside the buffer will include intensive noxious weed control, habitat structure installation, dense native plantings, and mulching to enhance the buffer. The proposal preserves the majority of each property in restored open space. The restoration of the ecological functions and the proposed modest single-family residences are compatible with the purpose of the environment and setting. 2. Standards should be established for shoreline stabilization measures, vegetation conservation, water quality and shoreline modifications within the “urban conservancy” designation. These standards should ensure that new development does not result in a net loss of shoreline ecological functions or further degrade other shoreline values. The proposed single-family residences are designed to result in “no net loss” of shoreline ecological functions or to degrade other shoreline values (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, April 2020). 3. Public access and public recreation objectives should be implemented whenever feasible and significant ecological impacts can be mitigated. The properties in question are zoned for residential use and privately owned. No public access or recreation currently exists on or over the properties. Access to the public proposed due to the residential nature of the properties, and because path installation to City standards would involve further disturbance to the stream buffer and shoreline area and possibly the floodplain. Disturbance as proposed is minimized and confined to the portions of the properties furthest from the River. 4. Water-oriented uses should be given priority over non-water-oriented uses. For shoreline areas with commercial development or adjacent to commercial navigable waters, water dependent uses should be given highest priority. Commercial development is not proposed with this proposal. Currently access to the waterfront is limited and/or impossible due to the overgrowth of Himalayan Blackberry bushes. The lots currently sit vacant and unused. The proposal would provide living quarters for inhabitants to enjoy the aesthetic and calming benefits of living within the visual vicinity of the Green River. 5. Existing mining and related activities may be an appropriate use within the urban conservancy environment when conducted in a manner consistent with the environment polices and the provisions of WAC 173-26-241 (3) (h) and when located consistent with mineral resource lands designation criteria pursuant to RCW 36.70A.170 and WAC 365- 57 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 4 190-070. No new mining uses or expansion of existing mines should be permit ted within the shoreline jurisdiction. Does not apply. No mining activities are proposed. SMP 4.4 General Policies and Regulations SMP 4.4.1 Conservation and Restoration 4. Promote vegetation restoration, and the control of invasive weed and nonnative species to avoid adverse impacts to hydrology and to reduce the hazard of slope failures or accelerated erosion. The three properties are currently overgrown with invasive Himalayan Blackberry, the proposal includes vegetation restoration that will involve the removal and replacement of the blackberry with native riparian plant species. SMP 4.4.2 Shoreline Vegetation Conservation 1. Developments and activities in the City’s shoreline should be planned and designed to retain native vegetation or replace shoreline vegetation with native species to achieve no net loss of the ecological functions and ecosystem-wide processes performed by vegetation. Vegetation removal within each building site will be limited to primarily invasive Himalayan Blackberry, a Class 3 noxious weed. Only one significant tree will be removed. Removed vegetation will be replaced with dense native plantings consisting of bigleaf maple, black cottonwood, Douglas fir, western red cedar, vine maple, Redosier dogwood, Indian plum, Redflower currant, salmonberry, Sitka willow and snowberry. No net loss of ecological functions and ecosystem-wide processes are expected (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, April 2020). 2. Wood debris should be left in the river corridors to enhance wildlife habitat and shoreline ecological functions, except where it threatens personal safety or critical infrastructure, such as bridge pilings. In such cases where debris poses a threat, it should be dislodged, but should not be removed from river. The segment of the Green River located adjacent to the project site does not include significant habitat features such as log jams, beaver dams, aquatic vegetation, large rocks or boulders, side channels and/or undercut banks. There is limited natural cover such as shade or submerged or overhanging large wood debris (LWD). Any LWD found in the river corridor will be left in place, pending safety. The proposed species, densities, and distribution of native plantings will provide opportunities for LWD and organic matter production that currently do not exist or is otherwise extremely limited within the site. SMP 4.4.3 Environmental Impact Mitigation 58 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 5 1. All shoreline use and development should be carried out in a manner that avoids and minimizes adverse impacts to that the resulting ecological condition does not become worse than the current condition. This means assuring no net loss of ecological functions and processes and protecting critical areas designated in Appendix A, Chapter 16.10 “Critical Areas” that are located in the shoreline. Should a proposed use and development potentially create significant adverse environmental impacts not otherwise avoided or mitigated by compliance with the master program, the Director should require mitigation measures to ensure no net loss of shoreline ecological functions. The proposed single-family residences are designed to result in “no net loss” of shoreline ecological functions or to degrade other shoreline values (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, April 2020). Mitigation involving the restoration of the shoreline buffer with the removal of invasive plant species and the dense planting of native riparian plant species is proposed to offset the minimal impacts posed by the three single family residences along 104th PL SE. SMP 4.4.4 Critical Areas 1. Provide a level of protection to critical areas within the shoreline that is at least equal to that which is provided by the City’s critical a reas regulations adopted pursuant to the Growth Management Act and the City’s Comprehensive Plan. If conflicts between the SMP and the critical area regulations arise, the regulations that are most consistent with the SMA or its WAC provisions will govern. The level of protection provided meets all critical areas regulations excepting the shoreline variance request included with this proposal to reduce the width of the stream buffer for Lots B and C. Per SMP 4.4.5, stream buffer widths may be reduced by up to 35% provided the applicant demonstrates that a reduction will not result in any adverse impact to the stream. The standard 100’ stream buffer for Lot B is proposed to be reduced by 17%. On Lot C the stream buffer is proposed to be reduced by 26.8%. Both reductions are less than 35% and have been mitigated for by restoring the degraded shoreline area. Per Evergreen Aquatic’s report and mitigation plan the proposed project results in “no net loss” of shoreline ecological functions. 2. Allow activities in critical areas that protect and, where possible, restore the ecological functions and ecosystem-wide processes of the City’s shoreline. Because the project includes three contiguous lots, the project presents a unique opportunity to restore the ecological functions of a substantial stretch of the Green River’s shoreline area from its current degraded Himalayan Blackberry dominated landscape to one that will ultimately resemble a forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, April 2020). This will increase and/or provide opportunities for structural habitat diversity, shade, and large woody debris production that currently either does not exist or is limited within the project site. 59 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 6 3. Preserve, protect, restore, and/or mitigate wetlands within and associated with the City’s shorelines to achieve no net loss of wetland area and wetland functions. No wetlands are present on any of the three subject lots. As such, no net loss of wetland area or functions is proposed or expected. 4. Developments in shoreline areas that are identified as geologically hazardous or pose a foreseeable risk to people and improvements during the life of the development should not be allowed. The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Polger and Niggermann, 2007 in Critical Areas Report-Bergquist Engineering Services Company, LLC, April 2020) The City and County designate portions of the subject properties as being within the “Channel Migration Moderate Hazard” area. The risk of flood and erosion is somewhat diminished by control of flows during floods by the Howard A Hansen Dam and even though massive flood events occurred almost annually in the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located for the last 130 years or so of map and air photographic record (Critical Areas Report-Bergquist Engineering Services Company, LLC, April 2020). No development is proposed within the “Channel Migration Moderate Hazard” area of each lot. All three homes will be constructed outside that hazard area. Portions of the site are also within the City’s “Critical Erosion Hazard Area”, due to the presence of silty fine SAND underlying the steep cut slope along the east side of 104th PL SE. Some signs of erosion above the revetment on the opposite bank of the Green River from the properties was observed, but no erosion on site has been observed. The City also classifies the cut slope, which is located offsite on City property, as a Class IV/Very High Hazard Landslide Hazard Area because the slope was excavated to an inclination greater than 40% and is approximately 25’ high. The vegetation growing along the in-slope ditch and the lack of debris along the base of the slope indicates the dense silt SAND forming the slope does not appear to be eroding in the immediate vicinity of the project site. Down the road, to the south of the project there has been some slope movement noted. Slope stability analysis conducted by Bergquist found that the slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated, but that slope movement (lateral spreading) is not likely to occur on the subject projects (Critical Areas Report-Bergquist Engineering Services Company, LLC, April 2020). This slope should not be subject to regulation due to it being manmade. Subsurface exploration and engineering analysis will be performed prior to foundation design. Deep foundation systems will likely involve driven or drilled piles to mitigate liquefiable soil conditions. Another method to be explored would involve installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. 60 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 7 Overall, analysis by Bergquist concludes that the current geologic conditions of the site make the proposed single-family development challenging but do not render the site unbuildable. They recommend additional steps during construction and design beyond what is normal standard building practices. 4.4.6 Public Access (including views) 2. Protection and enhancement of the public’s physical and visual access to shorelines should be encouraged. The public’s visual access to the shoreline of Green River along the frontages of the three properties will be protected by compliance with the single-family residential height limitation of 35’ for properties with R5 zoning in the Lea Hill Overlay. The building’s height is not expected to impair views and existing trees on the properties and in the area are greater than 35’ in height. Amberview Apartments located to the east of the subject properties are located uphill from the project sites and thus will not have their views impacted by the proposed construction of three moderately sized single-family residences. 4.4.7 Flood Hazard Reduction 2. Discourage development within the floodplains associated with the City’s shorelines that would individually or cumulatively result in an increase to the risk of flood damage. No development is proposed within the floodplain. The proposed residences will be built above base flood elevation to reduce the risk of flood damage. 4.4.8 Water Quality, Storm water and Non-Point Pollution 2. Storm water management treatment, conveyance, or discharge facilities should be discouraged in the shoreline jurisdiction, unless no other feasible alternative is available. Runoff from the site currently sheet flows directly into the Green River. Storm water from the proposed development will be mitigated using basic dispersion trenches with native vegetated flow paths. Three basic dispersion trenches will be located within the shoreline jurisdiction as no other feasible alternative is available as the entirety of each subject property is within shoreline jurisdiction and sending stormwater offsite is not feasible or allowed. The dispersion trenches located within 75’ of the Green Riverbank will not adversely affect the stability of the bank (Critical Areas Report-Bergquist Engineering Services Company, LLC, April 2020). The onsite drainage mitigation emulates existing conditions. Final selection and design of the stormwater handling systems will be based on home design within the conceptual footprints proposed here. 4. Encourage conservation of existing shoreline vegetation which provides water quality protection by slowing and filtering stormwater runoff. The entire proposed stream buffer will be restored from its predominantly invasive and alien vegetative state to native plantings. After restoration this area, including the dispersion trenches’ vegetated flow paths, the designed dispersion system will ultimately slow and filter stormwater runoff while preserving the natural shoreline. 61 of 721 Goulet Residences: Lots A, B, &C Shoreline Conditional Use Permit Written Statement & Criterion Compliance Summary April 2020 8 • The proposed use is consistent with the following policies of The Auburn Comprehensive Plan: General Land Use Policies LU-1 Regulations for new developments and infill should address the following elements: b. Relationship to nearby existing or future transit services The properties are located in the Sound Transit Regional Transit Authority taxing district and are located less than half a mile from Metro bus route #181’s stop on 8th Street NE as well as Lea Hill Rd SE. d. Environmental protection and preservation of natural features As described herein, restoration of the degraded shoreline along the three subject properties is an unique opportunity of the proposed single family development. e. Preservation of areas that can support low-impact development techniques The development proposed is low impact in that disturbance will be restricted onsite as far from the Green River as possible. As such, only a small minority of each property will be disturbed and used for home development, while much of each property is restored and preserved for perpetuity. g. Efficient and effective delivery of utility service Utilities already exist in 104th Pl SE including sewer, water, electricity, phone, etc as there are homes already constructed to the south of the project site. h. Innovative design The design takes the specific challenges of the project site and proposes solutions with design, including reduced building footprints, minimum width driveways, and siting to minimize the impacts of the proposed homes on the environment. j. Long-term maintenance considerations The native vegetation chosen to restore the reduced stream buffer have been chosen for being well suited for this specific ecosystem. The ultimate result will not require irrigation and will resemble the forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, April 2020). Single Family Residential Designation LU-17 Provide a variety of housing typologies to suit the needs of various potential residents. Three mid-high-income single-family residences are proposed to be added to the available inventory of housing products meant to suit the needs of various potential Auburn residents. 62 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance SHORELINE VARIANCE LOT B: WRITTEN STATEMENT 1. The shoreline designation according to the Shoreline Master Program: Urban Conservancy 2. The name of the shoreline (water body) that the site of the proposal is associated with: Green River 3. A specific description of the proposed project, including the proposed use(s) and the activities necessary to accomplish the project: The proposal includes applying for a Shoreline Conditional Use Permit and Shoreline Variance to permit the buildable space on Lot B so that it accommodates the future construction of a multi-story single -family home within the existing residential lot (Lot B) along the eastern bank of the Green River. The existing property (Parcel #: 334100-0095) is surrounded bordered by two other properties owned by the applicant, zoned R-5 and with similar land use proposals. The subject property is encumbered by the following mapped areas and/or classifications: a. Groundwater Protection Zone 2: Groundwater occurs that is a current or potential future source of drinking water for the City of Auburn. b. Class IV/Very High Landslide Hazard Area: There is a cut slope located offsite, on City property on the east side of 104th Place SE that was excavated to an inclination greater than 40%. Bergquist Engineering has determined that a 23’ buffer is required from the toe of slope, this buffer does not encroach onto the existing Lot B. c. Critical Erosion Hazard Area: Per evaluation by Bergquist Engineering Services Company, LLC, this classification is likely due to the presence of the silty fine SAND underlying the steep cut slope located offsite along the east side of 104th Place Southeast. d. Riparian Habitat Zone : The property is located within 250’ of the Green River’s Ordinary High Water Mark (OHWM). e. Shoreline Management Zone-Urban Conservancy: The property is located within 200’ of the Green River’s OHWM. f. Moderate Channel Migration Hazard Area: The City of Auburn recently modified the channel migration zone boundaries with GeoEngineers, Inc (2018). No development or work is proposed within the mapped Moderate Channel Migration Hazard Area with this proposal. g. Type S Stream, 100’ Stream Buffer: This variance is being requested to reduce the width of stream buffer to allow reasonable use of Lot B. The stream buffer on Lot B is proposed to be reduced by approximately 5.5’ to a width of approximately 94.5’. h. 100-year floodplain : The existing parcel contains a mapped 100 year floodplain in the westernmost portion of the parcel along the bank of the Green River—no development or work is proposed below the base flood elevation of 67.3’, or within the flood plain with this proposal. 63 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance No development is proposed below the base flood elevation of the lot (BFE=67.3’), within the floodplain, or within the “Channel Migration Moderate Hazard” area of the property. Lot B’s development proposal requires unavoidable shoreline buffer impacts. As such the stream’s 100’ standard buffer width will be reduced by approximately 5.5%. Restoration and mitigation for the reduced buffer will include invasive plant/noxious weed species removal, installing logs for habitat, native plantings, mulching, critical area fencing, signage, and protection. Basic dispersion trenches with native vegetated flow paths and other storm water mitigation BMPs are conceptualized to mitigate stormwater runoff as a result of the final building design (to be determined at the building permit stage of the project). 4. A general description of the property’s existing physical characteristics, improvements, and structures: Lot B, parcel # 334100-0095, is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. The site is within NW 17-21-05, W.M, King County, Washington. The lot is currently undeveloped vacant land that is moderately forested. The parcel is vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry. Fine silty SAND describes the majority of the parcel’s underlying soil type. Topography within the project site is characterized by a moderately steep to near vertical riverbank that transitions to nearly flat or gently sloping land throughout the central portion of the site to a short-inclined transition along 104th PL SE. There are no wetlands within or immediately adjacent to the site. The green River, a Type S water exists along the western limits of the site. Lot B measures approximately 13,601 SF in area and maintains approximately 108 LF of shoreline frontage along the eastern bank of the Green River. 5. A general description of adjacent (within 1,000 feet in all directions) use, structures, improvements, intensity of development, and physical characteristics: Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Residential development along the west side of 104th PL SE extends back to the early 1900’s and existing development generally includes one- or two-story single family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th ST, most residence are of a conventional on-site stick-built construction averaging 2,510 SF (dwelling unit + accessory structures) in footprint. Most residences are setback from the Green River and are located close to 104th PL SE. See Figure 1 land uses within 1000’ of Lot B. Residential uses surround the project site of varying densities. 64 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance CRITERION COMPLIANCE REPORT FOR SHORELINE VARIANCE PER SMP 16.08.058 1. The strict requirements of the bulk, dimensional, or performance standards set forth in the master program precludes or significantly interferes with a reasonable use of the property not otherwise prohibited by the SMP. The requirements of the SMP to maintain a 100’ standard stream buffer from the OHWM of the Green River and a sewer line (requiring a 15’ building setback from the line) that runs through the northeastern portion of the property to serve the abutting neighbor to the south would result in a buildable area of only 2,268 SF for Lot B. This would preclude or significantly interfere with all reasonable use of the property for marketable single family use as this small buildable space needs to accommodate the livable space of the home, a 20’x20’ garage, storm water mitigation BMPs and grading/clearing during construction. 2. The hardship described above is specifically related to the property and is the result of unique conditions such as irregular lot shape, size, or natural features and not, for example from deed restrictions of the applicant’s own actions. The hardship described above is specifically related to the properties shape (depth) as bound by 104th PL SE to the northeast and the Green River to the southwest. While the sewer line could be relocated to increase the buildable area on the lot, the disturbance associated with such relocation would produce greater impact to the shoreline zone than proposed herein. Additionally, the cost of moving the sewer line is prohibitive to the property owners. 3. The design of the project will be compatible with other permitted activities within the area and with uses planned for the area under the comprehensive plan and SMP and will not cause adverse impacts to the shoreline environment. Please see below for project’s consistency with the comprehensive plan and SMP. The proposed single-family residence on Lot B is designed to result in “no net loss” of shoreline ecological functions or to degrade other shoreline values (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, Revised October 2020). SMP 4.4 General Policies and Regulations SMP 4.4.1 Conservation and Restoration 4. Promote vegetation restoration, and the control of invasive weed and nonnative species to avoid adverse impacts to hydrology and to reduce the hazard of slope failures or accelerated erosion. Lot B is currently overgrown with invasive Himalayan Blackberry, the proposal includes vegetation restoration that will involve the removal and replacement of the blackberry with native riparian plant species. SMP 4.4.2 Shoreline Vegetation Conservation 1. Developments and activities in the City’s shoreline should be planned and designed to retain native vegetation or replace shoreline vegetation with 65 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance native species to achieve no net loss of the ecological functions and ecosystem-wide processes performed by vegetation. Vegetation removal within each building site will be limited to primarily invasive Himalayan Blackberry, a Class 3 noxious weed. Only one significant tree will be removed. Removed vegetation will be replaced with dense native plantings consisting of bigleaf maple, black cottonwood, Douglas fir, western red cedar, vine maple, Redosier dogwood, Indian plum, Redflower currant, salmonberry, Sitka willow and snowberry. No net loss of ecological functions and ecosystem-wide processes are expected (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, Revised October 2020). 2. Wood debris should be left in the river corridors to enhance wildlife habitat and shoreline ecological functions, except where it threatens personal safety or critical infrastructure, such as bridge pilings. In such cases where debris poses a threat, it should be dislodged, but should not be removed from river. The segment of the Green River located adjacent to Lot B does not include significant habitat features such as log jams, beaver dams, aquatic vegetation, large rocks or boulders, side channels and/or undercut banks. There is limited natural cover such as shade or submerged or overhanging large wood debris (LWD). Any LWD found in the river corridor will be left in place, pending safety. The proposed species, densities, and distribution of native plantings will provide opportunities for LWD and organic matter production that currently do not exist or is otherwise extremely limited within the site. SMP 4.4.3 Environmental Impact Mitigation 1. All shoreline use and development should be carried out in a manner that avoids and minimizes adverse impacts to that the resulting ecological condition does not become worse than the current condition. This means assuring no net loss of ecological functions and processes and protecting critical areas designated in Appendix A, Chapter 16.10 “Critical Areas” that are located in the shoreline. Should a proposed use and development potentially create significant adverse environmental impacts not otherwise avoided or mitigated by compliance with the master program, the Director should require mitigation measures to ensure no net loss of shoreline ecological functions. The proposed single-family residence on Lot B is designed to result in “no net loss” of shoreline ecological functions or to degrade other shoreline values (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, 66 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance Revised October 2020). Mitigation involving the restoration of the shoreline buffer with the removal of invasive plant species and the dense planting of native riparian plant species is proposed to offset the minimal impacts posed by the single family residence along 104th PL SE. SMP 4.4.4 Critical Areas 1. Provide a level of protection to critical areas within the shoreline that is at least equal to that which is provided by the City’s critical areas regulations adopted pursuant to the Growth Management Act and the City’s Comprehensive Plan. If conflicts between the SMP and the critical area regulations arise, the regulations that are most consistent with the SMA or its WAC provisions will govern. The level of protection provided meets all critical areas regulations excepting the shoreline variance requested here to reduce the width of the stream buffer for Lot B. Per SMP 4.4.5, stream buffer widths may be reduced by up to 35% provided the applicant demonstrates that a reduction will not result in any adverse impact to the stream. The standard 100’ stream buffer for Lot B the stream buffer minimum width is proposed to be reduced by 5.5% only. This reduction is less than 35% and will been mitigated for by restoring the degraded shoreline area. Per Evergreen Aquatic’s report and mitigation plan the proposed project results in “no net loss” of shoreline ecological functions. 2. Allow activities in critical areas that protect and, where possible, restore the ecological functions and ecosystem-wide processes of the City’s shoreline. Because the project abuts two similar development projects on simultaneous timelines, with collaborative owners, the three contiguous lots, present a unique opportunity to restore the ecological functions of a substantial stretch of the Green River’s shoreline area from its current degraded Himalayan Blackberry dominated landscape to one that will ultimately resemble a forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, Revised October 2020). This will increase and/or provide opportunities for structural habitat diversity, shade, and large woody debris production that currently either does not exist or is limited within the project site. While a variance to reduce the bulk dimensions of the standard stream buffer is only being requested for Lot B here and Lot C to the south, mitigation is provided on all three lots, including on Lot A where no buffer reduction is required or requested. 67 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance 3. Preserve, protect, restore, and/or mitigate wetlands within and associated with the City’s shorelines to achieve no net loss of wetland area and wetland functions. No wetlands are present on Lot B. As such, no net loss of wetland area or functions is proposed or expected. 4. Developments in shoreline areas that are identified as geologically hazardous or pose a foreseeable risk to people and improvements during the life of the development should not be allowed. The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Polger and Niggermann, 2007 in Critical Areas Report- Bergquist Engineering Services Company, LLC, Revised November 2020). The City and County designate portions of the subject properties as being within the “Channel Migration Moderate Hazard” area. The risk of flood and erosion is somewhat diminished by control of flows during floods by the Howard A Hansen Dam and even though massive flood events occurred almost annually in the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located for the last 130 years or so of map and air photographic record (Critical Areas Report-Bergquist Engineering Services Company, LLC, Revised November 2020). No development is proposed within the “Channel Migration Moderate Hazard” area of the subject lot. The future home will be constructed outside that hazard area. Portions of the site are also within the City’s “Critical Erosion Hazard Area”, due to the presence of silty fine SAND underlying the steep cut slope along the east side of 104th PL SE. Some signs of erosion above the revetment on the opposite bank of the Green River from the properties was observed, but no erosion on site has been observed. The City also classifies the cut slope, which is located offsite on City property, as a Class IV/Very High Hazard Landslide Hazard Area because the slope was excavated to an inclination greater than 40% and is approximately 25’ high. The vegetation growing along the in-slope ditch and the lack of debris along the base of the slope indicates the dense silt SAND forming the slope does not appear to be eroding in the immediate vicinity of the project site. Down the road, to the south of the project there has been some slope movement noted. Slope stability analysis conducted by Bergquist found that the slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated, but that slope movement (lateral spreading) is not likely to occur on the 68 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance subject projects (Critical Areas Report-Bergquist Engineering Services Company, LLC, Revised November 2020). This slope has a recommended 23’ buffer that does not encroach onto Lot B. Subsurface exploration and engineering analysis will be performed prior to foundation design. Deep foundation systems will likely involve driven or drilled piles to mitigate liquefiable soil conditions. Another method to be explored would involve installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. Overall, analysis by Bergquist concludes that the current geologic conditions of the site make the proposed single-family development challenging but do not render the site unbuildable. They recommend additional steps during construction and design beyond what is normal standard building practices. Bergquist does not recommend any shoreline stability in the form of bulkheads or revetments. 4.4.6 Public Access (including views) 2. Protection and enhancement of the public’s physical and visual access to shorelines should be encouraged. The public’s visual access to the shoreline of Green River along the frontage of Lot B will be protected by compliance with the single-family residential height limitation of 35’ for properties with R5 zoning in the Lea Hill Overlay. The building’s height is not expected to impair views and an existing 36” Douglas-Fir tree and three 28” bigleaf maple trees on Lot B near the road, are all greater than 35’ in height and are proposed for retention. Amberview Apartments located to the east of the subject properties are located uphill from the project sites and thus will not have their views impacted by the proposed construction of the moderately sized single-family residence. 4.4.7 Flood Hazard Reduction 2. Discourage development within the floodplains associated with the City’s shorelines that would individually or cumulatively result in an increase to the risk of flood damage. No development is proposed within the floodplain. The proposed residence will be built above base flood elevation to reduce the risk of flood damage. 4.4.8 Water Quality, Storm water and Non-Point Pollution 2. Storm water management treatment, conveyance, or discharge facilities should be discouraged in the shoreline jurisdiction, unless no other feasible alternative is available. 69 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance Runoff from the site currently sheet flows directly into the Green River. Storm water from the proposed development will be mitigated using basic dispersion trenches with native vegetated flow paths and other stormwater mitigation BMPs. The conceptual dispersion trench and other BMPs on Lot B are located approximately 95’ from the Green Riverbank and will not adversely affect the stability of the bank (Critical Areas Report-Bergquist Engineering Services Company, LLC, Revised November 2020). Bergquist does not recommend any shoreline stability in the form of bulkheads or revetments. The onsite drainage mitigation emulates existing conditions. Final selection and design of the stormwater handling systems will be based on home design within the conceptual footprints proposed here. 4. Encourage conservation of existing shoreline vegetation which provides water quality protection by slowing and filtering stormwater runoff. The entire proposed stream buffer will be restored from its predominantly invasive and alien vegetative state to native plantings. After restoration this area, including the dispersion trench’s vegetated flow paths, the designed dispersion system will ultimately slow and filter stormwater runoff while preserving the natural shoreline. • The proposed use is consistent with the following policies of The Auburn Comprehensive Plan: General Land Use Policies LU-1 Regulations for new developments and infill should address the following elements: b. Relationship to nearby existing or future transit services The Lot B, parcel # 334100-0095, is located in the Sound Transit Regional Transit Authority taxing district and is located less than half a mile from Metro bus route #181’s stop on 8th Street NE as well as Lea Hill Rd SE. d. Environmental protection and preservation of natural features As described herein, restoration of the degraded shoreline along the three subject properties is an unique opportunity of the proposed single family development. e. Preservation of areas that can support low-impact development techniques The development proposed is low impact in that disturbance will be restricted onsite as far from the Green River as possible. As such, only a small minority of Lot 70 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance B, 19.1% of the lot’s gross area, will be disturbed and used for home development, while the majority of the property will be restored and preserved for perpetuity. g. Efficient and effective delivery of utility service Utilities already exist in 104th Pl SE including sewer, water, electricity, phone, etc as the nearby neighboring properties to the north and south of Lot B are already developed with a single family residences. h. Innovative design The design takes the specific challenges of the project site and proposes solutions with design, including reduced building footprints, minimum width driveways, and siting to minimize the impacts of the proposed homes on the environment. j. Long-term maintenance considerations The native vegetation chosen to restore the reduced stream buffer have been chosen for being well suited for this specific ecosystem. The ultimate result will not require irrigation and will resemble the forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, Revised October 2020). Single Family Residential Designation LU-17 Provide a variety of housing typologies to suit the needs of various potential residents. One mid-high-income single-family residence is proposed on the existing Lot B, parcel # 334100-00095 to be added to the available inventory of housing products meant to suit the needs of various potential Auburn residents. 4. The variance authorized does not constitute a grant of special privilege not enjoyed by other properties in the area, and will be the minimum necessary to afford relief; Table 1 of Section 4.4.5 SMP allows for the reduction by up to 35% of the Class 1 Stream 100’ buffer in Urban Conservancy provided the applicant demonstrates that a reduction will not result in any adverse impact to the stream. This codified relief from the strict application of the stream buffer is available to all properties in the area should they seek it and does not constitute a grant of special privilege. As such the following enhancements have been provided to mitigate the potential impacts of reducing the buffer on Lot B by approximately 5.5% of its width. Additionally, the majority of the lots, zoned for single family residential use, on 104th PL SE are already developed with residences which exist within the 100’ stream buffer. Many of the developments took place prior to the SMP and as such weren’t faced with the restrictions of the 100’ stream buffer. As such, allowing for a reduction with mitigation of the stream buffer 71 of 721 Written Statement & Criterion Compliance Lot B Shoreline Variance for Lot B does not constitute a grant of special privilege not enjoyed by the already developed lots on the same road. 5. The public interest will suffer no substantial detrimental effect. Reducing the bulk dimensions of the Stream buffer by approximately 5.5% on Lot B will not pose any threat or detrimental effect to the public interest—conversely the public interest will benefit from the restoration of the Green River’s shoreline on this lot through the mitigation and enhancements proposed to offset the minimal reduction needed to allow for reasonable use of the property. The proposed dwelling will be placed above the base flood elevation and is located outside the Channel Migration Hazard Area as well as the flood plain, as such no flooding hazards to the public or future residents is foreseen on Lot B in association with the reduction of the stream buffer. 6. Variance permits for development that will be located either waterward of the ordinary high water mark or within marshes, bog or swamps as designated in Chapter 173-22 WAC may be authorized, provided the applicant can demonstrate all the criteria stated above as well as the following: a. That the strict application of the bulk, dimensional or performance standards set forth in this SMP precludes all reasonable use of the property not otherwise prohibited by this SMP; and b. That the public rights of navigation and use of the shorelines will not be adversely affected by the granting of the variance. No development is proposed to be located either waterward of the OHWM or within any marsh, bog or swamp. As such this criteria doesn’t apply to the project. CUMULATIVE CONSIDERATIONS (RCW 90.58) A shoreline variance to reduce the standard stream buffer from 100’ by approximately 5.5% is being requested for Lot B as described above. Additionally, a similar variance is being requested for Lot C (parcel # 3341000100 abutting Lot B to the south) to reduce the standard stream buffer width by approximately 9.5% to allow for the reasonable use of the lot and develop a modest single family residence. Finally, while no variance is required to reduce the buffer width on Lot A (parcel # 3341000090 abutting Lot B to the north), a shoreline conditional use permit is being requested to allow for the development of a single family residence on that lot as well. The cumulative impact of these projects on the three parcels has been evaluated and a “no net loss” of shoreline function or resources has been determined by Peter Super (wetland biologist) in the Critical Area Report: Wetlands & Streams. The mitigation proposed for Lots B & C to reduce the standard stream buffer is bolstered and supported by additional enhancements to the standard 100’ stream buffer area proposed to be maintained on Lot A. As such the project proposes a unique opportunity to enhance and restore approximately 317-feet of a currently degraded reach of the Green River. It is rare that three river front parcels are proposed for development simultaneously and to have collaborative ownership parties. 72 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance SHORELINE VARIANCE LOT C: WRITTEN STATEMENT 1. The shoreline designation according to the Shoreline Master Program: Urban Conservancy 2. The name of the shoreline (water body) that the site of the proposal is associated with: Green River A specific description of the proposed project, including the proposed use(s) and the activities necessary to accomplish the project: The proposal includes applying for a Shoreline Conditional Use Permit and Shoreline Variance to permit the buildable space on Lot C so that it accommodates the future construction of a multi-story single-family home within the existing residential lot (Lot C) along the eastern bank of the Green River. The existing property (Parcel #: 334100-0100) is bordered to the north by Lot B, another property owned by the applicant, zoned R-5 and with similar land use proposals. To the south, an existing offsite SFR dwelling built in 2005 exists. The subject property is encumbered by the following mapped areas and/or classifications: a. Groundwater Protection Zone 2: Groundwater occurs that is a current or potential future source of drinking water for the City of Auburn. b. Class IV/Very High Landslide Hazard Area: There is a cut slope located offsite, on City property on the east side of 104th Place SE that was excavated to an inclination greater than 40%. Bergquist Engineering has determined that a 23’ buffer is required from the toe of slope, this buffer does not encroach onto the existing Lot C. c. Critical Erosion Hazard Area: Per evaluation by Bergquist Engineering Services Company, LLC, this classification is likely due to the presence of the silty fine SAND underlying the steep cut slope located offsite along the east side of 104th Place Southeast. d. Riparian Habitat Zone : The property is located within 250’ of the Green River’s Ordinary High Water Mark (OHWM). e. Shoreline Management Zone-Urban Conservancy: The property is located within 200’ of the Green River’s OHWM. f. Moderate Channel Migration Hazard Area: The City of Auburn recently modified the channel migration zone boundaries with GeoEngineers, Inc (2018). No development or work is proposed within the mapped Moderate Channel Migration Hazard Area with this proposal. g. Type S Stream, 100’ Stream Buffer: This variance is being requested to reduce the width of stream buffer to allow reasonable use of Lot C. The stream buffer on Lot C is proposed to be reduced by approximately 9.5’ to a width of approximately 90.5’. h. 100-year floodplain : The existing parcel contains a mapped 100 year floodplain in the westernmost portion of the parcel along the bank of the Green River—no development or work is proposed below the base flood elevation of 67.4’, or within the flood plain with this proposal. 73 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance 3. No development is proposed below the base flood elevation of the lot (BFE=67.4’), within the floodplain, or within the “Channel Migration Moderate Hazard” area of the property. Lot C’s development proposal requires unavoidable shoreline buffer impacts. As such the stream’s 100’ standard buffer width will be reduced by approximately 9.5%. Restoration and mitigation for the reduced buffer will include invasive plant/noxious weed species removal, installing logs for habitat, native plantings, mulching, critical area fencing, signage, and protection. Basic dispersion trenches with native vegetated flow paths and other storm water mitigation BMPs are conceptualized to mitigate stormwater runoff as a result of the final building design (to be determined at the building permit stage of the project). 4. A general description of the property’s existing physical characteristics, improvements, and structures: Lot C, parcel # 3341000100, is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. The site is within NW 17-21-05, W.M, King County, Washington. The lot is currently undeveloped vacant land that is moderately forested. The parcel is vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry. Fine silty SAND describes the majority of the parcel’s underlying soil type. Topography within the project site is characterized by a moderately steep to near vertical riverbank that transitions to nearly flat or gently sloping land throughout the central portion of the site to a short-inclined transition along 104th PL SE. There are no wetlands within or immediately adjacent to the site. The green River, a Type S water exists along the western limits of the site. Lot C measures approximately 13,021 SF in area and maintains approximately 92 LF of shoreline frontage along the eastern bank of the Green River. 5. 6. A general description of adjacent (within 1,000 feet in all directions) use, structures, improvements, intensity of development, and physical characteristics: Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Residential development along the west side of 104th PL SE extends back to the early 1900’s and existing development generally includes one- or two-story single family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th ST, most residence are of a conventional on-site stick-built construction averaging 2,510 SF (dwelling unit + accessory structures) in footprint. Most residences are setback from the Green River and are located close to 104th PL SE. See Figure 1 land uses within 1000’ of Lot C. Residential uses surround the project site of varying densities. 74 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance CRITERION COMPLIANCE REPORT FOR SHORELINE VARIANCE PER SMP 16.08.058 1. The strict requirements of the bulk, dimensional, or performance standards set forth in the master program precludes or significantly interferes with a reasonable use of the property not otherwise prohibited by the SMP. The requirements of the SMP to maintain a 100’ standard stream buffer from the OHWM of the Green River and a sewer line (requiring a 15’ building setback from the line) that runs through the northeastern portion of the property to serve the abutting neighbor to the south would result in a buildable area of only 1,527 SF for Lot C. This would preclude or significantly interfere with all reasonable use of the property for marketable single family use as this small buildable space needs to accommodate the livable space of the home, a 20’x20’ garage, storm water mitigation BMPs and grading/clearing during construction. 2. The hardship described above is specifically related to the property and is the result of unique conditions such as irregular lot shape, size, or natural features and not, for example from deed restrictions of the applicant’s own actions. The hardship described above is specifically related to the properties shape (depth) as bound by 104th PL SE to the northeast and the Green River to the southwest. While the sewer line could be relocated to increase the buildable area on the lot, the resulting dimensions and configuration would still prove infeasible for construction of a single family residence and the disturbance associated with such relocation would produce greater impact to the shoreline buffer than proposed herein. Additionally, the cost of moving the sewer line is prohibitive to the property owners. 3. The design of the project will be compatible with other permitted activities within the area and with uses planned for the area under the comprehensive plan and SMP and will not cause adverse impacts to the shoreline environment. Please see below for project’s consistency with the comprehensive plan and SMP. The proposed single-family residence on Lot C is designed to result in “no net loss” of shoreline ecological functions or to degrade other shoreline values (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, 2020). SMP 4.4 General Policies and Regulations SMP 4.4.1 Conservation and Restoration 4. Promote vegetation restoration, and the control of invasive weed and nonnative species to avoid adverse impacts to hydrology and to reduce the hazard of slope failures or accelerated erosion. Lot C is currently overgrown with invasive Himalayan Blackberry, the proposal includes vegetation restoration that will involve the removal and replacement of the blackberry with native riparian plant species. SMP 4.4.2 Shoreline Vegetation Conservation 75 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance 1. Developments and activities in the City’s shoreline should be planned and designed to retain native vegetation or replace shoreline vegetation with native species to achieve no net loss of the ecological functions and ecosystem-wide processes performed by vegetation. Vegetation removal within each building site will be limited to primarily invasive Himalayan Blackberry, a Class 3 noxious weed. Only one significant tree will be removed. Removed vegetation will be replaced with dense native plantings consisting of bigleaf maple, black cottonwood, Douglas fir, western red cedar, vine maple, Redosier dogwood, Indian plum, Redflower currant, salmonberry, Sitka willow and snowberry. No net loss of ecological functions and ecosystem-wide processes are expected (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, Revised October 2020). 2. Wood debris should be left in the river corridors to enhance wildlife habitat and shoreline ecological functions, except where it threatens personal safety or critical infrastructure, such as bridge pilings. In such cases where debris poses a threat, it should be dislodged, but should not be removed from river. The segment of the Green River located adjacent to Lot C does not include significant habitat features such as log jams, beaver dams, aquatic vegetation, large rocks or boulders, side channels and/or undercut banks. There is limited natural cover such as shade or submerged or overhanging large wood debris (LWD). Any LWD found in the river corridor will be left in place, pending safety. The proposed species, densities, and distribution of native plantings will provide opportunities for LWD and organic matter production that currently do not exist or is otherwise extremely limited within the site. SMP 4.4.3 Environmental Impact Mitigation 1. All shoreline use and development should be carried out in a manner that avoids and minimizes adverse impacts to that the resulting ecological condition does not become worse than the current condition. This means assuring no net loss of ecological functions and processes and protecting critical areas designated in Appendix A, Chapter 16.10 “Critical Areas” that are located in the shoreline. Should a proposed use and development potentially create significant adverse environmental impacts not otherwise avoided or mitigated by compliance with the master program, the Director should require mitigation measures to ensure no net loss of shoreline ecological functions. 76 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance The proposed single-family residence on Lot C is designed to result in “no net loss” of shoreline ecological functions or to degrade other shoreline values (Critical Area Report: Wetlands & Streams, Evergreen Aquatic Resource Consultants, LLC, Revised October 2020). Mitigation involving the restoration of the shoreline buffer with the removal of invasive plant species and the dense planting of native riparian plant species is proposed to offset the minimal impacts posed by the single family residence along 104th PL SE. SMP 4.4.4 Critical Areas 1. Provide a level of protection to critical areas within the shoreline that is at least equal to that which is provided by the City’s critical areas regulations adopted pursuant to the Growth Management Act and the City’s Comprehensive Plan. If conflicts between the SMP and the critical area regulations arise, the regulations that are most consistent with the SMA or its WAC provisions will govern. The level of protection provided meets all critical areas regulations excepting the shoreline variance requested here to reduce the width of the stream buffer for Lot C. Per SMP 4.4.5, stream buffer widths may be reduced by up to 35% provided the applicant demonstrates that a reduction will not result in any adverse impact to the stream. The standard 100’ stream buffer for Lot C the stream buffer is proposed to be reduced by 9.5%. This reduction is less than 35% and will been mitigated for by restoring the degraded shoreline area. Per Evergreen Aquatic’s report and mitigation plan the proposed project results in “no net loss” of shoreline ecological functions. 2. Allow activities in critical areas that protect and, where possible, restore the ecological functions and ecosystem-wide processes of the City’s shoreline. Because the project abuts two similar development projects on simultaneous timelines, with collaborative owners, the three contiguous lots, present a unique opportunity to restore the ecological functions of a substantial stretch of the Green River’s shoreline area from its current degraded Himalayan Blackberry dominated landscape to one that will ultimately resemble a forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, Revised October 2020). This will increase and/or provide opportunities for structural habitat diversity, shade, and large woody debris production that currently either does not exist or is limited within the project site. While a variance to reduce the bulk dimensions of the standard stream buffer is only being requested for Lot C here and Lot B to the north, mitigation is provided on all three lots, included Lot A where no buffer reduction is required or requested. 77 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance 3. Preserve, protect, restore, and/or mitigate wetlands within and associated with the City’s shorelines to achieve no net loss of wetland area and wetland functions. No wetlands are present on Lot C. As such, no net loss of wetland area or functions is proposed or expected. 4. Developments in shoreline areas that are identified as geologically hazardous or pose a foreseeable risk to people and improvements during the life of the development should not be allowed. The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Polger and Niggermann, 2007 in Critical Areas Report- Bergquist Engineering Services Company, LLC, Revised October 2020) The City and County designate portions of the subject properties as being within the “Channel Migration Moderate Hazard” area. The risk of flood and erosion is somewhat diminished by control of flows during floods by the Howard A Hansen Dam and even though massive flood events occurred almost annually in the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located for the last 130 years or so of map and air photographic record (Critical Areas Report-Bergquist Engineering Services Company, LLC, Revised October 2020). No development is proposed within the “Channel Migration Moderate Hazard” area of each lot. The future home will be constructed outside that hazard area. Portions of the site are also within the City’s “Critical Erosion Hazard Area”, due to the presence of silty fine SAND underlying the steep cut slope along the east side of 104th PL SE. Some signs of erosion above the revetment on the opposite bank of the Green River from the properties was observed, but no erosion on site has been observed. The City also classifies the cut slope, which is located offsite on City property, as a Class IV/Very High Hazard Landslide Hazard Area because the slope was excavated to an inclination greater than 40% and is approximately 25’ high. The vegetation growing along the in-slope ditch and the lack of debris along the base of the slope indicates the dense silt SAND forming the slope does not appear to be eroding in the immediate vicinity of the project site. Down the road, to the south of the project there has been some slope movement noted. Slope stability analysis conducted by Bergquist found that the slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated, but that slope movement (lateral spreading) is not likely to occur on the 78 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance subject projects (Critical Areas Report-Bergquist Engineering Services Company, LLC, Revised November 2020). This slope has a recommended 23’ buffer that does not encroach onto Lot B. Subsurface exploration and engineering analysis will be performed prior to foundation design. Deep foundation systems will likely involve driven or drilled piles to mitigate liquefiable soil conditions. Another method to be explored would involve installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. Overall, analysis by Bergquist concludes that the current geologic conditions of the site make the proposed single-family development challenging but do not render the site unbuildable. They recommend additional steps during construction and design beyond what is normal standard building practices. Bergquist does not recommend any shoreline stability in the form of bulkheads or revetments. 4.4.6 Public Access (including views) 2. Protection and enhancement of the public’s physical and visual access to shorelines should be encouraged. The public’s visual access to the shoreline of Green River along the frontage of Lot C will be protected by compliance with the single-family residential height limitation of 35’ for properties with R5 zoning in the Lea Hill Overlay. The building’s height is not expected to impair views and an existing 12” cottonwood tree on Lot C near the road, is likely greater than 35’ in height and is proposed for retention. Amberview Apartments located to the east of the subject properties are located uphill from the project sites and thus will not have their views impacted by the proposed construction of the moderately sized single-family residence. 4.4.7 Flood Hazard Reduction 2. Discourage development within the floodplains associated with the City’s shorelines that would individually or cumulatively result in an increase to the risk of flood damage. No development is proposed within the floodplain. The proposed residence will be built above base flood elevation to reduce the risk of flood damage. 4.4.8 Water Quality, Storm water and Non-Point Pollution 2. Storm water management treatment, conveyance, or discharge facilities should be discouraged in the shoreline jurisdiction, unless no other feasible alternative is available. 79 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance Runoff from the site currently sheet flows directly into the Green River. Storm water from the proposed development will be mitigated using basic dispersion trenches with native vegetated flow paths other stormwater mitigation BMPs. The conceptual dispersion trench and other BMPs on Lot C will be located approximately 90.5’ from the Green Riverbank and will not adversely affect the stability of the bank (Critical Areas Report-Bergquist Engineering Services Company, LLC, Revised November 2020). Bergquist does not recommend any shoreline stability in the form of bulkheads or revetments. The onsite drainage mitigation emulates existing conditions. Final selection and design of the stormwater handling systems will be based on home design within the conceptual footprints proposed here. 4. Encourage conservation of existing shoreline vegetation which provides water quality protection by slowing and filtering stormwater runoff. The entire proposed stream buffer will be restored from its predominantly invasive and alien vegetative state to native plantings. After restoration this area, including the dispersion trench’s vegetated flow paths, the designed dispersion system will ultimately slow and filter stormwater runoff while preserving the natural shoreline. • The proposed use is consistent with the following policies of The Auburn Comprehensive Plan: General Land Use Policies LU-1 Regulations for new developments and infill should address the following elements: b. Relationship to nearby existing or future transit services The Lot C, parcel # 334100-0100, is located in the Sound Transit Regional Transit Authority taxing district and is located less than half a mile from Metro bus route #181’s stop on 8th Street NE as well as Lea Hill Rd SE. d. Environmental protection and preservation of natural features As described herein, restoration of the degraded shoreline along the three subject properties is an unique opportunity of the proposed single family development. e. Preservation of areas that can support low-impact development techniques The development proposed is low impact in that disturbance will be restricted onsite as far from the Green River as possible. As such, only a small minority of Lot 80 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance C, 17.8% of the lot’s gross area, will be disturbed and used for home development, while the majority of the property will be restored and preserved for perpetuity. g. Efficient and effective delivery of utility service Utilities already exist in 104th Pl SE including sewer, water, electricity, phone, etc as the abutting property to the south of Lot C is already developed with a single family residence. h. Innovative design The design takes the specific challenges of the project site and proposes solutions with design, including reduced building footprints, minimum width driveways, and siting to minimize the impacts of the proposed homes on the environment. j. Long-term maintenance considerations The native vegetation chosen to restore the reduced stream buffer have been chosen for being well suited for this specific ecosystem. The ultimate result will not require irrigation and will resemble the forested condition typical of the western hemlock (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973) (Critical Areas Report, Evergreen Aquatics, Revised October 2020). Single Family Residential Designation LU-17 Provide a variety of housing typologies to suit the needs of various potential residents. One mid-high-income single-family residence is proposed on the existing Lot C, parcel # 334100-0100 to be added to the available inventory of housing products meant to suit the needs of various potential Auburn residents. 4. The variance authorized does not constitute a grant of special privilege not enjoyed by other properties in the area, and will be the minimum necessary to afford relief; Table 1 of Section 4.4.5 SMP allows for the reduction by up to 35% of the Class 1 Stream 100’ buffer in Urban Conservancy provided the applicant demonstrates that a reduction will not result in any adverse impact to the stream. This codified relief from the strict application of the stream buffer is available to all properties in the area should they seek it and does not constitute a grant of special privilege. As such the following enhancements have been provided to mitigate the potential impacts of reducing the buffer on Lot C by approximately 9.5% of its width. Additionally, the majority of the lots, zoned for single family residential use, on 104th PL SE are already developed with residences which exist within the 100’ stream buffer. Many of the developments took place prior to the SMP and as such weren’t faced with the restrictions of the 100’ stream buffer. As such, allowing for a reduction with mitigation of the stream buffer 81 of 721 Written Statement & Criterion Compliance Lot C Shoreline Variance for Lot C does not constitute a grant of special privilege not enjoyed by the already developed lots on the same road. 5. The public interest will suffer no substantial detrimental effect. Reducing the bulk dimensions of the Stream buffer by approximately 9.5% on Lot C will not pose any threat or detrimental effect to the public interest—conversely the public interest will benefit from the restoration of the Green River’s shoreline on this lot through the mitigation and enhancements proposed to offset the minimal reduction needed to allow for reasonable use of the property. The proposed dwelling will be placed above the base flood elevation and is located outside the Channel Migration Hazard Area as well as the flood plain, as such no flooding hazards to the public or future residents is foreseen on Lot C in association with the reduction of the stream buffer. 6. Variance permits for development that will be located either waterward of the ordinary high water mark or within marshes, bog or swamps as designated in Chapter 173-22 WAC may be authorized, provided the applicant can demonstrate all the criteria stated above as well as the following: a. That the strict application of the bulk, dimensional or performance standards set forth in this SMP precludes all reasonable use of the property not otherwise prohibited by this SMP; and b. That the public rights of navigation and use of the shorelines will not be adversely affected by the granting of the variance. No development is proposed to be located either waterward of the OHWM or within any marsh, bog or swamp. As such this criteria doesn’t apply to the project. CUMULATIVE CONSIDERATIONS (RCW 90.58) A shoreline variance to reduce the standard stream buffer from 100’ by approximately 9.5% is being requested for Lot C as described above. Additionally, a similar variance is being requested for Lot B (parcel # 3341000095 abutting Lot C to the north) to reduce the standard stream buffer width by approximately 5.5% to allow for the reasonable use of the lot and develop a modest single family residence. Finally, while no variance is required to reduce the buffer width on Lot A (parcel # 3341000090 abutting Lot B to the north), a shoreline conditional use permit is being requested to allow for the development of a single family residence on that lot as well. The cumulative impact of these projects on the three parcels has been evaluated and a “no net loss” of shoreline function or resources has been determined by Peter Super (wetland biologist) in the Critical Area Report: Wetlands & Streams. The mitigation proposed for Lots B & C to reduce the standard stream buffer is bolstered and supported by additional enhancements to the standard 100’ stream buffer area proposed to be maintained on Lot A. As such the project proposes a unique opportunity to enhance and restore a currently degraded reach of the Green River. It is rare that three river front parcels are proposed for development simultaneously and to have collaborative ownership parties. 82 of 721 83 of 721 84 of 721 85 of 721 86 of 721 87 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences 32XXX 104th Place SE – Auburn, Washington King County Tax Parcel # 34100-0090, -0095, & -0100 Prepared for: Launce P Goulet & Bruce Goulet 3226 S 198th Street SeaTac, Washington 98188 Prepared by: Evergreen Aquatic Resource Consultants, LLC PO Box 1721 Issaquah, Washington 98027 April 10, 2020 (revised May 14, 2021) Project Number 19046 88 of 721 WETLAND DELINEATION • MITIGATION DESIGN • COMPLIANCE MONITORING April 10, 2020 (revised May 14, 2021) Project Number 19046 Launce P Goulet & Bruce Goulet 3226 S 198th Street SeaTac, Washington 98188 Subject: Critical Area Report: Wetlands & Streams Proposed Goulet Single-Family Residences 32XXX 104th Place SE – Auburn, Washington Launce and Bruce: Evergreen Aquatic Resource Consultants, LLC is pleased to present this critical area report for your three lot residential project located at approximately 32XXX 104th Place SE in Auburn, Washington. The proposed project includes the development of buildable areas on three undeveloped lots located along the east bank of the Green River. The project results in consolidated buildable areas designated along 104th Place SE and a “no net loss” of shoreline buffer ecological functions. The information presented in this report is based on an analysis of conditions within and adjacent to the project site, a review of site design and analysis provided by others, an examination of the critical area and shoreline development standards contained within Auburn City Code (ACC) 16.08 (Shoreline Management Administration and Permitting Procedures) and ACC 16.10 (Critical Areas), and the best available science regarding shoreline ecological functions. I understand that this report will be used, in part, to obtain planning approvals and construction permits for the proposed project. I trust that this report meets your present needs. If you have any questions regarding this report or require additional assistance with this project, please do not hesitate to call or email. Sincerely, Evergreen Aquatic Resource Consultants, LLC Peter P. Super Professional Wetland Scientist PO Box 1721 Issaquah, Washington 98027 (425) 677-7166 www.evergreenarc.com 89 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences 32XXX 104th Place SE – Auburn, Washington King County Tax Parcel # 34100-0090, -0095, & -0100 Prepared for: Launce P Goulet & Bruce Goulet 3226 S 198th Street SeaTac, Washington 98188 Prepared by: Evergreen Aquatic Resource Consultants, LLC PO Box 1721 – Issaquah, Washington 98027 425.677.7166 (t) | www.evergreenarc.com April 10, 2020 (revised May 14, 2021) Project No. 19046 90 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page i April 10, 2020 (revised May 14, 2021) 1.0 INTRODUCTION ...................................................................................................................................... 1 2.0 PROJECT SITE ........................................................................................................................................... 1 3.0 WETLAND DELINEATION AND STREAM DETERMINATION .............................................................. 1 3.1 Methodology ........................................................................................................................................................................... 2 3.2 Background Research ........................................................................................................................................................... 3 3.3 Site Assessment ...................................................................................................................................................................... 4 4.0 PROPOSED PROJECT ............................................................................................................................... 5 4.1 Project Purpose and Need .................................................................................................................................................. 5 4.2 Project Site Limitations ......................................................................................................................................................... 5 4.3 Minimum Necessary Impact ............................................................................................................................................... 6 4.4 Compatibility with Adjacent Land use ............................................................................................................................ 6 4.5 Proposed Construction Process and Methods ............................................................................................................ 6 4.6 Unique Benefits of Project ................................................................................................................................................... 7 4.7 Alternatives Considered ....................................................................................................................................................... 7 5.0 MITIGATION SEQUENCING .................................................................................................................... 7 5.1 Avoidance and Minimization of Impacts ....................................................................................................................... 8 5.2 Restoration of Temporary Impacts .................................................................................................................................. 8 5.3 Reduction and Elimination of Impacts Over Time ..................................................................................................... 8 5.4 Compensatory Mitigation.................................................................................................................................................... 8 5.5 Monitoring and Maintenance ............................................................................................................................................ 9 6.0 SHORELINE FUNCTIONAL ASSESSMENT ............................................................................................. 9 6.1 Existing Shoreline Conditions ......................................................................................................................................... 10 6.2 Impact Assessment.............................................................................................................................................................. 11 6.3 Shoreline Function “No Net Loss” ................................................................................................................................. 12 7.0 CONCLUSION ......................................................................................................................................... 13 8.0 REPORT LIMITATIONS .......................................................................................................................... 13 9.0 REFERENCES ........................................................................................................................................... 14 LIST OF ATTACHMENTS Attachment 1 – Vicinity Map Attachment 2 – Aerial Photograph Showing Project Site Attachment 3 – Wetland Determination Form Attachment 4 – Photos of Vegetation, Soils, and Hydrology Conditions at Wetland Determination Point Attachment 5 – Existing Conditions Map Attachment 6 – Simple Sketch of OHWM Cross Section Attachment 7 – Site Plan 91 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 1 April 10, 2020 (revised May 14, 2021) 1.0 INTRODUCTION This critical area report describes wetland and stream conditions within and adjacent to a proposed three lot residential project located at approximately 32XXX 104th Place SE in Auburn, Washington. This report also describes how the proposed project incorporates shoreline protection and conservation measures through appropriate mitigation sequencing and how the proposed project results in a “no net loss” of shoreline ecological functioning. This report should be reviewed in combination with the mitigation plan entitled “Shoreline Buffer Mitigation Plan: Proposed Goulet Single Family residences”, dated April 10, 2020 (revised May 14, 2021). It is understood that this report may be used, in part, to obtain planning approvals and construction permits for the proposed project. 2.0 PROJECT SITE The project site consists of three slightly irregularly shaped residential lots located at approximately 32XXX 104th Place SE in Auburn, Washington. Each lot is undeveloped and situated along the east bank of the Green River in the northwest quarter of Section 17, Township 21 North, Range 5 East, W.M. The three lots are referred to individually as “Lot A”, “Lot B”, and “Lot C”. Table 1 summarizes general information for each lot. TABLE 1 – GENERAL LOT INFORMATION REFERENCE PARCEL NUMBER LOT AREA COMPREHENSIVE PLAN DESIGNATION ZONING DESIGNATION Lot A 334100-0090 14,628 sf single family R-5 Lot B 334100-0095 13,601 sf single family R-5 Lot C 334100-0100 13,021 sf single family R-5 The project site is bound by 104th Place SE to the east, single family development to the south, a small undeveloped lot to the north, and the Green River to the west. Vegetation within the site supports a mix of dense shrubbery with scattered trees. Topography within the site is characterized by a moderately steep to a near vertical riverbank that transitions to nearly flat to gently sloping land throughout the central portion of the site to a short, inclined transition along 104th Place SE. Total elevation change across the site is approximately 14 feet ranging from an elevation of 60 feet (NAVD 88) near the ordinary high water mark (OHWM) of the Green River to approximately 74 feet (NAVD 88) along 104th Place SE. The project site can be accessed from Auburn City Hall by travelling east on E Main Street for approximately 1.0 miles and then turning left on R Street NE. After traveling north on R Street NE for approximately 0.5 miles, turn right onto 8th Street NE. After traveling east on 8th Street NE for approximately 0.25 miles turn right onto 104th Place SE. The project site is located on the west side of 104th Place SE approximately 450 feet south of 8th Street NE. Attachment 1 to this report is a vicinity map showing the location of the project site and Attachment 2 to this report is a recent aerial photograph showing the project site. 3.0 WETLAND DELINEATION AND STREAM DETERMINATION On October 4, 2019 and October 22, 2019, a detailed wetland delineation and stream determination site assessment was completed. The purpose of the assessment was to formally delineate and rate (classify) 92 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 2 April 10, 2020 (revised May 14, 2021) wetlands and streams that are located within or immediately adjacent to the project site. As a result of this work, it was determined that wetlands do not exist within or adjacent to the site and that the Green River, a Type S water, exists along the western limits of the site. 3.1 Methodology Prior to conducting the October 2019 site assessments, background research was completed to gather natural resource and land use related information regarding the project site and local vicinity. This research included review of readily available critical area maps, soil surveys, environmental studies of the site, and aerial photographs. Wetland determinations made during the site assessments employed the “routine determination” methods required for “on-site inspections” as described in the 1987 Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory 1987). Vegetation, soil, and hydrology characteristics were examined at multiple locations and then compared to the specific criteria established for the three wetland indicators described in the Regional Supplement To The Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0) (US Army Corps of Engineers 2010). When hydrophytic vegetation, hydric soil, and wetland hydrology indicators were present, an area was determined to be a wetland. In the absence of all three indicators and/or when exclusionary situations apply, an area was considered non-wetland, or “upland”. Wetland determination points were marked on-site using sequentially numbered orange flagging. Stream determinations made during the site assessments utilized the definitions and related water typing criteria described in Washington Administrative Code (WAC) 222-16-030/031 (Water Typing System) and Auburn City Code (ACC) 16.10 (Critical Areas). An aquatic feature was considered a stream if there was clear evidence of the passage of water including, but not limited to, defined channels, swales, and/or hydraulically sorted gravel and silt beds. Fisheries utilization within a stream considered the width and gradient of the stream as well as records of any known fish use within the stream and/or connected downstream waters, including wetlands. The OHWM for each stream was marked on-site using sequentially numbered blue flagging. OHWM determinations were based on the methodologies outlined in Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State (Washington State Department of Ecology 2016). The site assessments were conducted during the late growing season and considered the climatic conditions prior to and during the inspection. In addition, natural seasonal variations related to the time of year were considered. Weather conditions during the October 4, 2019 assessment included partly cloudy sky conditions with ambient air temperatures ranging to approximately 65° F. Prior to conducting the site assessment, historic precipitation data was obtained from King County’s Hydrologic Information Center webpage. Precipitation received within the local area for the seven days preceding the determination as measured at Lower Green River Rain Gauge (Station 32U) was 0.14 inches. Precipitation during the twelve month period preceding the determination was 5.83 inches (13.85 percent) less than the historic mean of 42.12 inches for the 31 year period of available record (s = 7.52 inches). The lower than normal precipitation did not limit or otherwise prevent an accurate assessment of critical area conditions. The October 22, 2019 assessment was conducted after a seven day period of heavy rainfall totaling 3.3 inches. At the time of the site assessments, access was not granted to review adjacent private properties. Off- site areas were evaluated using information obtained from readily available literature and aerial photographs as well as by observing conditions directly from the project site and/or from improved 93 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 3 April 10, 2020 (revised May 14, 2021) portions of public right-of-way or other publicly owned property. Where assessed, off-site wetlands and streams were noted only to the degree necessary to determine buffer widths and any related buffer encroachment onto the project site. Access limitations did not limit or otherwise prevent an accurate assessment of critical area conditions. 3.2 Background Research The project site exists within the Middle Green River – Auburn drainage area of Water Resource Inventory Area (WRIA) 9 – Duwamish/Green River Basin. The main channel of the Green River (09- 001) is mapped along the western project site limits. The Green River has been assigned hydrologic unit code (HUC) 17110013 by the United States Geologic Survey. The United States Department of Agriculture (USDA), Natural Resources Conservation Service’s (NRCS’s) online Web Soil Survey maps mixed alluvial land (Ma) throughout the project site. The mixed alluvial land soil type consists of a variety of alluvial soils in areas that are too small and too closely associated to map separately (Snyder et al., 1973). In general, mixed alluvial soils comprise sands, gravelly sands, and silty clay loam and include land that is well to very poorly drained (Snyder et al., 1973). The mixed alluvial land soil type is not listed as a hydric (wetland) soil by the USDA’s online Soil Data Access (SDA) Hydric Soil List. A recent geotechnical evaluation of the project site by Bergquist Engineering Services, LLC (2020) determined that soils within the site generally comprise a shallow rooting layer overlying a light gray to light brown colored silty fine sand ranging in depth to seven feet below the soil surface. The origin of surficial soils was determined to be alluvial (overbank deposits from the Green River). No surface or groundwater was encountered on the site at the time of a September 2018 geotechnical evaluation; however, soil moisture was encountered in three test pits at depths beginning at 7 feet below the soil surface. The depth of soil moisture generally corresponded to the water surface elevation of the Green River at the time of the evaluation. In a subsequent February 9, 2020 geotechnical evaluation, groundwater was observed near the soil surface and surface water had accumulated in low areas during and after a period of sustained heavy rainfall. The project site contains a mapped 100 year floodplain in the western portion of the site along the bank of the Green River. Preliminary base flood elevation (BFE) determinations made by Encompass Engineering & Surveying reveal that the BFE’s within the project site increase from north to south ranging from 67.20 feet (NAVD 88) on Lot A to 67.40 feet (NAVD 88) on Lot C. The project site contains a moderate channel migration hazard area. King County identifies the hazard area as a “channel migration hazard areas, moderate”, which is defined as the portion of the channel migration zone, as shown on King County’s Channel Migration Zone map, that lies between the severe channel migration hazard area and the outer boundaries of the channel migration zone. Recent analysis completed by the City of Auburn has resulted in modification to the mapped channel migration hazard area, though the channel migration area remains limited to the western portion of the project site. A recent assessment completed by Bergquist Engineering Services Company, LLC (2020) determined that although the portion of the Green River valley that includes the project site has been subject to massive flood events, no evidence exists of historic or current channel migration along or within the site itself. Observations made by Bergquist Engineering Services Company, LLC during a February 9, 2020 flood event revealed that flooding within the site is limited to the extreme western portions of 94 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 4 April 10, 2020 (revised May 14, 2021) the site when river flows are above the Howard Hansen Dam maximum design flow of volume of 12,000 cubic feet per second (cfs) as measured at the Auburn gauge. The project site is located within a “Groundwater Protection Zone 2”. Groundwater protection areas are lands beneath which groundwater occurs that is a current or potential future source of drinking water for the City of Auburn. A 2017 critical area evaluation of the project site completed by Sewall Wetland Consulting, Inc. determined that wetlands do not exist within the project site and that the Green River exists along the western site limits. Vegetation within the site at the time of the 2017 evaluation was described as dense stands of Himalayan blackberry (Rubus armeniacus, FAC) with scattered upland trees. Soils encountered within the site were a dry, dark brown (10YR 3/3) to dark yellowish-brown (10YR 3/4) sandy loam. Based on a review of readily available aerial photographs dating back to 1936, conditions within the project site appear to be largely unchanged for several decades. The site has been vegetated with a mix of shrubs and scattered trees. Other than the Green River located along the western property line, ponded water, wetlands, soil saturation, and/or drainage features were not observable on historic aerial photographs showing the site. 3.3 Site Assessment 3.3.1 Wetland Determination Based on a review of site conditions, it was determined that wetlands do not exist within the project site. Vegetation within the site comprises dense Himalayan blackberry with scattered bigleaf maple (Acer macrophyllum, FACU), black cottonwood (Populus balsamifera, FAC), Douglas-fir (Pseudotsuga menziesii, FACU), and black locust (Robina pseudoacacia, FACU). Occasional red alder (Alnus rubra, FAC), red-osier dogwood (Cornus sericea, FACW), western swordfern (Polystichum munitum, FACU), salmonberry (R. spectabilis, FAC), Sitka willow (Salix sitchensis, FACW), and common snowberry (Symphoricarpos albus, FACU) exist along or near the bank of the Green River. Soils within the site were generally a very dark brown (10YR 2/2) silt loam overlying a dark brown (10YR 3/3) to dark yellowish brown (10YR 4/3) gravelly sandy loam. Field indicators of wetland hydrology were not observed within the site. Attachment 3 to this report is a wetland determination form corresponding to site observations. Attachment 4 to this report includes photographs showing representative vegetation, soil, and hydrologic vegetation conditions within the site at the time of the wetland determination. 3.3.2 Stream Determination The project site maintains approximately 317 feet of shoreline frontage along the east bank of the Green River at approximately river mile (RM) 31.25. The on-site riverbank comprises silty to clayey soils and measures approximately six to eight feet high with slopes ranging from less than ten percent on Lot B to nearly vertical in places on Lot A and Lot C. The OHWM of the Green River occurs at a distinct change within the project site where vegetation transitions quickly from a narrow band of scattered red-osier dogwood and Sitka willow to dense Himalayan blackberry with occasional red alder, sword fern, salmonberry, and common snowberry. The riverbank below the OHWM is largely unvegetated though occasional common ladyfern (Athyrium filix-femina, FAC), reed canarygrass (Phalaris arundinacea, FACW), and small fruited bulrush (Scirpus microcarpus, OBL) exist in small patches. The limits of the OHWM were flagged “OHWM 1” through “OHWM 9”. Attachment 5 to 95 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 5 April 10, 2020 (revised May 14, 2021) this report includes a map showing the delineated OHWM. Attachment 6 to this report includes photographs of the OHWM and a simple sketch of the shoreline cross-section. The Green River has been inventoried by the City of Auburn as a Type S Water (“Shoreline of the State”). The City of Auburn’s Shoreline Master Program (2009) establishes a 200 foot shoreline management zone (SMZ) along the OHWM of the Green River. The SMZ located within the project has been designated an “Urban Conservancy” shoreline environment. A 100 foot shoreline buffer is required from the OHWM within urban conservancy shoreline management zones. The shoreline buffer occupies the western and central portions of the project site. Per City of Auburn shoreline regulations, the shoreline buffer is to be protected, enhanced, and revegetated as applicable under the ACC 16.10.090 (Critical Areas: Buffer Areas and Setbacks). 4.0 PROPOSED PROJECT The proposed project includes the designation of small residential buildable areas on all three lots. The project has considered site limitations as well as overall compatibility of the project with adjacent land uses, construction practices, and project alternatives. To minimize environmental impacts, the project includes consolidated buildable areas that utilize minimum property line and easement setbacks as well as minimum width and length driveways. Each buildable area avoids the mapped 100 year floodplain, the mapped moderate channel migration area, and related buffers. Designation of buildable areas does require unavoidable shoreline buffer impacts on Lot B and Lot C. These impacts reduce the standard 100 foot wide shoreline buffer on both lots. Proposed buffer reductions range from a maximum of 5.5 feet on Lot B to a maximum of 10.5 feet on a Lot C. All proposed buffer reductions will occur within areas of existing degraded buffer. Table 2 summarizes proposed buffer widths for each lot. TABLE 2 – PROPOSED SHORELINE BUFFER REDUCTIONS LOT PROPOSED MINIMUM BUFFER WIDTH PERCENT BUFFER WIDTH REDUCTION Lot A 100 feet 0% Lot B 94.5 feet 5.5% Lot C 89.5 feet 10.5% This report section describes the proposed project in detail. Attachment 7 to this report includes a site plan showing the proposed project. 4.1 Project Purpose and Need The purpose of the proposed project is to provide a buildable area within each lot that allows for the minimum single-family residential use allowed by the underlying R-5 zoning designation. The project provides needed residential housing opportunity within the local area. 4.2 Project Site Limitations The project site comprises three legally established residential lots. Development opportunities within each lot are considerably constrained by the combination of relatively small lot size and the presence of various critical areas. The Green River exists along the western property line of each lot and the standard width shoreline buffer and 200 foot shoreline management zone encumber each lot. The site also includes and/or exists adjacent to several geologic and flood hazards. In addition, a sewer line and sewer related easement exists along the eastern property line of each lot. 96 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 6 April 10, 2020 (revised May 14, 2021) 4.3 Minimum Necessary Impact The proposed project strikes a balance between the landowner’s reasonable use of the site and the specific environmental protection objectives established by ACC 16.08 (Shoreline Management Administration and Permitting Procedures) and ACC 16.10 (Critical Areas). The proposed project results in consolidated buildable areas along 104th Place SE and the enhancement of degraded shoreline areas located throughout the balance of each lot. No change to the underlying zoning density or land subdivision is proposed. Future residential development within each lot will occur within the designated buildable areas. 4.4 Compatibility with Adjacent Land use Land use surrounding the project site is residential in nature and comprises a mix of single-family residences and undeveloped lots. Residential development within the local area extends back to the early 1900’s. Current development generally includes one or two story single-family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th Street, most residences are of a conventional on-site “stick-built” construction and have been constructed close to 104th Place SE. The proposed project is compatible with the adjacent residential use because the project is residential in nature and proposes buildable areas within each lot that are relatively small in size and located along 104th Place SE. 4.5 Conceptual Construction Process and Methods Although specific plans for the construction of single-family residences within each lot are not available at this time, it is anticipated that construction of residences within each lot will include the following processes and methods: Construction Access Construction access to each buildable area will be directly from 104th Place SE. No specialized to temporary access points or routes are proposed. Access will be established at the start of construction and will be maintained through the duration of construction. Clearing and Grading Vegetation within each buildable area will be removed and minimal grading will be necessary to level and prepare each building site for construction. Shallow excavations will be required for foundation construction and utility installations. Fill imported to the site will be limited, obtained from a commercial materials supplier, and will comprise only the minimum necessary to level each building site and to support foundations, concrete slabs, and driving surface. Vegetation removal within each building site will be limited to primarily Himalayan blackberry and a few scattered trees. No grading or filling is proposed within the Green River, associated flood hazard areas, or reduced buffer areas. Stormwater Management Temporary erosion and sediment control (TESC) measures will be installed prior to the start of construction and will be properly maintained during the entire construction period. TESC measures will conform to City of Auburn standards and may include, at a minimum, filter fabric (silt) fencing, temporary cover, and rock construction entrance best management practices (BMP’s). Permanent 97 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 7 April 10, 2020 (revised May 14, 2021) stormwater management for the completed project will conform to City of Auburn standards. Conceptual design for permanent stormwater management includes the collection of stormwater runoff from impervious surfaces and dispersion via a gravel lined trenches or similar BMP’s. Stormwater infiltration will occur between the developed portion of each lot and the Green River. Utility Installation Power, telephone, cable, sewer, and water connections to each lot will be from existing utilities located in 104th Place SE. Building Construction Proposed building construction is anticipated to include conventional framing construction methods. Foundation design and construction methods will depend on the results of future geotechnical analysis; however, it is anticipated that foundation design could include one or more of the following: conventional spread footings, driven pipe piles, and/or drilled augercast piles. Critical Area Protection and Enhancement During construction, shoreline buffer limits would be marked using hi-visibility plastic orange construction fencing. No construction staging or material stockpiling will occur within the designated shoreline buffer areas. Following construction, a permanent cedar split rail fence would be installed along the reduced shoreline buffer and the shoreline buffer will be enhanced per a City of Auburn approved mitigation plan. 4.6 Unique Benefits of Project Because the project includes three contiguous lots, the project presents a unique opportunity to enhance a substantial stretch of river shoreline area in a comprehensive and cohesive manner. In the absence of the project, shoreline enhancements would only be achievable only through a piecemeal approach on a per lot basis as each site is developed individually. 4.7 Alternatives Considered No alternative location exists within the lots that presents less environmental impact for the proposed development. The primary consideration addressed during project design was to maximize the distance of the proposed buildable areas from the Green River. This was achieved by utilizing site designs, which include minimum width and length driveways, and minimum width setbacks. It is not possible to locate buildable areas on Lot B and Lot C without encroaching the standard width shoreline buffer. 5.0 MITIGATION SEQUENCING This report section describes the specific mitigation sequencing the project has undertaken to avoid, minimize, restore, and compensate for shoreline buffer impacts. As a general overview, the proposed project has employed the following environmental protection and conservation measures: Limiting the amount, type, and location of development within the project site; The use of protective buffers from designated critical areas; The use of appropriate construction practices; 98 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 8 April 10, 2020 (revised May 14, 2021) The use of site-specific stormwater management practices during and after construction; and On-site shoreline buffer enhancements. 5.1 Avoidance and Minimization of Impacts The proposed project avoids in-water water work and the buildable areas within each lot have been located in the eastern portion of each lot to maximize the distance from the Green River. Permanent alteration within the shoreline buffer is minimized by limiting overall buildable area, maintaining the smallest setbacks from the existing sewer easement as possible, and utilizing minimum length driveways. During construction, it is anticipated that TESC measures will limit the off-site migration of sediment. Impervious surfacing will be limited within each lot and a conceptual permanent drainage control plan has been developed to manage stormwater generated by eventual building construction. Maintaining an enhanced buffer from the Green River further minimizes impacts by providing physical separation between the buildable areas and the Green River. 5.2 Restoration of Temporary Impacts The project does not propose temporary impacts that require restoration. All disturbed areas are within the designated buildable areas and will be permanently stabilized following construction. 5.3 Reduction and Elimination of Impacts Over Time It is anticipated that future building construction will utilize high quality/low maintenance materials that ensure sustainability over time. It is also anticipated that future maintenance activities for the residences will be limited in scope and will be consistent with standard building repair and/or maintenance practices. The native plants used in the buffer enhancement work have been selected for the specific sunlight and hydrologic conditions present within each planting area, which ensures the long-term success and sustainability of the enhancement work. 5.4 Compensatory Mitigation The proposed project includes buffer enhancement on each lot as compensatory mitigation. The proposed mitigation is detailed on the plan entitled “Shoreline Buffer Mitigation Plan: Proposed Goulet Single Family Residences”, dated April 10, 2020 (revised May 14, 2021). The mitigation will occur on-site and will comprise the enhancement of degraded shoreline buffer areas. The proposed mitigation will be completed as a single phase at the landowner’s expense and will completed prior to the issuance of the final certificate of occupancy any future residence construction. Specific mitigation goals, objectives, and performance standards are detailed on the mitigation plan. The overall goal and objective of the mitigation is to enhance stream buffer conditions within each lot and to provide for a “no net loss” in shoreline ecological functioning. This will be achieved by: 1) removing noxious weeds; 2) installing site appropriate enhancements; and 3) permanently protecting the enhanced buffer. Specific components of the mitigation include the following: Intensive noxious weed control. Habitat structure installation – logs with and without rootwads as well as snags. Dense native plantings – the effective plant spacing will be 9 feet on-center for trees and 4 feet on-center for shrubs. Application of dense mulch throughout all planting areas. Critical area fencing and signage. 99 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 9 April 10, 2020 (revised May 14, 2021) Two years of temporary irrigation. Five years of maintenance and monitoring. Permanent preservation using a long-term protection notice on title. The mitigation utilizes best management practices (BMP’s) in design to ensure the mitigation results in a diverse assemblage of native plants, high native plant coverage, a significant reduction in non- native plant species, and incorporates an appropriate monitoring program. It is expected that over time, the buffer enhancements will develop into a forested riparian floodplain condition typical of the western hemlock (Tsuga heterophylla) forest zone of Washington State. Based on the proposed planting plant species and installation densities, the distribution and abundance of native vegetation within the site will increase and/or will provide opportunities for structural habitat diversity, shade, and large woody debris (LWD) production that currently either does not exist or is otherwise limited within the project site. 5.5 Monitoring and Maintenance A monitoring and maintenance plan for the compensatory mitigation is included on the mitigation plan. This work includes specific inspections and oversight by a qualified professional during construction as well as a detailed five year maintenance and monitoring program. The maintenance and monitoring program is designed to effectively monitor the buffer enhancements and assess performance of the enhancements relative to the standards established for the project. Also included is specific language to ensure the buffer enhancement satisfies all performance standards. Should monitoring reveal that the performance standards for the respective year are not met, appropriate contingency plans will be developed by the landowner to address any deficiency. A detailed contingency planning process is described on the mitigation plan. A mitigation bond or similar assurance device will be provided by the landowner for the proposed mitigation and will remain in place through the duration of monitoring. 6.0 SHORELINE FUNCTIONAL ASSESSMENT The City of Auburn’s SMP establishes a “no net loss’” standard for development within urban conservancy shoreline areas. This standard ensures that new shoreline development or uses are located and designed to avoid loss or degradation of shoreline ecological functions. WAC 173-26- 020(13) describes “ecological functions” as “…the work performed or role played by the physical, chemical, and biological processes that contribute to the maintenance of the aquatic and terrestrial environments that constitutes [a] shoreline’s natural ecosystem…”. River, stream, and floodplain shoreline ecological functions are grouped into four categories: hydrologic, shoreline vegetation, hyporheic, and habitat (WAC 173-26-201[3][d][i][C]). This report section describes existing shoreline functions, project impacts, and how a “no net loss” of shoreline ecological function is maintained. Functional analysis is qualitative in nature, utilizes the best available science, and applies an ecosystem-based approach that provides analysis at a site- specific scale. Given the size and landscape position of the project site, many of the shoreline functions provided by the site are determined by processes and land use conditions that occur on a much larger ecological scale than the site. Analysis in this report does not address the influence of broader policies or land use actions that may affect functioning on a broader watershed scale. 100 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 10 April 10, 2020 (revised May 14, 2021) 6.1 Existing Shoreline Conditions Existing shoreline conditions within the project site reflect a complex geologic history, proximity to the Green River, and historic land use. Geologic processes affecting the project site include repeated glaciations as well as ongoing alluvial deposition resulting from the erosion of volcanic lahar flows by the Green River (Bergquist Engineering Services Company, LLC 2020). Soils within the site comprise mainly loose silty fine sand flood deposits. Shallow groundwater conditions within the site are influenced by the water surface elevation of the Green River. The Green River has a history of severe flooding; however, over the last century levees and revetments (principally rock-armored banks) have been constructed along the Green River upstream and across from the project site. The Matson revetment and Barnet levee are located across from the site, the Porter Bridge levee is located downstream of the site, and the Fenster Levee is located upstream of the site. Beginning in 1906, the White River was diverted from the Green River through a series of natural and man-made events and since 1961 the flow of the Green River has been controlled by the Howard Hansen Dam. The combination of a confined channel and controlled river flows has, in very general terms, narrowed and reduced channel migration within the segment of Green River located near the project site (King County 1993). Although the portion of the Green River valley that includes the project site has been subject to massive flood events, no evidence exists of historic or current channel migration along or within the site itself. Recent observations reveal that flooding is limited to the extreme western portions of the site when river flows are above the Howard Hansen Dam maximum design flow of volume of 12,000 cfs as measured at the Auburn gauge. The segment of the Green River located adjacent to the project site does not include significant habitat features such as log jams, beaver dams, aquatic vegetation, large rocks or boulders, side channels, and undercut banks. Instream physical habitat is simple and comprises uniform run habitat with glide habitat present upstream and downstream of the site (R2 Resource Consultants, Inc. 2014). The river segment directly adjacent to the site includes limited natural cover such as shade or submerged or overhanging large wood debris (LWD). The project site is located within the western hemlock forest zone as described by Franklin and Dyrness (1973). Mid- to late-successional conditions typical of this forest type include a dominance by conifers such as Douglas-fir, western redcedar (Thuja plicata), and western hemlock, with the species specific present depending upon the site hydrologic and stand age characteristics. Persistent understory species would typically include vine maple (Acer circinatum), salal (Gaultheria shallon), Oregon grape (Mahonia nervosa), devil’s club (Oplopanax horridus), western swordfern (Polystichum munitum), salmonberry (Rubus spectabilis), and red huckleberry (Vaccinium parvifolium). Historic vegetation within the site likely comprised a mixed hardwood-conifer riverine forest consisting of western redcedar and western hemlock mixed with younger stands of red alder, black cottonwood, and willow within frequently disturbed landscapes such as floodplain features (R2 Resource Consultants, Inc. 2014; Knutson and Naef, 1997). Prior to 1936, the project site was cleared of native vegetation and used as farmland. Around 1957, intensive agricultural use had ended. Since that time, the site has remained vacant and vegetation has been allowed to grow in a relatively uncontrolled or unmaintained manner. Overall, plant species richness within the site is low, tree canopy coverage is low, and no significant habitat features or 101 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 11 April 10, 2020 (revised May 14, 2021) vegetation structure is present. Currently, vegetation within the site is dominated by Himalayan blackberry, a Class C noxious weed, as well as a few scattered native trees and shrubs. A recent tree inventory completed by Layton Tree Consulting, LLC identified 35 trees within the site, of which 23 were considered “significant” trees per ACC 18.50.045. Tree species that are present include red alder, bigleaf maple, black cottonwood, and Douglas-fir, though non-native black locust and one cherry plum (Prunus cerasifera) also exist as a significant component. Overall, the condition of trees was rated as mostly “fair” (i.e., minor to moderate structural defects, asymmetric or unbalanced crown or canopies, average or normal vigor, foliage color, and foliage density), with most trees also rated as “fair” for retention suitability (i.e., average health condition and/or have structural defects that can be mitigated with treatment). Runoff from the project site currently infiltrates within the site or sheet flows to the Green River. The site is not known to contain or present a significant source for water quality contaminants. The segment of the Green River located adjacent to the site is not 303d listed; however, the Green River is 303d listed for dissolved oxygen approximately two miles downstream of the site and approximately 1.5 miles upstream of the site (Ecology 2020). The Green River currently has Environmental Protection Agency (EPA) approved total maximum daily load (TMDL) water quality improvement projects for temperature, dissolved oxygen, and ammonia-n (Washington State Department of Ecology 2011; United States Department of Environmental Protection Agency, 1992). 6.2 Impact Assessment Direct impacts related to the proposed project include the permanent loss of shoreline vegetation due to the development of buildable areas within the eastern portions of each site. Vegetation to be removed includes dense Himalayan blackberry and 14 trees, though four of the trees comprise a single multi-stem clump of non-native black locust. Trees to be removed from the project site include three bigleaf maples (16”, 30”, and 11” DBH), four black cottonwood (36”, 30”, 41” and 34” DBH), two Douglas-fir (31” and 36” DBH), and five black locust (13”, 13”, 11”, 10”, and 9” DBH). Because of the proximity of the proposed development, it is not feasible to retain the trees. The largest trees range from 98 to 132 feet in height and exist approximately 125 to 140 feet from the OHWM of the Green River. The trees exist outside of flood hazard and channel migration zones as well as the 50 foot wide channel migration zone buffer. The trees provide limited natural cover or contributions to the physical habitat conditions within or along the Green River due to tree density, distribution, and species composition as well as the proximity of the trees to the river combined with the highly managed nature the river flows. Five of the 14 trees to be removed are black locust, which is a designated “weed of concern” in King County. In addition to the installation of 272 trees as general shoreline enhancements, the loss of trees within the project site will be offset by installing 21 logs and three snags within the retained buffer shoreline buffer. Logs will measure a minimum of 15 feet long by a 12 inches in diameter and will include a mix of logs with and without rootwads. Snags will be derived from native conifer species measuring 12 inches minimum in diameter and a minimum of 15 feet tall. No work is proposed below the OHWM of the Green River and the project maintains existing floodplain conditions. Stormwater discharge from the project site will be controlled per City of Auburn standards and will be allowed to disperse and infiltrate between the buildable area of each lot and the Green River. Indirect impacts resulting from the proposed project include temporary short-term noise impacts within the shoreline consistent with standard residential construction practices. Construction noise 102 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 12 April 10, 2020 (revised May 14, 2021) may temporarily flush and/or displace wildlife, if present, within the buildable area and local vicinity. Construction noise is expected to be limited and of relatively short duration. The proposed project is a stand-alone project. It does not provide additional utility or road connections and there are no known projects that are dependent upon and/or are related to the project. Proposed use of the project site for residential use is not unique to the local area and is consistent with the uses allowed by City of Auburn’s codes and regulations. Although the proposed project results in anthropogenic improvements within shoreline areas, the proposed project does not present a unique or specialized use that does not already exist within the local area. 6.3 Shoreline Function “No Net Loss” 6.3.1 Hydrologic Functions In rivers and associated floodplains, shoreline hydrologic functions are important to transporting water and sediment across the natural range of flow variability as well as providing opportunities to attenuate flow energy, develop channel complexity (pools, riffles, gravel bars), provide nutrient flux, and recruit LWD or other organic materials. The proposed project results in a “no net loss” of hydrologic functions by avoiding work in flood hazards and related flood hazard buffers. This preserves the potential for river flow variability that currently exists within each lot. Hydrologic functions related to general channel formation processes would not be affected by the project and cannot be reasonably enhanced as part of the project due to the highly managed nature of the segment of the Green River located adjacent to the project site. 6.3.2 Vegetation Functions In rivers and associated floodplains, shoreline vegetation functions are important to maintaining temperature, removing excessive nutrients and toxic compounds, attenuating wave energy, sediment removal and stabilization, and providing LWD and other organic matter. The proposed project provides for a “no net loss” in vegetation functioning by providing buffer enhancements that include the control of non-native plants as well as the installation of dense native trees and shrubs. It is expected that over time, the buffer enhancements will develop into a mixed hardwood-conifer riparian forest typical of the western hemlock forest zone of Washington State. Although 14 trees will be removed from the project site, the trees are located approximately 125 to 140 feet from the OHWM of the Green River. The proposed species, densities, and distribution of native plantings will provide opportunities for LWD and organic matter production that currently do not exist or is otherwise extremely limited within the site. 6.3.3 Hyporheic Functions In rivers and associated floodplains, hyporheic functions are important to removing excessive nutrients and toxic compounds, water storage, vegetation support, sediment storage, and base flow maintenance. The proposed project provides for a “no net loss” of shoreline hyporheic functions by limiting impervious surfacing associated with the project, maximizing the distance of impervious surfacing from the Green River, and by infiltrating stormwater generated within each building site in the shoreline area that exists between the building site and the Green River. 103 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 13 April 10, 2020 (revised May 14, 2021) 6.3.4 Habitat Functions In rivers and associated floodplains, shoreline habitat functions provide the space or conditions for bird, mammal, amphibian, and fish reproduction, resting, hiding, and migration. In addition, habitat functions can provide migration corridors, food chain support, and habitat corridor linkages as part of the broader landscape. The proposed project provides for a “no net loss” of shoreline habitat functions by providing buffer enhancements that include control of non-native species as well as the installation of habitat structures and dense native plantings in the shoreline area. The cumulative effects of the proposed mitigation are enhancement of a large contiguous segment of river shoreline area that will provide habitat opportunities for native fauna. 7.0 CONCLUSION Wetland and stream conditions within a proposed three lot residential project located at approximately 32XXX 104th Place SE are consistent with the findings of a 2017 critical area designation report prepared by Sewall Wetland Consulting, Inc. Wetlands do not exist within the project site and the Green River, a Type S water, exists along the western site limits. A 100 foot shoreline buffer is required from the OHWM of the Green River. This buffer encumbers much of project site. On-site buffer is degraded and dominated by Himalayan blackberry, a Class C noxious weed. The proposed project includes the development of consolidated buildable areas within each lot. To minimize environmental impacts, the project includes compact building footprints, which utilize minimum property line and easement setbacks as well as minimum width and length driveways. The proposed project completely avoids a mapped 100 year floodplain, a moderate channel migration area, and related buffers. Buildable areas on Lot B and Lot C require unavoidable shoreline buffer impacts, which effectively reduces the standard 100 foot wide shoreline buffer by a range of 5.5 to 10.5 feet. The proposed project has incorporated mitigation sequencing to avoid, minimize, and compensate for shoreline buffer impacts. The project results in a “no net loss” of shoreline ecological functioning by incorporating thoughtful consideration of the location of each buildable area and by proposing the enhancement of degraded buffer on each lot. Although all shoreline ecological functioning is maintained by the project, vegetation and habitat are shoreline functions that are significantly improved by the project. It is expected that over time that the distribution and abundance of native vegetation within the site will increase and the proposed buffer enhancements will develop into a mixed hardwood-conifer riverine forest typical of the western hemlock of Washington State. The future distribution and abundance of native vegetation within the site will provide opportunities for structural habitat diversity, shade, and LWD production that currently either does not exist or is otherwise limited within the project site. 8.0 REPORT LIMITATIONS Within the limitations of scope, schedule, and budget, the critical area consulting services summarized in this report conform to the generally accepted standard of care in effect at the time the work was conducted. The findings and conclusions present in this report represent a best professional opinion based on the site design available by the project proponent, information obtained during the course of study, and current best available science. No other warranty, express or implied, is made. This report describes site conditions per the City of Auburn critical area and shoreline regulations in effect at the time of report preparation. The study of wetlands, streams, and shorelines is an inexact science. All findings 104 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 14 April 10, 2020 (revised May 14, 2021) and conclusions presented in this report should be considered preliminary until reviewed and confirmed by the City of Auburn. 9.0 REFERENCES Auburn City Code 16.08 (Shoreline Management Administraive and Permitting Procedures) available at the following website: https://auburn.municipal.codes/ACC/16.08. Accessed February 21, 2020. Auburn City Code 16.10 (Critical Areas) available at the following website: https://auburn.municipal.codes/ACC/16.10. Accessed February 21, 2020. Auburn, City of. 2009. Auburn Shoreline Master Program. Approved by the Washington State Department of Ecology (as submitted) May 20, 2009. Adopted by the City of Auburn April, 20, 2009. Obtained from the following website: https://www.auburnwa.gov/UserFiles/Servers/Server_11470554/File/City%20Hall/Community%20Deve lopment/Zoning%20and%20Land%20Use/Shoreline%20Master%20Program/Shoreline%20Master%20 Program%202009.pdf. Accessed February 21, 2020. Bergquist Engineering Services Company, LLC. Critical Areas Report: Proposed Single Family Residences, Parcels 3341000090, 3341000095, 3441000010, Auburn Washington. Prepared for Launce P. Goulet. October 8, 2020 (marked as Report 1, Revision2). Environmental Laboratory. (1987). Corps of Engineers Wetlands Delineation Manual. Vicksburg, MS: Technical Report Y-87-1. US Army Engineer Waterway Experiment Station. Franklin J. F & C.T. Dyrness. 1973. Natural Vegetation of Oregon and Washington. Originally published by the United States Forest Service but reprinted by the Oregon State University Press in 1988. 452 p. King County. 2020. iMap online GIS available at the following website: https://gismaps.kingcounty.gov/iMap/. Accessed February 21, 2020. Knutson, K. L., and V. L. Naef. 1997. Management Recommendations for Washington’s Priority Habitats: Riparian. Washington Department of Fish and Wildlife. 181 p. Lawrence, Dustin. 2019. Personal communication with Mariah Gill regarding “Comments – Launce Gouilet Project”. Email dated May 23, 2019 9:47AM. R2 Resource Consultants, Inc. 2014. Lower Green/Duwamish River Habitat Assessment: Final Report. Prepared for WRIA 9 Implementation Technical Committee. April 2014. Sewall Wetland Consulting, Inc. 2017. Letter to Lonnie Goulet regarding “Critical Area Designation Report – Parcels #3341000009, 3341000095, 334100010; City of Auburn, Washington; SWC Job #17-17-194”. October 2, 2017. Snyder, D. Gale, P, and Pringle, R. 1973. Soil Survey of King County Area, Washington. United States Department of Agriculture, Soil Conservation Services. Issued November 1973. United States Army Corps of Engineers. (2010). Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0.). Vicksburg, MS: US Army Engineer Research and Development Center: ed. J.S. Wakeley, R.W. Lichvar, and C.V. Noble. ERDC/EL TR-10-3. 105 of 721 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 15 April 10, 2020 (revised May 14, 2021) United States Environmental Protection Agency Region 10. 1992. Memorandum to the attention on WD- 139 regarding “Recommendation for TMDL Approval – Duwamish Waterway and River – South of line bearing 254 True from the NW corner of Berth 3, Terminal 37 to River Mile (RM) 11.0 – Waterbody Segment No. WA-09-1010”. December 29, 1992. Washington State Department of Ecology Publication No. 92-10-204. United States Department of Agriculture, National Resources Conservation Service. “Web Soil Survey” available at the following website: websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx. Accessed October 4, 2019. United States Department of Agriculture, National Resources Conservation Service. “Soil Data Access (SDA) Hydric Soil List” available at the following website: www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcseprd1316620.html. Accessed October 4, 2019. Washington Administrative Code (WAC) 222-16-031 (Interim Water Typing System) available at the following website: https://apps.leg.wa.gov/wac/default.aspx?cite=222-16-031. Accessed October 4, 2019. Washington Administrative Code (WAC) 173-26 (State Master Program Approval/Amendment Procedures and Master Program Guidelines available at the following website: https://apps.leg.wa.gov/wac/default.aspx?cite=173-26. Accessed February 21, 2020. Washington State Department of Ecology. 2020. Washington State Water Quality Atlas online mapper avialble at the following website: https://fortress.wa.gov/ecy/waterqualityatlas/map.aspx. Accessed February 21, 2020. Washngton State Department of Ecology. 2016. Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State. October 2016 – Final Review. Publication No. 16- 06-029. Washington State Department of Ecology. 2011. Green River Temperature Total Maximum Daily Load: Water Quality Improvement Report. June 2011. Publication No. 11-10-046. 106 of 721 Attachment 1 Proposed Goulet Single Family Residences Vicinity Map Evergreen Aquatic Wetland Delineation Mitigation Design Compliance Monitoring Resource Consultants, LLC Gree n R i v e r Road S E 104th Ave SELea Hill Rd SE8th ST NE 4th ST NE East Main ST West Mai n S T 14th ST NE 22nd ST NE Auburn Way NE ST NEM ST NERivervi e w DR NE I ST NED ST NEC ST NWA ST NWB ST NW15th ST NE 15th ST NW 12th ST NE H a r v e y R d N E West Valley Hwy167 18Auburn Way N2nd ST NW M ST NE4th ST NE K ST NEJ ST NER ST SET ST SEV ST SEL ST SE4th ST SE Cross ST SE 112th PL SE105th PL SE PROJECT SITE PROJECT SITE THE PROJECT SITE CAN BE ACCESSED FROM SR 167 BY TAKING THE 15TH STREET NW EXIT AND HEADING EAST FOR 1.1 MILES. 15TH STREET NW TURNS INTO HARVEY ROAD NE AT ITS INTERSECTION WITH AUBURN WAY N. CONTINUE SOUTHEAST ON HARVEY ROAD NE FOR APPROXIMATELY 0.5 MILES, THEN TURN LEFT ONTO 8TH STREET NE. TRAVEL EAST ON 8TH STREET NE FOR APPROXIMATELY 0.5 MILES AND THEN TURN RIGHT ONTO 104TH PLACE SE. THE PROJECT SITE IS LOCATED ON THE WEST SIDE OF 104TH PLACE SE APPROXIMATELY 450 FEET SOUTH OF 8TH STREET NE. PROJECT SITE 04/10/2020 rev. 05/14/2021107 of 721 Attachment 2 Proposed Goulet Single Family Residences Aerial Photograph Showing Project Site Evergreen Aquatic Wetland Delineation Mitigation Design Compliance Monitoring Resource Consultants, LLC Green River LOT A TPN 334100-0090 (14,628 SF - 0.33 ACRES ) LOT B TPN 334100-0095 (13,601 SF - 0.31 ACRES) LOT C TPN 334100-0100 (13,021 SF - 0.30 ACRES) 04/10/2020 rev. 05/14/2021108 of 721 WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys, and Coast Region VEGETATION Tree Stratum (Plot Size: 10 meter) Absolute % Cover Dominant Species? Indicator Status Dominance Test Worksheet: 1. Alnus rubra 35 YES FAC Number of Dominant Species That Are OBL, FACW, or FAC: 3 (A) 2. Acer macrophyllum 15 YES FACU 3. Populus balsamifera 5 NO FAC Total Number of Dominant Species Across All Strata: 4 (B) 4. 55 = Total Cover Percent of Dominant Species That Are OBL, FACW, or FAC: 75 (A/B) Sapling/Shrub Stratum (Plot Size: 5 meter) 1. Prevalence Index worksheet: 2. Total % Cover of: Multiply by: 3. OBL species x1 = 4. FACW species x2 = 5. FAC species x3 = n/a = Total Cover FACU species x4 = Herb Stratum (Plot Size: 1 meter) UPL species x5 = 1. Column Totals: (A) (B) 2. Prevalence Index = 3. Hydrophytic Vegetation Indicators: 4. YES Dominance Test is >50% 5. Prevalence Index is <3.01 6. Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) 7. 8. Wetland Non-Vascular Plants1 9. Problematic Hydrophytic Vegetation1 (Explain) 10. 1 Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic. 11. n/a = Total Cover Woody Vine Stratum (Plot Size: 1 meter) Hydrophytic Vegetation Present? Yes No 1. Rubus armeniacus 100 YES FAC 2. 100 = Total Cover % Bare Ground in Herb Stratum – n/a Remarks: Plant species scientific names and wetland indicator statuses are per USDA PLANTS online database available on 10/03/2019 at: http://plants.usda.gov. Project Site: 32XXX 104th Place SE City/County: Auburn Sampling Date: 10/04/2019 Applicant/Owner: Goulet State: WA Sampling Point: DP 1 Investigator(s): Peter P. Super – Professional Wetland Scientist Section, Township, Range: NW S17, T 21 N, R 5 E Landform (hillslope, terrace, etc.): floodplain terrace Local relief (concave, convex, none): none Slope (%): flat Subregion (LRR): A Lat: 47.31423 Long: -122.20452 Datum: NAD 88 Soil Map Unit Name: Mixed alluvial land (Ma) NWI classification: None Are climatic / hydrologic conditions on the site typical for this time of year? Yes No (If no, explain in Remarks.) Are Vegetation , Soil , Or Hydrology , significantly disturbed? Are “Normal Circumstances” present? Yes No Are Vegetation , Soil , Or Hydrology , naturally problematic? (If needed, explain any answers in Remarks.) SUMMARY OF FINDINGS Hydrophytic Vegetation Present? Yes No Is the Sampling Area within a Wetland? Hydric Soil Present? Yes No Wetland Hydrology Present? Yes No Remarks: ATTACHMENT 3 NO 109 of 721 SOIL DP 1 Profile Description: Depth (inches) Matrix Redox Features Color (moist) % Color (Moist) % Type1 Loc2 Texture Remarks 0 to 2 10YR 2/2 1000 silt loam 2 to 12 10YR 3/3 100 silt loam 12 to 18+ 10YR 4/3 100 gravelly sandy loam 1Type: C= Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains. 2Location: PL=Pore Lining, M=Matrix Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3: Histosol (A1) Sandy Redox (S5) 2 cm Muck (A10) Histic Epipedon (A2) Stripped Matrix (S6) Red Parent Material (TF2) Black Histic (A3) Loamy Mucky Mineral (F1) (except MLRA 1) Other (Explain in Remarks) Hydrogen Sulfide (A4) Loamy Gleyed Matrix (F2) Depleted Below Dark Surface (A11) Depleted Matrix (F3) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic. Thick Dark Surface (A12) Redox Dark Surface (F6) Sandy Mucky Mineral (S1) Depleted Dark Surface (F7) Sandy Gleyed Matrix (S4) Redox Depressions (F8) Restrictive Layer (if present): None Present Hydric Soils Present? Yes No Type: Depth (Inches): Remarks: Soil textures stated are apparent field textures. Soil colors are for moist soil per Munsell Soil Color Charts (GretagMacbeth 2001 with updated color charts). HYDROLOGY Wetland Hydrology Indicators: Primary Indicators (minimum of one required; check all that apply) Secondary Indicators (2 or more required) Surface Water (A1) Water-Stained Leaves (B9) Water-Stained Leaves (B9) High Water Table (A2) (except MLRA 1, 2, 4A, and 4B) (MLRA 1, 2, 4A, and 4B) Saturation (A3) Salt Crust (B11) Drainage Patterns (B10) Water Marks (B1) Aquatic Invertebrates (B13) Dry-Season Water Table (C2) Sediment Deposits (B2) Hydrogen Sulfide Odor (C1) Saturation Visible on Aerial Imagery (C9) Drift Deposits (B3) Oxidized Rhizospheres along Living Roots (C3) Geomorphic Position (D2) Algal Mat or Crust (B4) Presence of Reduced Iron (C4) Shallow Aquitard (D3) Iron Deposits (B5) Recent Iron Reduction in Tilled Soils (C6) FAC-Neutral Test (D5) Surface Soil Cracks (B6) Stunted or Stresses Plants (D1) (LRR A) Raised Ant Mounds (D6) (LRR A) Inundation Visible on Aerial Imagery (B7) Other (Explain in Remarks) Frost-Heave Hummocks (D7) Sparsely Vegetated Concave Surface (B8) Field Observations: Surface Water Present? Yes No Depth (inches): n/a Wetland Hydrology Present? Yes No Water Table Present? Yes No Depth (inches): n/a Saturation Present? (includes capillary fringe) Yes No Depth (inches): n/a Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: Project Site: 32XXX 104th Place SE – Auburn, Washington 110 of 721 Attachment 4 Proposed Goulet Single Family Residences Photographs of Vegetation, Soils, and Hydrology Conditions at Wetland Determination Point Evergreen Aquatic Wetland Delineation Mitigation Design Compliance Monitoring Resource Consultants, LLC Representative Soil and Hydrologic Conditions at Wetland Determination Point Located in the Center of the Project Site Date of Photograph = 10/04/2019 Representative Vegetation at Wetland Determination Point Located in the Center of the Project Site Date of Photograph = 10/04/2019 04/10/2020 rev. 05/14/2021111 of 721 OHWM9 OHWM1 OHWM2 OHWM3 OHWM4 OHWM5 OHWM6 OHWM7 OHWM8 CHANNEL MIGRATION ZONE 50' CHANNEL MIGRATION ZONE BUFFER 100 YEAR FLOODPLAIN (HATCHED AREA) ORDINARY HIGH WATER MARK FLAGGED 10/04/2019 GREEN RIVER (TYPE S WATER) URBAN CONSERVANCY SHORELINE DESIGNATION TOE OF STEEP SLOPE TOP OF RIVER BANK BASE FLOOD ELEVATION = 67.30' BASE FLOOD ELEVATION = 67.20' 15' SEWER SETBACK (HATCHED AREA) BASE FLOOD ELEVATION = 67.40' Attachment 5 Proposed Goulet Single Family Residences Existing Conditions Map Evergreen Aquatic Wetland Delineation Mitigation Design Compliance Monitoring Resource Consultants, LLC 0 20 40 N Horizontal Datum: NAD 83/91 Vertical Datum: NAVD 88 Approximate location of wetland determination point DP 1 104th P lace SE 04/10/2020 rev. 05/14/2021112 of 721 Attachment 6 Proposed Goulet Single Family Residences Simple Sketch of OHWM Cross Section Evergreen Aquatic Wetland Delineation Mitigation Design Compliance Monitoring Resource Consultants, LLC OHWM Top of bank Unvegetated river bottom (silts and clay with occasional cobble) water surface on 10/04/19 at 570 cfs water surface on 12/20/19 at 2,440 cfs Distinct grade break at top of bank Date of Photograph = 10/04/2019 River discharge = 579 cfs Date of Photograph = 12/20/2019 River discharge = 2,440 cfs 100 Year floodplain and channel migration limits willow and redosier dogwood along OHWM reed canarygrass and small fruited bulrush present in flatter areas below the OHWM. Dense Himalayan blackberry with occasional red alder, salmonberry, and snowberry, immediately above OHWM Dense Himalayan blackberry 04/10/2020 rev. 05/14/2021113 of 721 PROPOSED REDUCED SHORELINE BUFFER (WIDTH VARIES) PROPOSED SHORELINE BUFFER REDUCTION (HATCHED AREA) Attachment 7 Proposed Goulet Single Family Residences Site Plan Evergreen Aquatic Wetland Delineation Mitigation Design Compliance Monitoring Resource Consultants, LLC 0 20 40 N Horizontal Datum: NAD 83/91 Vertical Datum: NAVD 88 Buffer Reduction Legend Proposed buffer reduction 104th P lace SE 04/10/2020 rev. 05/14/2021114 of 721 Wetland Delineation Mitigation Design Mitigation Monitoring PO BOX 1721 ISSAQUAH, WASHINGTON 98027 TEL - (425) 677-7166 WWW.EVERGREENARC.COM Resource Consultants, LLC Evergreen Aquatic PROJECT NO: 19046 DATE: 04/10/2020 DESCRIPTIONDATENO SHEET NUMBER: 1/5 SHEET TITLE: COVERSHEET VICINITY MAP: PROJECT SITE LEGAL DESCRIPTIONS: LOT A - TAX PARCEL NUMBER 334100-0090 THAT PORTION OF LOT 20, C.D. HILLMAN'S GREEN RIVER ADDITION, DIVISION No. 1, ACCORDING TO THE PLAT RECORDED IN VOLUME 17 OF PLATS, PAGE 67, IN KING COUNTY, WASHINGTON, AND UNPLATTED PORTION OF GOVERNMENT LOT 2, IN SECTION 17, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, DESCRIBED AS A WHOLE AS FOLLOWS: BEGINNING AT A POINT ON THE EASTERLY LINE OF SAID LOT 20, DISTANT THEREON, SOUTH 17°00' EAST 9.002 FEET FROM THE NORTHEASTERLY CORNER OF SAID LOT 20; THENCE SOUTH 17°00' EAST ALONG THE NORTHEASTERLY LINE OF SAID LOT 20, A DISTANCE OF 60.00 FEET; THENCE SOUTH 73° 00' WEST 125.00 FEET, MORE OR LESS TO THE EASTERLY BANK OF THE GREEN RIVER; THENCE NORTHERLY ALONG SAID BANK TO A POINT WHICH BEARS NORTH 89°41'07" WEST FROM THE POINT OF BEGINNING; THENCE SOUTH 89°41'07" EAST 155.00 FEET, MORE OR LESS TO THE POINT OF BEGINNING. LOT B - TAX PARCEL NUMBER 334100-0095 THOSE PORTIONS OF LOTS 20 AND 21, C.D. HILLMAN'S GREEN RIVER ADDITION, DIVISION No. 1, ACCORDING TO THE PLAT RECORDED IN VOLUME 17 OF PLATS, PAGE 67, IN KING COUNTY, WASHINGTON, AND UNPLATTED PORTION OF GOVERNMENT LOT 2, IN SECTION 17, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, DESCRIBED AS A WHOLE AS FOLLOWS: BEGINNING AT A POINT ON THE EASTERLY LINE OF SAID LOT 20, DISTANT THEREON, SOUTH 17°00' EAST 69.002 FEET FROM THE NORTHEASTERLY CORNER OF SAID LOT 20; THENCE SOUTH 17°00' EAST ALONG THE NORTHEASTERLY LINE OF SAID LOT 20, A DISTANCE OF 28.656 FEET TO THE NORTHEASTERLY CORNER OF LOT 21; THENCE SOUTH 31°03' EAST ALONG THE NORTHEASTERLY LINE OF SAID LOT 21, A DISTANCE OF 40.00 FEET; THENCE SOUTH 58°57' WEST 135.00 FEET, MORE OR LESS TO THE EASTERLY BANK OF THE GREEN RIVER; THENCE NORTHERLY ALONG SAID BANK TO A POINT WHICH BEARS SOUTH 73°00' WEST FROM THE POINT OF BEGINNING; THENCE NORTH 73°00' EAST 125.00 FEET, MORE OR LESS TO THE POINT OF BEGINNING. LOT C - - TAX PARCEL NUMBER 334100-0100 THOSE PORTIONS OF LOTS 21 AND 22, C.D. HILLMAN'S GREEN RIVER ADDITION, DIVISION No. 1, ACCORDING TO THE PLAT RECORDED IN VOLUME 17 OF PLATS, PAGE 67, IN KING COUNTY, WASHINGTON, AND UNPLATTED PORTION OF GOVERNMENT LOT 2, IN SECTION 17, TOWNSHIP 21 NORTH, RANGE 5 EAST, W.M., IN KING COUNTY, WASHINGTON, DESCRIBED AS A WHOLE AS FOLLOWS: BEGINNING AT A POINT ON THE EASTERLY LINE OF SAID LOT 20, DISTANT THEREON, SOUTH 17°00' EAST 97.658 FEET FROM THE NORTHEASTERLY CORNER OF SAID LOT 20 OF C.D. HILLMAN'S GREEN RIVER ADDITION; THENCE SOUTH 31°03' EAST ALONG THE NORTHEASTERLY LINES OF SAID LOT 21 AND 22, A DISTANCE OF 90.00 FEET; THENCE SOUTH 58°57' WEST 135.00 FEET, MORE OR LESS TO THE EASTERLY BANK OF THE GREEN RIVER: THENCE NORTHERLY ALONG SAID BANK TO A POINT WHICH BEARS SOUTH 58°57' WEST FROM THE TRUE POINT OF BEGINNING; THENCE NORTH 58°57' EAST 135.00 FEET TO THE TRUE POINT OF BEGINNING. PROJECT: SHORELINE BUFFER MITIGATION PLAN PROPOSED GOULET SINGLE FAMILY RESIDENCES KING COUNTY TAX PARCEL #334100-0090 (LOT A) #334100-0095 (LOT B) #334100-0100 (LOT C) PREPARED FOR: LAUNCE P. GOULET & BRUCE GOULET 3226 S 198TH STREET SEATAC, WASHINGTON 98188 RECORD DRAWING CERTIFICATION THESE DRAWINGS CONFORM TO THE CONTRACTOR'S CONSTRUCTION RECORDS. BY DATE TITLE/POSITION CONFIRMED BY CITY DATE PROJECT REF: THESE PLANS ARE APPROVED FOR CONFORMANCE WITH THE CITY OF AUBURN'S CRITICAL AREA REQUIREMENTS. APPROVED BY: DATE APPROVED: SITE ADDRESS: 32XXX 104TH PLACE SE AUBURN, WASHINGTON 98092 LATITUDE: 47.31444 LONGITUDE: -122.20469 SECTION/TOWNSHIP/RANGE: NW 17-21-5 KING COUNTY TAX PARCEL 334100-0090, 334100-0095, 334100-0100 Gree n R i v e r Road S E 104th Ave SELea Hill Rd SE8th ST NE 4th ST NE East Main ST West Mai n S T 14th ST NE 22nd ST NE Auburn Way NE ST NEM ST NERivervi e w DR NE I ST NED ST NEC ST NWA ST NWB ST NW15th ST NE 15th ST NW 12th ST NE H a r v e y R d N E West Valley Hwy167 18Auburn Way N2nd ST NW M ST NE4th ST NE K ST NEJ ST NER ST SET ST SEV ST SEL ST SE4th ST SE Cros s ST SE 112th PL SE105th PL SE PROJECT SITE PROJECT SITE THE UNDERGROUND ROUTING AND CONDITION OF BURIED UTILITIES HAS NOT BEEN VERIFIED OR CONFIRMED. FIELD LOCATE, VERIFY DEPTH OF, AND ADEQUATELY PROTECT ALL UTILITIES PRIOR TO THE START OF WORK. Know what's below. before you dig.Call R GOALS, SCHEDULE, & PERFORMANCE STANDARDS: GOAL/OBJECTIVE ENHANCE BUFFERS BY INSTALLING DENSE NATIVE PLANTINGS. MEASUREMENT OF SUCCESS IS PLANT SURVIVAL. INCREASE NATIVE PLANT COVERAGE WITHIN ENHANCED BUFFERS. MEASUREMENT OF SUCCESS IS PERCENT COVERAGE. INCREASE NATIVE PLANT SPECIES DIVERSITY WITHIN ENHANCED BUFFERS. MEASUREMENT OF SUCCESS IS PLANT DIVERSITY. MAINTAIN LIMITED NOXIOUS WEED COVERAGE WITHIN ENHANCED BUFFERS. MEASUREMENT OF SUCCESS IS PERCENT COVERAGE. PERMANENT PRESERVATION AND PROTECTION OF THE ENHANCEMENT AREA. PERFORMANCE STANDARDS ·100% SURVIVAL BY INSTALLED PLANT STOCK AFTER THE FIRST GROWING SEASON (YEAR 1). ·85% SURVIVAL BY INSTALLED PLANT STOCK AFTER THE SECOND GROWING SEASON (YEAR 2). ·15% COVERAGE AFTER THE FIRST GROWING SEASON (YEAR 1). ·35% COVERAGE AFTER THE THIRD GROWING SEASON (YEAR 3). ·50% COVERAGE AFTER THE FIFTH GROWING SEASON (YEAR 5). THE SUCCESSFUL ESTABLISHMENT OF 3 TREE SPECIES AND 5 SHRUB SPECIES WITHIN EACH PLANTING AREA. LESS THAN 10% COVERAGE BY CLASS "A", "B", AND "C" NOXIOUS WEEDS INCLUDING NON-REGULATED "B" AND "C" NOXIOUS WEEDS AND "WEEDS OF CONCERN". THE PRESENCE OF CRITICAL AREA FENCING AND SIGNAGE IN GOOD WORKING CONDITION. SCHEDULE EARLY SPRING AND LATE SUMMER OF YEARS 1 & 2 FOLLOWING PLANT INITIAL INSTALLATION EARLY SPRING AND LATE SUMMER OF YEARS 1, 2, 3, 4, & 5 FOLLOWING PLANT INITIAL INSTALLATION EARLY SPRING AND LATE SUMMER OF YEARS 1, 2, 3, 4, & 5 FOLLOWING PLANT INITIAL INSTALLATION EARLY SPRING AND LATE SUMMER OF YEARS 1, 2, 3, 4, & 5 FOLLOWING PLANT INITIAL INSTALLATION EARLY SPRING AND LATE SUMMER OF YEARS 1, 2, 3, 4, & 5 FOLLOWING PLANT INITIAL INSTALLATION MONITORING PLAN: PLAN GOALS, OBJECTIVES, AND PERFORMANCE STANDARDS MITIGATION PLAN GOALS, MONITORING SCHEDULE, AND PERFORMANCE STANDARDS ARE OUTLINED BELOW. THE BROAD GOAL/OBJECTIVE OF THIS PLAN IS TO PROVIDE A "NO NET LOSS" IN SHORELINE ECOLOGICAL FUNCTIONING. THE GOALS OF THIS PLAN ARE CONSIDERED ACHIEVED WHEN THE PERFORMANCE STANDARDS ARE SATISFIED. MONITORING PLAN AS-BUILT FOLLOWING COMPLETION OF THE WORK SHOWN ON THIS PLAN, A QUALIFIED PROFESSIONAL SHALL PREPARE AN AS-BUILT OF THE COMPLETED WORK. THE AS-BUILT SHALL SUMMARIZE THE COMPLETED WORK AS WELL AS ANY DEVIATIONS FROM THE APPROVED VERSION OF THIS PLAN. IN ADDITION TO THE AS-BUILT, BASELINE MONITORING DATA SHALL BE COLLECTED AND PERMANENT PHOTO POINTS SHALL BE ESTABLISHED TO PHOTOGRAPHICALLY DOCUMENT REPRESENTATIVE CONDITIONS WITHIN EACH BUFFER ENHANCEMENT AREA. BASELINE MONITORING DATA COLLECTED AND REPORTED AS PART OF THE AS-BUILT SHALL BE CONSISTENT WITH THAT DESCRIBED FOR "ANNUAL MONITORING" (SEE BELOW). THE AS-BUILT AND BASELINE MONITORING DATA SHALL BE SUBMITTED TO CITY OF AUBURN NO LATER THAN 30 DAYS FROM THE DATE THAT THE WORK SHOWN ON THIS PLAN HAS BEEN COMPLETED. ANNUAL MONITORING (5 YEARS) ANNUAL MONITORING SHALL BE COMPLETED FOR A PERIOD OF FIVE (5) YEARS. UNLESS OTHERWISE ALLOWED BY THE CITY OF AUBURN, ANNUAL MONITORING SHALL BE COMPLETED BY A QUALIFIED PROFESSIONAL AND SHALL COMPRISE A "BIANNUAL" SITE INVESTIGATIONS CONDUCTED IN EARLY SPRING AND LATE SUMMER OF EACH YEAR WITH REPORTING TO CITY OF AUBURN NO LATER THAN DECEMBER 1. THE PURPOSE OF ANNUAL MONITORING IS TO EVALUATE CONDITIONS WITHIN EACH BUFFER ENHANCEMENT AREA PER THE CURRENT YEAR'S PERFORMANCE STANDARDS. THE FOLLOWING INFORMATION SHALL BE COLLECTED AND ASSESSED RELATIVE TO THE PERFORMANCE STANDARDS ESTABLISHED FOR THE PROJECT: ·THE PERCENT SURVIVAL OF INSTALLED PLANT STOCK (ALL YEARS). A DIRECT COUNT INVENTORY AND ASSESSMENT OF ALL INSTALLED PLANTS SHALL BE USED TO EVALUATE PERCENT SURVIVAL. THE RATIONALE FOR POOR CONDITIONS, IF PRESENT, WILL BE DETERMINED TO THE EXTENT FEASIBLE. ·THE PERCENT COVER BY NATIVE PLANT SPECIES (ALL YEARS). INSTALLED PLANT STOCK PERCENT COVERAGE SHALL BE ASSESSED USING APPROPRIATELY SIZED SAMPLE PLOTS OR LINE INTERCEPT TRANSECTS. ·INSTALLED PLANT SPECIES DIVERSITY (ALL YEARS). A TALLY OF ALL INSTALLED PLANT SPECIES PRESENT SHALL BE USED TO EVALUATE PLANT SPECIES DIVERSITY. ·THE PERCENT COVERAGE BY NON-NATIVE OR NOXIOUS WEED SPECIES (ALL YEARS). NON-NATIVE OR NOXIOUS WEED SPECIES PERCENT COVERAGE SHALL BE ASSESSED USING APPROPRIATELY SIZED SAMPLE PLOTS OR LINE INTERCEPT TRANSECTS. IN ADDITION TO VEGETATION SAMPLING, PHOTOGRAPHS OF BUFFER AREAS SHALL BE TAKEN FROM THE PERMANENT PHOTO POINTS ESTABLISHED DURING THE AS-BUILT. CONTINGENCY PLAN: SHOULD ANY MONITORING ASSESSMENT REVEAL THAT THE PERFORMANCE STANDARDS FOR THE RESPECTIVE YEAR ARE NOT SATISFIED, THE PERMITTEE SHALL WORK WITH THE CITY OF AUBURN, TO DEVELOP A CONTINGENCY PLAN TO ADDRESS THE DEFICIENCY(IES). CONTINGENCY PLANS CAN INCLUDE, BUT ARE NOT LIMITED TO, THE FOLLOWING ACTIONS: 1. ADDITIONAL PLANT INSTALLATION; 2. EROSION CONTROL; 3. HERBIVORY PROTECTION; 4. MODIFICATION TO THE IRRIGATION REGIME; AND/OR 5. PLANT SUBSTITUTIONS OF TYPE, SIZE, QUANTITY, AND LOCATION. SUCH CONTINGENCY PLAN SHALL BE SUBMITTED TO THE CITY OF AUBURN, BY JANUARY 31 OF ANY YEAR WHEN DEFICIENCIES ARE DISCOVERED. UNLESS OTHERWISE APPROVED BY THE CITY OF AUBURN,, ACTIONS SPECIFIED ON AN APPROVED CONTINGENCY PLAN MUST BE COMPLETED WITHIN 60 DAYS. IF THE FAILURE IS SUBSTANTIAL, THE CITY OF AUBURN, MAY EXTEND THE COMPLIANCE MONITORING PERIOD FOR THE ENHANCEMENT WORK. MAINTENANCE PLAN: INSTALLED PLANTS SHALL BE MAINTAINED AT REGULAR INTERVALS DURING THE MONITORING PERIOD TO PROMOTE THE SUCCESSFUL ESTABLISHMENT AND VIGOROUS GROWTH OF THE INSTALLED PLANT STOCK. GENERAL MAINTENANCE SHALL INCLUDE: 1. RE-APPLYING BARK MULCH TO MAINTAIN A 6" MINIMUM APPLIED THICKNESS - YEAR 1 ONLY. 3. THE PRUNING OF INSTALLED PLANTS TO REMOVE DEAD WOOD AND PROMOTE VIGOROUS PLANT GROWTH AND PROPER FORM. 4. THE REPLACEMENT OF PLANTS THAT APPEAR TO BE IN DISTRESS AND/OR DISEASED. 5. THE REMOVAL OF TRASH, LITTER, AND/OR OTHER NON-DECOMPOSING DEBRIS. GENERAL MAINTENANCE WORK SHALL OCCUR MONTHLY DURING THE GROWING SEASON AND/OR AT A FREQUENCY OTHERWISE NECESSARY TO ENSURE THE SUCCESSFUL ESTABLISHMENT AND VIGOROUS GROWTH OF THE INSTALLED PLANTS. LONG TERM PROTECTION NOTICE: LONG TERM PROTECTION OF THE SHORELINE BUFFER SHOWN ON THESE PLANS IS PROVIDED BY THE DESIGNATION OF THIS AREA AS A SEPARATE TRACT ON WHICH DEVELOPMENT IS PROHIBITED, AND PROTECTED BY EXECUTION OF AN EASEMENT DEDICATED TO THE CITY. THE EASEMENT GRANTS THE CITY ACCESS TO THE ON-SITE MITIGATION AREAS FOR PURPOSES OF MONITORING, MAINTAINING, PRESERVING AND ENHANCING THE ON-SITE WETLAND AND ASSOCIATED BUFFER AREAS. THE LOCATION AND LIMITATIONS OF ASSOCIATED WITH THE SHORELINE AND ITS BUFFER SHALL BE SHOWN ON HE FACE OF THE DEED OR PLAT APPLICABLE TO THE PROPERTY AND SHALL BE RECORDED WITH THE KING COUNTY RECORDING DEPARTMENT. SITE PLAN NOTES: 1. CAUTION: THE PROJECT SITE CONTAINS GEOLOGIC HAZARDS, WHICH MAY OR MAY NOT BE SHOW IN THEIR ENTIRETY ON THESE DRAWINGS. REFER TO REPORTS DESIGN, AND/OR ANALYSIS BY OTHERS FOR MORE INFORMATION. 2. CAUTION: THE PROJECT SITE CONTAINS FLOOD HAZARD AREAS, WHICH MAY OR MAY NOT BE SHOWN IN THEIR ENTIRETY ON THESE DRAWINGS. REFER TO REPORTS DESIGN, AND/OR ANALYSIS BY OTHERS FOR MORE INFORMATION. 3. REFER TO SITE ENGINEERING AND ARCHITECTURAL PLANS FOR EROSION CONTROL, PERMANENT DRAINAGE CONTROL, BUILDING CONSTRUCTION, AND RELATED SITE IMPROVEMENTS. PLAN REFERENCES: 1. "GOULET RESIDENCES - SHORELINE CUP PLAN SET" BY ENCOMPASS ENGINEERING & SURVEYING, DATED 04/27/2021, INCLUDING BOUNDARY & TOPOGRAPHIC SURVEY, EXISTING CONDITIONS PLAN, PROPOSED SITE PLAN, PROPOSED GRADING & DRAINAGE PLAN, AND LOT SECTIONS. BASE DRAWINGS HAVE BEEN MODIFIED FROM THEIR ORIGINAL FORMAT TO ENHANCE VISUAL PRESENTATION AND/OR TO HIGHLIGHT SPECIFIC INFORMATION. 2. "CRITICAL AREAS REPORT: PROPOSED SINGLE-FAMILY RESIDENCES; PARCELS 3341000090, 3341000095, 3341000010 - AUBURN, WASHINGTON" BY BERGQUIST ENGINEERING SERVICES COMPANY, LLC DATED 10/8/2020 (MARKED AS REPORT 1, REVISION 2). 3. "ARBORIST REPORT - GOULET AUBURN PROJECT" BY LAYTON TREE CONSULTING, LLC DATED MAY 12, 2021. GENERAL CONSTRUCTION NOTES: 1. CONSTRUCTION SHALL BE IN ACCORDANCE WITH ALL CITY OF AUBURN CODES, ORDINANCES, AND REGULATIONS. 2. BEFORE THE START OF ANY CONSTRUCTION, A PRE-CONSTRUCTION MEETING MUST BE HELD BETWEEN CITY OF AUBURN, THE OWNER, AND THE PLAN DESIGNER. 3. A COPY OF THESE APPROVED DRAWINGS MUST BE ON THE JOB SITE WHENEVER CONSTRUCTION IS IN PROGRESS. 4. SITE CONDITIONS MAY VARY BASED ON SEASON AND/OR TIME OF YEAR. THE CONSTRUCTION CONTRACTOR SHALL ACCOMMODATE REALIZED AND ANTICIPATED SITE CONDITIONS WHEN COMPLETING THE WORK SHOWN ON THESE DRAWINGS. 5. THE CONSTRUCTION CONTRACTOR SHALL BE RESPONSIBLE FOR PROVIDING ADEQUATE SAFEGUARDS, SAFETY DEVICES, PROTECTIVE EQUIPMENT, FLAGGERS, AND ANY OTHER NEEDED ACTIONS TO PROTECT THE LIFE, HEALTH, AND SAFETY OF THE PUBLIC, AND TO PROTECT PROPERTY IN CONNECTION WITH THE PERFORMANCE OF THE WORK SHOWN ON THESE DRAWINGS. ANY WORK WITHIN THE TRAVELED RIGHT-OF-WAY THAT MAY INTERRUPT NORMAL TRAFFIC FLOW SHALL REQUIRE TRAFFIC CONTROL IN ACCORDANCE WITH ANY AND ALL CITY OF AUBURN STANDARDS. RECOMMENDED CONSTRUCTION SEQUENCE: 1. INSTALL TREE PROTECTION. 2. INSTALL TEMPORARY STREAM BUFFER PROTECTION FENCING. 3. CONTROL NOXIOUS WEEDS. 4. INSTALL LOGS. 5. INSTALL NATIVE PLANTINGS. 6. INSTALL MULCH. 7. REMOVE TEMPORARY STREAM BUFFER PROTECTION FENCING. 8. INSTALL CRITICAL AREA FENCING AND SIGNAGE. 9. REMOVE TREE PROTECTION. 10. MAINTAIN AND MONITOR MITIGATION FOR 5 YEARS. PLAN SHEET INDEX: SHEET 1 - COVERSHEET SHEET 2 - EXISTING CONDITIONS SHEET 3 - SHORELINE BUFFER REDUCTION PLAN SHEET 4 - SHORELINE BUFFER ENHANCEMENT PLAN SHEET 5 - MITIGATION BOND ESTIMATES SHORELINE BUFFER MITIGATION PLAN PROPOSED GOULET SINGLE FAMILY RESIDENCES ±32XXX 104TH PLACE SOUTHEAST - AUBURN, WASHINGTON KING COUNTY TAX PARCEL # 341000090, 341000095, 341000100 REVISED PER NEW SITE PLAN10/28/201 REVISED PER NEW SITE PLAN05/14/212 115 of 721 68' OHWM9 OHWM1 OHWM2 OHWM3 OHWM4 OHWM5 OHWM6 OHWM7 OHWM8 CHANNEL MIGRATION ZONE 50' CHANNEL MIGRATION ZONE BUFFER 100 YEAR FLOODPLAIN (HATCHED AREA)66' 6 4 '62'60' 7 2 '70'6 8 '66'64' 7 4 '60'62' 7 0 ' 7 4 ' 68'68'7 2 ' 100' SHORELINE BUFFER N74°15'2 4 " E 1 6 1 . 3 1 ' N88°25'43"W 185.33' N60°1 2' 2 4" E 1 4 9. 7 2' N60°1 2' 2 4" E 1 4 0. 2 5'N29°47 '36 "W 39 .99 'N15°44'36"W 28.66 'N15°44'36"W 59.99 ' ORDINARY HIGH WATER MARK FLAGGED 10/04/2019 BUILDABLE AREA = 1,518 SF (HATCHED AREA) BUILDABLE AREA = 2,256 SF (HATCHED AREA) GREEN RIVER (TYPE S WATER) URBAN CONSERVANCY SHORELINE DESIGNATION BUILDABLE AREA = 3,028 SF (HATCHED AREA) TOE OF STEEP SLOPE 200' SHORELINE MANAGEMENT ZONE 23 ' STEEP SLOPE BUFFER (HATCHED AREA) TOP OF RIVER BANK BASE FLOOD ELEVATION = 67.30' BASE FLOOD ELEVATION = 67.20' UTILITY EASEMENT RECORDING NUMBER 2000091000505 N29°47 '36 "W 90 .00 ' 15' SEWER SETBACK (HATCHED AREA) BASE FLOOD ELEVATION = 67.40' Wetland Delineation Mitigation Design Mitigation Monitoring PO BOX 1721 ISSAQUAH, WASHINGTON 98027 TEL - (425) 677-7166 WWW.EVERGREENARC.COM Resource Consultants, LLC Evergreen Aquatic PROJECT NO: 19046 DATE: 04/10/2020 DESCRIPTIONDATENO SHEET NUMBER: 2/5 SHEET TITLE: EXISTING CONDITIONS RECORD DRAWING CERTIFICATION THESE DRAWINGS CONFORM TO THE CONTRACTOR'S CONSTRUCTION RECORDS. BY DATE TITLE/POSITION CONFIRMED BY CITY DATE PROJECT REF: THESE PLANS ARE APPROVED FOR CONFORMANCE WITH THE CITY OF AUBURN'S CRITICAL AREA REQUIREMENTS. APPROVED BY: DATE APPROVED: N 20100 HORIZONTAL DATUM: NAD 83/91 VERTICAL DATUM: NAVD 88 LOT B TPN 334100-0095 ZONING = R5 LOT A TPN 334100-0090 ZONING = R5 LOT C TPN 334100-0100 ZONING = R5 THE UNDERGROUND ROUTING AND CONDITION OF BURIED UTILITIES HAS NOT BEEN VERIFIED OR CONFIRMED. FIELD LOCATE, VERIFY DEPTH OF, AND ADEQUATELY PROTECT ALL UTILITIES PRIOR TO THE START OF WORK. Know what's below. before you dig.Call R LOT INFORMATION: GROSS EXISTING REQUIRED STREAM LOT BUILDABLE SHORELINE BUFFER LOT AREA AREA BUFFER AREA LOT A 14,628 SF 3,028 SF (20.7%) 100 FT 10,160 SF LOT B 13,601 SF 2,256 SF (16.6%) 100 FT 9,587 SF LOT C 13,021 SF 1,518 SF (11.7%) 100 FT 9,197 SF PROJECT: SHORELINE BUFFER MITIGATION PLAN PROPOSED GOULET SINGLE FAMILY RESIDENCES KING COUNTY TAX PARCEL #334100-0090 (LOT A) #334100-0095 (LOT B) #334100-0100 (LOT C) PREPARED FOR: LAUNCE P. GOULET & BRUCE GOULET 3226 S 198TH STREET SEATAC, WASHINGTON 98188 NORTHWEST 1 4 OF THE NORTHWEST 1 4 OF SECTION 17, TOWNSHIP 21N, RANGE 5 EAST, W.M. CITY OF AUBURN, STATE OF WASHINGTON REVISED PER NEW SITE PLAN10/28/201 REVISED PER NEW SITE PLAN05/14/212 116 of 721 PROPOSED REDUCED SHORELINE BUFFER (WIDTH VARIES) PROPOSED SHORELINE BUFFER REDUCTION (HATCHED AREA) 34" COTTONWOOD TREE TO BE REMOVED SALVAGE LOGS FOR MITIGATION 36", 30" & 41" COTTONWOOD TREES TO BE REMOVED SALVAGE LOGS FOR MITIGATION. 13"(X2), 11" 10", & 9" BLACK LOCUST. TREE TO BE REMOVED INSTALL TEMPORARY STREAM BUFFER FENCING AT BUFFER LIMITS. SEE DETAIL 3-1. 36" DOUGLAS-FIR. TREE TO BE REMOVED SALVAGE LOGS FOR MITIGATION STREAM BUFFER ENHANCEMENT LOT A (10,160 SF) CITY OF AUBURN MAY REQUIRE RESTRICTIVE COVENANTS, CONSERVATION EASEMENTS, OR TRACT DESIGNATION. STREAM BUFFER ENHANCEMENT LOT B (9,187 SF) CITY OF AUBURN MAY REQUIRE RESTRICTIVE COVENANTS, CONSERVATION EASEMENTS, OR TRACT DESIGNATION. STREAM BUFFER ENHANCEMENT LOT C (8,323 SF) AREA SUBJECT TO FUTURE RESTRICTIVE COVENANTS, CONSERVATION EASEMENTS, OR TRACT DESIGNATION UTILITY EASEMENT RECORDING NUMBER 2000091000505 INSTALL TEMPORARY STREAM BUFFER FENCING AT BUFFER LIMITS. SEE DETAIL 3-1. INSTALL TEMPORARY STREAM BUFFER FENCING AT BUFFER LIMITS. SEE DETAIL 3-1. CONCEPTUAL DRIVEWAY CONCEPTUAL DRIVEWAY CONCEPTUAL DRIVEWAY 11" BIGLEAF MAPLE. TREE TO BE REMOVED SALVAGE LOGS FOR MITIGATION. 11" DOUGLAS-FIR. TREE TO BE REMOVED SALVAGE LOGS FOR MITIGATION. 30" BIGLEAF MAPLE TREE TO BE REMOVED SALVAGE LOGS FOR MITIGATION 16" BIGLEAF MAPLE. TREE TO BE REMOVED SALVAGE LOGS FOR MITIGATION Wetland Delineation Mitigation Design Mitigation Monitoring PO BOX 1721 ISSAQUAH, WASHINGTON 98027 TEL - (425) 677-7166 WWW.EVERGREENARC.COM Resource Consultants, LLC Evergreen Aquatic PROJECT NO: 19046 DATE: 04/10/2020 DESCRIPTIONDATENO SHEET NUMBER: 3/5 SHEET TITLE: SHORELINE BUFFER REDUCTION PLAN RECORD DRAWING CERTIFICATION THESE DRAWINGS CONFORM TO THE CONTRACTOR'S CONSTRUCTION RECORDS. BY DATE TITLE/POSITION CONFIRMED BY CITY DATE PROJECT REF: THESE PLANS ARE APPROVED FOR CONFORMANCE WITH THE CITY OF AUBURN'S CRITICAL AREA REQUIREMENTS. APPROVED BY: DATE APPROVED: N 20100 HORIZONTAL DATUM: NAD 83/91 VERTICAL DATUM: NAVD 88 TEMPORARY STREAM BUFFER FENCING DETAIL1 3 NO SCALE PRIOR TO THE START OF CONSTRUCTION, ORANGE PLASTIC CONSTRUCTION FENCING SHALL BE INSTALLED AT THE STREAM BUFFER LIMITS SHOWN ON THIS DRAWING. THE FENCING SHALL REMAIN IN PLACE AND IN GOOD CONDITION THROUGHOUT THE CONSTRUCTION PERIOD. WOOD OR METAL POST ORANGE, UV RESISTANT HIGH TENSILE STRENGTH POLYETHYLENE LAMINAR BARRICADE FABRIC 4' MIN. THE UNDERGROUND ROUTING AND CONDITION OF BURIED UTILITIES HAS NOT BEEN VERIFIED OR CONFIRMED. FIELD LOCATE, VERIFY DEPTH OF, AND ADEQUATELY PROTECT ALL UTILITIES PRIOR TO THE START OF WORK. Know what's below. before you dig.Call R PROJECT: SHORELINE BUFFER MITIGATION PLAN PROPOSED GOULET SINGLE FAMILY RESIDENCES KING COUNTY TAX PARCEL #334100-0090 (LOT A) #334100-0095 (LOT B) #334100-0100 (LOT C) PREPARED FOR: LAUNCE P. GOULET & BRUCE GOULET 3226 S 198TH STREET SEATAC, WASHINGTON 98188 REVISED PER NEW SITE PLAN10/28/201 STREAM BUFFER REDUCTION SUMMARY: PROPOSED PERCENT EXISTING PROPOSED PERCENT BUFFER MINIMUM MIN. WIDTH BUFFER BUFFER AREA LOT WIDTH WIDTH CHANGE AREA AREA CHANGE LOT A 100 FT 100 FT 0 % 10,160 SF 10,160 SF 0.0% LOT B 100 FT 94.5 FT -5.5% 9,587 SF 9,187 SF -4.2% LOT C 100 FT 89.5 FT -10.5% 9,197 SF 8,323 SF -9.5% BUILDABLE AREA SUMMARY: BUILDABLE % OF LOT LOT AREA AREA LOT A 2,834 SF 19.4 % LOT B 2,597 SF 19.1 % LOT C 2,322 SF 17.8 % REVISED PER NEW SITE PLAN05/14/212 117 of 721 MITIGATION LEGEND: QUANTITY PER LOT DESCRIPTION LOT A LOT B LOT C FLAT BUFFER PLANTINGS 5,955 SF 5,908 SF 6,401 SF RIVERBANK PLANTINGS 4,205 SF 3,279 SF 1,922 SF LOG W/ ROOTWAD 2 2 2 LOG W/O ROOTWAD 4 6 5 SNAG 1 1 1 CRITICAL AREA FENCE 92 LF 84 LF 91 LF CRITICAL AREA SIGN 1 1 1 Wetland Delineation Mitigation Design Mitigation Monitoring PO BOX 1721 ISSAQUAH, WASHINGTON 98027 TEL - (425) 677-7166 WWW.EVERGREENARC.COM Resource Consultants, LLC Evergreen Aquatic PROJECT NO: 19046 DATE: 04/10/2020 DESCRIPTIONDATENO SHEET NUMBER: 4/5 THE UNDERGROUND ROUTING AND CONDITION OF BURIED UTILITIES HAS NOT BEEN VERIFIED OR CONFIRMED. FIELD LOCATE, VERIFY DEPTH OF, AND ADEQUATELY PROTECT ALL UTILITIES PRIOR TO THE START OF WORK. Know what's below. before you dig.Call R SHEET TITLE: SHORELINE BUFFER ENHANCEMENT PLAN NOXIOUS WEED CONTROL SPECIFICATIONS: PRIOR TO PLANT INSTALLATION, CONTROL NOXIOUS WEEDS IN WETLAND AND REDUCED WETLAND BUFFER. TARGET NOXIOUS WEED SPECIES SHALL INCLUDE THE FOLLOWING: ALL CLASS "A", "B", AND "C" NOXIOUS WEEDS (INCLUDING NON-REGULATED "B" AND "C" NOXIOUS WEEDS AND "WEEDS OF CONCERN") IDENTIFIED ON THE LATEST KING COUNTY NOXIOUS WEED LIST. DURING NOXIOUS WEED CONTROL WORK, EXISTING NATIVE VEGETATION SHALL BE PROTECTED FROM DAMAGE. ALL NOXIOUS WEED CONTROL CUTTINGS AND DEBRIS SHALL BE REMOVED FROM THE SITE. CONTROL METHODS: 1. REDUCE TOP GROWTH OF NOXIOUS WEEDS. ACCEPTABLE METHODS INCLUDE: POWER SAW, BRUSH HOG, LINE TRIMMER, LOPPERS, CLIPPERS, HAND PULLING, OR APPROVED EQUAL. 2. GRUB OUT LARGE ROOT CROWNS AND MAJOR ROOTS BY HAND USING CLAW MATTOCK, PULASKI, OR APPROVED EQUAL. PLANT MATERIAL SPECIFICATIONS: 1. PLANTS SHALL BE DERIVED FROM STOCK ACCLIMATED TO WESTERN WASHINGTON ENVIRONMENTAL CONDITIONS. 2. PLANTS SHALL BE NATIVE TO THE PACIFIC NORTHWEST, PREFERABLY THE PUGET SOUND REGION OF WASHINGTON STATE. PLANTS SHALL BE PROPAGATED FROM NATIVE STOCK; NO CULTIVARS OR HORTICULTURAL VARIETIES ARE ALLOWED. SALVAGED PLANTS ARE NOT ACCEPTABLE. 3. PLANTS SHALL BE NORMAL IN PATTERN OF GROWTH, HEALTHY, WELL-BRANCHED AND HAVE ALL LEADERS AND BUDS INTACT. TREES SHALL NOT HAVE SUNSCALDS, DISFIGURING KNOTS, FRESH CUTS OF LIMBS, DAMAGED LEADERS, AND/OR DEFORMED TRUNKS. 4. CONTAINERIZED PLANT STOCK SHALL BE GROWN IN A CONTAINER LONG ENOUGH TO DEVELOP A ROOT SYSTEM THAT REACHES THE EDGES OF THE CONTAINER IN WHICH IT HAS GROWN. TREES AND SHRUBS SHALL BE WELL ROOTED AND SHALL HAVE SUFFICIENT ROOT MASS TO HOLD TOGETHER THE SOIL, IN WHICH PLANT IS GROWING, WHEN REMOVED FROM THE POT. PLANT MATERIAL SOURCE: PLANTS SHALL BE DERIVED FROM STOCK ACCLIMATED TO WESTERN WASHINGTON ENVIRONMENTAL CONDITIONS, HAVING BEEN CONSISTENTLY CULTIVATED AND GROWN UNDER SIMILAR CONDITIONS. ACCEPTABLE PLANT SUPPLIERS INCLUDE PACIFIC PLANTS, INC. (WWW.PACIFICPLANTS.COM), STORM LAKE GROWERS (WWW.SLGROWERS.COM), SOUND NATIVE PLANTS (WWW.SOUNDNATIVEPLANTS.COM), OR APPROVED EQUAL INCLUDED ON THE FOLLOWING WEBSITE: HTTP://WWW.KINGCOUNTY.GOV/SERVICES/ENVIRONMENT/STEWARDSHIP/NW-YARD-AND-GARDEN/ NATIVE-PLANT-NURSERIES-WASHINGTON.ASPX TEMPORARY IRRIGATION REQUIREMENTS: TEMPORARY IRRIGATION SHALL BE PROVIDED FOR TWO (2) GROWING SEASONS FOLLOWING PLANT INSTALLATION. IRRIGATION SHALL PROVIDE A MINIMUM RAINFALL EQUIVALENT OF 1 INCH PER WEEK FROM JUNE 15 THROUGH SEPTEMBER 15. IRRIGATION SHALL BE APPLIED IN A MANNER THAT MAINTAINS PLANT HEALTH, PREVENTS WILTING, AND PROMOTES DEEP PLANT ROOT SYSTEMS. RECORD DRAWING CERTIFICATION THESE DRAWINGS CONFORM TO THE CONTRACTOR'S CONSTRUCTION RECORDS. BY DATE TITLE/POSITION CONFIRMED BY CITY DATE PROJECT REF: THESE PLANS ARE APPROVED FOR CONFORMANCE WITH THE CITY OF AUBURN'S CRITICAL AREA REQUIREMENTS. APPROVED BY: DATE APPROVED: NATIVE SOIL 5 8" MINUS CRUSHED ROCK BACKFILL. COMPACT TO 95% MIN. DENSITY MOUND TO DRAIN AWAY FROM POST SQUARE OR ROUND ROUGH CUT WOOD POST - UNTREATED (TYP) ROUGH CUT WOOD RAIL - UNTREATED (TYP)10' MAX 3' MIN. 12" - 18" 2' MIN. CRITICAL AREA SIGN CRITICAL AREA FENCE DETAIL NOTES: 1. FENCE SHALL BE COMMERCIALLY AVAILABLE CEDAR POST AND RAIL SYSTEM PER THE ABOVE MIN. SPECIFICATIONS. 2. WOOD SHALL BE WESTERN REDCEDAR OR EQUAL. CRITICAL AREA SIGN NOTES: 1. SIGN CONTENT SHOWN IS REPRESENTATIVE IN NATURE. FINAL SIGN CONTENT, COLOR, AND MATERIAL SHALL CONFORM TO THE CITY OF AUBURN STANDARDS. 2. ATTACH TO FENCE USING 5/16" DIA. GALVANIZED LAG BOLT. 3. SIGNS SHALL BE POSTED AT THE OUTER LIMITS OF THE STREAM BUFFER FACING AWAY FROM THE BUFFER. 4. SIGNS SHALL BE POSTED 1 SIGN PER LOT. Sensitive Area Boundary Help protect and care for this area. Trampling or cutting vegetation, placing fill or garbage, and any other activities that may disturb the sensitive area are prohibited, as regulated under Auburn City Code Chapter 16.10. Please contact City of Auburn at 253-931-3090 with questions or concerns. CRITICAL AREA FENCE DETAIL3 4 CRITICAL AREA SIGN DETAIL2 4 COMPACT SOIL UNDER ROOTBALL 6" MIN. MULCH 6" MIN. THICKNESS THROUGHOUT PLANTING AREA. FINISHED GRADE LEAVE NATIVE SOIL INTACT. DO NOT DISTURB. REMOVE CONTAINER. IF ROOTBOUND, LOOSEN ROOTS PRIOR TO PLANTING. 2X ROOT BALL NATIVE BACKFILL SET MAIN STEM(S) VERTICAL PLANT INSTALLATION DETAIL1 4 PLANTING PLAN NOTES: 1. PRIOR TO PLANT INSTALLATION, CONTROL NOXIOUS WEEDS. 2. PLANT MATERIAL QUALITY AND LOCATIONS SHALL BE INSPECTED BY PLAN DESIGNER PRIOR TO INSTALLATION. 3. PLANT LOCATIONS SHOWN ARE APPROXIMATE. ADJUST PLANT LOCATIONS TO ACCOMMODATE SITE CONDITIONS AND/OR PER PLAN DESIGNER AT TIME OF INSTALLATION. 4. FOLLOWING PLANT INSTALLATION, PLACE MULCH THROUGHOUT PLANTING AREA TO A MINIMUM DEPTH OF 6 INCHES. MULCH SPECIFICATION: MULCH SHALL BE COMMERCIALLY AVAILABLE "WSDOT WOOD CHIP MULCH" (WWW.PACIFICTOPSOILS.COM; 425-337-2700), ARBORIST CHIPS, OR APPROVED EQUAL. MULCH SHALL NOT CONTAIN RESIN, TANNIN, OR OTHER COMPOUNDS IN QUANTITIES THAT WOULD BE DETRIMENTAL TO PLANT LIFE. MULCH SHALL NOT BE DERIVED FROM STUMP GRINDINGS AND SHALL NOT CONTAIN SOIL. HOG FUEL OR EQUAL IS NOT ACCEPTABLE. SUBJECT TO REVIEW BY THE PLAN DESIGNER, LOCAL ARBORIST AND/OR COMMERCIAL TREE TRIMMING COMPANIES MAY BE ALTERNATIVE ACCEPTABLE MATERIAL SOURCES (WWW.DROPCHIP.IN). EXISTING NATIVE VEGETATION PROTECTION: EXISTING NATIVE VEGETATION (TREES AND SHRUBS) WITHIN PLANTING AREAS SHALL BE RETAINED AND PROTECTED WHILE COMPLETING THE ENHANCEMENT WORK SHOWN ON THIS PLAN. FLOOD HAZARD NOTE: CAUTION: THE PLANTING AREAS SHOWN ON THIS PLAN ARE LOCATED WITHIN FLOOD HAZARDS. SITE CONDITIONS MAY VARY BASED ON SEASON AND/OR TIME OF YEAR. WORK TO BE PERFORMED SHALL ACCOMMODATE REALIZED AND ANTICIPATED FLOOD CONDITIONS. PLANTING SCHEMATICS5 4 PLANT SCHEDULE: TOTAL QUANTITY PER LOT SYMBOL COMMON NAME SCIENTIFIC NAME WIS SIZE AND FORM QUANTITY LOT A LOT B LOT C BIGLEAF MAPLE ACER MACROPHYLLUM FACU 2 GALLON CONTAINERIZED 80 26 26 28 SITKA SPRUCE PICEA SITCHENSIS FAC 2 GALLON CONTAINERIZED 74 17 17 18 DOUGLAS-FIR PSEUDOTSUGA MENIESII FACU 2 GALLON CONTAINERIZED 29 10 9 10 WESTERN REDCEDAR THUJA PLICATA FAC 2 GALLON CONTAINERIZED 89 44 38 30 VINE MAPLE ACER CIRCINATUM FACU 2 GALLON CONTAINERIZED 51 17 17 18 REDOSIER DOGWOOD CORNUS SERICEA FACW 2 GALLON CONTAINERIZED 83 37 29 17 INDIAN PLUM OEMLERIA CERASFORMIS FACU 2 GALLON CONTAINERIZED 133 49 44 40 REDFLOWER CURRANT RIBIS SANGUINEUM FACU 2 GALLON CONTAINERIZED 66 21 21 23 SALMONBERRY RUBUS SPECTABILIS FAC 2 GALLON CONTAINERIZED 237 88 79 70 SITKA WILLOW SALIX SITCHENSIS FACW 4' LIVE STAKE; 4' O.C.110 42 38 30 SNOWBERRY SYMPHORICARPOS ALBUS FACU 2 GALLON CONTAINERIZED 198 68 65 65 TOTAL = 1,150 50' 50'25' SCALE = 1:10 NO SCALE NO SCALE NO SCALE 18" 12" RIVER BANKGREEN RIVERFLAT BUFFER N 20100 HORIZONTAL DATUM: NAD 83/91 VERTICAL DATUM: NAVD 88 SET STAKE VERTICAL WITH BUDS POINTING UP MIN. 1/2 OF STAKE INSTALLED BELOW GROUND. WHERE NECESSARY USE BAR TO PREPARE HOLE. COMPACT SOIL AROUND BASE OF STAKE AFTER INSTALLATION. LOG INSTALLATION DETAIL4 4 NO SCALE THESE PLANTING SCHEMATICS SHOW TYPICAL PLANT LAYOUT FOR 1,250 SF OF RIVER BANK PLANTING AND 2,500 SF OF FLAT BUFFER PLANTING. PROJECT: SHORELINE BUFFER MITIGATION PLAN PROPOSED GOULET SINGLE FAMILY RESIDENCES KING COUNTY TAX PARCEL #334100-0090 (LOT A) #334100-0095 (LOT B) #334100-0100 (LOT C) PREPARED FOR: LAUNCE P. GOULET & BRUCE GOULET 3226 S 198TH STREET SEATAC, WASHINGTON 98188 REVISED PER NEW SITE PLAN10/28/201 LOT B LOT A LOT C LOG/SNAG SPECIFICATIONS: 1. LOGS SHALL BE A 50%/50% MIX OF CONIFER AND DECIDUOUS SPECIES HAVING A MINIMUM DIAMETER OF 12 INCHES WITH BARK ATTACHED. 2. SNAGS SHALL BE CONIFER SPECIES MEASURING 12 INCHES MINIMUM DIAMETER WITH BARK ATTACHED AND FIVE (5) BRANCHES MINIMUM. 1/4 H (MIN.) 3' MIN. BACKFILL WITH COMPACTED NATIVE SOIL. NATIVE SOIL 15' (MIN.) 15' MIN. NATIVE SOIL1/2 DIA MIN REVISED PER NEW SITE PLAN05/14/212 118 of 721 Wetland Delineation Mitigation Design Mitigation Monitoring PO BOX 1721 ISSAQUAH, WASHINGTON 98027 TEL - (425) 677-7166 WWW.EVERGREENARC.COM Resource Consultants, LLC Evergreen Aquatic PROJECT NO: 19046 DATE: 04/10/2020 DESCRIPTIONDATENO SHEET NUMBER: 5/5 SHEET TITLE: MITIGATION BOND ESTIMATESRECORD DRAWING CERTIFICATION THESE DRAWINGS CONFORM TO THE CONTRACTOR'S CONSTRUCTION RECORDS. BY DATE TITLE/POSITION CONFIRMED BY CITY DATE PROJECT REF: THESE PLANS ARE APPROVED FOR CONFORMANCE WITH THE CITY OF AUBURN'S CRITICAL AREA REQUIREMENTS. APPROVED BY: DATE APPROVED: BOND ESTIMATE - LOT A1 5 BOND ESTIMATE - LOT B2 5 BOND ESTIMATE - LOT C3 5 THE UNDERGROUND ROUTING AND CONDITION OF BURIED UTILITIES HAS NOT BEEN VERIFIED OR CONFIRMED. FIELD LOCATE, VERIFY DEPTH OF, AND ADEQUATELY PROTECT ALL UTILITIES PRIOR TO THE START OF WORK. Know what's below. before you dig.Call R PROJECT: SHORELINE BUFFER MITIGATION PLAN PROPOSED GOULET SINGLE FAMILY RESIDENCES KING COUNTY TAX PARCEL #334100-0090 (LOT A) #334100-0095 (LOT B) #334100-0100 (LOT C) PREPARED FOR: LAUNCE P. GOULET & BRUCE GOULET 3226 S 198TH STREET SEATAC, WASHINGTON 98188 REVISED PER NEW SITE PLAN10/28/201 REVISED PER NEW SITE PLAN05/14/212 119 of 721 CRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCES PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010 AUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULET by:by:by:by: BERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLC BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1,,,, REVISION 2REVISION 2REVISION 2REVISION 2 November 4, 2020November 4, 2020November 4, 2020November 4, 2020 120 of 721 121 of 721 CRITICAL AREASCRITICAL AREASCRITICAL AREASCRITICAL AREAS REPORTREPORTREPORTREPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCESSSS PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095, , , , andandandand 3341000010334100001033410000103341000010 AUBURNAUBURNAUBURNAUBURN, WASHINGTON, WASHINGTON, WASHINGTON, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNMR. LAUNMR. LAUNMR. LAUNCCCCE P.E P.E P.E P. GOULETGOULETGOULETGOULET by:by:by:by: BERGQUIST ENGINEERING BERGQUIST ENGINEERING BERGQUIST ENGINEERING BERGQUIST ENGINEERING SERVICESSERVICESSERVICESSERVICES COMPANY, LLCCOMPANY, LLCCOMPANY, LLCCOMPANY, LLC BESBESBESBESCOCOCOCO PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: 2018201820182018214214214214, , , , REPORT 1REPORT 1REPORT 1REPORT 1, REVISION , REVISION , REVISION , REVISION 2222 NovemberNovemberNovemberNovember 4444, 2020, 2020, 2020, 2020 1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION This report presents the results of our geotechnical evaluation of critical areas for three proposed single-family residences to be constructed on King County Parcel Numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The parcels are located along the east bank of the Green River west of 104th Place Southeast, in the northwest quarter of the northwest quarter of Section 17, Township 21 North, Range 5 East, Willamette Meridian. The location of the project is shown on the Vicinity Map, Figure 1, on page A1 in Appendix A of this report. This report was revised because datum used for the current site plans, dated January 24, 2020 are NAVD 88, rather than the City of Auburn datum used on the originally submitted plans dated November 7, 2017. This report also provides additional information as a result of a site visit by Mr. Bergquist, who observed the level of the Green River on February 9, 2020, shortly after it exceeded the base flood elevation, and a follow-up visit by Messrs. Bergquist and Neal, who located and marked the maximum 2020 flood level. The geotechnical evaluation was performed by Bergquist Engineering Services Company, LLC (BESCO) to provide information or recommendations regarding: • erosion and slope stability characteristics, in accordance with Auburn City Code 16.10, • the risk of liquefaction and seismic design considerations, and • the influence of ground and surface water on the development. 122 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 2 of 15 This report is not intended to provide geotechnical criteria for design of the planned houses. The data for developing design criteria will be completed after critical area issues are addressed, and the various variances for these properties are obtained. The critical issues addressed in this report are; channel migration, landslide hazards, erosion hazards, flooding and seismic hazards. Mr. Launce P. Goulet authorized our work on March 19th, 2018 by signing and returning BESCO Proposal Number 1162018. 2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION The proposed project would involve construction of one multi-level house on each of the three vacant properties. The footprints and finished grades of the houses have not yet been finalized. 3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES The scope of services included the following steps: • an initial reconnaissance of the site by the geotechnical engineer; • excavating, logging, and sampling five test pits; logs of the test pits are presented in Appendix A on pages A3 through A7; • field and laboratory testing of selected soil samples, including visual classification and gradations; • a review of geologic and historic literature, and historic aerial photography; a list of references is contained in Appendix B; • measurement of a geotechnical cross-section for each parcel, and development of a geologic interpretation for the site by the engineering geologist; • a preliminary evaluation of soil strength and drainage characteristics; • evaluation of past and likely future migration of the Green River channel; • geotechnical slope stability analyses; • observation of the maximum recent flood elevation at the site; and • preparation of this report. Slope relationships for our cross-section were measured using a cloth tape, hand clinometer and Brunton compass in accordance with methodology outlined in Williamson, Neal and Larson (1991). The measurements used to develop the cross-sections and site plan are therefore, not of the precision and accuracy of a site survey prepared by a professional land surveyor, and should not be used for that purpose. 123 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 3 of 15 The recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical practices in the area. 4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION The information presented in this section was gathered by BESCO personnel for evaluation of critical area issues only. This site characterization was not intended to address the presence or likelihood of contamination on or around the site. Specialized methods and procedures, which were not a part of this scope of services, are required for an adequate environmental site assessment. 4.14.14.14.1 Topography and DevelopmentTopography and DevelopmentTopography and DevelopmentTopography and Development Parcels 3341000090, 3341000095, and 3341000010, referred to as Lots A, B, and C on the Site Plan, Figure 2, encompass 12,765, 11,644, and 11,777 square feet, respectively. The parcels are bounded on the east by 104th Place Southeast, on the west by the Green River, and to the north and south by developed single-family residential lots. Topographic relationships are shown on the sketch entitled, “Site Plan” presented on page A2 and on Cross-Sections A-A’, B-B’ C-C,’ and D-D’, presented on pages A20 through A22. Elevations shown on the cross-sections and test pit logs are based on a site and topographic plan for the parcels prepared by Encompass Engineering & Surveying, dated 9/1/2020, and our measurements. There is approximately 20 feet of relief on Parcel A, from an elevation of approximately 56 feet mean sea level (MSL) at the ordinary high water mark (OHWM) of the Green River at the northwest corner of the property to an elevation of approximately 76 feet MSL at the southeast property corner. There is approximately 20 feet of relief on Parcel B, from an elevation of approximately 56 feet MSL at the OHWM at the northwest corner of the property to an elevation of approximately 76 feet MSL at the northwest corner of the property. There is approximately 18 feet of relief on Parcel C, from an elevation of approximately 56 feet MSL along the OHWM and west parcel boundary to an elevation of approximately 74 feet MSL along the east parcel boundary and at the northeast corner. The eroded streambank of the Green River is inclined at from 10 percent to near-vertical. The ground surface is nearly level from the top of the streambank to the base of the fill slope just below 104th Place Southeast. It steepens to between 15 to 20 percent adjacent to 104th Place Southeast. The cut slope along the east side of 104th Place Southeast was constructed at approximately 1.18H:1V (horizontal:vertical) (85 percent). 124 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 4 of 15 The parcels are vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry and, along the river, morning glory. This vegetation reflects the year-round availability of water. A dead snag fell across the location of Cross-Section B-B’ apparently during the winter storms of 2020. 4.24.24.24.2 Area GeologyArea GeologyArea GeologyArea Geology The project area is situated in the Puget Sound basin, a structural low between the Cascade and Olympic Mountain physiographic provinces. The Puget Sound region has been subjected to at least six episodes of glaciations during the last two million years. The most recent glaciation, referred to as the Vashon stade of the Fraser glaciations, stalled and began rapid melting about 12,000 years ago. The glaciations left topography in the Puget Sound region characterized by north-south trending ridges and troughs. The troughs, such as the Puget Sound, Duwamish Channel, and Kent Valley, served as subglacial channels for southward-flowing meltwater. The glaciers formed deposits in front of advancing ice, along the ice margins, during the retreat of the ice front, and during interglacial periods. These deposits have subsequently been overridden and compacted by the advancing Vashon ice sheet. Some of the capping silts, sands, and gravels were likely deposited during Vashon glacial recession. Slope, fluvial, volcanic, and shoreline processes have shaped the land within the area over the 12,000 years since glacial retreat. Approximately 5,600 years ago, the Osceola Mudflow, a lahar originating from Mount Rainier, flowed down the West Fork of the White River and the White River valleys through the areas now occupied by Buckley, Enumclaw, and Auburn to as far north as Kent. The Electron Mudflow, also a Mount Rainier lahar, flowed down the Puyallup River through Orting and Puyallup and into the Kent Valley approximately 500 years ago. The White and Green Rivers have subsequently eroded through the lahars and infilled the floors of the resulting valleys with alluvial deposits. 4.34.34.34.3 SeismicitySeismicitySeismicitySeismicity The Puget Sound region is seismically active. Low magnitude earthquakes occur nearly every week within a 50-mile radius of the site. On April 13, 1949, the Olympia area experienced an earthquake having a Richter Magnitude 7.1 and, on April 29, 1965, the Tacoma-Seattle area experienced an earthquake having a Richter Magnitude 6.5 (Rogers, Walsh, Kockelman and Priest, 1991). On February 28, 2001, a magnitude 6.8 earthquake occurred just north of the Nisqually delta. 125 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 5 of 15 Great subduction zone earthquakes are the largest earthquakes in the world, and are the only source zones that can produce earthquakes greater than Magnitude 8.5. The Cascadia Subduction Zone, located off the coastlines of Washington, Oregon, and northern California, has produced magnitude 9.0 or greater earthquakes in the past. The last known megathrust earthquake in the northwest was in January, 1700 (Satake, Wang, and Atwater, 2003). Geological evidence indicates that such great earthquakes have occurred at least seven times in the last 3,500 years, a return interval of 400 to 600 years (Atwater and Hemphill-Haley, 1997). The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann, 2007). 4.44.44.44.4 Site GeologySite GeologySite GeologySite Geology Glacial and interglacial deposits are exposed in the Green River valley wall east of 104th Place Southeast. These deposits have been interpreted to include, from oldest (lowest on the slope) to youngest (top of the slope) the interglacial Puyallup Formation, overlain by glacial drift from the Salmon Springs glacial stade, and kame terrace deposits from the most recent (Vashon) stade. The glacially-derived deposits are overlain along the Green River and at the subject properties by Green River alluvial and fluvial (flood) deposits, consisting of fine sand with lenses of gravel, locally overlain by silt and clay (Mullineaux, 1965). Geologic processes on the properties are primarily associated with stream flow along the Green River. Flow is controlled in part by Howard A. Hansen Dam, which was constructed in Eagle Gorge and is used primarily for flood control in the lower Green-Duwamish valley (Galster, 1989). The primary process potentially affecting the properties is river erosion and deposition during flood events. While this risk is somewhat diminished by control of flows during floods by the aforementioned dam, the City of Auburn has designated portions of the properties as being a “channel migration area (CMA)” on their city flood map. The regulatory flood elevation for the river reach adjacent to the properties is 67.2 to 67.4 feet MSL. 4.5 4.5 4.5 4.5 Subsurface SoilsSubsurface SoilsSubsurface SoilsSubsurface Soils The subsurface soil conditions at this site are described in the following paragraphs and are presented graphically on the test pit logs. The test pit locations are shown on the Site Plan, Figure 2 in page A2 of Appendix A, and on Cross-Sections A-A’, B-B’, C-C’, and D-D’, Figures 3, 4, 5, and 6, respectively. 126 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 6 of 15 Soils were described and classified in general accordance with the Unified Soil Classification visual- manual procedure (American Society for Testing and Materials). A description of this system is included on page A10. Results of soil gradation tests are presented on pages A11 through A18. For purposes of explanation, we divided on-site soils into three soil units, SU-A, SU-B, and SU-C, based on origin and physical characteristics. Soil units are shown on the cross-sections; soil unit designations are intended to be local in scope, and not applicable outside the immediate area. A thin layer of organics, primarily blackberry roots, was noted at the top of each test pit. The roots generally reach to depths of 1.5 to 2 feet. SU-A was encountered along the base of the cut slope opposite the properties. Although the valley wall formed of this material is projected to be located beneath the east side of the property, it was not encountered in our test pits. SU-A consists of gray brown silty fine SAND (ASTM: SM). SU-A is a non-plastic soil that was moist, and was dense at the time of our field work. SU-A is interpreted to be an interglacial deposit. SU-B was encountered below depths of 7.0 feet in TP-1, 7.0 feet in TP-2, 7.5 feet in TP-3, and 6.5 in TP-5. SU-B is brown to gray in color, and ranges from silty fine SAND with silt interbeds to SILT with silty fine sand interbeds (ASTM: SM/ML to ML/SM). Orange-brown to black iron staining forms bands that become more frequent with depth. SU-B is a plastic soil that was moist to wet, with the natural moisture content ranging from below to above the plastic limit. SU-B was loose to soft at the time of our exploration. SU-B is interpreted to be an alluvial deposit, an overbank deposit of the Green River. SU-C was encountered overlying SU-B in all five test pits, from the ground surface to a depth of 7.0 feet in TP-1, between depths of 1.7 and 7.0 feet in TP-2, between 1.7 and 7.5 feet in TP-3, below 2.2 feet in TP-4, and from the ground surface to a depth of 6.5 feet in TP-5. SU-C consists of light brown to gray brown Silty fine SAND (ASTM: SM). SU-C is a non-plastic soil that was dry to locally moist, and was loose at the times of our exploration. SU-C is interpreted to be an alluvial deposit, an overbank deposit of the Green River). In addition to the soil units observed at the site, fill materials were encountered along the ground surface over the northern portion of the site and in TP-3 and TP-4, to depths of 1.7 feet in TP-3 and 127 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 7 of 15 2.2 feet in TP-4. This fill material consists of light brown silty fine SAND with coarse gravel (ASTM: SM), that ranged from a dry, non-plastic soil to a moist plastic soil with the natural moisture content below the plastic limit at the time of our exploration. This fill material appears to have been spread over the north parcel by heavy equipment and was dense at the time of our field work. Fill materials are also present beneath the outside shoulder of 104th Place Southeast along the east periphery of the parcels. It appears that the parcels have also been used as a location to dump garbage, particularly just downslope from the shoulder of the street. 4.64.64.64.6 Ground Water and Ground Water and Ground Water and Ground Water and DrainageDrainageDrainageDrainage At the time of our exploration, the King County region had experienced an extended, near record drought. Accordingly, no surface or ground water was encountered on the site. Soil moisture was encountered in three test pits at or just above the stream elevation. Water was encountered near the ground surface in the backfilled TP-2 by Mr. Bergquist during his February 9, 2020 site visit. No drainage features were observed on site. During our September 12, 2018 site visit, which followed a rain event, water had accumulated in low areas on the near-level ground surface. 4.74.74.74.7 Site ClassificationSite ClassificationSite ClassificationSite Classification The City of Auburn classifies all three project parcels as within a Critical Erosion Hazard Area under 16.10.080G, likely due to the presence of the silty fine SAND underlying the steep cut slope along the east side of 104th Place Southeast. The City also classifies the cut slope, which is located on City property, as a Class IV/Very High Hazard Landslide Hazard Area under 16.10.080G2d, since the slope was excavated to an inclination greater than 40 percent. Since the Green River is a Type S stream, the area within 250 feet of the OHWM is considered a riparian habitat zone. King County has classified the parcels as a “channel migration hazard area, moderate” for channel migration (King County, 1999). “Channel migration hazard area. Moderate” means a portion of the channel migration zone, as shown on the King County’s Channel Migration Zone map, that lies between the severe channel migration hazard area and the outer boundaries of the channel migration zone (King County, 2014). More recent analyses completed for the City of Auburn by GeoEngineers, Inc. (2018) has resulted in modification of the channel migration zone boundaries. The current regulatory base flood elevations are 67.2 to 67.4 feet MSL, based on FEMA’s FIRM mapping, effective August 19, 2020, using NAVD88 datum. All proposed building sites are 128 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 8 of 15 located above the base flood elevations. We noted that the US Geological Survey Green River gage near Auburn, located at River Mile 32.0 uses older datum for stage elevation (https://green2.kingcounty.gov/rivergagedata/gage-data.aspx?r=green). 5. 5. 5. 5. FLOODINGFLOODINGFLOODINGFLOODING AND AND AND AND CHANNELCHANNELCHANNELCHANNEL MIGRATIONMIGRATIONMIGRATIONMIGRATION The Green and White Rivers have a history of severe flooding. Until November 14, 1906, the White River occupied a channel west of the current Green River channel, and discharged into the Green River at about the current location of Pike Place Northeast (Anderson Map Company, 1907). On November 14, 1906, the area was inundated by a severe flood that changed the course of the White River to its current location, occupying what was previously the Stuck River. A diversion dam was subsequently constructed to make the change permanent (Perkins, 1993). Although this migration reduced flooding in the Kent Valley, the White River was flooding areas in Pierce County as well as the Kent Valley. This led to the construction of the Mud Mountain Dam on the White River in 1946. Even after flood levels on the White River were controlled, flooding continued unimpeded almost annually along the Green River valley. This led to the construction of the Fenster Levee on the west bank south of the properties in the 1960s (set back in 2014), the Howard A Hansen Dam, which was completed in 1961, and revetment adjacent to residences along the bank opposite the properties in 1973. The flood of record on the Green River occurred while the dam was under construction in November 1959, having a peak flow of 28,100 CFS (cubic feet per second) at the Auburn Gauge, located at River Mile 31.3 (US Geological Survey, 1975). The dam is operated such that maximum design flow is 12,000 CFS measured at the Auburn gauge. On February 9, 2020, flooding at the Green River Auburn gage reached a maximum flow of 12,080 CFS, which exceeded the design maximum flow for the site. At 12:30 pm on February 9, Mr. Bergquist visited the site and observed that the river had overtopped the bank and had reached a level just west of TP-2. We measured the high-water line at that location, which is 10 feet towards the river from TP-2 along Cross-Section B-B’. We staked this location for future reference. Refer to the Site Plan on Page A2, and Cross-Section B-B’, Figure 4 for the reference location. The proposed building sites are located above the base flood elevation and were not inundated by this flood event. Even though massive flood events occurred almost annually in the Green/White and later the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located. Maps dating back to 1888, and air photos dating 129 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 9 of 15 back to 1936 show the river in its current location adjacent to the properties. The current channel configuration is confined on the west bank by revetment and on both banks by the bridge at 8th Avenue Southeast. A list of maps and air photos used in this review is included with other references at the end of this report. 6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY The City of Auburn originally classified the site as an erosion hazard area and a landslide hazard area because of soil and slope characteristics along the 104th Place Southeast cut slope, which is managed by the City. As stated earlier, the cut slope was constructed at approximately 1.18H:1V, and is approximately 25 feet high, based on our measurements. The vegetation growing along the inslope ditch and the lack of debris along the base of the slope indicates the dense silty SAND forming the slope does not appear to be eroding. Slope movement was noted near the south end of 104th Place Southeast on 1996 air photos. Some of the debris flowed over the road and across downslope properties into the Green River, forming an earthen bar. 7777. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES Slope stability analyses were conducted using XSTABL Version 5.205, an integrated slope stability analysis program for personal computers developed by Dr. Sunil Sharma of Interactive Software Designs, Inc. The stability of the cut slope was analyzed with and without seismic loading (earthquake conditions), using Cross-Section C-C’ as a model. The near-level surface between the proposed building sites and the Green River channel was analyzed for the potential for lateral spread during an earthquake, also using Cross-Section C-C’ as a model. 7777.1.1.1.1 AssumptionsAssumptionsAssumptionsAssumptions Soil strength values for slope stability analysis were derived from the A.S.T.M. visual manual classification along with field testing, and correlated with tables in USDA Forest Service, 1994. Values for root cohesion for the dense vegetation growing along the cut slope were not considered, although it is apparent that they contribute to stability. For our analyses, we considered ground water to be mobile through the silty fine SAND forming the cut slope, without developing hydrostatic pressures. Values used for slope stability analyses are as follows: 130 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 10 of 15 TABLE 7.1 TABLE 7.1 TABLE 7.1 TABLE 7.1 –––– VALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSES SOIL UNITSOIL UNITSOIL UNITSOIL UNIT MOISTMOISTMOISTMOIST DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) SATURATED SATURATED SATURATED SATURATED DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) COHESION COHESION COHESION COHESION (PSF)(PSF)(PSF)(PSF) ANGLE OF ANGLE OF ANGLE OF ANGLE OF INTERNAL FRICTION INTERNAL FRICTION INTERNAL FRICTION INTERNAL FRICTION (DEGREES)(DEGREES)(DEGREES)(DEGREES) SU-A (SM) 132 138 0 38 SU-B (SM/ML) 84 112 0 27 SU-C (SM) 90 114 0 28 *Assumes fully saturated conditions for the soil unit. PCF and PSF are abbreviations for pounds per cubic foot and pounds per square foot, respectively. We did not include values for the fill material, since it does not extend southward to the cross- section analyzed. XSTABL and other slope stability programs calculate an estimated FOS (factor of safety), which is the result of dividing the total forces supporting the slope by the total forces that are tending to destabilize the slope. If the FOS is greater than 1.00, the slope is considered stable; if the FOS is less than 1.00, the slope is considered to be unstable. A FOS of 1.00 indicates the slope is in perfect equilibrium. The seismic coefficient applied to this project was 20 percent of the force of gravity which, in our judgment, is conservative considering the soils encountered at this site. The program was instructed to calculate the FOS for 1,000 potential shear surfaces during each iteration. The graphs contained in the appendix each show the locations of the 10 weakest surfaces analyzed within the slope segment selected for analysis, with the surface having the lowest FOS highlighted. 7777.2 .2 .2 .2 AAAAnalysesnalysesnalysesnalyses For the existing cut slope under static conditions, a FOS of 1.189 was calculated (refer to Graph GOULETW on page B1 in Appendix B). With seismic loading, the FOS was reduced to 0.808 (refer to Graph GOULETE2 on page B2 in Appendix B). For the near-level area adjacent to the Green River channel, a FOS of 1.265 was calculated under seismic loading (refer to Graph GOULETS2 on Page B3 in Appendix B). 8888. DISCUSSION. DISCUSSION. DISCUSSION. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions 131 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 11 of 15 encountered in the test pits adequately represent conditions near and between the test pits to the depths excavated. 9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS The following paragraphs present a summation of the area and site conditions as we interpret them. These conditions dictate the development considerations. 9.1 9.1 9.1 9.1 Flooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel Migration Flooding along the Green River is nearly an annual event, although the flooding occurs under controlled conditions as a result of the Howard A. Hanson Dam. Based on past records, floods reaching the base flood elevation occur one to two times a decade (Shannon & Wilson, 2002). Regulatory flood elevations are determined based on a model which assumes that Howard A. Hansen Dam functions properly, there is no channel migration, the revetments function as designed, and there are no blockages and sudden releases from significant events such as landslides or from log jams. A line delineating the base flood elevations for this project are shown on the Site Plan, located in Appendix A, Page A2. No evidence of channel migration within the straight reach adjacent to the properties was observed on 130 years of maps and air photos. This in part may be due to long-term efforts at maintaining the current west bank of the channel with revetments. Although there are signs of erosion above the revetment immediately opposite the properties, most of the erosion has occurred on the river bank adjacent to the properties. Given that the channel is confined by the revetments to the west, higher ground elevations on the property immediately to the south, and the abutments beneath the bridge on 8th Avenue, the river would, in our judgment, be likely to erode the loose silty fine SAND underlying much of the property. The channel migration zone boundary determined by GeoEngineers, Inc. (2018) for the City of Auburn and the 50-foot buffer required by the City are shown on the Site Plan. 9.2 9.2 9.2 9.2 Slope Stability and ErosionSlope Stability and ErosionSlope Stability and ErosionSlope Stability and Erosion The City of Auburn considers the cut slope along 104th Place Southeast a “landslide hazard area” because of the slope inclination and height, even though it is a constructed slope owned and maintained by the city, which is responsible for its stability. No evidence of cut slope erosion or instability was observed adjacent to the parcels, even following the February 2020 rain events. Our analyses indicate this slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated. 132 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 12 of 15 Our analyses indicate that slope movement (lateral spreading) is not likely to occur on the properties. The actual reaction to the seismic event, however, would be related to the strength and duration of shaking. There are no visible indicators that the dense silty fine SAND forming the cut slope, which is covered by dense brush, is subject to significant erosion. The more likely area to be eroded is the shoreline described above. 9.3 9.3 9.3 9.3 SeismicitySeismicitySeismicitySeismicity We conducted our subsurface exploration near the end of one of the driest summers on record, and encountered little ground water on our test pits. What we did encounter was situated at an elevation just above the level of the Green River at that time. It appears likely that the level of the river influences the ground water levels in the loose silty fine SAND beneath the site. The loose silty fine SAND underlying the site is classified as having a high susceptibility for liquefaction and Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann (2007). 10101010. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS Conditions underlying and adjacent to the property, along with City, County, and State regulations, make the proposed development at this site challenging. The conditions at the site, however, do not render the site unbuildable, but additional steps beyond what is normally standard building practices will likely be needed. If the building footprints are located as shown on the drawings, most of the footings will be founded in the loose silty fine SAND flood deposits. Prior to design of the foundations for the planned buildings, a thorough subsurface exploration and engineering analysis must be performed. The exploration should include test borings with groundwater monitoring wells so that the proper foundation types and load carrying capacities can be recommended. Liquefiable soil conditions can be mitigated by design of a suitable, deep foundation system for a specific structure that may incorporate driven or drilled piles. Another method involves installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. Therefore, we recommend that the building design process includes appropriate subsurface exploration as described above and development of engineering recommendations for design of a foundation system or soils improvement methods that will mitigate the effects of liquefaction. 133 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 13 of 15 There are no specific building plans at this time; therefore, we should be contacted for further recommendations once the designs of the specific structures are near completion. Reduction of the Green River Buffer for dispersion trenches to the normal 50 feet will not adversely affect the stability of the river bank in this location. Final selection and design of the storm water handling system(s) will be based on the concomitant impervious surfaces added to each property and on the results from the recommended subsurface exploration, and field and laboratory testing. Stormwater drainage design recommendations shall be provided and based on field testing of infiltration rates or other suitable methods. Our analyses indicate the over-steepened cut slope along 104th Place Southeast would likely become unstable under severe seismic shaking. Therefore, those responsible for maintaining public safety along City streets should address strengthening of the slope. We do not anticipate the need for an additional buffer beyond what is already provided by the drainage ditch and 104th Place Southeast, a width of approximately 23 feet. The recommended buffer is shown on the Site Plan, located in Appendix A, Page A2. Construction of a bulkhead or revetment on the river bank is not recommended for this reach of the river. However, maintenance of native vegetation is required within the river buffer. The present vegetation, however, consists of non-native, invasive species (blackberry and morning glory.) It will be necessary to clear the site in order to meet current standards. Removal of vegetation should be carefully performed so as to not adversely affect slope stability along the river bank. 11.11.11.11. REPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Launce Goulet to obtain a building permit variance for proposed residences to be constructed on King County tax parcel numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The recommendations are based on surface and subsurface information obtained by Bergquist Engineering Services Company, LLC (BESCO), and on an updated topographic survey provided by Encompass Engineering & Surveying. If there are any revisions to the plans or if conditions are encountered on site that deviate from our observations, BESCO must be notified immediately to determine whether changes to our recommendations are required. oOo 134 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 14 of 15 REFERENCESREFERENCESREFERENCESREFERENCES American Society for Testing and Materials, Description and Identification of Soils (Visual-Manual Procedure ASTM D2488): Annual Book of ASTM Standards, Section Four-Construction, Vol. 04-08, D2488-06, pp. 251-259. Anderson Bertrand & Company, 1888, Anderson’s New Map of King County, Washington Territory: Anderson, Bertrand & Company, Seattle, Washington Anderson Map Company, 1907, Anderson Map Coz Map of Auburn: Anderson Map Company, Seattle, Washington Atwater, B.F., and Hemphill-Haley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay, Washington: U.S. Geological Survey Professional Paper 1576, 108 p. City of Auburn, 2018, Green River to Auburn-Black Diamond Road: eGIS image of 1940 air photo mosaic, obtained via public information request. City of Auburn, 2005, Chapter 16.10 Critical Areas, Auburn Municipal Code Ord. 5894 § 1, 2005. City of Auburn, Washington, undated, City of Auburn GIS: https://maps.auburnwa.gov/Html5Viewer/index.html?viewer=public Galster, Richard W., 1989, Howard A. Hanson Dam: in Engineering Geology in Washington, Volume I, Washington Division of Geology and Earth Resources Bulletin 78, pp. 233-240. GeoEngineers, Inc., 2018, Channel Migration Zone Delineation, Middle Green River, RM 31.10 to 33.25, City of Auburn, Pierce (sic) County, Washington, for City of Auburn: report by GeoEngineers, Inc., dated December 28, 2018, 53p. King County, 2014, Chapter 21A-24, Rules and Regulations of the Department of Permitting and Environmental Review and Department of Natural Resources and Parks, Critical Areas: Designation, Classification and Mapping of Channel Migration Zones: Effective Date: June 14, 1999, most recent amendment September 7, 2017, 5 p., Appendix A, 20 p. Mullineaux, D.R., 1965, Geologic Map of the Auburn Quadrangle, King and Pierce Counties, Washington: United States Geological Survey Geologic Quadrangle Map GQ-406, Scale 1:24000. 135 of 721 Critical Areas Report November 4, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 2 Bergquist Engineering Services Company, LLC Page 15 of 15 Palmer, S.P., Magsino, S.L., Bilderback, E.L., Poelstra, J.L., Folger, D.S., and Niggermann, R.A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources, Open File Report 2004-20. Perkins, S.J., 1993, Green River Channel Migration Study: King County Department of Public Works, Surface Water Management Division, Seattle, WA, 81 p. Rogers, A.M., Walsh, T.J., Kockelman, W.J., and Priest, G.R., 1991, Earthquake Hazards in the Pacific Northwest: An Overview: US Geological Survey Open-File Report 91-441-0, p. 4. Satake, K., Wang, K., and Atwater, B., 2003, Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions: Journal of Geophysical Research, v. 108, 2535, doi:10.1029/2003JB002521 Shannon & Wilson, Inc., 2002, Preliminary Risk-Based Flood Damage Analysis, Green River Flood Control District, King County, Washington: Shannon & Wilson, Inc., submitted to Mr. Dave Clark, Water and Land Resources Division, Department of Natural Resources, Seattle, Washington, January 2002, 41 p. USDA Forest Service, 1984, Slope Stability Reference Guide for National Forests in the Pacific Northwest: Forest Service Engineering Staff, Washington, D.C., EM-7170-13, August 1994, pp. 345-400. US Geological Survey, 1975, Magnitude and Frequency of Floods in Washington, US Geological Survey Open File Report 74-336, Tacoma, WA, p. 24 Washington Department of Natural Resources, 1961, Symbol A-95, Flight 17, Exposures 8, 9, and 10: Aerial photographs dated 8-7-1961. Washington Department of Natural Resources, 1996, Symbol NW-96, Roll 49, Flight 49, Exposures 18, 19, and 20: Aerial photographs dated 6-20-1996. Williamson, D.A., Neal, K.G., and Larson, D.A., 1991, The Field-Developed Cross-Section: A Systematic Method of Portraying Dimensional Subsurface Information and Modeling for Geotechnical Interpretation and Analysis: Association of Engineering Geologists, Proceedings, 34th Annual Meeting, pp. 719-738. 136 of 721 137 of 721 138 of 721 139 of 721 140 of 721 141 of 721 142 of 721 143 of 721 144 of 721 TEST PIT LOG NOTESTEST PIT LOG NOTESTEST PIT LOG NOTESTEST PIT LOG NOTES These notes and test pit logs are intended for use with this geotechnical report for the purposes and project described therein. The test pit logs depict BESCO’s interpretation of subsurface conditions at the location of the test pit on the date noted. Subsurface conditions may vary, and groundwater levels may change because of seasonal variations or numerous other factors. Accordingly, the test pit logs should not be made a part of construction plans or be used to define construction conditions. The approximate locations of the test pits are shown on the Site Plan. The test pits were located in the field by estimating distances from existing site features. “Sample Type” refers to the sampling method and equipment used during exploration where: • "BS” indicates a bulk sample taken from the ground surface or from the backhoe bucket. “Moisture Content” refers to the moisture content of the soil expressed in percent by weight as determined in the laboratory. “Description and Classification” refer to the materials encountered in the test pit. The descriptions and classifications are generally based on visual examination in the field and laboratory. Where noted, laboratory tests were performed to determine the soil classification. The terms and symbols used in the test pit logs are in general accordance with the Unified Soil Classification System. Laboratory tests are performed in general accordance with applicable procedures described by the American Society for Testing and Materials. “” Indicates location of groundwater at the time noticed. Indicates location of seepage of water and the time noticed. TERMS for RELATIVE DENSITY of NON-COHESIVE SOIL Term Standard Penetration Resistance “N” Very Loose 4 or less Loose 5 to 10 Medium Dense 11 to 30 Dense 31 to 50 Very Dense Over 50 blows/foot A8 145 of 721 TEST PIT LOG NOTES continuedTEST PIT LOG NOTES continuedTEST PIT LOG NOTES continuedTEST PIT LOG NOTES continued TERMS for RELATIVE CONSISTENCY of COHESIVE SOIL Term Unconfined Compressive Strength Very Soft 0 to 0.25 tons/square-foot Soft 0.25 to 0.50 tsf Medium Stiff 0.50 to 1.00 tsf Stiff 1.00 to 2.00 tsf Very Stiff 2.00 to 4.00 tsf Hard Over 4.00 tsf DEFINITION of MATERIAL by DIAMETER of PARTICLE Boulder 8-inches+ Cobble 3 to 8 inches Gravel 3 inches to 5mm Coarse Sand 5mm to 0.6mm Medium Sand 0.6mm to 0.2mm Fine Sand 0.2mm to 0.074mm Silt 0.074 to 0.005mm Clay less than 0.005mm EXPLORATION METHODOLOGYEXPLORATION METHODOLOGYEXPLORATION METHODOLOGYEXPLORATION METHODOLOGY On September 16, 2018, five test pits were excavated at the site using a Cat 360 rubber track-mounted excavator. Test Pit TP-1 is located at Cross-Section C-C’, Station 10+18.0, and was excavated to a depth of 9.0 feet. Test Pit TP-2 is located at Cross-Section B-B’, Station 10+52.0 and was excavated to a depth of 9.6 feet. Test Pit TP-3 is located at Cross-Section A-A’, Station 10+84.1 and was excavated to a depth of 8.7 feet. Test Pit TP-4 is located at Cross- Section D-D’, Station 10+40.5 and was excavated to a depth of 8.9 feet. Test Pit TP-5 is located at Cross-Section D-D’, Station 11+16.4 and was excavated to a depth of 9.6 feet. Descriptions of observations and test results are provided on the test pit logs. Locations of the test pits are shown on the sketch entitled Site Plan on page A2. Grab samples of soil were obtained at select locations in each test pit to reflect changes in soil characteristics. Soil layers were described and classified using the Unified Soil Classification System visual-manual procedure, ASTM D2488 (American Society for Testing and Materials). The following page contains a table describing the elements of the system. A9 146 of 721 GROUP SYMBOL MAJOR DIVISIONS GW GP GM GC SW SP SM SC GROUP SYMBOL MAJOR DIVISIONS ML CL OL MH CH OH PT Highly organic soils Bergquist Engineering Services Company, LLC UNIFIED SOIL CLASSIFICATION SYSTEM PEAT, MUCK, and other highly organic soils SILTS and CLAYS Liquid limit greater than 50 Inorganic SILTS, Micaceous or Diatomaceous fine SANDS or SILTS, Elastic SILTS Inorganic CLAYS of high plasticity, fat CLAYS Organic CLAYS of medium to high plasticity Organic SILTS, or organic Silty CLAYS of low plasticity SANDS More than half of coarse fraction is smaller than No. 4 sieve. Note: Coarse-grained soils receive dual symbols if they contain between 5 and 12 percent fines. FINE-GRAINED SOILS (More than 50% fines. Fines are materials passing the # 200 sieve) Well-graded SANDS or Gravelly SANDS mixtures, less than 5% fines. SILTS and CLAYS Liquid limit less than 50 Note: Fine-grained soils receive dual symbols if their limits plot left of the "A" Line and have a plasticity index (PI) of 4 to 7 percent. DESCRIPTION Inorganic SILTS, very fine SANDS, ROCK FLOUR, Silty or Clayey SANDS Inorganic CLAYS of low to medium plasticity, Gravelly CLAYS, Sandy CLAYS, Silty CLAYS, Lean CLAYS Poorly graded SANDS or Gravelly SANDS mixtures, less than 5% fines. Silty SANDS, SAND-SILT mixtures, more than 12% fines. Clayey SANDS, SAND-CLAY mixtures, more than 12% fines UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) COARSE GRAINED SOILS (Less than 50% fines. Fines are soils passing the # 200 sieve.) DESCRIPTION Well-graded GRAVELS or GRAVEL-SAND mixtures, less than 5% fines. GRAVELS More than half of coarse fraction is larger than No. 4 sieve. Poorly graded GRAVELS or GRAVEL-SAND mixtures, less than 5% fines. Silty GRAVELS, GRAVEL- SAND-SILT mixtures, more than 12% fines. Clayey GRAVELS, GRAVEL- SAND-CLAY mixtures, more than 12% fines. A10 147 of 721 148 of 721 149 of 721 150 of 721 151 of 721 152 of 721 153 of 721 154 of 721 155 of 721 156 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 157 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 158 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 159 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 160 of 721 161 of 721 162 of 721 163 of 721 164 of 721 165 of 721 166 of 721 167 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 1 | P a g e Table of Contents Chapter 1: Project Overview ......................................................................................................................... 2 Chapter 2: Existing Conditions ...................................................................................................................... 4 Chapter 3: Off-Site Analysis (Minimum Requirement #10) .......................................................................... 7 Chapter 4: Permanent Stormwater Control Plan ........................................................................................ 10 Chapter 5: Discussion of Minimum Requirements ..................................................................................... 14 List of Figures Figure 1 – Vicinity Map Figure 2 – USGS Soils Map and Legend Figure 3 – Existing Conditions Map Figure 4 – Downstream Map Figure 5 – Developed Conditions Map Figure 6 – Drainage Review Flow Chart List of Appendices Appendix A – Hydraulic/Hydrologic Analysis and Modeling Results Appendix B – Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 168 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 2 | P a g e Chapter 1: Project Overview Project: Lot A: Goulet Residence Address: 32XXX 104th Place SE, Auburn, WA 98092 Tax Parcel #: 334100-0090 Site Area: 14,628 SF (0.34 Acres) Site Location: The site is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. The site is within NW 17-21-05, W.M, King County, Washington. Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Please refer to the Vicinity Map below. Figure 1 – Vicinity Map Proposed Improvements: Lot A is a 14,628 SF lot located on the eastern shore of the Green River in Auburn, Washington. The site is currently vacant and moderately forested. The project proposes to construct a 1,568 SF single-family residential home with attached garage and an approximately 391 SF driveway with access to 104th Place SE. This corresponds to an impervious lot coverage of 13.4%, which complies with the maximum lot coverage of 35%. Stormwater runoff from the developed site will be mitigated via a basic dispersion trench as described in Chapter 4 of this Drainage Report. SITE Amberview Apartments Green River Lot A 169 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 3 | P a g e Site Constraints: The property is located directly adjacent to the Green River and is within the Urban Conservancy Shoreline Designation; therefore, the project is subject to the City of Auburn Shoreline Master Program (SMP). The SMP requires that a 100 FT buffer from the ordinary high-water mark of the Green River be maintained for all development activities. The development proposed on Lot A will remain outside of the required 100 FT stream buffer. 170 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 4 | P a g e Chapter 2: Existing Conditions The project site is zoned R5 residential and is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. Single family residences have been constructed several parcels to the north and south of the site, although the site is directly adjacent to several undeveloped lots. The Green River borders the site to the west. An existing conditions map is provided as Figure 3 at the end of this Chapter. Critical Areas: The site is directly adjacent to the Green River and is located within the Urban Conservancy Shoreline Designation; therefore, development is subject to the City of Auburn Shoreline Master Program (SMP). The SMP requires that a 100 FT buffer from the ordinary high-water mark of the Green River be maintained for all development activities. There is also a 50 FT channel migration hazard buffer associated with the lot. Soils: Per the United States Geological Survey (USGS), the entire project site is underlain with mixed alluvial soils at approximately 5-8% slopes (Map Unit Ma). Please refer to the USGS Map and Table below. Figure 2 – USGS Soils Map and Legend Lot A 171 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 5 | P a g e The subject site was also investigated by Bergquist Engineering Services (BES). Based on the BES Critical Areas Report dated April 9, 2020 (Appendix B), the site is underlain by fine loose silty sand alluvial deposits from the Green River. Due to the parcel being located within an Erosion Hazard Zone, Habitat Protection Zone, River Channel Buffer Zone, and Groundwater Protection Zone, the site falls within the City of Auburn’s Infiltration Infeasibility Area. Based on BES’s Report in Appendix B, dispersion of stormwater is feasible as long as the dispersion trench is at least 50 feet from the ordinary high-water mark of Green River. Please refer to Chapter 4 for additional discussion on feasible stormwater BMPs. 172 of 721 173 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 7 | P a g e Chapter 3: Off-Site Analysis (Minimum Requirement #10) A qualitative downstream analysis was performed by Encompass Engineering and Surveying on Friday December 12, 2019. The proposed project site is currently undeveloped and moderately forested. The site slopes to the west toward the Green River at approximately 5-8%. There are no upstream areas tributary to the project site. Runoff from the project site sheet flows directly into the Green River. The Green River flows to the north under the SE 320th Street bridge and takes a turn to the east near the 104th Avenue SE Park. This location is approximately ¼ mile downstream of the project site, and is where the Level 1 Downstream Analysis was concluded. During the downstream analysis, no signs of erosion or downstream drainage problems were observed. In addition, there were no downstream drainage complaints found on King County iMap. Please refer to the Downstream Drainage Map, Drainage System Table, and photographs on the following pages for additional details. Figure 4 – Downstream Drainage Map 174 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 8 | P a g e Off-site Analysis Drainage System Table Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % ¼ ml = 1,320 ft. constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts A SHEET FLOW VEGETATION 5-8% 0’ NO NO POINT OF DISCHARGE B RIVER CHANNEL GREEN RIVER NA 2,190’ NO NO FLOWS NORTH ALONG WESTERN PROPERTY LINE, PASSES UNDER THE SE 320TH ST BRIDGE, AND BEND TO THE EAST NEAR 104TH AVE SE PARK. THIS IS WHERE ANALYSIS WAS CONCLUDED. Photo 1 – Project Site from 104th Place SE 175 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 9 | P a g e Photo 2 – Green River from Site Looking North Photo 3 – Green River from SE 320th Street Bridge Looking North 176 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 10 | P a g e Chapter 4: Permanent Stormwater Control Plan The 14,628 SF (0.34 AC) site is currently undeveloped and moderately forested. The project proposes to construct a 1,568 SF (0.036 AC) single-family residential home with attached garage and an approximately 391 SF (0.009 AC) driveway with access to 104th Place SE. The site is contained within a single drainage basin that discharges to the west toward the Green River. Runoff generated by the proposed improvements will be managed onsite. A Developed Conditions Map is provided as Figure 5 at the end of this Chapter. Pre-Developed Site Hydrology The 4,896 SF (0.112 AC) within the limits of construction have been modeled as 100% forested with moderate slopes in the pre-developed condition. Developed Site Hydrology As described in the Section on the following page pertaining to the on-site stormwater management system (Minimum Requirement #5), basic dispersion is proposed to mitigate runoff from the proposed impervious areas on-site. Therefore, these areas have been modeled as 90% impervious and 10% lawn in the hydraulic/hydrologic model for the developed condition. All new pervious area has been modeled as 100% pasture by utilizing post construction soil depth and quality. The area within the limits of construction was modeled as follows for the developed condition: Feature Area Developed Conditions Model Roof Area 1,568 SF (0.036 Ac) 1,411 SF (0.032 AC) Roof, flat; 157 SF (0.004 AC) lawn, moderate slope Driveway 391 SF (0.009 Ac) 352 SF (0.008 AC) Driveway, moderate slope; 39 SF (0.001 AC) lawn, moderate slope New Pervious 2,937 (0.067 Ac) 2,937 SF (0.067 AC) pasture, moderate slopes TOTAL AREA 4,896 SF (0.112 Ac) See Above The resulting increase in flow from the 100-year storm event is 0.0308 CFS as shown in the table below. The full WWHM output is included in Appendix A. 177 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 11 | P a g e On-Site Stormwater Management System – Minimum Requirement #5 This project is considered to be a new development, located inside of the Urban Growth Area, and triggers only Minimum Requirements #1 - #5 (See Chapter 5 for further discussion). To meet the applicable requirements per Figure 2.5.1 of the City of Auburn Supplemental Manual, this project proposes to apply On-site Stormwater Management List #1. Due to the parcel being located within an Erosion Hazard Zone, Habitat Protection Zone, River Channel Buffer Zone, and Groundwater Protection Zone, the site falls within the City of Auburn’s Infiltration Infeasibility Area. This means that stormwater runoff mitigation through full infiltration (BMP T5.10A), rain gardens (BMP T5.14A), Bioretention (BMP T7.30), and Permeable Pavement (BMP T5.15) are not considered feasible for the site. The remaining applicable BMPs have been considered below in the order listed for each type of surface. Lawn and Landscaped Areas: 1. Post-Construction Soil Quality and Depth (BMP T5.13): This BMP will be implemented throughout the pervious areas of the site. Approximately 2,937 SF of new pervious surface areas will utilize this BMP. Outside of the project clearing limits, topso il will remain undisturbed. Topsoil that is disturbed by construction will be stockpiled in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible. Areas within the clearing limits designated to be pervious surfaces, will re-establish soil quality per the requirements detailed in Volume V BMP T5.13. Per the DOE Manual, areas meeting these guidelines have been modeled as “Pasture” rather than “Lawn” in the Flow Control Analysis detailed above in Chapter 4 of this Drainage Report. Roofs: 1. Full Dispersion (BMP T5.30): Full dispersion is not feasible for the project. The site does not allow for the minimum 100 FT native vegetated flowpath segment required to utilize full dispersion BMPs. 2. Downspout Dispersion Systems (BMP T5.10B): According to the BES Critical Areas Report (Appendix B), downspout dispersion is feasible for the project so long as the dispersion device is at least 50 feet from the ordinary high-water mark of Green River. Therefore, a 50 FT gravel filled basic dispersion trench with notched board and 25 FT native vegetated flowpath will be utilized to manage runoff from the 1,568 SF roof area. This is well within the 3,500 SF capacity of the trench. 3. Perforated Stub-out Connections (BMP T5.10C): No additional roof areas to mitigate. Other Hard Surfaces: 1. Full Dispersion (BMP T5.30): Full Dispersion is not feasible for the project. The site design does not allow for the minimum 100 FT native vegetated flowpath segment required to utilize full dispersion BMPs. This BMP is feasible for the project as Basic Dispersion. A basic dispersion system in the form of a 50 FT gravel filled dispersion trench with notched board and 25 FT native vegetated flowpath will be utilized to manage runoff from the site as described above. In addition to the 1,568 SF roof area, the 391 SF driveway will also be directed to this dispersion trench. The combined tributary area is 1,959 SF, which is within the 3,500 SF limit. 178 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 12 | P a g e 2. Concentrated Flow Dispersion (BMP T5.11) or Sheet Flow Dispersion (BMP T5.12): No additional hard surfaces to mitigate. 179 of 721 180 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 14 | P a g e Chapter 5: Discussion of Minimum Requirements The City of Auburn manages stormwater generated by development through adoption of the 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual). The City also has developed their own Supplement to the SMMWW which provides additional or modified requirements to the SMMWW (Supplemental Manual). Both manuals have been utilized in the design of this project. For simplicity, both manuals in conjunction will be referred to as “the drainage manual” unless one or the other is specified. The total proposed impervious area is 1,959 SF, which is less than 5,000 SF. Therefore, the project is required to comply with Minimum Requirements 1 through 5. Discussion of these minimum requirements is contained in this Chapter. Figure 6 – Flow Chart for Determining Minimum Requirements for New Developments 181 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 15 | P a g e Minimum Requirement #1: Preparation of Stormwater Site Plans The Stormwater Site Plan has been prepared in accordance with the 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual) and the 2017 City of Auburn Supplemental Manual to the Ecology Stormwater Management Manual for Western Washington (Supplemental Manual). Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (CSWPPP) A CSWPPP, which will serve to minimize soil erosion/sedimentation during the proposed site construction, will be prepared for approval by the City of Auburn with final engineering. Minimum Requirement #3: Source Control of Pollution Actions taken each day in and around homes have a profound effect on surface water quality and fish habitat in this region. Stormwater goes directly to rivers, streams and to Puget Sound. Stormwater does not go to the wastewater treatment plant. Any pollutants that get into the stormwater go directly to surface water. Small amounts of pollution from many different sources can significantly affect our waterways. Yard maintenance, waste storage, car washing and maintenance, and pool cleaning are some of the activities that can adversely impact water quality. An Operations & Maintenance Manual that addresses source control best management practices (BMPs) for single-family residential homeowners will be provided with final engineering. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The proposed on-site drainage patterns emulate those of the existing site conditions. Stormwater runoff from the site is proposed to be mitigated via dispersion as described in Chapter 4 of this Drainage Report. The associated native vegetated flowpaths will drain toward the Green River, as they do in the existing condition. Minimum Requirement #5: On-Site Stormwater Management The project proposes to utilize basic dispersion via a 50 FT gravel filled dispersion trench with 25 FT native vegetated flowpath to mitigate runoff from the proposed 1,568 SF residence and 391 SF driveway. Please refer to Chapter 4 of this Report for further discussion on how the applicable BMPs were selected. Minimum Requirement #10: Off-Site Analysis and Mitigation The site is located directly adjacent to the Green River, which flows to the north along the western property line. No erosion or drainage problems currently exist on the site, and no off-site drainage complaints have been found within a quarter mile downstream of the project. Please refer to Chapter 3 of this Drainage Report for additional discussion. 182 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 16 | P a g e Appendix A Hydraulic/Hydrologic Analysis and Modeling Results 183 of 721 WWHM2012 PROJECT REPORT 184 of 721 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 2 General Model Information Project Name:WWHM Model_Lot A Site Name:Goulet Lot A Site Address: City: Report Date:3/3/2020 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 185 of 721 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.112 Pervious Total 0.112 Impervious Land Use acre Impervious Total 0 Basin Total 0.112 Element Flows To: Surface Interflow Groundwater 186 of 721 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.005 C, Pasture, Mod 0.067 Pervious Total 0.072 Impervious Land Use acre ROOF TOPS FLAT 0.032 DRIVEWAYS MOD 0.008 Impervious Total 0.04 Basin Total 0.112 Element Flows To: Surface Interflow Groundwater 187 of 721 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 5 Routing Elements Predeveloped Routing 188 of 721 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 6 Mitigated Routing 189 of 721 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.112 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.072 Total Impervious Area:0.04 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.003335 5 year 0.005464 10 year 0.006834 25 year 0.008462 50 year 0.009591 100 year 0.010645 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.017612 5 year 0.023141 10 year 0.027093 25 year 0.032432 50 year 0.036666 100 year 0.041128 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.004 0.025 1950 0.005 0.022 1951 0.007 0.016 1952 0.002 0.012 1953 0.002 0.012 1954 0.003 0.015 1955 0.005 0.016 1956 0.004 0.015 1957 0.003 0.019 1958 0.003 0.014 190 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 8 1959 0.003 0.014 1960 0.005 0.018 1961 0.003 0.016 1962 0.002 0.012 1963 0.002 0.016 1964 0.003 0.014 1965 0.002 0.019 1966 0.002 0.012 1967 0.005 0.023 1968 0.003 0.023 1969 0.003 0.017 1970 0.002 0.017 1971 0.003 0.019 1972 0.006 0.022 1973 0.002 0.011 1974 0.003 0.018 1975 0.004 0.020 1976 0.003 0.015 1977 0.000 0.013 1978 0.002 0.017 1979 0.001 0.023 1980 0.007 0.029 1981 0.002 0.018 1982 0.004 0.027 1983 0.004 0.019 1984 0.002 0.013 1985 0.001 0.017 1986 0.006 0.017 1987 0.005 0.022 1988 0.002 0.013 1989 0.001 0.018 1990 0.012 0.043 1991 0.006 0.029 1992 0.003 0.013 1993 0.003 0.011 1994 0.001 0.011 1995 0.004 0.016 1996 0.008 0.022 1997 0.007 0.018 1998 0.002 0.016 1999 0.007 0.033 2000 0.003 0.017 2001 0.000 0.017 2002 0.003 0.023 2003 0.004 0.022 2004 0.005 0.033 2005 0.003 0.016 2006 0.004 0.015 2007 0.009 0.038 2008 0.011 0.029 2009 0.005 0.021 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0121 0.0428 2 0.0111 0.0376 3 0.0091 0.0329 191 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 9 4 0.0085 0.0329 5 0.0073 0.0292 6 0.0072 0.0292 7 0.0065 0.0290 8 0.0065 0.0269 9 0.0064 0.0253 10 0.0057 0.0231 11 0.0055 0.0228 12 0.0052 0.0227 13 0.0051 0.0226 14 0.0050 0.0222 15 0.0050 0.0219 16 0.0047 0.0218 17 0.0046 0.0216 18 0.0045 0.0216 19 0.0044 0.0205 20 0.0042 0.0195 21 0.0039 0.0195 22 0.0038 0.0190 23 0.0038 0.0189 24 0.0037 0.0189 25 0.0037 0.0184 26 0.0036 0.0182 27 0.0035 0.0179 28 0.0034 0.0177 29 0.0033 0.0177 30 0.0029 0.0175 31 0.0029 0.0175 32 0.0029 0.0171 33 0.0028 0.0169 34 0.0028 0.0168 35 0.0028 0.0167 36 0.0028 0.0165 37 0.0027 0.0161 38 0.0027 0.0160 39 0.0026 0.0157 40 0.0026 0.0157 41 0.0025 0.0156 42 0.0025 0.0156 43 0.0025 0.0156 44 0.0024 0.0152 45 0.0023 0.0152 46 0.0023 0.0147 47 0.0023 0.0147 48 0.0022 0.0142 49 0.0022 0.0138 50 0.0021 0.0136 51 0.0020 0.0133 52 0.0020 0.0132 53 0.0018 0.0132 54 0.0017 0.0128 55 0.0016 0.0124 56 0.0014 0.0123 57 0.0013 0.0123 58 0.0013 0.0116 59 0.0009 0.0113 60 0.0005 0.0113 61 0.0004 0.0111 192 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 10193 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 11 Duration Flows Flow(cfs)Predev Mit Percentage Pass/Fail 0.0017 17085 77385 452 Fail 0.0017 15490 73086 471 Fail 0.0018 14072 68957 490 Fail 0.0019 12803 65150 508 Fail 0.0020 11569 61471 531 Fail 0.0021 10521 58049 551 Fail 0.0021 9567 54969 574 Fail 0.0022 8752 52103 595 Fail 0.0023 8040 49344 613 Fail 0.0024 7349 46799 636 Fail 0.0025 6737 44403 659 Fail 0.0025 6192 42179 681 Fail 0.0026 5730 40147 700 Fail 0.0027 5311 38158 718 Fail 0.0028 4924 36340 738 Fail 0.0029 4567 34564 756 Fail 0.0029 4235 32939 777 Fail 0.0030 3951 31313 792 Fail 0.0031 3643 29837 819 Fail 0.0032 3388 28404 838 Fail 0.0033 3133 27057 863 Fail 0.0033 2915 25816 885 Fail 0.0034 2704 24597 909 Fail 0.0035 2488 23528 945 Fail 0.0036 2314 22458 970 Fail 0.0037 2136 21410 1002 Fail 0.0037 1972 20463 1037 Fail 0.0038 1824 19537 1071 Fail 0.0039 1702 18670 1096 Fail 0.0040 1577 17851 1131 Fail 0.0041 1442 17098 1185 Fail 0.0041 1325 16365 1235 Fail 0.0042 1232 15657 1270 Fail 0.0043 1147 14972 1305 Fail 0.0044 1085 14318 1319 Fail 0.0045 1020 13708 1343 Fail 0.0045 947 13154 1389 Fail 0.0046 886 12596 1421 Fail 0.0047 824 12119 1470 Fail 0.0048 760 11627 1529 Fail 0.0049 725 11154 1538 Fail 0.0049 674 10714 1589 Fail 0.0050 623 10262 1647 Fail 0.0051 589 9837 1670 Fail 0.0052 549 9471 1725 Fail 0.0053 506 9086 1795 Fail 0.0053 469 8735 1862 Fail 0.0054 427 8425 1973 Fail 0.0055 388 8108 2089 Fail 0.0056 356 7820 2196 Fail 0.0057 328 7552 2302 Fail 0.0057 297 7289 2454 Fail 0.0058 270 7016 2598 Fail 0.0059 241 6731 2792 Fail 194 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 12 0.0060 218 6500 2981 Fail 0.0061 197 6246 3170 Fail 0.0061 173 5978 3455 Fail 0.0062 152 5754 3785 Fail 0.0063 130 5572 4286 Fail 0.0064 119 5379 4520 Fail 0.0065 104 5191 4991 Fail 0.0065 95 5011 5274 Fail 0.0066 83 4825 5813 Fail 0.0067 74 4669 6309 Fail 0.0068 69 4519 6549 Fail 0.0069 61 4348 7127 Fail 0.0069 53 4169 7866 Fail 0.0070 46 4023 8745 Fail 0.0071 39 3878 9943 Fail 0.0072 29 3730 12862 Fail 0.0073 25 3595 14380 Fail 0.0074 22 3465 15750 Fail 0.0074 20 3354 16770 Fail 0.0075 17 3230 19000 Fail 0.0076 14 3138 22414 Fail 0.0077 12 3035 25291 Fail 0.0078 8 2930 36625 Fail 0.0078 7 2843 40614 Fail 0.0079 7 2757 39385 Fail 0.0080 7 2661 38014 Fail 0.0081 6 2573 42883 Fail 0.0082 6 2483 41383 Fail 0.0082 6 2396 39933 Fail 0.0083 6 2321 38683 Fail 0.0084 6 2252 37533 Fail 0.0085 5 2184 43680 Fail 0.0086 5 2123 42460 Fail 0.0086 5 2059 41180 Fail 0.0087 5 2001 40020 Fail 0.0088 5 1946 38920 Fail 0.0089 5 1887 37740 Fail 0.0090 5 1832 36640 Fail 0.0090 4 1780 44500 Fail 0.0091 4 1733 43325 Fail 0.0092 3 1676 55866 Fail 0.0093 3 1629 54300 Fail 0.0094 3 1585 52833 Fail 0.0094 3 1532 51066 Fail 0.0095 3 1494 49800 Fail 0.0096 3 1458 48600 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. 195 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. 196 of 721 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 14 LID Report 197 of 721 WWHM Model_Lot A 3/3/2020 7:51:30 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 198 of 721 WWHM Model_Lot A 3/3/2020 7:51:30 AM Page 16 Appendix Predeveloped Schematic 199 of 721 WWHM Model_Lot A 3/3/2020 7:51:33 AM Page 17 Mitigated Schematic 200 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM Model_Lot A.wdm MESSU 25 PreWWHM Model_Lot A.MES 27 PreWWHM Model_Lot A.L61 28 PreWWHM Model_Lot A.L62 30 POCWWHM Model_Lot A1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 11 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO 201 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 19 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 11 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 202 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 20 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 11 0.112 COPY 501 12 PERLND 11 0.112 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC 203 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 21 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN 204 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM Model_Lot A.wdm MESSU 25 MitWWHM Model_Lot A.MES 27 MitWWHM Model_Lot A.L61 28 MitWWHM Model_Lot A.L62 30 POCWWHM Model_Lot A1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 17 PERLND 14 IMPLND 4 IMPLND 6 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 17 C, Lawn, Mod 1 1 1 1 27 0 14 C, Pasture, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 17 0 0 1 0 0 0 0 0 0 0 0 0 14 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO 205 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 23 <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 17 0 0 4 0 0 0 0 0 0 0 0 0 1 9 14 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 17 0 0 0 0 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 17 0 4.5 0.03 400 0.1 0.5 0.996 14 0 4.5 0.06 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 17 0 0 2 2 0 0 0 14 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 17 0.1 0.25 0.25 6 0.5 0.25 14 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 17 0 0 0 0 2.5 1 0 14 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 6 DRIVEWAYS/MOD 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 6 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 6 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 206 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 24 4 0 0 0 0 0 6 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 6 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 6 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 6 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 17 0.005 COPY 501 12 PERLND 17 0.005 COPY 501 13 PERLND 14 0.067 COPY 501 12 PERLND 14 0.067 COPY 501 13 IMPLND 4 0.032 COPY 501 15 IMPLND 6 0.008 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO 207 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 25 HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN 208 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 26 Predeveloped HSPF Message File 209 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 27 Mitigated HSPF Message File 210 of 721 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. 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Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com 211 of 721 Lot A: Goulet Residence Preliminary Storm Drainage Report 17 | P a g e Appendix B Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 212 of 721 CRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCES PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010 AUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULET by:by:by:by: BERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLC BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1, REVISION 1, REVISION 1, REVISION 1, REVISION 1 APRIL 9, 2020APRIL 9, 2020APRIL 9, 2020APRIL 9, 2020 213 of 721 Bergqoist Engineering Services 27207 8th Avenue S R O. Box 13309 Des Moines, Washington 98198 Des Moines, Washington 98198 Phone: 253,941.9399 • Fax 253,941,9499 • E-mail: soilsengineering@aol,conn April 9, 2020 Mr. Launce Goulet 3226 S 198'^ Street SeaTac, Washington 98188 Re: Critical Area Report Proposed Single-Family Residences King County Parcel Numbers; 3341000090, 3341000095, and 33410000210 Auburn, Washington BESCO Project No.: 2018214, Report 1, Revision 1 Dear Launce: Bergquist Engineering Services Company, LLC is pleased to provide this Critical Area Report for the referenced King County parcels. The attached report summarizes project and site data, describes the services we performed, and presents our conclusions relative to soil erosion and channel migration and the stability of the off-site, steep slope along the east side of 104'*" Place SE. We appreciate the opportunity to be of service to you. If you have any questions concerning this report, or if we may be of additional service, please contact us. Copies to: Addressee (5) DOWN TO EARTH ENGINEERING SOLUTIONS 214 of 721 TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS 1. INTRODUCTION ......................................................................................................................... 1 2. PROJECT DESCRIPTION ............................................................................................................. 2 3. SCOPE OF SERVICES .................................................................................................................. 2 4. SITE CHARACTERIZATION ......................................................................................................... 3 4.1 Topography and Development ....................................................................................... 3 4.2 Area Geology ................................................................................................................... 4 4.3 Seismicity ......................................................................................................................... 4 4.4 Site Geology ..................................................................................................................... 5 4.5 Subsurface Soils ............................................................................................................... 5 4.6 Ground Water and Drainage........................................................................................... 7 4.7 Site Classification ............................................................................................................. 7 5. FLOODING AND CHANNEL MIGRATION .................................................................................. 8 6. EROSION AND SLOPE STABILITY ............................................................................................... 9 7. SLOPE STABILITY ANALYSIS ....................................................................................................... 9 7.1 Assumptions .................................................................................................................... 9 7.2 Analysis ........................................................................................................................... 10 8. DISCUSSION .............................................................................................................................. 10 9. CONCLUSIONS .......................................................................................................................... 11 9.1 Flooding and Channel Migration ............................................................................. 11 9.2 Slope Stability and Erosion ...................................................................................... 11 9.3 Seismicity .................................................................................................................. 12 10. RECOMMENDATIONS .............................................................................................................. 12 11. PEPORT LIMITATIONS .............................................................................................................. 13 APPENDIXAPPENDIXAPPENDIXAPPENDIX AAAA Vicinity Map ................................................................................................................................. A1 Site Plan .................................................................................................................................. A2 Logs of Test Pits ................................................................................................................................ A3 Test Pit Log Notes ............................................................................................................................ A8 Unified Soil Classification System ................................................................................................... A10 Particle Size Distribution Reports ................................................................................................... A11 Cross Sections ................................................................................................................................. A20 APPENDIX BAPPENDIX BAPPENDIX BAPPENDIX B Computer Printouts of Slope Stability Analyses ............................................................................. B1 Notes .................................................................................................................................. B4 215 of 721 CRITICAL AREASCRITICAL AREASCRITICAL AREASCRITICAL AREAS REPORTREPORTREPORTREPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCESSSS PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095, , , , andandandand 3341000010334100001033410000103341000010 AUBURNAUBURNAUBURNAUBURN, WASHINGTON, WASHINGTON, WASHINGTON, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNMR. LAUNMR. LAUNMR. LAUNCCCCE P.E P.E P.E P. GOULETGOULETGOULETGOULET by:by:by:by: BERGQUIST BERGQUIST BERGQUIST BERGQUIST ENGINEERING SERVICESENGINEERING SERVICESENGINEERING SERVICESENGINEERING SERVICES COMPANY, LLCCOMPANY, LLCCOMPANY, LLCCOMPANY, LLC BESBESBESBESCOCOCOCO PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: 2018201820182018214214214214, , , , REPORT 1REPORT 1REPORT 1REPORT 1, R, R, R, REVISION EVISION EVISION EVISION 1111 April 9April 9April 9April 9, 2020, 2020, 2020, 2020 1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION This report presents the results of our geotechnical evaluation of critical areas for three proposed single-family residences to be constructed on King County Parcel Numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The parcels are located along the east bank of the Green River west of 104th Place Southeast, in the northwest quarter of the northwest quarter of Section 17, Township 21 North, Range 5 East, Willamette Meridian. The location of the project is shown on the Vicinity Map, Figure 1, on page A1 in Appendix A of this report. This report was revised because datum used for the current site plans, dated January 24, 2020 are NAVD 88, rather than the City of Auburn datum used on the originally submitted plans dated November 7, 2017. This report also provides additional information as a result of a site visit by Mr. Bergquist, who observed the level of the Green River on February 9, 2020, shortly after it exceeded the base flood elevation, and a follow-up visit by Messrs. Bergquist and Neal, who located and marked the maximum 2020 flood level. The geotechnical evaluation was performed by Bergquist Engineering Services Company, LLC (BESCO) to provide information or recommendations regarding: • erosion and slope stability characteristics, in accordance with Auburn City Code 16.10, • the risk of liquefaction and seismic design considerations, and • the influence of ground and surface water on the development. 216 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 2 of 15 This report is not intended to provide geotechnical criteria for design of the planned houses. The data for developing design criteria will be completed after critical area issues are addressed, and the various variances for these properties are obtained. The critical issues addressed in this report are; channel migration, landslide hazards, erosion hazards, flooding and seismic hazards. Mr. Launce P. Goulet authorized our work on March 19th, 2018 by signing and returning BESCO Proposal Number 1162018. 2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION The proposed project would involve construction of one multi-level house on each of the three vacant properties. The footprints and finished grades of the houses have not yet been finalized. 3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES The scope of services included the following steps: • an initial reconnaissance of the site by the geotechnical engineer; • excavating, logging, and sampling five test pits; logs of the test pits are presented in Appendix A on pages A3 through A7; • field and laboratory testing of selected soil samples, including visual classification and gradations; • a review of geologic and historic literature, and historic aerial photography; a list of references is contained in Appendix B; • measurement of a geotechnical cross-section for each parcel, and development of a geologic interpretation for the site by the engineering geologist; • a preliminary evaluation of soil strength and drainage characteristics; • evaluation of past and likely future migration of the Green River channel; • geotechnical slope stability analyses; • observation of the maximum recent flood elevation at the site; and • preparation of this report. Slope relationships for our cross-section were measured using a cloth tape, hand clinometer and Brunton compass in accordance with methodology outlined in Williamson, Neal and Larson (1991). The measurements used to develop the cross-sections and site plan are therefore, not of the precision and accuracy of a site survey prepared by a professional land surveyor, and should not be used for that purpose. 217 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 3 of 15 The recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical practices in the area. 4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION The information presented in this section was gathered by BESCO personnel for evaluation of critical area issues only. This site characterization was not intended to address the presence or likelihood of contamination on or around the site. Specialized methods and procedures, which were not a part of this scope of services, are required for an adequate environmental site assessment. 4.14.14.14.1 Topography and DevelopmentTopography and DevelopmentTopography and DevelopmentTopography and Development Parcels 3341000090, 3341000095, and 3341000010, referred to as Lots A, B, and C on the Site Plan, Figure 2, encompass 12,765, 11,644, and 11,777 square feet, respectively. The parcels are bounded on the east by 104th Place Southeast, on the west by the Green River, and to the north and south by developed single-family residential lots. Topographic relationships are shown on the sketch entitled, “Site Plan” presented on page A2 and on Cross-Sections A-A’, B-B’ C-C,’ and D-D’, presented on pages A20 through A22. Elevations shown on the cross-sections and test pit logs are based on a site and topographic plan for the parcels prepared by Encompass Engineering & Surveying, dated 1/14/2020, and our measurements. There is approximately 20 feet of relief on Parcel A, from an elevation of approximately 56 feet mean sea level (MSL) at the ordinary high water mark (OHWM) of the Green River at the northwest corner of the property to an elevation of approximately 76 feet MSL at the southeast property corner. There is approximately 20 feet of relief on Parcel B, from an elevation of approximately 56 feet MSL at the OHWM at the northwest corner of the property to an elevation of approximately 76 feet MSL at the northwest corner of the property. There is approximately 18 feet of relief on Parcel C, from an elevation of approximately 56 feet MSL along the OHWM and west parcel boundary to an elevation of approximately 74 feet MSL along the east parcel boundary and at the northeast corner. The eroded streambank of the Green River is inclined at from 10 percent to near-vertical. The ground surface is nearly level from the top of the streambank to the base of the fill slope just below 104th Place Southeast. It steepens to between 15 to 20 percent adjacent to 104th Place Southeast. The cut slope along the east side of 104th Place Southeast was constructed at approximately 1.18H:1V (horizontal:vertical) (85 percent). 218 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 4 of 15 The parcels are vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry and, along the river, morning glory. This vegetation reflects the year-round availability of water. A dead snag fell across the location of Cross-Section B-B’ apparently during the winter storms of 2020. 4.24.24.24.2 Area GeologyArea GeologyArea GeologyArea Geology The project area is situated in the Puget Sound basin, a structural low between the Cascade and Olympic Mountain physiographic provinces. The Puget Sound region has been subjected to at least six episodes of glaciations during the last two million years. The most recent glaciation, referred to as the Vashon stade of the Fraser glaciations, stalled and began rapid melting about 12,000 years ago. The glaciations left topography in the Puget Sound region characterized by north-south trending ridges and troughs. The troughs, such as the Puget Sound, Duwamish Channel, and Kent Valley, served as subglacial channels for southward-flowing meltwater. The glaciers formed deposits in front of advancing ice, along the ice margins, during the retreat of the ice front, and during interglacial periods. These deposits have subsequently been overridden and compacted by the advancing Vashon ice sheet. Some of the capping silts, sands, and gravels were likely deposited during Vashon glacial recession. Slope, fluvial, volcanic, and shoreline processes have shaped the land within the area over the 12,000 years since glacial retreat. Approximately 5,600 years ago, the Osceola Mudflow, a lahar originating from Mount Rainier, flowed down the West Fork of the White River and the White River valleys through the areas now occupied by Buckley, Enumclaw, and Auburn to as far north as Kent. The Electron Mudflow, also a Mount Rainier lahar, flowed down the Puyallup River through Orting and Puyallup and into the Kent Valley approximately 500 years ago. The White and Green Rivers have subsequently eroded through the lahars and infilled the floors of the resulting valleys with alluvial deposits. 4.34.34.34.3 SeismicitySeismicitySeismicitySeismicity The Puget Sound region is seismically active. Low magnitude earthquakes occur nearly every week within a 50-mile radius of the site. On April 13, 1949, the Olympia area experienced an earthquake having a Richter Magnitude 7.1 and, on April 29, 1965, the Tacoma-Seattle area experienced an earthquake having a Richter Magnitude 6.5 (Rogers, Walsh, Kockelman and Priest, 1991). On February 28, 2001, a magnitude 6.8 earthquake occurred just north of the Nisqually delta. 219 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 5 of 15 Great subduction zone earthquakes are the largest earthquakes in the world, and are the only source zones that can produce earthquakes greater than Magnitude 8.5. The Cascadia Subduction Zone, located off the coastlines of Washington, Oregon, and northern California, has produced magnitude 9.0 or greater earthquakes in the past. The last known megathrust earthquake in the northwest was in January, 1700 (Satake, Wang, and Atwater, 2003). Geological evidence indicates that such great earthquakes have occurred at least seven times in the last 3,500 years, a return interval of 400 to 600 years (Atwater and Hemphill-Haley, 1997). The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann, 2007). 4.44.44.44.4 Site GeologySite GeologySite GeologySite Geology Glacial and interglacial deposits are exposed in the Green River valley wall east of 104th Place Southeast. These deposits have been interpreted to include, from oldest (lowest on the slope) to youngest (top of the slope) the interglacial Puyallup Formation, overlain by glacial drift from the Salmon Springs glacial stade, and kame terrace deposits from the most recent (Vashon) stade. The glacially-derived deposits are overlain along the Green River and at the subject properties by Green River alluvial and fluvial (flood) deposits, consisting of fine sand with lenses of gravel, locally overlain by silt and clay (Mullineaux, 1965). Geologic processes on the properties are primarily associated with stream flow along the Green River. Flow is controlled in part by Howard A. Hansen Dam, which was constructed in Eagle Gorge and is used primarily for flood control in the lower Green-Duwamish valley (Galster, 1989). The primary process potentially affecting the properties is river erosion and deposition during flood events. While this risk is somewhat diminished by control of flows during floods by the aforementioned dam, the City of Auburn has designed much of the properties as being a “channel migration area (CMA)” on their city flood map. The regulatory flood elevation for the river reach adjacent to the properties is 66 to 67 feet MSL. 4.5 4.5 4.5 4.5 Subsurface SoilsSubsurface SoilsSubsurface SoilsSubsurface Soils The subsurface soil conditions at this site are described in the following paragraphs and are presented graphically on the test pit logs. The test pit locations are shown on the Site Plan, Figure 2 in page A2 of Appendix A, and on Cross-Sections A-A’, B-B’, C-C’, and D-D’, Figures 3, 4, 5, and 6, respectively. 220 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 6 of 15 Soils were described and classified in general accordance with the Unified Soil Classification visual- manual procedure (American Society for Testing and Materials). A description of this system is included on page A10. Results of soil gradation tests are presented on pages A11 through A18. For purposes of explanation, we divided on-site soils into three soil units, SU-A, SU-B, and SU-C, based on origin and physical characteristics. Soil units are shown on the cross-sections; soil unit designations are intended to be local in scope, and not applicable outside the immediate area. A thin layer of organics, primarily blackberry roots, was noted at the top of each test pit. The roots generally reach to depths of 1.5 to 2 feet. SU-A was encountered along the base of the cut slope opposite the properties. Although the valley wall formed of this material is projected to be located beneath the east side of the property, it was not encountered in our test pits. SU-A consists of gray brown silty fine SAND (ASTM: SM). SU-A is a non-plastic soil that was moist, and was dense at the time of our field work. SU-A is interpreted to be an interglacial deposit. SU-B was encountered below depths of 7.0 feet in TP-1, 7.0 feet in TP-2, 7.5 feet in TP-3, and 6.5 in TP-5. SU-B is brown to gray in color, and ranges from silty fine SAND with silt interbeds to SILT with silty fine sand interbeds (ASTM: SM/ML to ML/SM). Orange-brown to black iron staining forms bands that become more frequent with depth. SU-B is a plastic soil that was moist to wet, with the natural moisture content ranging from below to above the plastic limit. SU-B was loose to soft at the time of our exploration. SU-B is interpreted to be an alluvial deposit, an overbank deposit of the Green River. SU-C was encountered overlying SU-B in all five test pits, from the ground surface to a depth of 7.0 feet in TP-1, between depths of 1.7 and 7.0 feet in TP-2, between 1.7 and 7.5 feet in TP-3, below 2.2 feet in TP-4, and from the ground surface to a depth of 6.5 feet in TP-5. SU-C consists of light brown to gray brown Silty fine SAND (ASTM: SM). SU-C is a non-plastic soil that was dry to locally moist, and was loose at the times of our exploration. SU-C is interpreted to be an alluvial deposit, an overbank deposit of the Green River). In addition to the soil units observed at the site, fill materials were encountered along the ground surface over the northern portion of the site and in TP-3 and TP-4, to depths of 1.7 feet in TP-3 and 221 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 7 of 15 2.2 feet in TP-4. This fill material consists of light brown silty fine SAND with coarse gravel (ASTM: SM), that ranged from a dry, non-plastic soil to a moist plastic soil with the natural moisture content below the plastic limit at the time of our exploration. This fill material appears to have been spread over the north parcel by heavy equipment and was dense at the time of our field work. Fill materials are also present beneath the outside shoulder of 104th Place Southeast along the east periphery of the parcels. It appears that the parcels have also been used as a location to dump garbage, particularly just downslope from the shoulder of the street. 4.64.64.64.6 Ground Water and Ground Water and Ground Water and Ground Water and DrainageDrainageDrainageDrainage At the time of our exploration, the King County region had experienced an extended, near record drought. Accordingly, no surface or ground water was encountered on the site. Soil moisture was encountered in three test pits at or just above the stream elevation. Water was encountered near the ground surface in the backfilled TP-2 by Mr. Bergquist during his February 9, 2020 site visit. No drainage features were observed on site. During our September 12, 2018 site visit, which followed a rain event, water had accumulated in low areas on the near-level ground surface. 4.74.74.74.7 Site ClassificationSite ClassificationSite ClassificationSite Classification The City of Auburn classifies all three project parcels as within a Critical Erosion Hazard Area under 16.10.080G, likely due to the presence of the silty fine SAND underlying the steep cut slope along the east side of 104th Place Southeast. The City also classifies the cut slope, which is located on City property, as a Class IV/Very High Hazard Landslide Hazard Area under 16.10.080G2d, since the slope was excavated to an inclination greater than 40 percent. Since the Green River is a Type S stream, the area within 250 feet of the OHWM is considered a riparian habitat zone. King County has classified the parcels as a “channel migration hazard area, moderate” for channel migration (King County, 1999). “Channel migration hazard area. Moderate” means a portion of the channel migration zone, as shown on the King County’s Channel Migration Zone map, that lies between the severe channel migration hazard area and the outer boundaries of the channel migration zone (King County, 2014). The current regulatory base flood elevation is based on NAVD 88, while the map originally provided to us dated November 7, 2017 used the older City of Auburn datum, which is approximately 3.6 feet lower in elevation. This discrepancy led to the conclusion stated in our 222 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 8 of 15 original report that: “…the building sites all fall below or at the base flood elevation for the Green River (City of Auburn, 2017).” This conclusion was incorrect. Based on the new data, all building sites are located above the base flood elevation. We noted that the US Geological Survey Green River gage near Auburn, located at River Mile 32.0 uses the older datum for stage elevation (https://green2.kingcounty.gov/rivergagedata/gage-data.aspx?r=green). 5. 5. 5. 5. FLOODINGFLOODINGFLOODINGFLOODING AND AND AND AND CHANNELCHANNELCHANNELCHANNEL MIGRATIONMIGRATIONMIGRATIONMIGRATION The Green and White Rivers have a history of severe flooding. Until November 14, 1906, the White River occupied a channel west of the current Green River channel, and discharged into the Green River at about the current location of Pike Place Northeast (Anderson Map Company, 1907). On November 14, 1906, the area was inundated by a severe flood that changed the course of the White River to its current location, occupying what was previously the Stuck River. A diversion dam was subsequently constructed to make the change permanent (Perkins, 1993). Although this migration reduced flooding in the Kent Valley, the White River was flooding areas in Pierce County as well as the Kent Valley. This led to the construction of the Mud Mountain Dam on the White River in 1946. Even after flood levels on the White River were controlled, flooding continued unimpeded almost annually along the Green River valley. This led to the construction of the Fenster Levee on the west bank south of the properties in the 1960s (set back in 2014), the Howard A Hansen Dam, which was completed in 1961, and revetment adjacent to residences along the bank opposite the properties in 1973. The flood of record on the Green River occurred while the dam was under construction in November 1959, having a peak flow of 28,100 CFS (cubic feet per second) at the Auburn Gauge, located at River Mile 31.3 (US Geological Survey, 1975). The dam is operated such that maximum design flow is 12,000 CFS measured at the Auburn gauge. On February 9, 2020, flooding at the Green River Auburn gage reached a maximum flow of 12,080 CFS, which exceeded the design maximum flow for the site. At 12:30 pm on February 9, Mr. Bergquist visited the site and observed that the river had overtopped the bank and had reached a level just west of TP-2. We measured the high-water line at that location, which is 10 feet towards the river from TP-2 along Cross-Section B-B’ (refer to the Site Plan on Page A2, and Cross-Section B-B’, Figure 4 for the reference location). We staked this location for future reference. The proposed building sites are not located below the base flood elevation and were not inundated by this flood event. 223 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 9 of 15 Even though massive flood events occurred almost annually in the Green/White and later the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located. Maps dating back to 1888, and air photos dating back to 1936 show the river in its current location adjacent to the properties. The current channel configuration is confined on the west bank by revetment and on both banks by the bridge at 8th Avenue Southeast. A list of maps and air photos used in this review is included with other references at the end of this report. 6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY The City of Auburn originally classified the site as an erosion hazard area and a landslide hazard area because of soil and slope characteristics along the 104th Place Southeast cut slope, which is managed by the City. As stated earlier, the cut slope was constructed at approximately 1.18H:1V, and is approximately 25 feet high, based on our measurements. The vegetation growing along the inslope ditch and the lack of debris along the base of the slope indicates the dense silty SAND forming the slope does not appear to be eroding. Slope movement was noted near the south end of 104th Place Southeast on 1996 air photos. Some of the debris flowed over the road and across downslope properties into the Green River, forming an earthen bar. 7777. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES Slope stability analyses were conducted using XSTABL Version 5.205, an integrated slope stability analysis program for personal computers developed by Dr. Sunil Sharma of Interactive Software Designs, Inc. The stability of the cut slope was analyzed with and without seismic loading (earthquake conditions), using Cross-Section C-C’ as a model. The near-level surface between the proposed building sites and the Green River channel was analyzed for the potential for lateral spread during an earthquake, also using Cross-Section C-C’ as a model. 7777.1.1.1.1 AssumptionsAssumptionsAssumptionsAssumptions Soil strength values for slope stability analysis were derived from the A.S.T.M. visual manual classification along with field testing, and correlated with tables in USDA Forest Service, 1994. Values for root cohesion for the dense vegetation growing along the cut slope were not considered, although it is apparent that they contribute to stability. For our analyses, we considered ground water to be mobile through the silty fine SAND forming the cut slope, without developing hydrostatic pressures. Values used for slope stability analyses are as follows: 224 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 10 of 15 TABLE 7.1 TABLE 7.1 TABLE 7.1 TABLE 7.1 –––– VALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSES SOIL UNITSOIL UNITSOIL UNITSOIL UNIT MOISTMOISTMOISTMOIST DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) SATURATED SATURATED SATURATED SATURATED DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) COHESION COHESION COHESION COHESION (PSF)(PSF)(PSF)(PSF) ANGLE OF ANGLE OF ANGLE OF ANGLE OF INTERNALINTERNALINTERNALINTERNAL FRICTION FRICTION FRICTION FRICTION (DEGREES)(DEGREES)(DEGREES)(DEGREES) SU-A (SM) 132 138 0 38 SU-B (SM/ML) 84 112 0 27 SU-C (SM) 90 114 0 28 *Assumes fully saturated conditions for the soil unit. PCF and PSF are abbreviations for pounds per cubic foot and pounds per square foot, respectively. We did not include values for the fill material, since it does not extend southward to the cross- section analyzed. XSTABL and other slope stability programs calculate an estimated FOS (factor of safety), which is the result of dividing the total forces supporting the slope by the total forces that are tending to destabilize the slope. If the FOS is greater than 1.00, the slope is considered stable; if the FOS is less than 1.00, the slope is considered to be unstable. A FOS of 1.00 indicates the slope is in perfect equilibrium. The seismic coefficient applied to this project was 20 percent of the force of gravity which, in our judgment, is conservative considering the soils encountered at this site. The program was instructed to calculate the FOS for 1,000 potential shear surfaces during each iteration. The graphs contained in the appendix each show the locations of the 10 weakest surfaces analyzed within the slope segment selected for analysis, with the surface having the lowest FOS highlighted. 7777.2 .2 .2 .2 AAAAnalysesnalysesnalysesnalyses For the existing cut slope under static conditions, a FOS of 1.189 was calculated (refer to Graph GOULETW on page B1 in Appendix B). With seismic loading, the FOS was reduced to 0.808 (refer to Graph GOULETE2 on page B2 in Appendix B). For the near-level area adjacent to the Green River channel, a FOS of 1.265 was calculated under seismic loading (refer to Graph GOULETS2 on Page B3 in Appendix B). 8888. DISCUSSION. DISCUSSION. DISCUSSION. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions 225 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 11 of 15 encountered in the test pits adequately represent conditions near and between the test pits to the depths excavated. 9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS The following paragraphs present a summation of the area and site conditions as we interpret them. These conditions dictate the development considerations. 9.1 9.1 9.1 9.1 Flooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel Migration Flooding along the Green River is nearly an annual event, although the flooding occurs under controlled conditions as a result of the Howard A. Hanson Dam. Based on past records, floods reaching the base flood elevation occur one to two times a decade (Shannon & Wilson, 2002). Regulatory flood elevations are determined based on a model which assumes that Howard A. Hansen Dam functions properly, there is no channel migration, the revetments function as designed, and there are no blockages and sudden releases from significant events such as landslides or from log jams. No evidence of channel migration within the straight reach adjacent to the properties was observed on 130 years of maps and air photos. This in part may be due to long-term efforts at maintaining the current west bank of the channel with revetments. Although there are signs of erosion above the revetment immediately opposite the properties, most of the erosion has occurred on the river bank adjacent to the properties. Given that the channel is confined by the revetments to the west, higher ground elevations on the property immediately to the south, and the abutments beneath the bridge on 8th Avenue, the river would, in our judgment, be likely to erode the loose silty fine SAND underlying much of the property. 9.2 9.2 9.2 9.2 Slope Stability and ErosionSlope Stability and ErosionSlope Stability and ErosionSlope Stability and Erosion The City of Auburn considers the cut slope along 104th Place Southeast a “landslide hazard area” because of the slope inclination and height, even though it is a constructed slope owned and maintained by the city, which is responsible for its stability. No evidence of cut slope erosion or instability was observed adjacent to the parcels, even following the February 2020 rain events. Our analyses indicate this slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated. Our analyses indicate that slope movement (lateral spreading) is not likely to occur on the properties. The actual reaction to the seismic event, however, would be related to the strength and duration of shaking. 226 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 12 of 15 There are no visible indicators that the dense silty fine SAND forming the cut slope, which is covered by dense brush, is subject to significant erosion. The more likely area to be eroded is the shoreline described above. 9.3 9.3 9.3 9.3 SeismicitySeismicitySeismicitySeismicity We conducted our subsurface exploration near the end of one of the driest summers on record, and encountered little ground water on our test pits. What we did encounter was situated at an elevation just above the level of the Green River at that time. It appears likely that the level of the river influences the ground water levels in the loose silty fine SAND beneath the site. The loose silty fine SAND underlying the site is classified as having a high susceptibility for liquefaction and Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann (2007). 10101010. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS Conditions underlying and adjacent to the property, along with City, County, and State regulations, make the proposed development at this site challenging. The conditions at the site, however, do not render the site unbuildable, but additional steps beyond what is normally standard building practices will likely be needed. If the building footprints are located as shown on the drawings, most of the footings will be founded in the loose silty fine SAND flood deposits. Prior to design of the foundations for the planned buildings, a thorough subsurface exploration and engineering analysis must be performed. The exploration should include test borings with groundwater monitoring wells so that the proper foundation types and load carrying capacities can be recommended. Liquefiable soil conditions can be mitigated by design of a suitable, deep foundation system for a specific structure that may incorporate driven or drilled piles. Another method involves installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. Therefore, we recommend that the building design process includes appropriate subsurface exploration as described above and development of engineering recommendations for design of a foundation system or soils improvement methods that will mitigate the effects of liquefaction. There are no specific building plans at this time; therefore, we should be contacted for further recommendations once the designs of the specific structures are near completion. 227 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 13 of 15 Reduction of the Green River Buffer for dispersion trenches to the normal 50 feet will not adversely affect the stability of the river bank in this location. Final selection and design of the stormwater handling system(s) will be based on the concomitant impervious surfaces added to each property and on the results from the recommended subsurface exploration, and field and laboratory testing. Our analyses indicate the over-steepened cut slope along 104th Place Southeast would likely become unstable under severe seismic shaking. Therefore, those responsible for maintaining public safety along City streets should address strengthening of the slope. We do not anticipate the need for an additional buffer beyond what is already provided by the drainage ditch and 104th Place Southeast. Maintenance of native vegetation is required within the river buffer. The present vegetation, however, consists of non-native, invasive species (blackberry and morning glory. It will be necessary to clear the site in order to meet current standards. Removal of vegetation should be carefully performed so as to not adversely affect slope stability along the river bank. 11.11.11.11. REPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Launce Goulet to obtain a building permit variance for proposed residences to be constructed on King County tax parcel numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The recommendations are based on surface and subsurface information obtained by Bergquist Engineering Services Company, LLC (BESCO), and on an updated topographic survey provided by Encompass Engineering & Surveying. If there are any revisions to the plans or if conditions are encountered on site that deviate from our observations, BESCO must be notified immediately to determine whether changes to our recommendations are required. oOo 228 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 14 of 15 REFERENCESREFERENCESREFERENCESREFERENCES American Society for Testing and Materials, Description and Identification of Soils (Visual-Manual Procedure ASTM D2488): Annual Book of ASTM Standards, Section Four-Construction, Vol. 04-08, D2488-06, pp. 251-259. Anderson Bertrand & Company, 1888, Anderson’s New Map of King County, Washington Territory: Anderson, Bertrand & Company, Seattle, Washington Anderson Map Company, 1907, Anderson Map Coz Map of Auburn: Anderson Map Company, Seattle, Washington Atwater, B.F., and Hemphill-Haley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay, Washington: U.S. Geological Survey Professional Paper 1576, 108 p. City of Auburn, 2018, Green River to Auburn-Black Diamond Road: eGIS image of 1940 air photo mosaic, obtained via public information request. City of Auburn, 2005, Chapter 16.10 Critical Areas, Auburn Municipal Code Ord. 5894 § 1, 2005. City of Auburn, Washington, undated, City of Auburn GIS: https://maps.auburnwa.gov/Html5Viewer/index.html?viewer=public Galster, Richard W., 1989, Howard A. Hanson Dam: in Engineering Geology in Washington, Volume I, Washington Division of Geology and Earth Resources Bulletin 78, pp. 233-240. King County, 2014, Chapter 21A-24, Rules and Regulations of the Department of Permitting and Environmental Review and Department of Natural Resources and Parks, Critical Areas: Designation, Classification and Mapping of Channel Migration Zones: Effective Date: June 14, 1999, most recent amendment September 7, 2017, 5 p., Appendix A, 20 p. Mullineaux, D.R., 1965, Geologic Map of the Auburn Quadrangle, King and Pierce Counties, Washington: United States Geological Survey Geologic Quadrangle Map GQ-406, Scale 1:24000. 229 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 15 of 15 Palmer, S.P., Magsino, S.L., Bilderback, E.L., Poelstra, J.L., Folger, D.S., and Niggermann, R.A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources, Open File Report 2004-20. Perkins, S.J., 1993, Green River Channel Migration Study: King County Department of Public Works, Surface Water Management Division, Seattle, WA, 81 p. Rogers, A.M., Walsh, T.J., Kockelman, W.J., and Priest, G.R., 1991, Earthquake Hazards in the Pacific Northwest: An Overview: US Geological Survey Open-File Report 91-441-0, p. 4. Satake, K., Wang, K., and Atwater, B., 2003, Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions: Journal of Geophysical Research, v. 108, 2535, doi:10.1029/2003JB002521 Shannon & Wilson, Inc., 2002, Preliminary Risk-Based Flood Damage Analysis, Green River Flood Control District, King County, Washington: Shannon & Wilson, Inc., submitted to Mr. Dave Clark, Water and Land Resources Division, Department of Natural Resources, Seattle, Washington, January 2002, 41 p. USDA Forest Service, 1984, Slope Stability Reference Guide for National Forests in the Pacific Northwest: Forest Service Engineering Staff, Washington, D.C., EM-7170-13, August 1994, pp. 345-400. US Geological Survey, 1975, Magnitude and Frequency of Floods in Washington, US Geological Survey Open File Report 74-336, Tacoma, WA, p. 24 Washington Department of Natural Resources, 1961, Symbol A-95, Flight 17, Exposures 8, 9, and 10: Aerial photographs dated 8-7-1961. Washington Department of Natural Resources, 1996, Symbol NW-96, Roll 49, Flight 49, Exposures 18, 19, and 20: Aerial photographs dated 6-20-1996. Williamson, D.A., Neal, K.G., and Larson, D.A., 1991, The Field-Developed Cross-Section: A Systematic Method of Portraying Dimensional Subsurface Information and Modeling for Geotechnical Interpretation and Analysis: Association of Engineering Geologists, Proceedings, 34th Annual Meeting, pp. 719-738. 230 of 721 231 of 721 232 of 721 233 of 721 Bergquist Engineering Services Company, LLC A3 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----1111 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section CSection CSection CSection C----C’, Station 10+18.1C’, Station 10+18.1C’, Station 10+18.1C’, Station 10+18.1 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITOMONITOMONITOMONITORED BY RED BY RED BY RED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PIT 66.6 feet66.6 feet66.6 feet66.6 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 7.0 SM Silty fine SAND; light brown color; dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River). Started digging 1126. Roots top 2 feet 7.0 to 9.0 SM/ML Silty fine SAND with SILT with fine sand interbeds; light gray color with orange- brown and black iron staining; moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Black and orange brown bands where stained. No water encountered. Test pit completed 1154 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 234 of 721 Bergquist Engineering Services Company, LLC A4 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----2222 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section Section Section Section BBBB----B’, Station 10+52.0B’, Station 10+52.0B’, Station 10+52.0B’, Station 10+52.0 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE TYPE TYPE TYPE OF EQUIPMENTOF EQUIPMENTOF EQUIPMENTOF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber tRubber tRubber tRubber trackrackrackrack----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 68.768.768.768.7 feetfeetfeetfeet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 1.7 SM Silty fine SAND; brown color; dry (NPL), loose. Origin: Topsoil Started digging 1206. Roots top 1.7 feet 1.7 to 7.0 SM Silty fine SAND; light brown color; dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Black and orange bands where stained. Particle size distribution test 7.0 to 9.0 SM/ML Silty fine SAND with SILT with fine sand interbeds; brown to gray colors with orange iron staining; moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River). Forms clumps 9.0 to 9.6 ML/SM SILT with fine sand, with silty fine SAND interbeds; gray color with orange iron staining; wet (APL), soft to loose. Origin: Alluvial (overbank deposit from Green River) Particle size distribution test Wet soil encountered at bottom of test pit. Test pit completed 1227 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 235 of 721 Bergquist Engineering Services Company, LLC A5 TEST PIT NUMTEST PIT NUMTEST PIT NUMTEST PIT NUMBER:BER:BER:BER: TPTPTPTP----3333 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section ASection ASection ASection A----A’, Station 10+84.1A’, Station 10+84.1A’, Station 10+84.1A’, Station 10+84.1 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY KennKennKennKenneth G. Nealeth G. Nealeth G. Nealeth G. Neal ELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PIT 68.1 feet68.1 feet68.1 feet68.1 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 1.7 SM Silty fine SAND with coarse Gravel; light brown color; moist (BPL), dense. Origin: Fill Started digging 1244. Roots top 1.2 feet Particle size distribution test Very hard digging 1.7 to 7.5 SM Silty fine SAND; light gray brown color with increased orange-brown staining with depth, moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open 7.5 to 8.7 ML/SM SILT with fine sand with silty fine SAND with SILT interbeds; brown to gray colors with orange iron staining; moist (BPL to APL), soft to loose. Origin: Alluvial (overbank deposit from Green River). Forms clumps Particle size distribution test No water encountered Test pit completed 1310 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 236 of 721 Bergquist Engineering Services Company, LLC A6 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----4444 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section DSection DSection DSection D----D’, Station 10+40.5D’, Station 10+40.5D’, Station 10+40.5D’, Station 10+40.5 DATE EXPLDATE EXPLDATE EXPLDATE EXPLOREDOREDOREDORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 71.3 feet71.3 feet71.3 feet71.3 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 2.2 SM Silty fine SAND with coarse gravel; light brown color; dry (NPL), dense. Origin: Fill Started digging 1330. Roots top 1.2 feet Some clasts remold by hand pressure to SM Very hard digging 2.2 to 8.9 SM Silty fine SAND; light gray brown color, dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open Particle size distribution test Particle size distribution test No water encountered Test pit completed 1400 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 237 of 721 Bergquist Engineering Services Company, LLC A7 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----5555 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section DSection DSection DSection D----D’, Station 11+16.4D’, Station 11+16.4D’, Station 11+16.4D’, Station 11+16.4 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 69.1 feet69.1 feet69.1 feet69.1 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SUNIFIED SUNIFIED SUNIFIED SOIL OIL OIL OIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 6.5 SM Silty fine SAND; light brown color; dry to moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Started digging 1415. Easy digging Particle size distribution test 6.5 to 9.0 ML/SM SILT with silty fine SAND and silty fine SAND interbeds; light gray with orange iron staining; moist (APL), soft to loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open Particle size distribution test 9.0 to 9.6 SM/ML Silty fine SAND with SILT with silty fine SAND interbeds; light gray color; wet (APL), loose to soft. Origin: Alluvial (overbank deposit from Green River). Wet soil encountered at bottom of test pit Test pit completed 1425 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 238 of 721 239 of 721 240 of 721 241 of 721 242 of 721 243 of 721 244 of 721 245 of 721 246 of 721 247 of 721 248 of 721 249 of 721 250 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 251 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 252 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 253 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 254 of 721 255 of 721 256 of 721 257 of 721 258 of 721 259 of 721 260 of 721 261 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 1 | P a g e Table of Contents Chapter 1: Project Overview ......................................................................................................................... 2 Chapter 2: Existing Conditions ...................................................................................................................... 4 Chapter 3: Off-Site Analysis (Minimum Requirement #10) .......................................................................... 7 Chapter 4: Permanent Stormwater Control Plan ........................................................................................ 10 Chapter 5: Discussion of Minimum Requirements ..................................................................................... 14 List of Figures Figure 1 – Vicinity Map Figure 2 – USGS Soils Map and Legend Figure 3 – Existing Conditions Map Figure 4 – Downstream Map Figure 5 – Developed Conditions Map Figure 6 – Drainage Review Flow Chart List of Appendices Appendix A – Hydraulic/Hydrologic Analysis and Modeling Results Appendix B – Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 262 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 2 | P a g e Chapter 1: Project Overview Project: Lot B: Goulet Residence Address: 32XXX 104th Place SE, Auburn, WA 98092 Tax Parcel #: 334100-0095 Site Area: 13,601 SF (0.31 Acres) Site Location: The site is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. The site is within NW 17-21-05, W.M, King County, Washington. Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Please refer to the Vicinity Map below. Figure 1 – Vicinity Map Proposed Improvements: Lot B is a 13,601 SF lot located on the eastern shore of the Green River in Auburn, Washington. The site is currently vacant and moderately forested. The project proposes to construct a 1,650 SF single-family residential home with attached garage and an approximately 377 SF driveway with access to 104th Place SE. This corresponds to an impervious lot coverage of 14.9%, which complies with the maximum lot coverage of 35%. Stormwater runoff from the developed site will be mitigated via a basic dispersion trench as described in Chapter 4 of this Drainage Report. SITE Amberview Apartments Green River Lot B 263 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 3 | P a g e Site Constraints: The property is located directly adjacent to the Green River and is within the Urban Conservancy Shoreline Designation; therefore, the project is subject to the City of Auburn Shoreline Master Program (SMP). The SMP requires that a 100 FT buffer from the ordinary high-water mark of the Green River be maintained for all development activities. However, due to site area constraints, a Shoreline Variance has been prepared under separate cover to modify the 100 FT stream buffer. Encroachment into the 100 FT stream buffer has been minimized to the maximum extent feasible; however, in order to provide the necessary flow control BMPs, the stream buffer is reduced to 85 FT in some areas on the site. 264 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 4 | P a g e Chapter 2: Existing Conditions The project site is zoned R5 residential and is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. Single family residences have been constructed several parcels to the north and south of the site, although the site is directly adjacent to several undeveloped lots. The Green River borders the site to the west. An existing conditions map is provided as Figure 3 at the end of this Chapter. Critical Areas: The site is directly adjacent to the Green River and is located within the Urban Conservancy Shoreline Designation; therefore, development is subject to the City of Auburn Shoreline Master Program (SMP). The SMP requires that a 100 FT buffer from the ordinary high-water mark of the Green River be maintained for all development activities. There is also a 50 FT channel migration hazard buffer associated with the lot. Soils: Per the United States Geological Survey (USGS), the entire project site is underlain with mixed alluvial soils at approximately 5-8% slopes (Map Unit Ma). Please refer to the USGS Map and Table below. Figure 2 – USGS Soils Map and Legend 265 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 5 | P a g e The subject site was also investigated by Bergquist Engineering Services (BES). Based on the BES Critical Areas Report dated April 9, 2020 (Appendix B), the site is underlain by fine loose silty sand alluvial deposits from the Green River. Due to the parcel being located within an Erosion Hazard Zone, Habitat Protection Zone, River Channel Buffer Zone, and Groundwater Protection Zone, the site falls within the City of Auburn’s Infiltration Infeasibility Area. Based on BES’s Report in Appendix B, dispersion of stormwater is feasible as long as the dispersion trench is at least 50 feet from the ordinary high-water mark of Green River. Please refer to Chapter 4 for additional discussion on feasible stormwater BMPs. 266 of 721 267 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 7 | P a g e Chapter 3: Off-Site Analysis (Minimum Requirement #10) A qualitative downstream analysis was performed by Encompass Engineering and Surveying on Friday December 12, 2019. The proposed project site is currently undeveloped and moderately forested. The site slopes to the west toward the Green River at approximately 5-8%. There are no upstream areas tributary to the project site. Runoff from the project site sheet flows directly into the Green River. The Green River flows to the north under the SE 320th Street bridge and takes a turn to the east near the 104th Avenue SE Park. This location is approximately ¼ mile downstream of the project site, and is where the Level 1 Downstream Analysis was concluded. During the downstream analysis, no signs of erosion or downstream drainage problems were observed. In addition, there were no downstream drainage complaints found on King County iMap. Please refer to the Downstream Drainage Map, Drainage System Table, and photographs on the following pages for additional details. Figure 4 – Downstream Drainage Map 268 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 8 | P a g e Off-site Analysis Drainage System Table Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % ¼ ml = 1,320 ft. constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts A SHEET FLOW VEGETATION 5-8% 0’ NO NO POINT OF DISCHARGE B RIVER CHANNEL GREEN RIVER NA 2,190’ NO NO FLOWS NORTH ALONG WESTERN PROPERTY LINE, PASSES UNDER THE SE 320TH ST BRIDGE, AND BEND TO THE EAST NEAR 104TH AVE SE PARK. THIS IS WHERE ANALYSIS WAS CONCLUDED. Photo 1 – Project Site from 104th Place SE 269 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 9 | P a g e Photo 2 – Green River from Site Looking North Photo 3 – Green River from SE 320th Street Bridge Looking North 270 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 10 | P a g e Chapter 4: Permanent Stormwater Control Plan The 13,601 SF (0.31 AC) site is currently undeveloped and moderately forested. The project proposes to construct a 1,650 SF (0.038 AC) single-family residential home with attached garage and an approximately 377 SF (0.009 AC) driveway with access to 104th Place SE. The site is contained within a single drainage basin that discharges to the west toward the Green River. Runoff generated by the proposed improvements will be managed onsite. A Developed Conditions Map is provided as Figure 5 at the end of this Chapter. Pre-Developed Site Hydrology The 5,495 SF (0.127 AC) within the limits of construction have been modeled as 100% forested with moderate slopes in the pre-developed condition. Developed Site Hydrology As described in the Section on the following page pertaining to the on-site stormwater management system (Minimum Requirement #5), basic dispersion is proposed to mitigate runoff from the proposed impervious areas on-site. Therefore, these areas have been modeled as 90% impervious and 10% lawn in the hydraulic/hydrologic model for the developed condition. All new pervious area has been modeled as 100% pasture by utilizing post construction soil depth and quality. The area within the limits of construction was modeled as follows for the developed condition: Feature Area Developed Conditions Model Roof Area 1,650 SF (0.038 Ac) 1,485 SF (0.034 AC) Roof, flat; 165 SF (0.004 AC) lawn, moderate slope Driveway 377 SF (0.009 Ac) 339 SF (0.008 AC) Driveway, moderate slope; 38 SF (0.001 AC) lawn, moderate slope New Pervious 3,468 SF (0.080 Ac) 3,468 SF (0.080 AC) Pasture, moderate slopes TOTAL AREA 5,495 SF (0.127 Ac) See Above The resulting increase in flow from the 100-year storm event is 0.0322 CFS as shown in the table below. The full WWHM output is included in Appendix A. 271 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 11 | P a g e On-Site Stormwater Management System – Minimum Requirement #5 This project is considered to be a new development, located inside of the Urban Growth Area, and triggers only Minimum Requirements #1 - #5 (See Chapter 5 for further discussion). To meet the applicable requirements per Figure 2.5.1 of the City of Auburn Supplemental Manual, this project proposes to apply On-site Stormwater Management List #1. Due to the parcel being located within an Erosion Hazard Zone, Habitat Protection Zone, River Channel Buffer Zone, and Groundwater Protection Zone, the site falls within the City of Auburn’s Infiltration Infeasibility Area. This means that stormwater runoff mitigation through full infiltration (BMP T5.10A), rain gardens (BMP T5.14A), Bioretention (BMP T7.30), and Permeable Pavement (BMP T5.15) are not considered feasible for the site. The remaining applicable BMPs have been considered below in the order listed for each type of surface. Lawn and Landscaped Areas: 1. Post-Construction Soil Quality and Depth (BMP T5.13): This BMP will be implemented throughout the pervious areas of the site. Approximately 3,468 SF of new pervious surface areas will utilize this BMP. Outside of the project clearing limits, topsoil will remain undisturbed. Topsoil that is disturbed by construction will be stockpiled in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible. Areas within the clearing limits designated to be pervious surfaces, will re-establish soil quality per the requirements detailed in Volume V BMP T5.13. Per the DOE Manual, areas meeting these guidelines have been modeled as “Pasture” rather than “Lawn” in the Flow Control Analysis detailed above in Chapter 4 of this Drainage Report. Roofs: 1. Full Dispersion (BMP T5.30): Full dispersion is not feasible for the project. The site does not allow for the minimum 100 FT native vegetated flowpath segment required to utilize full dispersion BMPs. 2. Downspout Dispersion Systems (BMP T5.10B): According to the BES Critical Areas Report (Appendix B), downspout dispersion is feasible for the project so long as the dispersion device is at least 50 feet from the ordinary high-water mark of Green River. Therefore, a 50 FT gravel filled basic dispersion trench with notched board and 25 FT native vegetated flowpath will be utilized to manage runoff from the 1,650 SF roof area. This is well within the 3,500 SF capacity of the trench. 3. Perforated Stub-out Connections (BMP T5.10C): No additional roof areas to mitigate. Other Hard Surfaces: 1. Full Dispersion (BMP T5.30): Full Dispersion is not feasible for the project. The site design does not allow for the minimum 100 FT native vegetated flowpath segment required to utilize full dispersion BMPs. This BMP is feasible for the project as Basic Dispersion. A basic dispersion system in the form of a 50 FT gravel filled dispersion trench with notched board and 25 FT native vegetated flowpath will be utilized to manage runoff from the site as described above. In addition to the 1,650 SF roof area, the 377 SF driveway will also be directed to this dispersion trench. The combined tributary area is 2,027 SF, which is within the 3,500 SF limit. 272 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 12 | P a g e 2. Concentrated Flow Dispersion (BMP T5.11) or Sheet Flow Dispersion (BMP T5.12): No additional hard surfaces to mitigate. 273 of 721 274 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 14 | P a g e Chapter 5: Discussion of Minimum Requirements The City of Auburn manages stormwater generated by development through adoption of the 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual). The City also has developed their own Supplement to the SMMWW which provides additional or modified requirements to the SMMWW (Supplemental Manual). Both manuals have been utilized in the design of this project. For simplicity, both manuals in conjunction will be referred to as “the drainage manual” unless one or the other is specified. The total proposed impervious area is 2,027 SF, which is less than 5,000 SF. Therefore, the project is required to comply with Minimum Requirements 1 through 5. Discussion of these minimum requirements is contained in this Chapter. Figure 6 – Flow Chart for Determining Minimum Requirements for New Developments 275 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 15 | P a g e Minimum Requirement #1: Preparation of Stormwater Site Plans The Stormwater Site Plan has been prepared in accordance with the 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual) and the 2017 City of Auburn Supplemental Manual to the Ecology Stormwater Management Manual for Western Washington (Supplemental Manual). Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (CSWPPP) A CSWPPP, which will serve to minimize soil erosion/sedimentation during the proposed site construction, will be prepared for approval by the City of Auburn with final engineering. Minimum Requirement #3: Source Control of Pollution Actions taken each day in and around homes have a profound effect on surface water quality and fish habitat in this region. Stormwater goes directly to rivers, streams and to Puget Sound. Stormwater does not go to the wastewater treatment plant. Any pollutants that get into the stormwater go directly to surface water. Small amounts of pollution from many different sources can significantly affect our waterways. Yard maintenance, waste storage, car washing and maintenance, and pool cleaning are some of the activities that can adversely impact water quality. An Operations & Maintenance Manual that addresses source control best management practices (BMPs) for single-family residential homeowners will be provided with final engineering. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The proposed on-site drainage patterns emulate those of the existing site conditions. Stormwater runoff from the site is proposed to be mitigated via dispersion as described in Chapter 4 of this Drainage Report. The associated native vegetated flowpaths will drain toward the Green River, as they do in the existing condition. Minimum Requirement #5: On-Site Stormwater Management The project proposes to utilize basic dispersion via a 50 FT gravel filled dispersion trench with 25 FT native vegetated flowpath to mitigate runoff from the proposed 1,650 SF residence and 377 SF driveway. Please refer to Chapter 4 of this Report for further discussion on how the applicable BMPs were selected. Minimum Requirement #10: Off-Site Analysis and Mitigation The site is located directly adjacent to the Green River, which flows to the north along the western property line. No erosion or drainage problems currently exist on the site, and no off-site drainage complaints have been found within a quarter mile downstream of the project. Please refer to Chapter 3 of this Drainage Report for additional discussion. 276 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 16 | P a g e Appendix A Hydraulic/Hydrologic Analysis and Modeling Results 277 of 721 WWHM2012 PROJECT REPORT 278 of 721 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 2 General Model Information Project Name:WWHM Model_Lot B Site Name:Goulet Lot A Site Address: City: Report Date:3/3/2020 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 279 of 721 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.127 Pervious Total 0.127 Impervious Land Use acre Impervious Total 0 Basin Total 0.127 Element Flows To: Surface Interflow Groundwater 280 of 721 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.005 C, Pasture, Mod 0.08 Pervious Total 0.085 Impervious Land Use acre ROOF TOPS FLAT 0.034 DRIVEWAYS MOD 0.008 Impervious Total 0.042 Basin Total 0.127 Element Flows To: Surface Interflow Groundwater 281 of 721 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 5 Routing Elements Predeveloped Routing 282 of 721 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 6 Mitigated Routing 283 of 721 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.127 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.085 Total Impervious Area:0.042 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.003781 5 year 0.006196 10 year 0.007749 25 year 0.009596 50 year 0.010875 100 year 0.01207 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.018697 5 year 0.024678 10 year 0.028968 25 year 0.034778 50 year 0.039398 100 year 0.044276 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.004 0.027 1950 0.005 0.023 1951 0.008 0.017 1952 0.003 0.012 1953 0.002 0.013 1954 0.003 0.016 1955 0.005 0.016 1956 0.004 0.016 1957 0.003 0.020 1958 0.004 0.015 284 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 8 1959 0.003 0.014 1960 0.006 0.019 1961 0.003 0.017 1962 0.002 0.013 1963 0.003 0.017 1964 0.004 0.015 1965 0.003 0.020 1966 0.002 0.013 1967 0.006 0.024 1968 0.003 0.024 1969 0.003 0.018 1970 0.003 0.018 1971 0.003 0.021 1972 0.006 0.023 1973 0.003 0.012 1974 0.003 0.019 1975 0.004 0.021 1976 0.003 0.016 1977 0.000 0.014 1978 0.003 0.018 1979 0.002 0.024 1980 0.007 0.032 1981 0.002 0.019 1982 0.005 0.029 1983 0.004 0.020 1984 0.002 0.014 1985 0.001 0.017 1986 0.006 0.018 1987 0.006 0.023 1988 0.002 0.014 1989 0.001 0.019 1990 0.014 0.047 1991 0.007 0.031 1992 0.003 0.014 1993 0.003 0.012 1994 0.001 0.012 1995 0.004 0.017 1996 0.010 0.024 1997 0.007 0.020 1998 0.002 0.016 1999 0.008 0.034 2000 0.003 0.019 2001 0.001 0.018 2002 0.003 0.024 2003 0.005 0.023 2004 0.005 0.035 2005 0.004 0.017 2006 0.004 0.016 2007 0.010 0.041 2008 0.013 0.031 2009 0.006 0.021 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0137 0.0467 2 0.0126 0.0410 3 0.0103 0.0347 285 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 9 4 0.0096 0.0344 5 0.0083 0.0317 6 0.0081 0.0314 7 0.0074 0.0314 8 0.0074 0.0288 9 0.0073 0.0271 10 0.0065 0.0243 11 0.0063 0.0242 12 0.0059 0.0242 13 0.0058 0.0242 14 0.0057 0.0238 15 0.0057 0.0233 16 0.0053 0.0231 17 0.0052 0.0230 18 0.0051 0.0229 19 0.0050 0.0215 20 0.0048 0.0209 21 0.0044 0.0206 22 0.0044 0.0203 23 0.0043 0.0201 24 0.0041 0.0199 25 0.0041 0.0197 26 0.0041 0.0193 27 0.0040 0.0191 28 0.0038 0.0190 29 0.0037 0.0186 30 0.0033 0.0185 31 0.0033 0.0183 32 0.0033 0.0182 33 0.0032 0.0179 34 0.0032 0.0179 35 0.0032 0.0176 36 0.0031 0.0174 37 0.0031 0.0173 38 0.0031 0.0171 39 0.0030 0.0167 40 0.0029 0.0166 41 0.0029 0.0166 42 0.0029 0.0164 43 0.0028 0.0164 44 0.0027 0.0162 45 0.0026 0.0161 46 0.0026 0.0157 47 0.0026 0.0156 48 0.0025 0.0150 49 0.0025 0.0146 50 0.0024 0.0142 51 0.0023 0.0141 52 0.0023 0.0140 53 0.0021 0.0138 54 0.0020 0.0136 55 0.0018 0.0132 56 0.0016 0.0130 57 0.0015 0.0129 58 0.0015 0.0124 59 0.0010 0.0120 60 0.0005 0.0119 61 0.0004 0.0116 286 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 10287 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 11 Duration Flows Flow(cfs)Predev Mit Percentage Pass/Fail 0.0019 17090 73727 431 Fail 0.0020 15490 69300 447 Fail 0.0021 14070 65193 463 Fail 0.0022 12808 61407 479 Fail 0.0023 11569 57878 500 Fail 0.0023 10519 54477 517 Fail 0.0024 9563 51376 537 Fail 0.0025 8759 48531 554 Fail 0.0026 8040 45879 570 Fail 0.0027 7347 43398 590 Fail 0.0028 6733 41088 610 Fail 0.0029 6192 38970 629 Fail 0.0030 5730 36938 644 Fail 0.0031 5309 35013 659 Fail 0.0032 4924 33238 675 Fail 0.0033 4571 31570 690 Fail 0.0033 4237 29944 706 Fail 0.0034 3951 28426 719 Fail 0.0035 3643 26993 740 Fail 0.0036 3390 25709 758 Fail 0.0037 3133 24469 781 Fail 0.0038 2915 23228 796 Fail 0.0039 2706 22116 817 Fail 0.0040 2490 21106 847 Fail 0.0041 2314 20114 869 Fail 0.0042 2136 19130 895 Fail 0.0043 1972 18195 922 Fail 0.0043 1825 17374 952 Fail 0.0044 1702 16593 974 Fail 0.0045 1577 15834 1004 Fail 0.0046 1442 15094 1046 Fail 0.0047 1325 14375 1084 Fail 0.0048 1232 13734 1114 Fail 0.0049 1147 13122 1144 Fail 0.0050 1083 12592 1162 Fail 0.0051 1020 12040 1180 Fail 0.0052 947 11507 1215 Fail 0.0052 886 10994 1240 Fail 0.0053 824 10500 1274 Fail 0.0054 760 10055 1323 Fail 0.0055 725 9634 1328 Fail 0.0056 674 9225 1368 Fail 0.0057 623 8866 1423 Fail 0.0058 589 8536 1449 Fail 0.0059 549 8192 1492 Fail 0.0060 506 7882 1557 Fail 0.0061 469 7595 1619 Fail 0.0062 427 7287 1706 Fail 0.0062 388 6981 1799 Fail 0.0063 356 6718 1887 Fail 0.0064 328 6425 1958 Fail 0.0065 298 6164 2068 Fail 0.0066 270 5929 2195 Fail 0.0067 241 5698 2364 Fail 288 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 12 0.0068 218 5505 2525 Fail 0.0069 198 5283 2668 Fail 0.0070 173 5108 2952 Fail 0.0071 152 4913 3232 Fail 0.0072 130 4738 3644 Fail 0.0072 119 4573 3842 Fail 0.0073 104 4383 4214 Fail 0.0074 95 4205 4426 Fail 0.0075 83 4036 4862 Fail 0.0076 74 3867 5225 Fail 0.0077 69 3726 5400 Fail 0.0078 61 3602 5904 Fail 0.0079 53 3454 6516 Fail 0.0080 46 3341 7263 Fail 0.0081 39 3223 8264 Fail 0.0082 29 3101 10693 Fail 0.0082 25 2979 11916 Fail 0.0083 22 2881 13095 Fail 0.0084 20 2791 13955 Fail 0.0085 17 2680 15764 Fail 0.0086 14 2597 18550 Fail 0.0087 12 2485 20708 Fail 0.0088 8 2408 30100 Fail 0.0089 7 2336 33371 Fail 0.0090 7 2257 32242 Fail 0.0091 7 2190 31285 Fail 0.0092 6 2130 35500 Fail 0.0092 6 2075 34583 Fail 0.0093 6 1993 33216 Fail 0.0094 6 1927 32116 Fail 0.0095 6 1874 31233 Fail 0.0096 5 1820 36400 Fail 0.0097 5 1759 35180 Fail 0.0098 5 1710 34200 Fail 0.0099 5 1652 33040 Fail 0.0100 5 1607 32140 Fail 0.0101 5 1568 31360 Fail 0.0101 5 1522 30440 Fail 0.0102 4 1485 37125 Fail 0.0103 4 1434 35850 Fail 0.0104 3 1384 46133 Fail 0.0105 3 1339 44633 Fail 0.0106 3 1290 43000 Fail 0.0107 3 1261 42033 Fail 0.0108 3 1218 40600 Fail 0.0109 3 1187 39566 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. 289 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. 290 of 721 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 14 LID Report 291 of 721 WWHM Model_Lot B 3/3/2020 8:05:41 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 292 of 721 WWHM Model_Lot B 3/3/2020 8:05:41 AM Page 16 Appendix Predeveloped Schematic 293 of 721 WWHM Model_Lot B 3/3/2020 8:05:43 AM Page 17 Mitigated Schematic 294 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM Model_Lot B.wdm MESSU 25 PreWWHM Model_Lot B.MES 27 PreWWHM Model_Lot B.L61 28 PreWWHM Model_Lot B.L62 30 POCWWHM Model_Lot B1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 11 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO 295 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 19 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 11 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 296 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 20 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 11 0.127 COPY 501 12 PERLND 11 0.127 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC 297 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 21 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN 298 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM Model_Lot B.wdm MESSU 25 MitWWHM Model_Lot B.MES 27 MitWWHM Model_Lot B.L61 28 MitWWHM Model_Lot B.L62 30 POCWWHM Model_Lot B1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 17 PERLND 14 IMPLND 4 IMPLND 6 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 17 C, Lawn, Mod 1 1 1 1 27 0 14 C, Pasture, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 17 0 0 1 0 0 0 0 0 0 0 0 0 14 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO 299 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 23 <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 17 0 0 4 0 0 0 0 0 0 0 0 0 1 9 14 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 17 0 0 0 0 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 17 0 4.5 0.03 400 0.1 0.5 0.996 14 0 4.5 0.06 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 17 0 0 2 2 0 0 0 14 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 17 0.1 0.25 0.25 6 0.5 0.25 14 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 17 0 0 0 0 2.5 1 0 14 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 6 DRIVEWAYS/MOD 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 6 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 6 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 300 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 24 4 0 0 0 0 0 6 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 6 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 6 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 6 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 17 0.005 COPY 501 12 PERLND 17 0.005 COPY 501 13 PERLND 14 0.08 COPY 501 12 PERLND 14 0.08 COPY 501 13 IMPLND 4 0.034 COPY 501 15 IMPLND 6 0.008 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO 301 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 25 HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN 302 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 26 Predeveloped HSPF Message File 303 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 27 Mitigated HSPF Message File 304 of 721 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2020; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com 305 of 721 Lot B: Goulet Residence Preliminary Storm Drainage Report 17 | P a g e Appendix B Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 306 of 721 CRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCES PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010 AUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULET by:by:by:by: BERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLC BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1, REVISION 1, REVISION 1, REVISION 1, REVISION 1 APRIL 9, 2020APRIL 9, 2020APRIL 9, 2020APRIL 9, 2020 307 of 721 Bergqoist Engineering Services 27207 8th Avenue S R O. Box 13309 Des Moines, Washington 98198 Des Moines, Washington 98198 Phone: 253,941.9399 • Fax 253,941,9499 • E-mail: soilsengineering@aol,conn April 9, 2020 Mr. Launce Goulet 3226 S 198'^ Street SeaTac, Washington 98188 Re: Critical Area Report Proposed Single-Family Residences King County Parcel Numbers; 3341000090, 3341000095, and 33410000210 Auburn, Washington BESCO Project No.: 2018214, Report 1, Revision 1 Dear Launce: Bergquist Engineering Services Company, LLC is pleased to provide this Critical Area Report for the referenced King County parcels. The attached report summarizes project and site data, describes the services we performed, and presents our conclusions relative to soil erosion and channel migration and the stability of the off-site, steep slope along the east side of 104'*" Place SE. We appreciate the opportunity to be of service to you. If you have any questions concerning this report, or if we may be of additional service, please contact us. Copies to: Addressee (5) DOWN TO EARTH ENGINEERING SOLUTIONS 308 of 721 TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS 1. INTRODUCTION ......................................................................................................................... 1 2. PROJECT DESCRIPTION ............................................................................................................. 2 3. SCOPE OF SERVICES .................................................................................................................. 2 4. SITE CHARACTERIZATION ......................................................................................................... 3 4.1 Topography and Development ....................................................................................... 3 4.2 Area Geology ................................................................................................................... 4 4.3 Seismicity ......................................................................................................................... 4 4.4 Site Geology ..................................................................................................................... 5 4.5 Subsurface Soils ............................................................................................................... 5 4.6 Ground Water and Drainage........................................................................................... 7 4.7 Site Classification ............................................................................................................. 7 5. FLOODING AND CHANNEL MIGRATION .................................................................................. 8 6. EROSION AND SLOPE STABILITY ............................................................................................... 9 7. SLOPE STABILITY ANALYSIS ....................................................................................................... 9 7.1 Assumptions .................................................................................................................... 9 7.2 Analysis ........................................................................................................................... 10 8. DISCUSSION .............................................................................................................................. 10 9. CONCLUSIONS .......................................................................................................................... 11 9.1 Flooding and Channel Migration ............................................................................. 11 9.2 Slope Stability and Erosion ...................................................................................... 11 9.3 Seismicity .................................................................................................................. 12 10. RECOMMENDATIONS .............................................................................................................. 12 11. PEPORT LIMITATIONS .............................................................................................................. 13 APPENDIXAPPENDIXAPPENDIXAPPENDIX AAAA Vicinity Map ................................................................................................................................. A1 Site Plan .................................................................................................................................. A2 Logs of Test Pits ................................................................................................................................ A3 Test Pit Log Notes ............................................................................................................................ A8 Unified Soil Classification System ................................................................................................... A10 Particle Size Distribution Reports ................................................................................................... A11 Cross Sections ................................................................................................................................. A20 APPENDIX BAPPENDIX BAPPENDIX BAPPENDIX B Computer Printouts of Slope Stability Analyses ............................................................................. B1 Notes .................................................................................................................................. B4 309 of 721 CRITICAL AREASCRITICAL AREASCRITICAL AREASCRITICAL AREAS REPORTREPORTREPORTREPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCESSSS PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095, , , , andandandand 3341000010334100001033410000103341000010 AUBURNAUBURNAUBURNAUBURN, WASHINGTON, WASHINGTON, WASHINGTON, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNMR. LAUNMR. LAUNMR. LAUNCCCCE P.E P.E P.E P. GOULETGOULETGOULETGOULET by:by:by:by: BERGQUIST BERGQUIST BERGQUIST BERGQUIST ENGINEERING SERVICESENGINEERING SERVICESENGINEERING SERVICESENGINEERING SERVICES COMPANY, LLCCOMPANY, LLCCOMPANY, LLCCOMPANY, LLC BESBESBESBESCOCOCOCO PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: 2018201820182018214214214214, , , , REPORT 1REPORT 1REPORT 1REPORT 1, R, R, R, REVISION EVISION EVISION EVISION 1111 April 9April 9April 9April 9, 2020, 2020, 2020, 2020 1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION This report presents the results of our geotechnical evaluation of critical areas for three proposed single-family residences to be constructed on King County Parcel Numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The parcels are located along the east bank of the Green River west of 104th Place Southeast, in the northwest quarter of the northwest quarter of Section 17, Township 21 North, Range 5 East, Willamette Meridian. The location of the project is shown on the Vicinity Map, Figure 1, on page A1 in Appendix A of this report. This report was revised because datum used for the current site plans, dated January 24, 2020 are NAVD 88, rather than the City of Auburn datum used on the originally submitted plans dated November 7, 2017. This report also provides additional information as a result of a site visit by Mr. Bergquist, who observed the level of the Green River on February 9, 2020, shortly after it exceeded the base flood elevation, and a follow-up visit by Messrs. Bergquist and Neal, who located and marked the maximum 2020 flood level. The geotechnical evaluation was performed by Bergquist Engineering Services Company, LLC (BESCO) to provide information or recommendations regarding: • erosion and slope stability characteristics, in accordance with Auburn City Code 16.10, • the risk of liquefaction and seismic design considerations, and • the influence of ground and surface water on the development. 310 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 2 of 15 This report is not intended to provide geotechnical criteria for design of the planned houses. The data for developing design criteria will be completed after critical area issues are addressed, and the various variances for these properties are obtained. The critical issues addressed in this report are; channel migration, landslide hazards, erosion hazards, flooding and seismic hazards. Mr. Launce P. Goulet authorized our work on March 19th, 2018 by signing and returning BESCO Proposal Number 1162018. 2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION The proposed project would involve construction of one multi-level house on each of the three vacant properties. The footprints and finished grades of the houses have not yet been finalized. 3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES The scope of services included the following steps: • an initial reconnaissance of the site by the geotechnical engineer; • excavating, logging, and sampling five test pits; logs of the test pits are presented in Appendix A on pages A3 through A7; • field and laboratory testing of selected soil samples, including visual classification and gradations; • a review of geologic and historic literature, and historic aerial photography; a list of references is contained in Appendix B; • measurement of a geotechnical cross-section for each parcel, and development of a geologic interpretation for the site by the engineering geologist; • a preliminary evaluation of soil strength and drainage characteristics; • evaluation of past and likely future migration of the Green River channel; • geotechnical slope stability analyses; • observation of the maximum recent flood elevation at the site; and • preparation of this report. Slope relationships for our cross-section were measured using a cloth tape, hand clinometer and Brunton compass in accordance with methodology outlined in Williamson, Neal and Larson (1991). The measurements used to develop the cross-sections and site plan are therefore, not of the precision and accuracy of a site survey prepared by a professional land surveyor, and should not be used for that purpose. 311 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 3 of 15 The recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical practices in the area. 4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION The information presented in this section was gathered by BESCO personnel for evaluation of critical area issues only. This site characterization was not intended to address the presence or likelihood of contamination on or around the site. Specialized methods and procedures, which were not a part of this scope of services, are required for an adequate environmental site assessment. 4.14.14.14.1 Topography and DevelopmentTopography and DevelopmentTopography and DevelopmentTopography and Development Parcels 3341000090, 3341000095, and 3341000010, referred to as Lots A, B, and C on the Site Plan, Figure 2, encompass 12,765, 11,644, and 11,777 square feet, respectively. The parcels are bounded on the east by 104th Place Southeast, on the west by the Green River, and to the north and south by developed single-family residential lots. Topographic relationships are shown on the sketch entitled, “Site Plan” presented on page A2 and on Cross-Sections A-A’, B-B’ C-C,’ and D-D’, presented on pages A20 through A22. Elevations shown on the cross-sections and test pit logs are based on a site and topographic plan for the parcels prepared by Encompass Engineering & Surveying, dated 1/14/2020, and our measurements. There is approximately 20 feet of relief on Parcel A, from an elevation of approximately 56 feet mean sea level (MSL) at the ordinary high water mark (OHWM) of the Green River at the northwest corner of the property to an elevation of approximately 76 feet MSL at the southeast property corner. There is approximately 20 feet of relief on Parcel B, from an elevation of approximately 56 feet MSL at the OHWM at the northwest corner of the property to an elevation of approximately 76 feet MSL at the northwest corner of the property. There is approximately 18 feet of relief on Parcel C, from an elevation of approximately 56 feet MSL along the OHWM and west parcel boundary to an elevation of approximately 74 feet MSL along the east parcel boundary and at the northeast corner. The eroded streambank of the Green River is inclined at from 10 percent to near-vertical. The ground surface is nearly level from the top of the streambank to the base of the fill slope just below 104th Place Southeast. It steepens to between 15 to 20 percent adjacent to 104th Place Southeast. The cut slope along the east side of 104th Place Southeast was constructed at approximately 1.18H:1V (horizontal:vertical) (85 percent). 312 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 4 of 15 The parcels are vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry and, along the river, morning glory. This vegetation reflects the year-round availability of water. A dead snag fell across the location of Cross-Section B-B’ apparently during the winter storms of 2020. 4.24.24.24.2 Area GeologyArea GeologyArea GeologyArea Geology The project area is situated in the Puget Sound basin, a structural low between the Cascade and Olympic Mountain physiographic provinces. The Puget Sound region has been subjected to at least six episodes of glaciations during the last two million years. The most recent glaciation, referred to as the Vashon stade of the Fraser glaciations, stalled and began rapid melting about 12,000 years ago. The glaciations left topography in the Puget Sound region characterized by north-south trending ridges and troughs. The troughs, such as the Puget Sound, Duwamish Channel, and Kent Valley, served as subglacial channels for southward-flowing meltwater. The glaciers formed deposits in front of advancing ice, along the ice margins, during the retreat of the ice front, and during interglacial periods. These deposits have subsequently been overridden and compacted by the advancing Vashon ice sheet. Some of the capping silts, sands, and gravels were likely deposited during Vashon glacial recession. Slope, fluvial, volcanic, and shoreline processes have shaped the land within the area over the 12,000 years since glacial retreat. Approximately 5,600 years ago, the Osceola Mudflow, a lahar originating from Mount Rainier, flowed down the West Fork of the White River and the White River valleys through the areas now occupied by Buckley, Enumclaw, and Auburn to as far north as Kent. The Electron Mudflow, also a Mount Rainier lahar, flowed down the Puyallup River through Orting and Puyallup and into the Kent Valley approximately 500 years ago. The White and Green Rivers have subsequently eroded through the lahars and infilled the floors of the resulting valleys with alluvial deposits. 4.34.34.34.3 SeismicitySeismicitySeismicitySeismicity The Puget Sound region is seismically active. Low magnitude earthquakes occur nearly every week within a 50-mile radius of the site. On April 13, 1949, the Olympia area experienced an earthquake having a Richter Magnitude 7.1 and, on April 29, 1965, the Tacoma-Seattle area experienced an earthquake having a Richter Magnitude 6.5 (Rogers, Walsh, Kockelman and Priest, 1991). On February 28, 2001, a magnitude 6.8 earthquake occurred just north of the Nisqually delta. 313 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 5 of 15 Great subduction zone earthquakes are the largest earthquakes in the world, and are the only source zones that can produce earthquakes greater than Magnitude 8.5. The Cascadia Subduction Zone, located off the coastlines of Washington, Oregon, and northern California, has produced magnitude 9.0 or greater earthquakes in the past. The last known megathrust earthquake in the northwest was in January, 1700 (Satake, Wang, and Atwater, 2003). Geological evidence indicates that such great earthquakes have occurred at least seven times in the last 3,500 years, a return interval of 400 to 600 years (Atwater and Hemphill-Haley, 1997). The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann, 2007). 4.44.44.44.4 Site GeologySite GeologySite GeologySite Geology Glacial and interglacial deposits are exposed in the Green River valley wall east of 104th Place Southeast. These deposits have been interpreted to include, from oldest (lowest on the slope) to youngest (top of the slope) the interglacial Puyallup Formation, overlain by glacial drift from the Salmon Springs glacial stade, and kame terrace deposits from the most recent (Vashon) stade. The glacially-derived deposits are overlain along the Green River and at the subject properties by Green River alluvial and fluvial (flood) deposits, consisting of fine sand with lenses of gravel, locally overlain by silt and clay (Mullineaux, 1965). Geologic processes on the properties are primarily associated with stream flow along the Green River. Flow is controlled in part by Howard A. Hansen Dam, which was constructed in Eagle Gorge and is used primarily for flood control in the lower Green-Duwamish valley (Galster, 1989). The primary process potentially affecting the properties is river erosion and deposition during flood events. While this risk is somewhat diminished by control of flows during floods by the aforementioned dam, the City of Auburn has designed much of the properties as being a “channel migration area (CMA)” on their city flood map. The regulatory flood elevation for the river reach adjacent to the properties is 66 to 67 feet MSL. 4.5 4.5 4.5 4.5 Subsurface SoilsSubsurface SoilsSubsurface SoilsSubsurface Soils The subsurface soil conditions at this site are described in the following paragraphs and are presented graphically on the test pit logs. The test pit locations are shown on the Site Plan, Figure 2 in page A2 of Appendix A, and on Cross-Sections A-A’, B-B’, C-C’, and D-D’, Figures 3, 4, 5, and 6, respectively. 314 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 6 of 15 Soils were described and classified in general accordance with the Unified Soil Classification visual- manual procedure (American Society for Testing and Materials). A description of this system is included on page A10. Results of soil gradation tests are presented on pages A11 through A18. For purposes of explanation, we divided on-site soils into three soil units, SU-A, SU-B, and SU-C, based on origin and physical characteristics. Soil units are shown on the cross-sections; soil unit designations are intended to be local in scope, and not applicable outside the immediate area. A thin layer of organics, primarily blackberry roots, was noted at the top of each test pit. The roots generally reach to depths of 1.5 to 2 feet. SU-A was encountered along the base of the cut slope opposite the properties. Although the valley wall formed of this material is projected to be located beneath the east side of the property, it was not encountered in our test pits. SU-A consists of gray brown silty fine SAND (ASTM: SM). SU-A is a non-plastic soil that was moist, and was dense at the time of our field work. SU-A is interpreted to be an interglacial deposit. SU-B was encountered below depths of 7.0 feet in TP-1, 7.0 feet in TP-2, 7.5 feet in TP-3, and 6.5 in TP-5. SU-B is brown to gray in color, and ranges from silty fine SAND with silt interbeds to SILT with silty fine sand interbeds (ASTM: SM/ML to ML/SM). Orange-brown to black iron staining forms bands that become more frequent with depth. SU-B is a plastic soil that was moist to wet, with the natural moisture content ranging from below to above the plastic limit. SU-B was loose to soft at the time of our exploration. SU-B is interpreted to be an alluvial deposit, an overbank deposit of the Green River. SU-C was encountered overlying SU-B in all five test pits, from the ground surface to a depth of 7.0 feet in TP-1, between depths of 1.7 and 7.0 feet in TP-2, between 1.7 and 7.5 feet in TP-3, below 2.2 feet in TP-4, and from the ground surface to a depth of 6.5 feet in TP-5. SU-C consists of light brown to gray brown Silty fine SAND (ASTM: SM). SU-C is a non-plastic soil that was dry to locally moist, and was loose at the times of our exploration. SU-C is interpreted to be an alluvial deposit, an overbank deposit of the Green River). In addition to the soil units observed at the site, fill materials were encountered along the ground surface over the northern portion of the site and in TP-3 and TP-4, to depths of 1.7 feet in TP-3 and 315 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 7 of 15 2.2 feet in TP-4. This fill material consists of light brown silty fine SAND with coarse gravel (ASTM: SM), that ranged from a dry, non-plastic soil to a moist plastic soil with the natural moisture content below the plastic limit at the time of our exploration. This fill material appears to have been spread over the north parcel by heavy equipment and was dense at the time of our field work. Fill materials are also present beneath the outside shoulder of 104th Place Southeast along the east periphery of the parcels. It appears that the parcels have also been used as a location to dump garbage, particularly just downslope from the shoulder of the street. 4.64.64.64.6 Ground Water and Ground Water and Ground Water and Ground Water and DrainageDrainageDrainageDrainage At the time of our exploration, the King County region had experienced an extended, near record drought. Accordingly, no surface or ground water was encountered on the site. Soil moisture was encountered in three test pits at or just above the stream elevation. Water was encountered near the ground surface in the backfilled TP-2 by Mr. Bergquist during his February 9, 2020 site visit. No drainage features were observed on site. During our September 12, 2018 site visit, which followed a rain event, water had accumulated in low areas on the near-level ground surface. 4.74.74.74.7 Site ClassificationSite ClassificationSite ClassificationSite Classification The City of Auburn classifies all three project parcels as within a Critical Erosion Hazard Area under 16.10.080G, likely due to the presence of the silty fine SAND underlying the steep cut slope along the east side of 104th Place Southeast. The City also classifies the cut slope, which is located on City property, as a Class IV/Very High Hazard Landslide Hazard Area under 16.10.080G2d, since the slope was excavated to an inclination greater than 40 percent. Since the Green River is a Type S stream, the area within 250 feet of the OHWM is considered a riparian habitat zone. King County has classified the parcels as a “channel migration hazard area, moderate” for channel migration (King County, 1999). “Channel migration hazard area. Moderate” means a portion of the channel migration zone, as shown on the King County’s Channel Migration Zone map, that lies between the severe channel migration hazard area and the outer boundaries of the channel migration zone (King County, 2014). The current regulatory base flood elevation is based on NAVD 88, while the map originally provided to us dated November 7, 2017 used the older City of Auburn datum, which is approximately 3.6 feet lower in elevation. This discrepancy led to the conclusion stated in our 316 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 8 of 15 original report that: “…the building sites all fall below or at the base flood elevation for the Green River (City of Auburn, 2017).” This conclusion was incorrect. Based on the new data, all building sites are located above the base flood elevation. We noted that the US Geological Survey Green River gage near Auburn, located at River Mile 32.0 uses the older datum for stage elevation (https://green2.kingcounty.gov/rivergagedata/gage-data.aspx?r=green). 5. 5. 5. 5. FLOODINGFLOODINGFLOODINGFLOODING AND AND AND AND CHANNELCHANNELCHANNELCHANNEL MIGRATIONMIGRATIONMIGRATIONMIGRATION The Green and White Rivers have a history of severe flooding. Until November 14, 1906, the White River occupied a channel west of the current Green River channel, and discharged into the Green River at about the current location of Pike Place Northeast (Anderson Map Company, 1907). On November 14, 1906, the area was inundated by a severe flood that changed the course of the White River to its current location, occupying what was previously the Stuck River. A diversion dam was subsequently constructed to make the change permanent (Perkins, 1993). Although this migration reduced flooding in the Kent Valley, the White River was flooding areas in Pierce County as well as the Kent Valley. This led to the construction of the Mud Mountain Dam on the White River in 1946. Even after flood levels on the White River were controlled, flooding continued unimpeded almost annually along the Green River valley. This led to the construction of the Fenster Levee on the west bank south of the properties in the 1960s (set back in 2014), the Howard A Hansen Dam, which was completed in 1961, and revetment adjacent to residences along the bank opposite the properties in 1973. The flood of record on the Green River occurred while the dam was under construction in November 1959, having a peak flow of 28,100 CFS (cubic feet per second) at the Auburn Gauge, located at River Mile 31.3 (US Geological Survey, 1975). The dam is operated such that maximum design flow is 12,000 CFS measured at the Auburn gauge. On February 9, 2020, flooding at the Green River Auburn gage reached a maximum flow of 12,080 CFS, which exceeded the design maximum flow for the site. At 12:30 pm on February 9, Mr. Bergquist visited the site and observed that the river had overtopped the bank and had reached a level just west of TP-2. We measured the high-water line at that location, which is 10 feet towards the river from TP-2 along Cross-Section B-B’ (refer to the Site Plan on Page A2, and Cross-Section B-B’, Figure 4 for the reference location). We staked this location for future reference. The proposed building sites are not located below the base flood elevation and were not inundated by this flood event. 317 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 9 of 15 Even though massive flood events occurred almost annually in the Green/White and later the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located. Maps dating back to 1888, and air photos dating back to 1936 show the river in its current location adjacent to the properties. The current channel configuration is confined on the west bank by revetment and on both banks by the bridge at 8th Avenue Southeast. A list of maps and air photos used in this review is included with other references at the end of this report. 6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY The City of Auburn originally classified the site as an erosion hazard area and a landslide hazard area because of soil and slope characteristics along the 104th Place Southeast cut slope, which is managed by the City. As stated earlier, the cut slope was constructed at approximately 1.18H:1V, and is approximately 25 feet high, based on our measurements. The vegetation growing along the inslope ditch and the lack of debris along the base of the slope indicates the dense silty SAND forming the slope does not appear to be eroding. Slope movement was noted near the south end of 104th Place Southeast on 1996 air photos. Some of the debris flowed over the road and across downslope properties into the Green River, forming an earthen bar. 7777. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES Slope stability analyses were conducted using XSTABL Version 5.205, an integrated slope stability analysis program for personal computers developed by Dr. Sunil Sharma of Interactive Software Designs, Inc. The stability of the cut slope was analyzed with and without seismic loading (earthquake conditions), using Cross-Section C-C’ as a model. The near-level surface between the proposed building sites and the Green River channel was analyzed for the potential for lateral spread during an earthquake, also using Cross-Section C-C’ as a model. 7777.1.1.1.1 AssumptionsAssumptionsAssumptionsAssumptions Soil strength values for slope stability analysis were derived from the A.S.T.M. visual manual classification along with field testing, and correlated with tables in USDA Forest Service, 1994. Values for root cohesion for the dense vegetation growing along the cut slope were not considered, although it is apparent that they contribute to stability. For our analyses, we considered ground water to be mobile through the silty fine SAND forming the cut slope, without developing hydrostatic pressures. Values used for slope stability analyses are as follows: 318 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 10 of 15 TABLE 7.1 TABLE 7.1 TABLE 7.1 TABLE 7.1 –––– VALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSES SOIL UNITSOIL UNITSOIL UNITSOIL UNIT MOISTMOISTMOISTMOIST DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) SATURATED SATURATED SATURATED SATURATED DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) COHESION COHESION COHESION COHESION (PSF)(PSF)(PSF)(PSF) ANGLE OF ANGLE OF ANGLE OF ANGLE OF INTERNALINTERNALINTERNALINTERNAL FRICTION FRICTION FRICTION FRICTION (DEGREES)(DEGREES)(DEGREES)(DEGREES) SU-A (SM) 132 138 0 38 SU-B (SM/ML) 84 112 0 27 SU-C (SM) 90 114 0 28 *Assumes fully saturated conditions for the soil unit. PCF and PSF are abbreviations for pounds per cubic foot and pounds per square foot, respectively. We did not include values for the fill material, since it does not extend southward to the cross- section analyzed. XSTABL and other slope stability programs calculate an estimated FOS (factor of safety), which is the result of dividing the total forces supporting the slope by the total forces that are tending to destabilize the slope. If the FOS is greater than 1.00, the slope is considered stable; if the FOS is less than 1.00, the slope is considered to be unstable. A FOS of 1.00 indicates the slope is in perfect equilibrium. The seismic coefficient applied to this project was 20 percent of the force of gravity which, in our judgment, is conservative considering the soils encountered at this site. The program was instructed to calculate the FOS for 1,000 potential shear surfaces during each iteration. The graphs contained in the appendix each show the locations of the 10 weakest surfaces analyzed within the slope segment selected for analysis, with the surface having the lowest FOS highlighted. 7777.2 .2 .2 .2 AAAAnalysesnalysesnalysesnalyses For the existing cut slope under static conditions, a FOS of 1.189 was calculated (refer to Graph GOULETW on page B1 in Appendix B). With seismic loading, the FOS was reduced to 0.808 (refer to Graph GOULETE2 on page B2 in Appendix B). For the near-level area adjacent to the Green River channel, a FOS of 1.265 was calculated under seismic loading (refer to Graph GOULETS2 on Page B3 in Appendix B). 8888. DISCUSSION. DISCUSSION. DISCUSSION. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions 319 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 11 of 15 encountered in the test pits adequately represent conditions near and between the test pits to the depths excavated. 9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS The following paragraphs present a summation of the area and site conditions as we interpret them. These conditions dictate the development considerations. 9.1 9.1 9.1 9.1 Flooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel Migration Flooding along the Green River is nearly an annual event, although the flooding occurs under controlled conditions as a result of the Howard A. Hanson Dam. Based on past records, floods reaching the base flood elevation occur one to two times a decade (Shannon & Wilson, 2002). Regulatory flood elevations are determined based on a model which assumes that Howard A. Hansen Dam functions properly, there is no channel migration, the revetments function as designed, and there are no blockages and sudden releases from significant events such as landslides or from log jams. No evidence of channel migration within the straight reach adjacent to the properties was observed on 130 years of maps and air photos. This in part may be due to long-term efforts at maintaining the current west bank of the channel with revetments. Although there are signs of erosion above the revetment immediately opposite the properties, most of the erosion has occurred on the river bank adjacent to the properties. Given that the channel is confined by the revetments to the west, higher ground elevations on the property immediately to the south, and the abutments beneath the bridge on 8th Avenue, the river would, in our judgment, be likely to erode the loose silty fine SAND underlying much of the property. 9.2 9.2 9.2 9.2 Slope Stability and ErosionSlope Stability and ErosionSlope Stability and ErosionSlope Stability and Erosion The City of Auburn considers the cut slope along 104th Place Southeast a “landslide hazard area” because of the slope inclination and height, even though it is a constructed slope owned and maintained by the city, which is responsible for its stability. No evidence of cut slope erosion or instability was observed adjacent to the parcels, even following the February 2020 rain events. Our analyses indicate this slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated. Our analyses indicate that slope movement (lateral spreading) is not likely to occur on the properties. The actual reaction to the seismic event, however, would be related to the strength and duration of shaking. 320 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 12 of 15 There are no visible indicators that the dense silty fine SAND forming the cut slope, which is covered by dense brush, is subject to significant erosion. The more likely area to be eroded is the shoreline described above. 9.3 9.3 9.3 9.3 SeismicitySeismicitySeismicitySeismicity We conducted our subsurface exploration near the end of one of the driest summers on record, and encountered little ground water on our test pits. What we did encounter was situated at an elevation just above the level of the Green River at that time. It appears likely that the level of the river influences the ground water levels in the loose silty fine SAND beneath the site. The loose silty fine SAND underlying the site is classified as having a high susceptibility for liquefaction and Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann (2007). 10101010. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS Conditions underlying and adjacent to the property, along with City, County, and State regulations, make the proposed development at this site challenging. The conditions at the site, however, do not render the site unbuildable, but additional steps beyond what is normally standard building practices will likely be needed. If the building footprints are located as shown on the drawings, most of the footings will be founded in the loose silty fine SAND flood deposits. Prior to design of the foundations for the planned buildings, a thorough subsurface exploration and engineering analysis must be performed. The exploration should include test borings with groundwater monitoring wells so that the proper foundation types and load carrying capacities can be recommended. Liquefiable soil conditions can be mitigated by design of a suitable, deep foundation system for a specific structure that may incorporate driven or drilled piles. Another method involves installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. Therefore, we recommend that the building design process includes appropriate subsurface exploration as described above and development of engineering recommendations for design of a foundation system or soils improvement methods that will mitigate the effects of liquefaction. There are no specific building plans at this time; therefore, we should be contacted for further recommendations once the designs of the specific structures are near completion. 321 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 13 of 15 Reduction of the Green River Buffer for dispersion trenches to the normal 50 feet will not adversely affect the stability of the river bank in this location. Final selection and design of the stormwater handling system(s) will be based on the concomitant impervious surfaces added to each property and on the results from the recommended subsurface exploration, and field and laboratory testing. Our analyses indicate the over-steepened cut slope along 104th Place Southeast would likely become unstable under severe seismic shaking. Therefore, those responsible for maintaining public safety along City streets should address strengthening of the slope. We do not anticipate the need for an additional buffer beyond what is already provided by the drainage ditch and 104th Place Southeast. Maintenance of native vegetation is required within the river buffer. The present vegetation, however, consists of non-native, invasive species (blackberry and morning glory. It will be necessary to clear the site in order to meet current standards. Removal of vegetation should be carefully performed so as to not adversely affect slope stability along the river bank. 11.11.11.11. REPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Launce Goulet to obtain a building permit variance for proposed residences to be constructed on King County tax parcel numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The recommendations are based on surface and subsurface information obtained by Bergquist Engineering Services Company, LLC (BESCO), and on an updated topographic survey provided by Encompass Engineering & Surveying. If there are any revisions to the plans or if conditions are encountered on site that deviate from our observations, BESCO must be notified immediately to determine whether changes to our recommendations are required. oOo 322 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 14 of 15 REFERENCESREFERENCESREFERENCESREFERENCES American Society for Testing and Materials, Description and Identification of Soils (Visual-Manual Procedure ASTM D2488): Annual Book of ASTM Standards, Section Four-Construction, Vol. 04-08, D2488-06, pp. 251-259. Anderson Bertrand & Company, 1888, Anderson’s New Map of King County, Washington Territory: Anderson, Bertrand & Company, Seattle, Washington Anderson Map Company, 1907, Anderson Map Coz Map of Auburn: Anderson Map Company, Seattle, Washington Atwater, B.F., and Hemphill-Haley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay, Washington: U.S. Geological Survey Professional Paper 1576, 108 p. City of Auburn, 2018, Green River to Auburn-Black Diamond Road: eGIS image of 1940 air photo mosaic, obtained via public information request. City of Auburn, 2005, Chapter 16.10 Critical Areas, Auburn Municipal Code Ord. 5894 § 1, 2005. City of Auburn, Washington, undated, City of Auburn GIS: https://maps.auburnwa.gov/Html5Viewer/index.html?viewer=public Galster, Richard W., 1989, Howard A. Hanson Dam: in Engineering Geology in Washington, Volume I, Washington Division of Geology and Earth Resources Bulletin 78, pp. 233-240. King County, 2014, Chapter 21A-24, Rules and Regulations of the Department of Permitting and Environmental Review and Department of Natural Resources and Parks, Critical Areas: Designation, Classification and Mapping of Channel Migration Zones: Effective Date: June 14, 1999, most recent amendment September 7, 2017, 5 p., Appendix A, 20 p. Mullineaux, D.R., 1965, Geologic Map of the Auburn Quadrangle, King and Pierce Counties, Washington: United States Geological Survey Geologic Quadrangle Map GQ-406, Scale 1:24000. 323 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 15 of 15 Palmer, S.P., Magsino, S.L., Bilderback, E.L., Poelstra, J.L., Folger, D.S., and Niggermann, R.A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources, Open File Report 2004-20. Perkins, S.J., 1993, Green River Channel Migration Study: King County Department of Public Works, Surface Water Management Division, Seattle, WA, 81 p. Rogers, A.M., Walsh, T.J., Kockelman, W.J., and Priest, G.R., 1991, Earthquake Hazards in the Pacific Northwest: An Overview: US Geological Survey Open-File Report 91-441-0, p. 4. Satake, K., Wang, K., and Atwater, B., 2003, Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions: Journal of Geophysical Research, v. 108, 2535, doi:10.1029/2003JB002521 Shannon & Wilson, Inc., 2002, Preliminary Risk-Based Flood Damage Analysis, Green River Flood Control District, King County, Washington: Shannon & Wilson, Inc., submitted to Mr. Dave Clark, Water and Land Resources Division, Department of Natural Resources, Seattle, Washington, January 2002, 41 p. USDA Forest Service, 1984, Slope Stability Reference Guide for National Forests in the Pacific Northwest: Forest Service Engineering Staff, Washington, D.C., EM-7170-13, August 1994, pp. 345-400. US Geological Survey, 1975, Magnitude and Frequency of Floods in Washington, US Geological Survey Open File Report 74-336, Tacoma, WA, p. 24 Washington Department of Natural Resources, 1961, Symbol A-95, Flight 17, Exposures 8, 9, and 10: Aerial photographs dated 8-7-1961. Washington Department of Natural Resources, 1996, Symbol NW-96, Roll 49, Flight 49, Exposures 18, 19, and 20: Aerial photographs dated 6-20-1996. Williamson, D.A., Neal, K.G., and Larson, D.A., 1991, The Field-Developed Cross-Section: A Systematic Method of Portraying Dimensional Subsurface Information and Modeling for Geotechnical Interpretation and Analysis: Association of Engineering Geologists, Proceedings, 34th Annual Meeting, pp. 719-738. 324 of 721 325 of 721 326 of 721 327 of 721 Bergquist Engineering Services Company, LLC A3 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----1111 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section CSection CSection CSection C----C’, Station 10+18.1C’, Station 10+18.1C’, Station 10+18.1C’, Station 10+18.1 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITOMONITOMONITOMONITORED BY RED BY RED BY RED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PIT 66.6 feet66.6 feet66.6 feet66.6 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 7.0 SM Silty fine SAND; light brown color; dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River). Started digging 1126. Roots top 2 feet 7.0 to 9.0 SM/ML Silty fine SAND with SILT with fine sand interbeds; light gray color with orange- brown and black iron staining; moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Black and orange brown bands where stained. No water encountered. Test pit completed 1154 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 328 of 721 Bergquist Engineering Services Company, LLC A4 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----2222 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section Section Section Section BBBB----B’, Station 10+52.0B’, Station 10+52.0B’, Station 10+52.0B’, Station 10+52.0 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE TYPE TYPE TYPE OF EQUIPMENTOF EQUIPMENTOF EQUIPMENTOF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber tRubber tRubber tRubber trackrackrackrack----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 68.768.768.768.7 feetfeetfeetfeet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 1.7 SM Silty fine SAND; brown color; dry (NPL), loose. Origin: Topsoil Started digging 1206. Roots top 1.7 feet 1.7 to 7.0 SM Silty fine SAND; light brown color; dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Black and orange bands where stained. Particle size distribution test 7.0 to 9.0 SM/ML Silty fine SAND with SILT with fine sand interbeds; brown to gray colors with orange iron staining; moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River). Forms clumps 9.0 to 9.6 ML/SM SILT with fine sand, with silty fine SAND interbeds; gray color with orange iron staining; wet (APL), soft to loose. Origin: Alluvial (overbank deposit from Green River) Particle size distribution test Wet soil encountered at bottom of test pit. Test pit completed 1227 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 329 of 721 Bergquist Engineering Services Company, LLC A5 TEST PIT NUMTEST PIT NUMTEST PIT NUMTEST PIT NUMBER:BER:BER:BER: TPTPTPTP----3333 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section ASection ASection ASection A----A’, Station 10+84.1A’, Station 10+84.1A’, Station 10+84.1A’, Station 10+84.1 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY KennKennKennKenneth G. Nealeth G. Nealeth G. Nealeth G. Neal ELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PIT 68.1 feet68.1 feet68.1 feet68.1 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 1.7 SM Silty fine SAND with coarse Gravel; light brown color; moist (BPL), dense. Origin: Fill Started digging 1244. Roots top 1.2 feet Particle size distribution test Very hard digging 1.7 to 7.5 SM Silty fine SAND; light gray brown color with increased orange-brown staining with depth, moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open 7.5 to 8.7 ML/SM SILT with fine sand with silty fine SAND with SILT interbeds; brown to gray colors with orange iron staining; moist (BPL to APL), soft to loose. Origin: Alluvial (overbank deposit from Green River). Forms clumps Particle size distribution test No water encountered Test pit completed 1310 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 330 of 721 Bergquist Engineering Services Company, LLC A6 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----4444 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section DSection DSection DSection D----D’, Station 10+40.5D’, Station 10+40.5D’, Station 10+40.5D’, Station 10+40.5 DATE EXPLDATE EXPLDATE EXPLDATE EXPLOREDOREDOREDORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 71.3 feet71.3 feet71.3 feet71.3 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 2.2 SM Silty fine SAND with coarse gravel; light brown color; dry (NPL), dense. Origin: Fill Started digging 1330. Roots top 1.2 feet Some clasts remold by hand pressure to SM Very hard digging 2.2 to 8.9 SM Silty fine SAND; light gray brown color, dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open Particle size distribution test Particle size distribution test No water encountered Test pit completed 1400 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 331 of 721 Bergquist Engineering Services Company, LLC A7 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----5555 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section DSection DSection DSection D----D’, Station 11+16.4D’, Station 11+16.4D’, Station 11+16.4D’, Station 11+16.4 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 69.1 feet69.1 feet69.1 feet69.1 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SUNIFIED SUNIFIED SUNIFIED SOIL OIL OIL OIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 6.5 SM Silty fine SAND; light brown color; dry to moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Started digging 1415. Easy digging Particle size distribution test 6.5 to 9.0 ML/SM SILT with silty fine SAND and silty fine SAND interbeds; light gray with orange iron staining; moist (APL), soft to loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open Particle size distribution test 9.0 to 9.6 SM/ML Silty fine SAND with SILT with silty fine SAND interbeds; light gray color; wet (APL), loose to soft. Origin: Alluvial (overbank deposit from Green River). Wet soil encountered at bottom of test pit Test pit completed 1425 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 332 of 721 333 of 721 334 of 721 335 of 721 336 of 721 337 of 721 338 of 721 339 of 721 340 of 721 341 of 721 342 of 721 343 of 721 344 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 345 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 346 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 347 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 348 of 721 349 of 721 350 of 721 351 of 721 352 of 721 353 of 721 354 of 721 355 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 1 | P a g e Table of Contents Chapter 1: Project Overview ......................................................................................................................... 2 Chapter 2: Existing Conditions ...................................................................................................................... 4 Chapter 3: Off-Site Analysis (Minimum Requirement #10) .......................................................................... 7 Chapter 4: Permanent Stormwater Control Plan ........................................................................................ 10 Chapter 5: Discussion of Minimum Requirements ..................................................................................... 14 List of Figures Figure 1 – Vicinity Map Figure 2 – USGS Soils Map and Legend Figure 3 – Existing Conditions Map Figure 4 – Downstream Map Figure 5 – Developed Conditions Map Figure 6 – Drainage Review Flow Chart List of Appendices Appendix A – Hydraulic/Hydrologic Analysis and Modeling Results Appendix B – Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 356 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 2 | P a g e Chapter 1: Project Overview Project: Lot C: Goulet Residence Address: 32XXX 104th Place SE, Auburn, WA 98092 Tax Parcel #: 334100-0100 Site Area: 13,021 SF (0.30 Acres) Site Location: The site is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. The site is within NW 17-21-05, W.M, King County, Washington. Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Please refer to the Vicinity Map below. Figure 1 – Vicinity Map Proposed Improvements: Lot C is a 13,021 SF lot located on the eastern shore of the Green River in Auburn, Washington. The site is currently vacant and moderately forested. The project proposes to construct a 1,650 SF single-family residential home with attached garage and an approximately 340 SF driveway with access to 104th Place SE. This corresponds to an impervious lot coverage of 15.3%, which complies with the maximum lot coverage of 35%. Stormwater runoff from the developed site will be mitigated via a basic dispersion trench as described in Chapter 4 of this Drainage Report. SITE Amberview Apartments Green River Lot C 357 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 3 | P a g e Site Constraints: The property is located directly adjacent to the Green River and is within the Urban Conservancy Shoreline Designation; therefore, the project is subject to the City of Auburn Shoreline Master Program (SMP). The SMP requires that a 100 FT buffer from the ordinary high-water mark of the Green River be maintained for all development activities. However, due to site area constraints, a Shoreline Variance has been prepared under separate cover to modify the 100 FT stream buffer. Encroachment into the 100 FT stream buffer has been minimized to the maximum extent feasible; however, in order to provide the necessary flow control BMPs, the stream buffer is reduced to 73 FT in some areas on the site. 358 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 4 | P a g e Chapter 2: Existing Conditions The project site is zoned R5 residential and is located on the west side of 104th Avenue SE just south of the SE 320th Street intersection in Auburn, Washington. Single family residences have been constructed several parcels to the north and south of the site, although the site is directly adjacent to several undeveloped lots. The Green River borders the site to the west. An existing conditions map is provided as Figure 3 at the end of this Chapter. Critical Areas: The site is directly adjacent to the Green River and is located within the Urban Conservancy Shoreline Designation; therefore, development is subject to the City of Auburn Shoreline Master Program (SMP). The SMP requires that a 100 FT buffer from the ordinary high-water mark of the Green River be maintained for all development activities. There is also a 50 FT channel migration hazard buffer associated with the lot. Soils: Per the United States Geological Survey (USGS), the entire project site is underlain with mixed alluvial soils at approximately 5-8% slopes (Map Unit Ma). Please refer to the USGS Map and Table below. Figure 2 – USGS Soils Map and Legend Lot C 359 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 5 | P a g e The subject site was also investigated by Bergquist Engineering Services (BES). Based on the BES Critical Areas Report dated April 9, 2020 (Appendix B), the site is underlain by fine loose silty sand alluvial deposits from the Green River. Due to the parcel being located within an Erosion Hazard Zone, Habitat Protection Zone, River Channel Buffer Zone, and Groundwater Protection Zone, the site falls within the City of Auburn’s Infiltration Infeasibility Area. Based on BES’s Report in Appendix B, dispersion of stormwater is feasible as long as the dispersion trench is at least 50 feet from the ordinary high-water mark of Green River. Please refer to Chapter 4 for additional discussion on feasible stormwater BMPs. 360 of 721 361 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 7 | P a g e Chapter 3: Off-Site Analysis (Minimum Requirement #10) A qualitative downstream analysis was performed by Encompass Engineering and Surveying on Friday December 12, 2019. The proposed project site is currently undeveloped and moderately forested. The site slopes to the west toward the Green River at approximately 5-8%. There are no upstream areas tributary to the project site. Runoff from the project site sheet flows directly into the Green River. The Green River flows to the north under the SE 320th Street bridge and takes a turn to the east near the 104th Avenue SE Park. This location is approximately ¼ mile downstream of the project site, and is where the Level 1 Downstream Analysis was concluded. During the downstream analysis, no signs of erosion or downstream drainage problems were observed. In addition, there were no downstream drainage complaints found on King County iMap. Please refer to the Downstream Drainage Map, Drainage System Table, and photographs on the following pages for additional details. Figure 4 – Downstream Drainage Map 362 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 8 | P a g e Off-site Analysis Drainage System Table Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident see map Type: sheet flow, swale, stream, channel, pipe, pond; Size: diameter, surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % ¼ ml = 1,320 ft. constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion tributary area, likelihood of problem, overflow pathways, potential impacts A SHEET FLOW VEGETATION 5-8% 0’ NO NO POINT OF DISCHARGE B RIVER CHANNEL GREEN RIVER NA 2,190’ NO NO FLOWS NORTH ALONG WESTERN PROPERTY LINE, PASSES UNDER THE SE 320TH ST BRIDGE, AND BEND TO THE EAST NEAR 104TH AVE SE PARK. THIS IS WHERE ANALYSIS WAS CONCLUDED. Photo 1 – Project Site from 104th Place SE 363 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 9 | P a g e Photo 2 – Green River from Site Looking North Photo 3 – Green River from SE 320th Street Bridge Looking North 364 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 10 | P a g e Chapter 4: Permanent Stormwater Control Plan The 13,021 SF (0.30 AC) site is currently undeveloped and moderately forested. The project proposes to construct a 1,650 SF (0.038 AC) single-family residential home with attached garage and an approximately 340 SF (0.008 AC) driveway with access to 104th Place SE. The site is contained within a single drainage basin that discharges to the west toward the Green River. Runoff generated by the proposed improvements will be managed onsite. A Developed Conditions Map is provided as Figure 5 at the end of this Chapter. Pre-Developed Site Hydrology The 6,149 SF (0.141 AC) within the limits of construction have been modeled as 100% forested with moderate slopes in the pre-developed condition. Developed Site Hydrology As described in the Section on the following page pertaining to the on-site stormwater management system (Minimum Requirement #5), basic dispersion is proposed to mitigate runoff from the proposed impervious areas on-site. Therefore, these areas have been modeled as 90% impervious and 10% lawn in the hydraulic/hydrologic model for the developed condition. All new pervious area has been modeled as 100% pervious. The area within the limits of construction was modeled as follows for the developed condition: Feature Area Developed Conditions Model Roof Area 1,650 SF (0.038 Ac) 1,485 SF (0.034 AC) Roof, flat; 165 SF (0.004 AC) lawn, moderate slope Driveway 340 SF (0.008 Ac) 306 SF (0.007 AC) Driveway, moderate slope; 34 SF (0.001 AC) lawn, moderate slope New Pervious 4,159 SF (0.095 Ac) 4,159 SF (0.095 Ac) Pasture, moderate slopes TOTAL AREA 6,149 SF (0.141 Ac) See Above The resulting increase in flow from the 100-year storm event is 0.0322 CFS as shown in the table below. The full WWHM output is included in Appendix A. 365 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 11 | P a g e On-Site Stormwater Management System – Minimum Requirement #5 This project is considered to be a new development, located inside of the Urban Growth Area, and triggers only Minimum Requirements #1 - #5 (See Chapter 5 for further discussion). To meet the applicable requirements per Figure 2.5.1 of the City of Auburn Supplemental Manual, this project proposes to apply On-site Stormwater Management List #1. Due to the parcel being located within an Erosion Hazard Zone, Habitat Protection Zone, River Channel Buffer Zone, and Groundwater Protection Zone, the site falls within the City of Auburn’s Infiltration Infeasibility Area. This means that stormwater runoff mitigation through full infiltration (BMP T5.10A), rain gardens (BMP T5.14A), Bioretention (BMP T7.30), and Permeable Pavement (BMP T5.15) are not considered feasible for the site. The remaining applicable BMPs have been considered below in the order listed for each type of surface. Lawn and Landscaped Areas: 1. Post-Construction Soil Quality and Depth (BMP T5.13): This BMP will be implemented throughout the pervious areas of the site. Approximately 4,159 SF of new pervious surface areas will utilize this BMP. Outside of the project clearing limits, topsoil will remain undisturbed. Topsoil that is disturbed by construction will be stockpiled in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible. Areas within the clearing limits designated to be pervious surfaces, will re-establish soil quality per the requirements detailed in Volume V BMP T5.13. Per the DOE Manual, areas meeting these guidelines have been modeled as “Pasture” rather than “Lawn” in the Flow Control Analysis detailed above in Chapter 4 of this Drainage Report. Roofs: 1. Full Dispersion (BMP T5.30): Full dispersion is not feasible for the project. The site does not allow for the minimum 100 FT native vegetated flowpath segment required to utilize full dispersion BMPs. 2. Downspout Dispersion Systems (BMP T5.10B): According to the BES Critical Areas Report (Appendix B), downspout dispersion is feasible for the project so long as the dispersion device is at least 50 feet from the ordinary high-water mark of Green River. Therefore, a 50 FT gravel filled basic dispersion trench with notched board and 25 FT native vegetated flowpath will be utilized to manage runoff from the 1,650 SF roof area. This is well within the 3,500 SF capacity of the trench. 3. Perforated Stub-out Connections (BMP T5.10C): No additional roof areas to mitigate. Other Hard Surfaces: 1. Full Dispersion (BMP T5.30): Full Dispersion is not feasible for the project. The site design does not allow for the minimum 100 FT native vegetated flowpath segment required to utilize full dispersion BMPs. This BMP is feasible for the project as Basic Dispersion. A basic dispersion system in the form of a 50 FT gravel filled dispersion trench with notched board and 25 FT native vegetated flowpath will be utilized to manage runoff from the site as described above. In addition to the 1,650 SF roof area, the 340 SF driveway will also be directed to this dispersion trench. The combined tributary area is 1,990 SF, which is within the 3,500 SF limit. 366 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 12 | P a g e 2. Concentrated Flow Dispersion (BMP T5.11) or Sheet Flow Dispersion (BMP T5.12): No additional hard surfaces to mitigate. 367 of 721 368 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 14 | P a g e Chapter 5: Discussion of Minimum Requirements The City of Auburn manages stormwater generated by development through adoption of the 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual). The City also has developed their own Supplement to the SMMWW which provides additional or modified requirements to the SMMWW (Supplemental Manual). Both manuals have been utilized in the design of this project. For simplicity, both manuals in conjunction will be referred to as “the drainage manual” unless one or the other is specified. The total proposed impervious area is 1,990 SF, which is less than 5,000 SF. Therefore, the project is required to comply with Minimum Requirements 1 through 5. Discussion of these minimum requirements is contained in this Chapter. Figure 6 – Flow Chart for Determining Minimum Requirements for New Developments 369 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 15 | P a g e Minimum Requirement #1: Preparation of Stormwater Site Plans The Stormwater Site Plan has been prepared in accordance with the 2014 Department of Ecology Stormwater Management Manual for Western Washington (DOE Manual) and the 2017 City of Auburn Supplemental Manual to the Ecology Stormwater Management Manual for Western Washington (Supplemental Manual). Minimum Requirement #2: Construction Stormwater Pollution Prevention Plan (CSWPPP) A CSWPPP, which will serve to minimize soil erosion/sedimentation during the proposed site construction, will be prepared for approval by the City of Auburn with final engineering. Minimum Requirement #3: Source Control of Pollution Actions taken each day in and around homes have a profound effect on surface water quality and fish habitat in this region. Stormwater goes directly to rivers, streams and to Puget Sound. Stormwater does not go to the wastewater treatment plant. Any pollutants that get into the stormwater go directly to surface water. Small amounts of pollution from many different sources can significantly affect our waterways. Yard maintenance, waste storage, car washing and maintenance, and pool cleaning are some of the activities that can adversely impact water quality. An Operations & Maintenance Manual that addresses source control best management practices (BMPs) for single-family residential homeowners will be provided with final engineering. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls The proposed on-site drainage patterns emulate those of the existing site conditions. Stormwater runoff from the site is proposed to be mitigated via dispersion as described in Chapter 4 of this Drainage Report. The associated native vegetated flowpaths will drain toward the Green River, as they do in the existing condition. Minimum Requirement #5: On-Site Stormwater Management The project proposes to utilize basic dispersion via a 50 FT gravel filled dispersion trench with 25 FT native vegetated flowpath to mitigate runoff from the proposed 1,650 SF residence and 340 SF driveway. Please refer to Chapter 4 of this Report for further discussion on how the applicable BMPs were selected. Minimum Requirement #10: Off-Site Analysis and Mitigation The site is located directly adjacent to the Green River, which flows to the north along the western property line. No erosion or drainage problems currently exist on the site, and no off-site drainage complaints have been found within a quarter mile downstream of the project. Please refer to Chapter 3 of this Drainage Report for additional discussion. 370 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 16 | P a g e Appendix A Hydraulic/Hydrologic Analysis and Modeling Results 371 of 721 WWHM2012 PROJECT REPORT 372 of 721 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 2 General Model Information Project Name:WWHM Model_Lot C Site Name:Goulet Lot A Site Address: City: Report Date:3/3/2020 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year 373 of 721 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.141 Pervious Total 0.141 Impervious Land Use acre Impervious Total 0 Basin Total 0.141 Element Flows To: Surface Interflow Groundwater 374 of 721 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.005 C, Pasture, Mod 0.095 Pervious Total 0.1 Impervious Land Use acre ROOF TOPS FLAT 0.034 DRIVEWAYS MOD 0.007 Impervious Total 0.041 Basin Total 0.141 Element Flows To: Surface Interflow Groundwater 375 of 721 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 5 Routing Elements Predeveloped Routing 376 of 721 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 6 Mitigated Routing 377 of 721 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.141 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.1 Total Impervious Area:0.041 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.004198 5 year 0.006879 10 year 0.008603 25 year 0.010654 50 year 0.012074 100 year 0.013401 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.018673 5 year 0.024883 10 year 0.029371 25 year 0.035486 50 year 0.040374 100 year 0.045556 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.005 0.027 1950 0.006 0.023 1951 0.009 0.018 1952 0.003 0.012 1953 0.002 0.013 1954 0.004 0.016 1955 0.006 0.016 1956 0.005 0.016 1957 0.004 0.020 1958 0.004 0.015 378 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 8 1959 0.004 0.014 1960 0.006 0.020 1961 0.003 0.017 1962 0.002 0.013 1963 0.003 0.017 1964 0.004 0.014 1965 0.003 0.020 1966 0.003 0.013 1967 0.006 0.025 1968 0.004 0.024 1969 0.004 0.018 1970 0.003 0.018 1971 0.003 0.020 1972 0.007 0.023 1973 0.003 0.012 1974 0.003 0.019 1975 0.005 0.021 1976 0.003 0.016 1977 0.000 0.014 1978 0.003 0.017 1979 0.002 0.023 1980 0.008 0.033 1981 0.003 0.019 1982 0.005 0.029 1983 0.005 0.019 1984 0.003 0.013 1985 0.002 0.017 1986 0.007 0.019 1987 0.006 0.022 1988 0.003 0.013 1989 0.002 0.018 1990 0.015 0.049 1991 0.008 0.032 1992 0.003 0.014 1993 0.003 0.011 1994 0.001 0.012 1995 0.005 0.016 1996 0.011 0.025 1997 0.008 0.020 1998 0.002 0.016 1999 0.009 0.034 2000 0.003 0.019 2001 0.001 0.018 2002 0.004 0.024 2003 0.006 0.024 2004 0.006 0.034 2005 0.004 0.017 2006 0.005 0.016 2007 0.011 0.043 2008 0.014 0.032 2009 0.007 0.022 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0152 0.0490 2 0.0140 0.0429 3 0.0115 0.0343 379 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 9 4 0.0106 0.0336 5 0.0092 0.0327 6 0.0090 0.0324 7 0.0082 0.0320 8 0.0082 0.0292 9 0.0081 0.0274 10 0.0072 0.0253 11 0.0070 0.0248 12 0.0065 0.0243 13 0.0064 0.0238 14 0.0064 0.0235 15 0.0063 0.0234 16 0.0059 0.0233 17 0.0057 0.0232 18 0.0057 0.0223 19 0.0055 0.0218 20 0.0053 0.0212 21 0.0049 0.0205 22 0.0048 0.0204 23 0.0048 0.0201 24 0.0046 0.0200 25 0.0046 0.0196 26 0.0045 0.0194 27 0.0044 0.0192 28 0.0042 0.0189 29 0.0041 0.0186 30 0.0037 0.0185 31 0.0037 0.0179 32 0.0036 0.0179 33 0.0036 0.0178 34 0.0035 0.0177 35 0.0035 0.0175 36 0.0035 0.0174 37 0.0034 0.0174 38 0.0034 0.0170 39 0.0033 0.0167 40 0.0032 0.0166 41 0.0032 0.0164 42 0.0032 0.0164 43 0.0031 0.0163 44 0.0030 0.0162 45 0.0029 0.0160 46 0.0029 0.0160 47 0.0028 0.0156 48 0.0028 0.0148 49 0.0027 0.0145 50 0.0027 0.0143 51 0.0026 0.0138 52 0.0025 0.0136 53 0.0023 0.0135 54 0.0022 0.0135 55 0.0020 0.0132 56 0.0017 0.0127 57 0.0017 0.0126 58 0.0016 0.0125 59 0.0011 0.0121 60 0.0006 0.0115 61 0.0005 0.0112 380 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 10381 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 11 Duration Flows Flow(cfs)Predev Mit Percentage Pass/Fail 0.0021 17077 67696 396 Fail 0.0022 15496 63289 408 Fail 0.0023 14072 59311 421 Fail 0.0024 12799 55504 433 Fail 0.0025 11567 52060 450 Fail 0.0026 10523 48852 464 Fail 0.0027 9567 45900 479 Fail 0.0028 8752 43184 493 Fail 0.0029 8031 40660 506 Fail 0.0030 7349 38200 519 Fail 0.0031 6737 36083 535 Fail 0.0032 6192 34030 549 Fail 0.0033 5726 32105 560 Fail 0.0034 5309 30308 570 Fail 0.0035 4924 28575 580 Fail 0.0036 4569 26993 590 Fail 0.0037 4235 25517 602 Fail 0.0038 3953 24212 612 Fail 0.0039 3645 22907 628 Fail 0.0040 3388 21731 641 Fail 0.0041 3133 20574 656 Fail 0.0042 2917 19509 668 Fail 0.0043 2706 18506 683 Fail 0.0044 2490 17524 703 Fail 0.0045 2314 16626 718 Fail 0.0046 2136 15811 740 Fail 0.0047 1973 14953 757 Fail 0.0048 1824 14221 779 Fail 0.0049 1702 13531 795 Fail 0.0050 1577 12902 818 Fail 0.0051 1443 12277 850 Fail 0.0052 1325 11648 879 Fail 0.0053 1232 11116 902 Fail 0.0054 1147 10551 919 Fail 0.0055 1086 10055 925 Fail 0.0056 1020 9578 939 Fail 0.0057 947 9118 962 Fail 0.0058 885 8716 984 Fail 0.0059 824 8391 1018 Fail 0.0060 760 8029 1056 Fail 0.0061 725 7659 1056 Fail 0.0062 674 7347 1090 Fail 0.0063 623 7007 1124 Fail 0.0064 589 6705 1138 Fail 0.0065 549 6402 1166 Fail 0.0066 506 6145 1214 Fail 0.0067 469 5863 1250 Fail 0.0068 427 5606 1312 Fail 0.0069 388 5369 1383 Fail 0.0070 356 5163 1450 Fail 0.0071 328 4975 1516 Fail 0.0072 297 4772 1606 Fail 0.0073 270 4554 1686 Fail 0.0074 241 4385 1819 Fail 382 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 12 0.0075 218 4209 1930 Fail 0.0076 198 4025 2032 Fail 0.0077 173 3865 2234 Fail 0.0078 152 3709 2440 Fail 0.0079 130 3546 2727 Fail 0.0080 119 3390 2848 Fail 0.0081 104 3255 3129 Fail 0.0082 95 3114 3277 Fail 0.0083 83 2982 3592 Fail 0.0084 74 2847 3847 Fail 0.0085 69 2744 3976 Fail 0.0086 61 2624 4301 Fail 0.0087 53 2552 4815 Fail 0.0088 46 2460 5347 Fail 0.0090 39 2370 6076 Fail 0.0091 29 2299 7927 Fail 0.0092 25 2212 8848 Fail 0.0093 22 2134 9700 Fail 0.0094 20 2060 10300 Fail 0.0095 17 1992 11717 Fail 0.0096 14 1919 13707 Fail 0.0097 12 1869 15575 Fail 0.0098 8 1796 22450 Fail 0.0099 7 1741 24871 Fail 0.0100 7 1691 24157 Fail 0.0101 7 1643 23471 Fail 0.0102 6 1598 26633 Fail 0.0103 6 1533 25550 Fail 0.0104 6 1487 24783 Fail 0.0105 6 1436 23933 Fail 0.0106 6 1384 23066 Fail 0.0107 5 1337 26740 Fail 0.0108 5 1299 25979 Fail 0.0109 5 1261 25220 Fail 0.0110 5 1222 24440 Fail 0.0111 5 1172 23440 Fail 0.0112 5 1130 22600 Fail 0.0113 5 1099 21980 Fail 0.0114 4 1046 26150 Fail 0.0115 4 1005 25125 Fail 0.0116 3 968 32266 Fail 0.0117 3 941 31366 Fail 0.0118 3 917 30566 Fail 0.0119 3 878 29266 Fail 0.0120 3 859 28633 Fail 0.0121 3 828 27600 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. 383 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. 384 of 721 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 14 LID Report 385 of 721 WWHM Model_Lot C 3/3/2020 8:24:19 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 386 of 721 WWHM Model_Lot C 3/3/2020 8:24:19 AM Page 16 Appendix Predeveloped Schematic 387 of 721 WWHM Model_Lot C 3/3/2020 8:24:21 AM Page 17 Mitigated Schematic 388 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM Model_Lot C.wdm MESSU 25 PreWWHM Model_Lot C.MES 27 PreWWHM Model_Lot C.L61 28 PreWWHM Model_Lot C.L62 30 POCWWHM Model_Lot C1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 11 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO 389 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 19 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 11 0.2 0.5 0.35 6 0.5 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 390 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 20 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 11 0.141 COPY 501 12 PERLND 11 0.141 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC 391 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 21 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN 392 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM Model_Lot C.wdm MESSU 25 MitWWHM Model_Lot C.MES 27 MitWWHM Model_Lot C.L61 28 MitWWHM Model_Lot C.L62 30 POCWWHM Model_Lot C1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 17 PERLND 14 IMPLND 4 IMPLND 6 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 17 C, Lawn, Mod 1 1 1 1 27 0 14 C, Pasture, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 17 0 0 1 0 0 0 0 0 0 0 0 0 14 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO 393 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 23 <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 17 0 0 4 0 0 0 0 0 0 0 0 0 1 9 14 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 17 0 0 0 0 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 17 0 4.5 0.03 400 0.1 0.5 0.996 14 0 4.5 0.06 400 0.1 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 17 0 0 2 2 0 0 0 14 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 17 0.1 0.25 0.25 6 0.5 0.25 14 0.15 0.4 0.3 6 0.5 0.4 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 17 0 0 0 0 2.5 1 0 14 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 6 DRIVEWAYS/MOD 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 6 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 6 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 394 of 721 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 24 4 0 0 0 0 0 6 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 6 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 6 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 6 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 17 0.005 COPY 501 12 PERLND 17 0.005 COPY 501 13 PERLND 14 0.095 COPY 501 12 PERLND 14 0.095 COPY 501 13 IMPLND 4 0.034 COPY 501 15 IMPLND 6 0.007 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - 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Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com 399 of 721 Lot C: Goulet Residence Preliminary Storm Drainage Report 17 | P a g e Appendix B Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 400 of 721 CRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORTCRITICAL AREAS REPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCESFAMILY RESIDENCES PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010PARCELS 3341000090, 3341000095, and 3341000010 AUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTONAUBURN, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULETMR. LAUNCE P. GOULET by:by:by:by: BERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLCBERGQUIST ENGINEERING SERVICES COMPANY, LLC BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1BESCO PROJECT NUMBER: 2018214, REPORT 1, REVISION 1, REVISION 1, REVISION 1, REVISION 1 APRIL 9, 2020APRIL 9, 2020APRIL 9, 2020APRIL 9, 2020 401 of 721 Bergqoist Engineering Services 27207 8th Avenue S R O. Box 13309 Des Moines, Washington 98198 Des Moines, Washington 98198 Phone: 253,941.9399 • Fax 253,941,9499 • E-mail: soilsengineering@aol,conn April 9, 2020 Mr. Launce Goulet 3226 S 198'^ Street SeaTac, Washington 98188 Re: Critical Area Report Proposed Single-Family Residences King County Parcel Numbers; 3341000090, 3341000095, and 33410000210 Auburn, Washington BESCO Project No.: 2018214, Report 1, Revision 1 Dear Launce: Bergquist Engineering Services Company, LLC is pleased to provide this Critical Area Report for the referenced King County parcels. The attached report summarizes project and site data, describes the services we performed, and presents our conclusions relative to soil erosion and channel migration and the stability of the off-site, steep slope along the east side of 104'*" Place SE. We appreciate the opportunity to be of service to you. If you have any questions concerning this report, or if we may be of additional service, please contact us. Copies to: Addressee (5) DOWN TO EARTH ENGINEERING SOLUTIONS 402 of 721 TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS 1. INTRODUCTION ......................................................................................................................... 1 2. PROJECT DESCRIPTION ............................................................................................................. 2 3. SCOPE OF SERVICES .................................................................................................................. 2 4. SITE CHARACTERIZATION ......................................................................................................... 3 4.1 Topography and Development ....................................................................................... 3 4.2 Area Geology ................................................................................................................... 4 4.3 Seismicity ......................................................................................................................... 4 4.4 Site Geology ..................................................................................................................... 5 4.5 Subsurface Soils ............................................................................................................... 5 4.6 Ground Water and Drainage........................................................................................... 7 4.7 Site Classification ............................................................................................................. 7 5. FLOODING AND CHANNEL MIGRATION .................................................................................. 8 6. EROSION AND SLOPE STABILITY ............................................................................................... 9 7. SLOPE STABILITY ANALYSIS ....................................................................................................... 9 7.1 Assumptions .................................................................................................................... 9 7.2 Analysis ........................................................................................................................... 10 8. DISCUSSION .............................................................................................................................. 10 9. CONCLUSIONS .......................................................................................................................... 11 9.1 Flooding and Channel Migration ............................................................................. 11 9.2 Slope Stability and Erosion ...................................................................................... 11 9.3 Seismicity .................................................................................................................. 12 10. RECOMMENDATIONS .............................................................................................................. 12 11. PEPORT LIMITATIONS .............................................................................................................. 13 APPENDIXAPPENDIXAPPENDIXAPPENDIX AAAA Vicinity Map ................................................................................................................................. A1 Site Plan .................................................................................................................................. A2 Logs of Test Pits ................................................................................................................................ A3 Test Pit Log Notes ............................................................................................................................ A8 Unified Soil Classification System ................................................................................................... A10 Particle Size Distribution Reports ................................................................................................... A11 Cross Sections ................................................................................................................................. A20 APPENDIX BAPPENDIX BAPPENDIX BAPPENDIX B Computer Printouts of Slope Stability Analyses ............................................................................. B1 Notes .................................................................................................................................. B4 403 of 721 CRITICAL AREASCRITICAL AREASCRITICAL AREASCRITICAL AREAS REPORTREPORTREPORTREPORT PROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLEPROPOSED SINGLE----FAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCEFAMILY RESIDENCESSSS PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095PARCELS 3341000090, 3341000095, , , , andandandand 3341000010334100001033410000103341000010 AUBURNAUBURNAUBURNAUBURN, WASHINGTON, WASHINGTON, WASHINGTON, WASHINGTON prepared for:prepared for:prepared for:prepared for: MR. LAUNMR. LAUNMR. LAUNMR. LAUNCCCCE P.E P.E P.E P. GOULETGOULETGOULETGOULET by:by:by:by: BERGQUIST BERGQUIST BERGQUIST BERGQUIST ENGINEERING SERVICESENGINEERING SERVICESENGINEERING SERVICESENGINEERING SERVICES COMPANY, LLCCOMPANY, LLCCOMPANY, LLCCOMPANY, LLC BESBESBESBESCOCOCOCO PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: PROJECT NUMBER: 2018201820182018214214214214, , , , REPORT 1REPORT 1REPORT 1REPORT 1, R, R, R, REVISION EVISION EVISION EVISION 1111 April 9April 9April 9April 9, 2020, 2020, 2020, 2020 1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION1. INTRODUCTION This report presents the results of our geotechnical evaluation of critical areas for three proposed single-family residences to be constructed on King County Parcel Numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The parcels are located along the east bank of the Green River west of 104th Place Southeast, in the northwest quarter of the northwest quarter of Section 17, Township 21 North, Range 5 East, Willamette Meridian. The location of the project is shown on the Vicinity Map, Figure 1, on page A1 in Appendix A of this report. This report was revised because datum used for the current site plans, dated January 24, 2020 are NAVD 88, rather than the City of Auburn datum used on the originally submitted plans dated November 7, 2017. This report also provides additional information as a result of a site visit by Mr. Bergquist, who observed the level of the Green River on February 9, 2020, shortly after it exceeded the base flood elevation, and a follow-up visit by Messrs. Bergquist and Neal, who located and marked the maximum 2020 flood level. The geotechnical evaluation was performed by Bergquist Engineering Services Company, LLC (BESCO) to provide information or recommendations regarding: • erosion and slope stability characteristics, in accordance with Auburn City Code 16.10, • the risk of liquefaction and seismic design considerations, and • the influence of ground and surface water on the development. 404 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 2 of 15 This report is not intended to provide geotechnical criteria for design of the planned houses. The data for developing design criteria will be completed after critical area issues are addressed, and the various variances for these properties are obtained. The critical issues addressed in this report are; channel migration, landslide hazards, erosion hazards, flooding and seismic hazards. Mr. Launce P. Goulet authorized our work on March 19th, 2018 by signing and returning BESCO Proposal Number 1162018. 2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION2. PROJECT DESCRIPTION The proposed project would involve construction of one multi-level house on each of the three vacant properties. The footprints and finished grades of the houses have not yet been finalized. 3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES3. SCOPE OF SERVICES The scope of services included the following steps: • an initial reconnaissance of the site by the geotechnical engineer; • excavating, logging, and sampling five test pits; logs of the test pits are presented in Appendix A on pages A3 through A7; • field and laboratory testing of selected soil samples, including visual classification and gradations; • a review of geologic and historic literature, and historic aerial photography; a list of references is contained in Appendix B; • measurement of a geotechnical cross-section for each parcel, and development of a geologic interpretation for the site by the engineering geologist; • a preliminary evaluation of soil strength and drainage characteristics; • evaluation of past and likely future migration of the Green River channel; • geotechnical slope stability analyses; • observation of the maximum recent flood elevation at the site; and • preparation of this report. Slope relationships for our cross-section were measured using a cloth tape, hand clinometer and Brunton compass in accordance with methodology outlined in Williamson, Neal and Larson (1991). The measurements used to develop the cross-sections and site plan are therefore, not of the precision and accuracy of a site survey prepared by a professional land surveyor, and should not be used for that purpose. 405 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 3 of 15 The recommendations and advice presented in this report have been made in accordance with generally accepted geotechnical practices in the area. 4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION4. SITE CHARACTERIZATION The information presented in this section was gathered by BESCO personnel for evaluation of critical area issues only. This site characterization was not intended to address the presence or likelihood of contamination on or around the site. Specialized methods and procedures, which were not a part of this scope of services, are required for an adequate environmental site assessment. 4.14.14.14.1 Topography and DevelopmentTopography and DevelopmentTopography and DevelopmentTopography and Development Parcels 3341000090, 3341000095, and 3341000010, referred to as Lots A, B, and C on the Site Plan, Figure 2, encompass 12,765, 11,644, and 11,777 square feet, respectively. The parcels are bounded on the east by 104th Place Southeast, on the west by the Green River, and to the north and south by developed single-family residential lots. Topographic relationships are shown on the sketch entitled, “Site Plan” presented on page A2 and on Cross-Sections A-A’, B-B’ C-C,’ and D-D’, presented on pages A20 through A22. Elevations shown on the cross-sections and test pit logs are based on a site and topographic plan for the parcels prepared by Encompass Engineering & Surveying, dated 1/14/2020, and our measurements. There is approximately 20 feet of relief on Parcel A, from an elevation of approximately 56 feet mean sea level (MSL) at the ordinary high water mark (OHWM) of the Green River at the northwest corner of the property to an elevation of approximately 76 feet MSL at the southeast property corner. There is approximately 20 feet of relief on Parcel B, from an elevation of approximately 56 feet MSL at the OHWM at the northwest corner of the property to an elevation of approximately 76 feet MSL at the northwest corner of the property. There is approximately 18 feet of relief on Parcel C, from an elevation of approximately 56 feet MSL along the OHWM and west parcel boundary to an elevation of approximately 74 feet MSL along the east parcel boundary and at the northeast corner. The eroded streambank of the Green River is inclined at from 10 percent to near-vertical. The ground surface is nearly level from the top of the streambank to the base of the fill slope just below 104th Place Southeast. It steepens to between 15 to 20 percent adjacent to 104th Place Southeast. The cut slope along the east side of 104th Place Southeast was constructed at approximately 1.18H:1V (horizontal:vertical) (85 percent). 406 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 4 of 15 The parcels are vegetated with second-growth maple and cottonwood, with a dense ground cover of blackberry and, along the river, morning glory. This vegetation reflects the year-round availability of water. A dead snag fell across the location of Cross-Section B-B’ apparently during the winter storms of 2020. 4.24.24.24.2 Area GeologyArea GeologyArea GeologyArea Geology The project area is situated in the Puget Sound basin, a structural low between the Cascade and Olympic Mountain physiographic provinces. The Puget Sound region has been subjected to at least six episodes of glaciations during the last two million years. The most recent glaciation, referred to as the Vashon stade of the Fraser glaciations, stalled and began rapid melting about 12,000 years ago. The glaciations left topography in the Puget Sound region characterized by north-south trending ridges and troughs. The troughs, such as the Puget Sound, Duwamish Channel, and Kent Valley, served as subglacial channels for southward-flowing meltwater. The glaciers formed deposits in front of advancing ice, along the ice margins, during the retreat of the ice front, and during interglacial periods. These deposits have subsequently been overridden and compacted by the advancing Vashon ice sheet. Some of the capping silts, sands, and gravels were likely deposited during Vashon glacial recession. Slope, fluvial, volcanic, and shoreline processes have shaped the land within the area over the 12,000 years since glacial retreat. Approximately 5,600 years ago, the Osceola Mudflow, a lahar originating from Mount Rainier, flowed down the West Fork of the White River and the White River valleys through the areas now occupied by Buckley, Enumclaw, and Auburn to as far north as Kent. The Electron Mudflow, also a Mount Rainier lahar, flowed down the Puyallup River through Orting and Puyallup and into the Kent Valley approximately 500 years ago. The White and Green Rivers have subsequently eroded through the lahars and infilled the floors of the resulting valleys with alluvial deposits. 4.34.34.34.3 SeismicitySeismicitySeismicitySeismicity The Puget Sound region is seismically active. Low magnitude earthquakes occur nearly every week within a 50-mile radius of the site. On April 13, 1949, the Olympia area experienced an earthquake having a Richter Magnitude 7.1 and, on April 29, 1965, the Tacoma-Seattle area experienced an earthquake having a Richter Magnitude 6.5 (Rogers, Walsh, Kockelman and Priest, 1991). On February 28, 2001, a magnitude 6.8 earthquake occurred just north of the Nisqually delta. 407 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 5 of 15 Great subduction zone earthquakes are the largest earthquakes in the world, and are the only source zones that can produce earthquakes greater than Magnitude 8.5. The Cascadia Subduction Zone, located off the coastlines of Washington, Oregon, and northern California, has produced magnitude 9.0 or greater earthquakes in the past. The last known megathrust earthquake in the northwest was in January, 1700 (Satake, Wang, and Atwater, 2003). Geological evidence indicates that such great earthquakes have occurred at least seven times in the last 3,500 years, a return interval of 400 to 600 years (Atwater and Hemphill-Haley, 1997). The immediate vicinity of the site is classified as having a medium to high susceptibility for liquefaction and is classified as Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann, 2007). 4.44.44.44.4 Site GeologySite GeologySite GeologySite Geology Glacial and interglacial deposits are exposed in the Green River valley wall east of 104th Place Southeast. These deposits have been interpreted to include, from oldest (lowest on the slope) to youngest (top of the slope) the interglacial Puyallup Formation, overlain by glacial drift from the Salmon Springs glacial stade, and kame terrace deposits from the most recent (Vashon) stade. The glacially-derived deposits are overlain along the Green River and at the subject properties by Green River alluvial and fluvial (flood) deposits, consisting of fine sand with lenses of gravel, locally overlain by silt and clay (Mullineaux, 1965). Geologic processes on the properties are primarily associated with stream flow along the Green River. Flow is controlled in part by Howard A. Hansen Dam, which was constructed in Eagle Gorge and is used primarily for flood control in the lower Green-Duwamish valley (Galster, 1989). The primary process potentially affecting the properties is river erosion and deposition during flood events. While this risk is somewhat diminished by control of flows during floods by the aforementioned dam, the City of Auburn has designed much of the properties as being a “channel migration area (CMA)” on their city flood map. The regulatory flood elevation for the river reach adjacent to the properties is 66 to 67 feet MSL. 4.5 4.5 4.5 4.5 Subsurface SoilsSubsurface SoilsSubsurface SoilsSubsurface Soils The subsurface soil conditions at this site are described in the following paragraphs and are presented graphically on the test pit logs. The test pit locations are shown on the Site Plan, Figure 2 in page A2 of Appendix A, and on Cross-Sections A-A’, B-B’, C-C’, and D-D’, Figures 3, 4, 5, and 6, respectively. 408 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 6 of 15 Soils were described and classified in general accordance with the Unified Soil Classification visual- manual procedure (American Society for Testing and Materials). A description of this system is included on page A10. Results of soil gradation tests are presented on pages A11 through A18. For purposes of explanation, we divided on-site soils into three soil units, SU-A, SU-B, and SU-C, based on origin and physical characteristics. Soil units are shown on the cross-sections; soil unit designations are intended to be local in scope, and not applicable outside the immediate area. A thin layer of organics, primarily blackberry roots, was noted at the top of each test pit. The roots generally reach to depths of 1.5 to 2 feet. SU-A was encountered along the base of the cut slope opposite the properties. Although the valley wall formed of this material is projected to be located beneath the east side of the property, it was not encountered in our test pits. SU-A consists of gray brown silty fine SAND (ASTM: SM). SU-A is a non-plastic soil that was moist, and was dense at the time of our field work. SU-A is interpreted to be an interglacial deposit. SU-B was encountered below depths of 7.0 feet in TP-1, 7.0 feet in TP-2, 7.5 feet in TP-3, and 6.5 in TP-5. SU-B is brown to gray in color, and ranges from silty fine SAND with silt interbeds to SILT with silty fine sand interbeds (ASTM: SM/ML to ML/SM). Orange-brown to black iron staining forms bands that become more frequent with depth. SU-B is a plastic soil that was moist to wet, with the natural moisture content ranging from below to above the plastic limit. SU-B was loose to soft at the time of our exploration. SU-B is interpreted to be an alluvial deposit, an overbank deposit of the Green River. SU-C was encountered overlying SU-B in all five test pits, from the ground surface to a depth of 7.0 feet in TP-1, between depths of 1.7 and 7.0 feet in TP-2, between 1.7 and 7.5 feet in TP-3, below 2.2 feet in TP-4, and from the ground surface to a depth of 6.5 feet in TP-5. SU-C consists of light brown to gray brown Silty fine SAND (ASTM: SM). SU-C is a non-plastic soil that was dry to locally moist, and was loose at the times of our exploration. SU-C is interpreted to be an alluvial deposit, an overbank deposit of the Green River). In addition to the soil units observed at the site, fill materials were encountered along the ground surface over the northern portion of the site and in TP-3 and TP-4, to depths of 1.7 feet in TP-3 and 409 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 7 of 15 2.2 feet in TP-4. This fill material consists of light brown silty fine SAND with coarse gravel (ASTM: SM), that ranged from a dry, non-plastic soil to a moist plastic soil with the natural moisture content below the plastic limit at the time of our exploration. This fill material appears to have been spread over the north parcel by heavy equipment and was dense at the time of our field work. Fill materials are also present beneath the outside shoulder of 104th Place Southeast along the east periphery of the parcels. It appears that the parcels have also been used as a location to dump garbage, particularly just downslope from the shoulder of the street. 4.64.64.64.6 Ground Water and Ground Water and Ground Water and Ground Water and DrainageDrainageDrainageDrainage At the time of our exploration, the King County region had experienced an extended, near record drought. Accordingly, no surface or ground water was encountered on the site. Soil moisture was encountered in three test pits at or just above the stream elevation. Water was encountered near the ground surface in the backfilled TP-2 by Mr. Bergquist during his February 9, 2020 site visit. No drainage features were observed on site. During our September 12, 2018 site visit, which followed a rain event, water had accumulated in low areas on the near-level ground surface. 4.74.74.74.7 Site ClassificationSite ClassificationSite ClassificationSite Classification The City of Auburn classifies all three project parcels as within a Critical Erosion Hazard Area under 16.10.080G, likely due to the presence of the silty fine SAND underlying the steep cut slope along the east side of 104th Place Southeast. The City also classifies the cut slope, which is located on City property, as a Class IV/Very High Hazard Landslide Hazard Area under 16.10.080G2d, since the slope was excavated to an inclination greater than 40 percent. Since the Green River is a Type S stream, the area within 250 feet of the OHWM is considered a riparian habitat zone. King County has classified the parcels as a “channel migration hazard area, moderate” for channel migration (King County, 1999). “Channel migration hazard area. Moderate” means a portion of the channel migration zone, as shown on the King County’s Channel Migration Zone map, that lies between the severe channel migration hazard area and the outer boundaries of the channel migration zone (King County, 2014). The current regulatory base flood elevation is based on NAVD 88, while the map originally provided to us dated November 7, 2017 used the older City of Auburn datum, which is approximately 3.6 feet lower in elevation. This discrepancy led to the conclusion stated in our 410 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 8 of 15 original report that: “…the building sites all fall below or at the base flood elevation for the Green River (City of Auburn, 2017).” This conclusion was incorrect. Based on the new data, all building sites are located above the base flood elevation. We noted that the US Geological Survey Green River gage near Auburn, located at River Mile 32.0 uses the older datum for stage elevation (https://green2.kingcounty.gov/rivergagedata/gage-data.aspx?r=green). 5. 5. 5. 5. FLOODINGFLOODINGFLOODINGFLOODING AND AND AND AND CHANNELCHANNELCHANNELCHANNEL MIGRATIONMIGRATIONMIGRATIONMIGRATION The Green and White Rivers have a history of severe flooding. Until November 14, 1906, the White River occupied a channel west of the current Green River channel, and discharged into the Green River at about the current location of Pike Place Northeast (Anderson Map Company, 1907). On November 14, 1906, the area was inundated by a severe flood that changed the course of the White River to its current location, occupying what was previously the Stuck River. A diversion dam was subsequently constructed to make the change permanent (Perkins, 1993). Although this migration reduced flooding in the Kent Valley, the White River was flooding areas in Pierce County as well as the Kent Valley. This led to the construction of the Mud Mountain Dam on the White River in 1946. Even after flood levels on the White River were controlled, flooding continued unimpeded almost annually along the Green River valley. This led to the construction of the Fenster Levee on the west bank south of the properties in the 1960s (set back in 2014), the Howard A Hansen Dam, which was completed in 1961, and revetment adjacent to residences along the bank opposite the properties in 1973. The flood of record on the Green River occurred while the dam was under construction in November 1959, having a peak flow of 28,100 CFS (cubic feet per second) at the Auburn Gauge, located at River Mile 31.3 (US Geological Survey, 1975). The dam is operated such that maximum design flow is 12,000 CFS measured at the Auburn gauge. On February 9, 2020, flooding at the Green River Auburn gage reached a maximum flow of 12,080 CFS, which exceeded the design maximum flow for the site. At 12:30 pm on February 9, Mr. Bergquist visited the site and observed that the river had overtopped the bank and had reached a level just west of TP-2. We measured the high-water line at that location, which is 10 feet towards the river from TP-2 along Cross-Section B-B’ (refer to the Site Plan on Page A2, and Cross-Section B-B’, Figure 4 for the reference location). We staked this location for future reference. The proposed building sites are not located below the base flood elevation and were not inundated by this flood event. 411 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 9 of 15 Even though massive flood events occurred almost annually in the Green/White and later the Green River valleys prior to dam construction, there is no evidence of channel migration along the reach where the properties are located. Maps dating back to 1888, and air photos dating back to 1936 show the river in its current location adjacent to the properties. The current channel configuration is confined on the west bank by revetment and on both banks by the bridge at 8th Avenue Southeast. A list of maps and air photos used in this review is included with other references at the end of this report. 6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY6. EROSION AND SLOPE STABILITY The City of Auburn originally classified the site as an erosion hazard area and a landslide hazard area because of soil and slope characteristics along the 104th Place Southeast cut slope, which is managed by the City. As stated earlier, the cut slope was constructed at approximately 1.18H:1V, and is approximately 25 feet high, based on our measurements. The vegetation growing along the inslope ditch and the lack of debris along the base of the slope indicates the dense silty SAND forming the slope does not appear to be eroding. Slope movement was noted near the south end of 104th Place Southeast on 1996 air photos. Some of the debris flowed over the road and across downslope properties into the Green River, forming an earthen bar. 7777. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES. SLOPE STABILITY ANALYSES Slope stability analyses were conducted using XSTABL Version 5.205, an integrated slope stability analysis program for personal computers developed by Dr. Sunil Sharma of Interactive Software Designs, Inc. The stability of the cut slope was analyzed with and without seismic loading (earthquake conditions), using Cross-Section C-C’ as a model. The near-level surface between the proposed building sites and the Green River channel was analyzed for the potential for lateral spread during an earthquake, also using Cross-Section C-C’ as a model. 7777.1.1.1.1 AssumptionsAssumptionsAssumptionsAssumptions Soil strength values for slope stability analysis were derived from the A.S.T.M. visual manual classification along with field testing, and correlated with tables in USDA Forest Service, 1994. Values for root cohesion for the dense vegetation growing along the cut slope were not considered, although it is apparent that they contribute to stability. For our analyses, we considered ground water to be mobile through the silty fine SAND forming the cut slope, without developing hydrostatic pressures. Values used for slope stability analyses are as follows: 412 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 10 of 15 TABLE 7.1 TABLE 7.1 TABLE 7.1 TABLE 7.1 –––– VALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSESVALUES USED FOR SLOPE STABILITY ANALYSES SOIL UNITSOIL UNITSOIL UNITSOIL UNIT MOISTMOISTMOISTMOIST DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) SATURATED SATURATED SATURATED SATURATED DENSITYDENSITYDENSITYDENSITY (PCF)(PCF)(PCF)(PCF) COHESION COHESION COHESION COHESION (PSF)(PSF)(PSF)(PSF) ANGLE OF ANGLE OF ANGLE OF ANGLE OF INTERNALINTERNALINTERNALINTERNAL FRICTION FRICTION FRICTION FRICTION (DEGREES)(DEGREES)(DEGREES)(DEGREES) SU-A (SM) 132 138 0 38 SU-B (SM/ML) 84 112 0 27 SU-C (SM) 90 114 0 28 *Assumes fully saturated conditions for the soil unit. PCF and PSF are abbreviations for pounds per cubic foot and pounds per square foot, respectively. We did not include values for the fill material, since it does not extend southward to the cross- section analyzed. XSTABL and other slope stability programs calculate an estimated FOS (factor of safety), which is the result of dividing the total forces supporting the slope by the total forces that are tending to destabilize the slope. If the FOS is greater than 1.00, the slope is considered stable; if the FOS is less than 1.00, the slope is considered to be unstable. A FOS of 1.00 indicates the slope is in perfect equilibrium. The seismic coefficient applied to this project was 20 percent of the force of gravity which, in our judgment, is conservative considering the soils encountered at this site. The program was instructed to calculate the FOS for 1,000 potential shear surfaces during each iteration. The graphs contained in the appendix each show the locations of the 10 weakest surfaces analyzed within the slope segment selected for analysis, with the surface having the lowest FOS highlighted. 7777.2 .2 .2 .2 AAAAnalysesnalysesnalysesnalyses For the existing cut slope under static conditions, a FOS of 1.189 was calculated (refer to Graph GOULETW on page B1 in Appendix B). With seismic loading, the FOS was reduced to 0.808 (refer to Graph GOULETE2 on page B2 in Appendix B). For the near-level area adjacent to the Green River channel, a FOS of 1.265 was calculated under seismic loading (refer to Graph GOULETS2 on Page B3 in Appendix B). 8888. DISCUSSION. DISCUSSION. DISCUSSION. DISCUSSION The recommendations presented in this report are based on our understanding of the project as presented in the Project Description Section and on the assumption that the subsurface conditions 413 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 11 of 15 encountered in the test pits adequately represent conditions near and between the test pits to the depths excavated. 9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS9. CONCLUSIONS The following paragraphs present a summation of the area and site conditions as we interpret them. These conditions dictate the development considerations. 9.1 9.1 9.1 9.1 Flooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel MigrationFlooding and Channel Migration Flooding along the Green River is nearly an annual event, although the flooding occurs under controlled conditions as a result of the Howard A. Hanson Dam. Based on past records, floods reaching the base flood elevation occur one to two times a decade (Shannon & Wilson, 2002). Regulatory flood elevations are determined based on a model which assumes that Howard A. Hansen Dam functions properly, there is no channel migration, the revetments function as designed, and there are no blockages and sudden releases from significant events such as landslides or from log jams. No evidence of channel migration within the straight reach adjacent to the properties was observed on 130 years of maps and air photos. This in part may be due to long-term efforts at maintaining the current west bank of the channel with revetments. Although there are signs of erosion above the revetment immediately opposite the properties, most of the erosion has occurred on the river bank adjacent to the properties. Given that the channel is confined by the revetments to the west, higher ground elevations on the property immediately to the south, and the abutments beneath the bridge on 8th Avenue, the river would, in our judgment, be likely to erode the loose silty fine SAND underlying much of the property. 9.2 9.2 9.2 9.2 Slope Stability and ErosionSlope Stability and ErosionSlope Stability and ErosionSlope Stability and Erosion The City of Auburn considers the cut slope along 104th Place Southeast a “landslide hazard area” because of the slope inclination and height, even though it is a constructed slope owned and maintained by the city, which is responsible for its stability. No evidence of cut slope erosion or instability was observed adjacent to the parcels, even following the February 2020 rain events. Our analyses indicate this slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated. Our analyses indicate that slope movement (lateral spreading) is not likely to occur on the properties. The actual reaction to the seismic event, however, would be related to the strength and duration of shaking. 414 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 12 of 15 There are no visible indicators that the dense silty fine SAND forming the cut slope, which is covered by dense brush, is subject to significant erosion. The more likely area to be eroded is the shoreline described above. 9.3 9.3 9.3 9.3 SeismicitySeismicitySeismicitySeismicity We conducted our subsurface exploration near the end of one of the driest summers on record, and encountered little ground water on our test pits. What we did encounter was situated at an elevation just above the level of the Green River at that time. It appears likely that the level of the river influences the ground water levels in the loose silty fine SAND beneath the site. The loose silty fine SAND underlying the site is classified as having a high susceptibility for liquefaction and Site Class D to E (Palmer, Magsino, Bilderback, Poelstra, Folger, and Niggermann (2007). 10101010. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS. RECOMMENDATIONS Conditions underlying and adjacent to the property, along with City, County, and State regulations, make the proposed development at this site challenging. The conditions at the site, however, do not render the site unbuildable, but additional steps beyond what is normally standard building practices will likely be needed. If the building footprints are located as shown on the drawings, most of the footings will be founded in the loose silty fine SAND flood deposits. Prior to design of the foundations for the planned buildings, a thorough subsurface exploration and engineering analysis must be performed. The exploration should include test borings with groundwater monitoring wells so that the proper foundation types and load carrying capacities can be recommended. Liquefiable soil conditions can be mitigated by design of a suitable, deep foundation system for a specific structure that may incorporate driven or drilled piles. Another method involves installing vertical wick drains and then preloading the site with a temporary surcharge consisting of compacted earthen fill. Therefore, we recommend that the building design process includes appropriate subsurface exploration as described above and development of engineering recommendations for design of a foundation system or soils improvement methods that will mitigate the effects of liquefaction. There are no specific building plans at this time; therefore, we should be contacted for further recommendations once the designs of the specific structures are near completion. 415 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 13 of 15 Reduction of the Green River Buffer for dispersion trenches to the normal 50 feet will not adversely affect the stability of the river bank in this location. Final selection and design of the stormwater handling system(s) will be based on the concomitant impervious surfaces added to each property and on the results from the recommended subsurface exploration, and field and laboratory testing. Our analyses indicate the over-steepened cut slope along 104th Place Southeast would likely become unstable under severe seismic shaking. Therefore, those responsible for maintaining public safety along City streets should address strengthening of the slope. We do not anticipate the need for an additional buffer beyond what is already provided by the drainage ditch and 104th Place Southeast. Maintenance of native vegetation is required within the river buffer. The present vegetation, however, consists of non-native, invasive species (blackberry and morning glory. It will be necessary to clear the site in order to meet current standards. Removal of vegetation should be carefully performed so as to not adversely affect slope stability along the river bank. 11.11.11.11. REPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONSREPORT LIMITATIONS The recommendations presented in this report are for the exclusive use of Mr. Launce Goulet to obtain a building permit variance for proposed residences to be constructed on King County tax parcel numbers 3341000090, 3341000095, and 3341000010 in Auburn, Washington. The recommendations are based on surface and subsurface information obtained by Bergquist Engineering Services Company, LLC (BESCO), and on an updated topographic survey provided by Encompass Engineering & Surveying. If there are any revisions to the plans or if conditions are encountered on site that deviate from our observations, BESCO must be notified immediately to determine whether changes to our recommendations are required. oOo 416 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 14 of 15 REFERENCESREFERENCESREFERENCESREFERENCES American Society for Testing and Materials, Description and Identification of Soils (Visual-Manual Procedure ASTM D2488): Annual Book of ASTM Standards, Section Four-Construction, Vol. 04-08, D2488-06, pp. 251-259. Anderson Bertrand & Company, 1888, Anderson’s New Map of King County, Washington Territory: Anderson, Bertrand & Company, Seattle, Washington Anderson Map Company, 1907, Anderson Map Coz Map of Auburn: Anderson Map Company, Seattle, Washington Atwater, B.F., and Hemphill-Haley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay, Washington: U.S. Geological Survey Professional Paper 1576, 108 p. City of Auburn, 2018, Green River to Auburn-Black Diamond Road: eGIS image of 1940 air photo mosaic, obtained via public information request. City of Auburn, 2005, Chapter 16.10 Critical Areas, Auburn Municipal Code Ord. 5894 § 1, 2005. City of Auburn, Washington, undated, City of Auburn GIS: https://maps.auburnwa.gov/Html5Viewer/index.html?viewer=public Galster, Richard W., 1989, Howard A. Hanson Dam: in Engineering Geology in Washington, Volume I, Washington Division of Geology and Earth Resources Bulletin 78, pp. 233-240. King County, 2014, Chapter 21A-24, Rules and Regulations of the Department of Permitting and Environmental Review and Department of Natural Resources and Parks, Critical Areas: Designation, Classification and Mapping of Channel Migration Zones: Effective Date: June 14, 1999, most recent amendment September 7, 2017, 5 p., Appendix A, 20 p. Mullineaux, D.R., 1965, Geologic Map of the Auburn Quadrangle, King and Pierce Counties, Washington: United States Geological Survey Geologic Quadrangle Map GQ-406, Scale 1:24000. 417 of 721 Critical Areas Report April 9, 2020 Auburn, Washington BESCO Project Number 2018214, Report 1, Revision 1 Bergquist Engineering Services Company, LLC Page 15 of 15 Palmer, S.P., Magsino, S.L., Bilderback, E.L., Poelstra, J.L., Folger, D.S., and Niggermann, R.A., 2007, Liquefaction susceptibility and site class maps of Washington State, by county: Washington Division of Geology and Earth Resources, Open File Report 2004-20. Perkins, S.J., 1993, Green River Channel Migration Study: King County Department of Public Works, Surface Water Management Division, Seattle, WA, 81 p. Rogers, A.M., Walsh, T.J., Kockelman, W.J., and Priest, G.R., 1991, Earthquake Hazards in the Pacific Northwest: An Overview: US Geological Survey Open-File Report 91-441-0, p. 4. Satake, K., Wang, K., and Atwater, B., 2003, Fault slip and seismic moment of the 1700 Cascadia earthquake inferred from Japanese tsunami descriptions: Journal of Geophysical Research, v. 108, 2535, doi:10.1029/2003JB002521 Shannon & Wilson, Inc., 2002, Preliminary Risk-Based Flood Damage Analysis, Green River Flood Control District, King County, Washington: Shannon & Wilson, Inc., submitted to Mr. Dave Clark, Water and Land Resources Division, Department of Natural Resources, Seattle, Washington, January 2002, 41 p. USDA Forest Service, 1984, Slope Stability Reference Guide for National Forests in the Pacific Northwest: Forest Service Engineering Staff, Washington, D.C., EM-7170-13, August 1994, pp. 345-400. US Geological Survey, 1975, Magnitude and Frequency of Floods in Washington, US Geological Survey Open File Report 74-336, Tacoma, WA, p. 24 Washington Department of Natural Resources, 1961, Symbol A-95, Flight 17, Exposures 8, 9, and 10: Aerial photographs dated 8-7-1961. Washington Department of Natural Resources, 1996, Symbol NW-96, Roll 49, Flight 49, Exposures 18, 19, and 20: Aerial photographs dated 6-20-1996. Williamson, D.A., Neal, K.G., and Larson, D.A., 1991, The Field-Developed Cross-Section: A Systematic Method of Portraying Dimensional Subsurface Information and Modeling for Geotechnical Interpretation and Analysis: Association of Engineering Geologists, Proceedings, 34th Annual Meeting, pp. 719-738. 418 of 721 419 of 721 420 of 721 421 of 721 Bergquist Engineering Services Company, LLC A3 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----1111 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section CSection CSection CSection C----C’, Station 10+18.1C’, Station 10+18.1C’, Station 10+18.1C’, Station 10+18.1 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITOMONITOMONITOMONITORED BY RED BY RED BY RED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PIT 66.6 feet66.6 feet66.6 feet66.6 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 7.0 SM Silty fine SAND; light brown color; dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River). Started digging 1126. Roots top 2 feet 7.0 to 9.0 SM/ML Silty fine SAND with SILT with fine sand interbeds; light gray color with orange- brown and black iron staining; moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Black and orange brown bands where stained. No water encountered. Test pit completed 1154 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 422 of 721 Bergquist Engineering Services Company, LLC A4 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----2222 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section Section Section Section BBBB----B’, Station 10+52.0B’, Station 10+52.0B’, Station 10+52.0B’, Station 10+52.0 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE TYPE TYPE TYPE OF EQUIPMENTOF EQUIPMENTOF EQUIPMENTOF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber tRubber tRubber tRubber trackrackrackrack----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 68.768.768.768.7 feetfeetfeetfeet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 1.7 SM Silty fine SAND; brown color; dry (NPL), loose. Origin: Topsoil Started digging 1206. Roots top 1.7 feet 1.7 to 7.0 SM Silty fine SAND; light brown color; dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Black and orange bands where stained. Particle size distribution test 7.0 to 9.0 SM/ML Silty fine SAND with SILT with fine sand interbeds; brown to gray colors with orange iron staining; moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River). Forms clumps 9.0 to 9.6 ML/SM SILT with fine sand, with silty fine SAND interbeds; gray color with orange iron staining; wet (APL), soft to loose. Origin: Alluvial (overbank deposit from Green River) Particle size distribution test Wet soil encountered at bottom of test pit. Test pit completed 1227 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 423 of 721 Bergquist Engineering Services Company, LLC A5 TEST PIT NUMTEST PIT NUMTEST PIT NUMTEST PIT NUMBER:BER:BER:BER: TPTPTPTP----3333 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section ASection ASection ASection A----A’, Station 10+84.1A’, Station 10+84.1A’, Station 10+84.1A’, Station 10+84.1 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY KennKennKennKenneth G. Nealeth G. Nealeth G. Nealeth G. Neal ELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PITELEVATION AT TOP OF TEST PIT 68.1 feet68.1 feet68.1 feet68.1 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 1.7 SM Silty fine SAND with coarse Gravel; light brown color; moist (BPL), dense. Origin: Fill Started digging 1244. Roots top 1.2 feet Particle size distribution test Very hard digging 1.7 to 7.5 SM Silty fine SAND; light gray brown color with increased orange-brown staining with depth, moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open 7.5 to 8.7 ML/SM SILT with fine sand with silty fine SAND with SILT interbeds; brown to gray colors with orange iron staining; moist (BPL to APL), soft to loose. Origin: Alluvial (overbank deposit from Green River). Forms clumps Particle size distribution test No water encountered Test pit completed 1310 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 424 of 721 Bergquist Engineering Services Company, LLC A6 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----4444 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section DSection DSection DSection D----D’, Station 10+40.5D’, Station 10+40.5D’, Station 10+40.5D’, Station 10+40.5 DATE EXPLDATE EXPLDATE EXPLDATE EXPLOREDOREDOREDORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 71.3 feet71.3 feet71.3 feet71.3 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL UNIFIED SOIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 2.2 SM Silty fine SAND with coarse gravel; light brown color; dry (NPL), dense. Origin: Fill Started digging 1330. Roots top 1.2 feet Some clasts remold by hand pressure to SM Very hard digging 2.2 to 8.9 SM Silty fine SAND; light gray brown color, dry (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open Particle size distribution test Particle size distribution test No water encountered Test pit completed 1400 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 425 of 721 Bergquist Engineering Services Company, LLC A7 TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER:TEST PIT NUMBER: TPTPTPTP----5555 PROJECT NAMEPROJECT NAMEPROJECT NAMEPROJECT NAME Goulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential DevelopmentGoulet Residential Development BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: BESCO PROJECT NUMBER: 2018214, 2018214, 2018214, 2018214, Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1Report 1, Revision 1 LOCATIONLOCATIONLOCATIONLOCATION CrossCrossCrossCross----Section DSection DSection DSection D----D’, Station 11+16.4D’, Station 11+16.4D’, Station 11+16.4D’, Station 11+16.4 DATE EXPLOREDDATE EXPLOREDDATE EXPLOREDDATE EXPLORED 09/16/1809/16/1809/16/1809/16/18 TYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENTTYPE OF EQUIPMENT Cat 360Cat 360Cat 360Cat 360 Rubber trackRubber trackRubber trackRubber track----mounted excavator mounted excavator mounted excavator mounted excavator MONITORED BYMONITORED BYMONITORED BYMONITORED BY Kenneth G. NealKenneth G. NealKenneth G. NealKenneth G. Neal ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT ELEVATION AT TOP OF TEST PIT 69.1 feet69.1 feet69.1 feet69.1 feet**** DEPTH (Feet)DEPTH (Feet)DEPTH (Feet)DEPTH (Feet) UNIFIED SUNIFIED SUNIFIED SUNIFIED SOIL OIL OIL OIL CLASSIFICATIONCLASSIFICATIONCLASSIFICATIONCLASSIFICATION******** DESCRIPTIONDESCRIPTIONDESCRIPTIONDESCRIPTION REMARKSREMARKSREMARKSREMARKS 0.0 to 6.5 SM Silty fine SAND; light brown color; dry to moist (NPL), loose. Origin: Alluvial (overbank deposit from Green River) Started digging 1415. Easy digging Particle size distribution test 6.5 to 9.0 ML/SM SILT with silty fine SAND and silty fine SAND interbeds; light gray with orange iron staining; moist (APL), soft to loose. Origin: Alluvial (overbank deposit from Green River) Easy digging. Hole stands open Particle size distribution test 9.0 to 9.6 SM/ML Silty fine SAND with SILT with silty fine SAND interbeds; light gray color; wet (APL), loose to soft. Origin: Alluvial (overbank deposit from Green River). Wet soil encountered at bottom of test pit Test pit completed 1425 hours 09/16/18 *Revised elevation based on 1/14/2020 topographic site plan provided by Encompass Engineering & Surveying, and our measurements. **Unified Soil Classification System, Visual Manual Procedure (American Society for Testing and Materials, 2007) Designations APL, BPL, and NPL refer to natural soil moisture contents above and below the plastic limit, and non-plastic soils, respectively. 426 of 721 427 of 721 428 of 721 429 of 721 430 of 721 431 of 721 432 of 721 433 of 721 434 of 721 435 of 721 436 of 721 437 of 721 438 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 439 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 440 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 441 of 721 LEGEND Contact surfaces are approximate. SU-A Gray brown Silty fine SAND (SM). Non-plastic, interglacial deposit. SU-B Brown to gray Silty fine SAND (SM) with Silt interbeds to SILT (ML), with fine sand interbeds. Plastic, alluvuial deposit. SU-C Light brown to gray-brown Silty fine SAND (SM) Non-plastic, alluvial deposit. FILL Light brown Silty fine SAND (SM) with coarse gravel. Non-plastic to plastic. 442 of 721 443 of 721 444 of 721 445 of 721 446 of 721 447 of 721 448 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 1 of 54 SEPA ENVIRONMENTAL CHECKLIST Purpose of checklist: Governmental agencies use this checklist to help determine whether the environmental impacts of your proposal are significant. This information is also helpful to determine if available avoidance, minimization or compensatory mitigation measures will address the probable significant impacts or if an environmental impact statement will be prepared to further analyze the proposal. Instructions for applicants: This environmental checklist asks you to describe some basic information about your proposal. Please answer each question accurately and carefully, to the best of your knowledge. You may need to consult with an agency specialist or private consultant for some questions. You may use “not applicable” or "does not apply" only when you can explain why it does not apply and not when the answer is unknown. You may also attach or incorporate by reference additional studies reports. Complete and accurate answers to these questions often avoid delays with the SEPA process as well as later in the decision- making process. The checklist questions apply to all parts of your proposal, even if you plan to do them over a period of time or on different parcels of land. Attach any additional information that will help describe your proposal or its environmental effects. The agency to which you submit this checklist may ask you to explain your answers or provide additional information reasonably related to determining if there may be significant adverse impact. Instructions for Lead Agencies: Please adjust the format of this template as needed. Additional information may be necessary to evaluate the existing environment, all interrelated aspects of the proposal and an analysis of adverse impacts. The checklist is considered the first but not necessarily the only source of information needed to make an adequate threshold determination. Once a threshold determination is made, the lead agency is responsible for the completeness and accuracy of the checklist and other supporting documents. Use of checklist for nonproject proposals: For nonproject proposals (such as ordinances, regulations, plans and programs), complete the applicable parts of sections A and B plus the SUPPLEMENTAL SHEET FOR NONPROJECT ACTIONS (part D). Please completely answer all questions that apply and note that the words "project," "applicant," and "property or site" should be read as "proposal," "proponent," and "affected geographic area," respectively. The lead agency may exclude (for non-projects) questions in Part B - Environmental Elements –that do not contribute meaningfully to the analysis of the proposal. 449 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 2 of 54 A. Background 1. Name of proposed project, if applicable: Lot A – King County Tax Parcel No. 334100-0090 Goulet Single Family Residence Lot B – King County Tax Parcel No. 334100-0095: Goulet Single Family Residence Lot C – King County Tax Parcel No. 334100-0100: Goulet Single Family Residence 2. Name of applicant: Lot A – King County Tax Parcel No. 334100-0090 Launce P Goulet Lot B – King County Tax Parcel No. 334100-0095: Launce P Goulet Lot C – King County Tax Parcel No. 334100-0100: Launce P Goulet 3. Address and phone number of applicant and contact person: Applicant Contact Person Launce P Goulet Encompass Engineering & Surveying 3226 S 196th Street Attn: Mariah Gill SeaTac, Washington 98188 165 NE Juniper Street, Suite 201 Steve Beck (applicant representative) 425-392-0250 425-444-0461 4. Date checklist prepared: April 8, 2020 (revised October 20, 2020) 450 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 3 of 54 5. Agency requesting checklist: City of Auburn 6. Proposed timing or schedule (including phasing, if applicable): Lot A – King County Tax Parcel No. 334100-0090 Permitting during 2020. Construction during 2021 or as otherwise allowed by permits. Lot B – King County Tax Parcel No. 334100-0095: Permitting during 2020. Construction during 2021 or as otherwise allowed by permits. Lot C – King County Tax Parcel No. 334100-0100: Permitting during 2020. Construction during 2021 or as otherwise allowed by permits. 7. Do you have any plans for future additions, expansion, or further activity related to or connected with this proposal? If yes, explain. Lot A – King County Tax Parcel No. 334100-0090 None proposed. Lot B – King County Tax Parcel No. 334100-0095: None proposed. Lot C – King County Tax Parcel No. 334100-0100: None proposed. 8. List any environmental information you know about that has been prepared, or will be prepared, directly related to this proposal. The following environmental information has been prepared for the proposed project: • “Boundary and Topographic Survey – Goulet Residences” by Encompass Engineering & Surveying, dated 10/16/2020. 451 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 4 of 54 • “CUP Plan Set– Goulet Residences” by Encompass Engineering & Surveying, dated 10/22/2020. • “Shoreline Variances Plan Set Lot B & C – Goulet Residences” by Encompass Engineering & Surveying, dated 10/22/2020. • “Critical Area Report: Wetlands and Streams – Proposed Goulet Singly Family Residences” by Evergreen Aquatic Resource Consultants, LLC, dated 04/08/2020, revised October 28, 2020. • “Shoreline Buffer Mitigation Plan - Proposed Goulet Single Family Residences” by Evergreen Aquatic Resource Consultants, LLC, dated 04/08/2020, revised October 28, 2020. • “Critical Areas Report: Proposed Single Family Residences Parcels 3341000090, 3341000095, and 3341000010 – Auburn, Washington” by Bergquist Engineering Services, dated October 8, 2020. (marked as Report 1, Revision 2). • Supplemental comments on “Critical Areas Report: Proposed Single Family Residences Parcels 3341000090, 3341000095, and 3341000010 – Auburn, Washington”. Prepared by Bergquist Engineering Services, dated December 5, 2018. • Washington State Joint Aquatic Resources Permit Application (JARPA) Form, dated 04/08/2020. 9. Do you know whether applications are pending for governmental approvals of other proposals directly affecting the property covered by your proposal? If yes, explain. None known. 10. List any government approvals or permits that will be needed for your proposal, if known. The following permits and/or approvals will be required from the City of Auburn for each lot: • Shoreline Variance • Shoreline Conditions Use Permit • Shoreline Substantial Development Permit • General Construction Permits: o Building o Right-of-way o Utilities o Grading permit 11. Give brief, complete description of your proposal, including the proposed uses and the size of the project and site. There are several questions later in this checklist that ask you to describe certain aspects of your proposal. You do not need to repeat those answers on this page. (Lead agencies may modify this form to include additional specific information on project description.) 452 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 5 of 54 Lot A – King County Tax Parcel No. 334100-0090: The proposed project includes the development of a residential buildable area within the eastern portion of Lot A. Lot A measures 14,628 sf (0.34 acres) and maintains approximately 117 lf of shoreline frontage along the east bank of the Green River. Lot A is currently undeveloped vacant land that is zoned “R-5” (residential, 5 dwelling units per acre). Lot B – King County Tax Parcel No. 334100-0095: The proposed project includes the development of a residential buildable area within the eastern portion of Lot B. Lot B measures 13,601 sf (0.31 acres) and maintains approximately 108 lf of shoreline frontage along the east bank of the Green River. Lot B is currently undeveloped vacant land that is zoned “R-5” (residential, 5 dwelling units per acre). Lot C – King County Tax Parcel No. 334100-0100 The proposed project includes the development of a residential buildable area within the eastern portion of Lot C. Lot C measures 13,021 sf (0.30 acres) and maintains approximately 92 lf of shoreline frontage along the east bank of the Green River. The lot is currently undeveloped vacant land that is zoned “R-5” (residential, 5 dwelling units per acre). 12. Location of the proposal. Give sufficient information for a person to understand the precise location of your proposed project, including a street address, if any, and section, township, and range, if known. If a proposal would occur over a range of area, provide the range or boundaries of the site(s). Provide a legal description, site plan, vicinity map, and topographic map, if reasonably available. While you should submit any plans required by the agency, you are not required to duplicate maps or detailed plans submitted with any permit applications related to this checklist. The proposed project will occur over three existing residential lots located west of 104th Place SE in Auburn, Washington. All three lots can be accessed from Auburn City Hall by traveling east on E Main Street for approximately 1.0 miles and then turning left on R Street NE. After traveling north on R Street NE for approximately 0.5 miles, turn right onto 8th Street NE. After traveling east on 8th Street NE for approximately 0.25 miles turn right onto 104th Place SE. The project site is located on the west side of 104th Place SE approximately 450 feet south of 8th Street NE. 453 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 6 of 54 Lat/Long for center of site = 47.31432,-122.20452 Lot A – King County Tax Parcel No. 334100-0090: Address: ±32XXX 104th Place SE – Auburn, Washington Project Site Lot A Lot B 1 0 4 t h PL SE C Green River Lot C 454 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 7 of 54 Legal Description: That portion of lot 20, c.d. Hillman's Green River Addition, Division No. 1, according to the plat recorded in Volume 17 of Plats, page 67, in King County, Washington, and unplatted portion of government Lot 2, in Section 17, Township 21 North, Range 5 East, W.M., in King County, Washington, described as a whole as follows: beginning at a point on the easterly line of said Lot 20, distant thereon, south 17°00' east 9.002 feet from the northeasterly corner of said Lot 20; thence south 17°00' east along the northeasterly line of said Lot 20, a distance of 60.00 feet; thence south 73° 00' west 125.00 feet, more or less to the easterly bank of the Green River; thence northerly along said bank to a point which bears north 89°41'07" west from the point of beginning; thence south 89°41'07" east 155.00 feet, more or less to the point of beginning. Lot B – King County Tax Parcel No. 334100-0095: Address: ±32XXX 104th Place SE – Auburn, Washington Legal Description: Those portions of Lots 20 and 21, c.d. Hillman's Green River Addition, Division No. 1, according to the plat recorded in Volume 17 of Plats, page 67, in King County, Washington, and unplatted portion of Government Lot 2, in Section 17, Township 21 North, Range 5 East, W.M., in King County, Washington, described as a whole as follows: beginning at a point on the easterly line of said Lot 20, distant thereon, south 17°00' east 69.002 feet from the northeasterly corner of said Lot 20; thence south 17°00' east along the northeasterly line of said Lot 20, a distance of 28.656 feet to the northeasterly corner of Lot 21; thence south 31°03' east along the northeasterly line of said Lot 21, a distance of 40.00 feet; thence south 58°57' west 135.00 feet, more or less to the easterly bank of the Green River; thence northerly along said bank to a point which bears south 73°00' west from the point of beginning; thence north 73°00' east 125.00 feet, more or less to the point of beginning. Lot C – King County Tax Parcel No. 334100-0100 Address: ±32XXX 104th Place SE – Auburn, Washington Legal Description: Those portions of Lots 21 and 22, c.d. Hillman's Green River Addition, Division No. 1, according to the Plat recorded in Volume 17 of Plats, page 67, in King County, Washington, and unplatted portion of Government Lot 2, in Section 17, Township 21 North, Range 5 East, W.M., in King County, Washington, described as a whole as follows: beginning at a point on the easterly line of said Lot 20, distant thereon, south 17°00' east 97.658 feet from the northeasterly corner of said 455 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 8 of 54 Lot 20 of c.d. Hillman's Green River Addition; thence south 31°03' east along the northeasterly lines of said Lot 21 and 22, a distance of 90.00 feet; thence south 58°57' west 135.00 feet, more or less to the easterly bank of the green river: thence northerly along said bank to a point which bears south 58°57' west from the true point of beginning; thence north 58°57' east 135.00 feet to the true point of beginning. B. Environmental Elements 1. Earth a. General description of the site: (circle one): Flat, rolling, hilly, steep slopes, mountainous, other _____________ Lot A – King County Tax Parcel No. 334100-0090: Topography in Lot A is characterized by a moderately steep river bank that transitions to nearly flat to gently sloping land throughout the central portion of the lot, to a short, inclined transition to 104th Place SE. Lot B – King County Tax Parcel No. 334100-0095: Topography in Lot B is characterized by a moderately steep river bank that transitions to nearly flat to gently sloping land throughout the central portion of the lot, to a short, steeply inclined transition to 104th Place SE. Lot C – King County Tax Parcel No. 334100-0100: Topography in Lot C is characterized by a moderately steep river bank that transitions to nearly flat to gently sloping land throughout the central portion of the lot, to a short, steeply inclined transition to 104th Place SE. b. What is the steepest slope on the site (approximate percent slope)? Lot A – King County Tax Parcel No. 334100-0090: Slopes within Lot A range from ±20% along the riverbank, to ±4 % in the central portion of the site, to ±33% near 104th PL SE. Lot B – King County Tax Parcel No. 334100-0095: Slopes within Lot B range from ±19% along the riverbank, to ±2 % in the central portion of the site, to ±35% near 104th PL SE. 456 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 9 of 54 Lot C – King County Tax Parcel No. 334100-0100: Slopes within Lot C the site range from ±62% along the riverbank, to ±2 % in the central portion of the site, to ±60% near 104th PL SE. c. What general types of soils are found on the site (for example, clay, sand, gravel, peat, muck)? If you know the classification of agricultural soils, specify them and note any agricultural land of long-term commercial significance and whether the proposal results in removing any of these soils. Lot A – King County Tax Parcel No. 334100-0090: A geotechnical investigation completed within Lot A revealed that silty fine sand is the general soil type present on Lot A. The origin for the soil type is alluvial (overbank deposits from the Green River). Lot B – King County Tax Parcel No. 334100-0095: A geotechnical investigation completed within Lot B revealed that silty fine sand is the general soil type present on Lot B. The origin for the soil type is alluvial (overbank deposits from the Green River). Lot C – King County Tax Parcel No. 334100-0090: A geotechnical investigation completed within Lot C revealed that silty fine sand is the general soil type present on Lot C. The origin for the soil type is alluvial (overbank deposits from the Green River). d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. Lot A – King County Tax Parcel No. 334100-0090: A cut slope located immediately east of Lot A along the east side of 104th Place NE is considered a landslide hazard based on slope inclination and height. Although historic slope movement was noted near the south end of 104th Place SE, geotechnical analysis revealed that evidence of erosion or instability was not present at the base of the slope located adjacent to Lot A. In addition, it was determined that the slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated. Based on geotechnical review of the steep slope hazard, a 23 foot buffer was recommended from the toe of the steep slope. The buffer does not encroach Lot A. 457 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 10 of 54 Lot A also contains a moderate channel migration hazard. Geotechnical analysis of the site revealed that there was no evidence of channel migration on Lot A during the last 130 years; however, the loose silty fine sand that is underlying most of the lot could be subject to erosion during river flooding. Lot A is also located within a mapped erosion hazard area. Lot B – King County Tax Parcel No. 334100-0095: A cut slope located immediately east of Lot B along the east side of 104th Place NE is considered a landslide hazard based on slope inclination and height. Although historic slope movement was noted near the south end of 104th Place SE, geotechnical analysis revealed that evidence of erosion or instability was not present at the base of the slope located adjacent to Lot B. In addition, it was determined that the slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated. Based on geotechnical review of the steep slope hazard, a 23 foot buffer was recommended from the toe of the steep slope. The buffer does not encroach Lot B. Lot B also contains a moderate channel migration hazard. Geotechnical analysis of the site revealed that there was no evidence of channel migration on Lot B during the last 130 years; however, the loose silty fine sand that is underlying most of the lot could be subject to erosion during river flooding. Lot B is also located within a mapped erosion hazard area. Lot C – King County Tax Parcel No. 334100-0100: A cut slope located immediately east of Lot C along the east side of 104th Place NE is considered a landslide hazard based on slope inclination and height. Although historic slope movement was noted near the south end of 104th Place SE, geotechnical analysis revealed that evidence of erosion or instability was not present at the base of the slope located adjacent to Lot C. In addition, it was determined that the slope is marginally stable under static conditions, but would likely become unstable under severe seismic shaking if the slope was saturated Based on geotechnical review of the steep slope hazard, a 23 foot buffer was recommended from the toe of the steep slope. The buffer slightly encroaches the eastern portion of Lot C, but does not encroach the buildable area designated Lot C. Lot C also contains a moderate channel migration hazard. Geotechnical analysis of the site revealed that there was no evidence of channel migration on Lot C during the last 130 years; however, the loose silty fine sand that is underlying most of the lot could be subject to erosion during river flooding. 458 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 11 of 54 Lot C is also located within a mapped erosion hazard area. e. Describe the purpose, type, total area, and approximate quantities and total affected area of any filling, excavation, and grading proposed. Indicate source of fill. Lot A – King County Tax Parcel No. 334100-0090: Filling, excavation, and grading within the Lot A will be minimal and limited to only that required to level and prepare the buildable area for future construction. Shallow excavations may be required for foundation construction and utility installations. Fill imported to the site may be limited, obtained from a commercial supplier, and will comprise only the materials necessary to level the site and support foundations, concrete slabs, and driving surfaces. Lot B – King County Tax Parcel No. 334100-0095: Filling, excavation, and grading within the Lot B will be minimal and limited to only that required to level and prepare the buildable area for future construction. Shallow excavations may be required for foundation construction and utility installations. Fill imported to the site may be limited, obtained from a commercial supplier, and will comprise only the materials necessary to level the site and support foundations, concrete slabs, and driving surfaces. Lot C – King County Tax Parcel No. 334100-0100: Filling, excavation, and grading within the Lot C will be minimal and limited to only that required to level and prepare the buildable area for future construction. Shallow excavations may be required for foundation construction and utility installations. Fill imported to the site may be limited, obtained from a commercial supplier, and will comprise only the materials necessary to level the site and support foundations, concrete slabs, and driving surfaces. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. Lot A – King County Tax Parcel No. 334100-0090: Lot A is located within a mapped erosion hazard area. In the absence of appropriate best management practices (BMP’s), erosion of exposed soils could occur during site clearing and construction prior to final site stabilization. In addition, the loose silty fine sand that is underlying most of the lot could be subject to erosion during river flooding. 459 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 12 of 54 .Lot B – King County Tax Parcel No. 334100-0095: Lot B is located within a mapped erosion hazard area. In the absence of appropriate best management practices (BMP’s), erosion of exposed soils could occur during site clearing and construction prior to final site stabilization. In addition, the loose silty fine sand that is underlying most of the lot could be subject to erosion during river flooding. Lot C – King County Tax Parcel No. 334100-0100: Lot C is located within a mapped erosion hazard area. In the absence of appropriate best management practices (BMP’s), erosion of exposed soils could occur during site clearing and construction prior to final site stabilization. In addition, the loose silty fine sand that is underlying most of the lot could be subject to erosion during river flooding. g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? Lot A – King County Tax Parcel No. 334100-0090: Less than 20% of Lot A will be covered by impervious surfaces after project construction. Impervious surfacing will include residential roof and driveway pavement surfaces. Lot B – King County Tax Parcel No. 334100-0095: Less than 20% of Lot B will be covered by impervious surfaces after project construction. Impervious surfacing will include residential roof and driveway pavement surfaces. Lot C – King County Tax Parcel No. 334100-0100: Less than 20% of Lot C will be covered by impervious surfaces after project construction. Impervious surfacing will include residential roof and driveway pavement surfaces. h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: Lot A – King County Tax Parcel No. 334100-0090: A temporary erosion control (TESC) plan will be prepared for and implemented during construction phases on Lot A to minimize the potential for erosion and the off-site migration of sediment and/or sediment laden water. All TESC measures will be per current City of Auburn standards. TESC measures will be installed prior to start of work and will be properly maintained and monitored during the entire construction period. At the end of 460 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 13 of 54 construction exposed soils will be stabilized by installing landscaping or similar permanent cover measures. Lot B – King County Tax Parcel No. 334100-0095: A temporary erosion control (TESC) plan will be prepared for and implemented during construction phases on Lot B to minimize the potential for erosion and the off-site migration of sediment and/or sediment laden water. All TESC measures will be per current City of Auburn standards. TESC measures will be installed prior to start of work and will be properly maintained and monitored during the entire construction period. At the end of construction exposed soils will be stabilized by installing landscaping or similar permanent cover measures. Lot C – King County Tax Parcel No. 334100-0100: A temporary erosion control (TESC) plan will be prepared for and implemented during construction phases on Lot C to minimize the potential for erosion and the off-site migration of sediment and/or sediment laden water. All TESC measures will be per current City of Auburn standards. TESC measures will be installed prior to start of work and will be properly maintained and monitored during the entire construction period. At the end of construction exposed soils will be stabilized by installing landscaping or similar permanent cover measures. 2. Air a. What types of emissions to the air would result from the proposal during construction, operation, and maintenance when the project is completed? If any, generally describe and give approximate quantities if known. Lot A – King County Tax Parcel No. 334100-0090: Fossil fuel combustion byproducts (exhaust emissions) from standard construction equipment will be present during construction. The completed project may emit fossil fuel combustion byproducts (exhaust emissions) related to the use of standard residential natural gas appliance and heating equipment. Lot B – King County Tax Parcel No. 334100-0095: Fossil fuel combustion byproducts (exhaust emissions) from standard construction equipment will be present during construction. The completed project may emit fossil fuel combustion byproducts (exhaust emissions) related to the use of standard residential natural gas appliance and heating equipment. 461 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 14 of 54 Lot C – King County Tax Parcel No. 334100-0100: Fossil fuel combustion byproducts (exhaust emissions) from standard construction equipment will be present during construction. The completed project may emit fossil fuel combustion byproducts (exhaust emissions) related to the use of standard residential natural gas appliance and heating equipment. b. Are there any off-site sources of emissions or odor that may affect your proposal? If so, generally describe. Lot A King County Tax Parcel No. 334100-0090: There are no known off-site sources of emissions or odors that affect Lot A. Lot B King County Tax Parcel No. 334100-0095: There are no known off-site sources of emissions or odors that affect Lot B. Lot A King County Tax Parcel No. 334100-0100: There are no known off-site sources of emissions or odors that affect Lot C. c. Proposed measures to reduce or control emissions or other impacts to air, if any: Lot A – King County Tax Parcel No. 334100-0090: All construction and future residential use within Lot A will conform to air quality regulations established by the City of Auburn, the Puget Sound Clean Air Agency (PSCAA), and other applicable regulatory agencies. Construction equipment will employ standard exhaust emission control devices. Appliances installed within the residence will conform to applicable efficiency and emission control standards. Lot B – King County Tax Parcel No. 334100-0095: All construction and future residential use within Lot B will conform to air quality regulations established by the City of Auburn, the Puget Sound Clean Air Agency (PSCAA), and other applicable regulatory agencies. Construction equipment will employ standard exhaust emission control devices. Appliances installed within the residence will conform to applicable efficiency and emission control standards. 462 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 15 of 54 Lot C – King County Tax Parcel No. 334100-0100: All construction and future residential use within Lot C will conform to air quality regulations established by the City of Auburn, the Puget Sound Clean Air Agency (PSCAA), and other applicable regulatory agencies. Construction equipment will employ standard exhaust emission control devices. Appliances installed within the residence will conform to applicable efficiency and emission control standards. 3. Water a. Surface Water : 1) Is there any surface water body on or in the immediate vicinity of the site (including year-round and seasonal streams, saltwater, lakes, ponds, wetlands)? If yes, describe type and provide names. If appropriate, state what stream or river it flows into. Lot A – King County Tax Parcel No. 334100-0090: Lot A maintains approximately 117 lf of shoreline frontage along the east bank of the Green River and 100 year floodplain and channel migration hazards associated with the Green River exist within Lot A. No other surface water features or related hazards exist within or immediately adjacent to the lot. Lot B – King County Tax Parcel No. 334100-0095: Lot B maintains approximately 108 lf of shoreline frontage along the east bank of the Green River and 100 year floodplain and channel migration hazards associated with the Green River exist within Lot B. No other surface water features or related hazards exist within or immediately adjacent to the lot. Lot C – King County Tax Parcel No. 334100-0100: Lot C maintains approximately 92 lf of shoreline frontage along the east bank of the Green River and 100 year floodplain and channel migration hazards associated with the Green River exist within Lot C. No other surface water features or related hazards exist within or immediately adjacent to the lot. 2) Will the project require any work over, in, or adjacent to (within 200 feet) the described waters? If yes, please describe and attach available plans. 463 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 16 of 54 Lot A – King County Tax Parcel No. 334100-0090: The buildable area within Lot A is located approximately 100 feet from the ordinary high water mark (OHWM) of the Green River. Lot B – King County Tax Parcel No. 334100-0095: The buildable area within Lot B is located approximately 95 feet from the ordinary high water mark (OHWM) of the Green River. Lot C – King County Tax Parcel No. 334100-0100: The buildable area within Lot C is located within approximately 90 feet from the ordinary high water mark (OHWM) of the Green River. 3) Estimate the amount of fill and dredge material that would be placed in or removed from surface water or wetlands and indicate the area of the site that would be affected. Indicate the source of fill material. Lot A – King County Tax Parcel No. 334100-0090: No work is proposed within surface waters or wetlands. Lot B – King County Tax Parcel No. 334100-0095: No work is proposed within surface waters or wetlands. Lot C – King County Tax Parcel No. 334100-0100: No work is proposed within surface waters or wetlands. 4) Will the proposal require surface water withdrawals or diversions? Give general description, purpose, and approximate quantities if known. Lot A – King County Tax Parcel No. 334100-0090: No surface water withdrawals or diversions are required. Lot B – King County Tax Parcel No. 334100-0095: No surface water withdrawals or diversions are required. 464 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 17 of 54 Lot C – King County Tax Parcel No. 334100-0100: No surface water withdrawals or diversions are required. 5) Does the proposal lie within a 100-year floodplain? If so, note location on the site plan. Lot A – King County Tax Parcel No. 334100-0090: Lot A contains a portion of the 100 year floodplain associated with the Green River; however, the proposed buildable area does not occur within the floodplain. The base flood elevation (BFE) for the lot has been determined to be 67.20 feet (NAVD 88). Lot development will occur outside of the floodplain. Lot B – King County Tax Parcel No. 334100-0095: Lot B contains a portion of the 100 year floodplain associated with the Green River; however, the proposed buildable area does not occur within the floodplain. The base flood elevation (BFE) for the lot has been determined to be 67.30 feet (NAVD 88). Lot development will occur outside of the floodplain. Lot C – King County Tax Parcel No. 334100-0100: Lot C contains a portion of the 100 year floodplain associated with the Green River; however, the proposed buildable area does not occur within the floodplain. The base flood elevation (BFE) for the lot has been determined to be 67.40 feet (NAVD 88). Lot development will occur outside of the floodplain. 6) Does the proposal involve any discharges of waste materials to surface waters? If so, describe the type of waste and anticipated volume of discharge. Lot A – King County Tax Parcel No. 334100-0090: The proposed project does not involve discharges of waste materials to surface waters. Lot B – King County Tax Parcel No. 334100-0095: The proposed project does not involve discharges of waste materials to surface waters. 465 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 18 of 54 Lot C – King County Tax Parcel No. 334100-0100: The proposed project does not involve discharges of waste materials to surface waters. b. Ground Water : 1) Will groundwater be withdrawn from a well for drinking water or other purposes? If so, give a general description of the well, proposed uses and approximate quantities withdrawn from the well. Will water be discharged to groundwater? Give general description, purpose, and approximate quantities if known. Lot A – King County Tax Parcel No. 334100-0090: No groundwater withdrawal is proposed and water will not be discharged to groundwater. Future residential development within Lot A will connect to a City of Auburn municipal water main located in 104th Place SE. Lot B – King County Tax Parcel No. 334100-0095: No groundwater withdrawal is proposed and water will not be discharged to groundwater. Future residential development within Lot B will connect to a City of Auburn municipal water main located in 104th Place SE. Lot C – King County Tax Parcel No. 334100-0100: No groundwater withdrawal is proposed and water will not be discharged to groundwater. Future residential development within Lot C will connect to a City of Auburn municipal water main located in 104th Place SE. 2) Describe waste material that will be discharged into the ground from septic tanks or other sources, if any (for example: Domestic sewage; industrial, containing the following chemicals. . . ; agricultural; etc.). Describe the general size of the system, the number of such systems, the number of houses to be served (if applicable), or the number of animals or humans the system(s) are expected to serve. Lot A – King County Tax Parcel No. 334100-0090: No waste material will be discharged into the ground by the project. Domestic sewage generated by future residential development within Lot A will drain to a City of Auburn sanitary sewer located in 104th Place SE. 466 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 19 of 54 Lot B – King County Tax Parcel No. 334100-0095: No waste material will be discharged into the ground by the project. Domestic sewage generated by future residential development within Lot B will drain to a City of Auburn sanitary sewer located in 104th Place SE. Lot C – King County Tax Parcel No. 334100-0100: No waste material will be discharged into the ground by the project. Domestic sewage generated by future residential development within Lot C will drain to a City of Auburn sanitary sewer located in 104th Place SE. c. Water runoff (including stormwater): 1) Describe the source of runoff (including storm water) and method of collection and disposal, if any (include quantities, if known). Where will this water flow? Will this water flow into other waters? If so, describe. Lot A – King County Tax Parcel No. 334100-0090: Stormwater will be generated by future residential roof and a driveway surfaces. Conceptual design for stormwater collection and disposal includes routing runoff from impervious surfaces to gravel lined dispersion trenches, splash blocks or similar best management practices (BMP’s). Dispersion will occur along the west edge of the buildable area to allow for dispersion and infiltration between the development area and the Green River. Lot B – King County Tax Parcel No. 334100-0095: Stormwater will be generated by future residential roof and a driveway surfaces. Conceptual design for stormwater collection and disposal includes routing runoff from impervious surfaces to gravel lined dispersion trenches, splash blocks or similar best management practices (BMP’s). Dispersion will occur along the west edge of the buildable area to allow for dispersion and infiltration between the development area and the Green River. Lot C – King County Tax Parcel No. 334100-0100: Stormwater will be generated by future residential roof and a driveway surfaces. Conceptual design for stormwater collection and disposal includes routing runoff from impervious surfaces to gravel lined dispersion trenches, splash blocks or similar best management practices (BMP’s). Dispersion will occur along the west edge of the buildable area to allow for dispersion and infiltration between the development area and the Green River. 467 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 20 of 54 2) Could waste materials enter ground or surface waters? If so, generally describe. Lot A – King County Tax Parcel No. 334100-0090: Proposed future use is residential. It is unlikely that waste materials associated with construction or future use of Lot A could enter ground or surface waters. Lot B – King County Tax Parcel No. 334100-0095: Proposed future use is residential. It is unlikely that waste materials associated with construction or future use of Lot B could enter ground or surface waters. Lot C – King County Tax Parcel No. 334100-0100: Proposed future use is residential. It is unlikely that waste materials associated with construction or future use of Lot C could enter ground or surface waters. 3) Does the proposal alter or otherwise affect drainage patterns in the vicinity of the site? If so, describe. Lot A – King County Tax Parcel No. 334100-0090: The proposed project does not alter or otherwise affect drainage patterns within the vicinity of Lot A. Lot B – King County Tax Parcel No. 334100-0095: The proposed project does not alter or otherwise affect drainage patterns within the vicinity of Lot B. Lot C – King County Tax Parcel No. 334100-0100: The proposed project does not alter or otherwise affected drainage patterns within the vicinity of Lot C. d. Proposed measures to reduce or control surface, ground, and runoff water, and drainage pattern impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: During construction a temporary erosion control (TESC) plan will be prepared and implemented per City of Auburn standards. TESC best management practices (BMP’s) may 468 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 21 of 54 include, but are not limited to, filter fabric (silt) fencing, temporary cover, and rock construction entrances. A permanent drainage control plan will be prepared and implemented per City of Auburn standards with final home design. Conceptual drainage control for the completed project includes storm water dispersion via gravel lined dispersion trench, splash blocks or similar BMP. Lot B – King County Tax Parcel No. 334100-0095: During construction a temporary erosion control (TESC) plan will be prepared and implemented per City of Auburn standards. TESC best management practices (BMP’s) may include, but are not limited to, filter fabric (silt) fencing, temporary cover, and rock construction entrances. A permanent drainage control plan will be prepared and implemented per City of Auburn standards with final home design. Conceptual drainage control for the completed project includes storm water dispersion via gravel lined dispersion trench, splash blocks or similar BMP. Lot C – King County Tax Parcel No. 334100-0100: During construction a temporary erosion control (TESC) plan will be prepared and implemented per City of Auburn standards. TESC best management practices (BMP’s) may include, but are not limited to, filter fabric (silt) fencing, temporary cover, and rock construction entrances. A permanent drainage control plan will be prepared and implemented per City of Auburn standards with final home design. Conceptual drainage control for the completed project includes storm water dispersion via gravel lined dispersion trench, splash blocks or similar BMP. 4. Plants a. Check the types of vegetation found on the site: __X__deciduous tree: alder, maple, aspen, other __X_evergreen tree: fir, cedar, pine, other __X__shrubs ____grass ____pasture ____crop or grain ____ Orchards, vineyards or other permanent crops. ____ wet soil plants: cattail, buttercup, bullrush, skunk cabbage, other 469 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 22 of 54 ____water plants: water lily, eelgrass, milfoil, other ____other types of vegetation Lot A – King County Tax Parcel No. 334100-0090: Vegetation present within the buildable area on Lot A includes dense Himalayan blackberry (Rubus armeniacus). The balance of the site includes dense Himalayan blackberry with a few scattered red alders (Alnus rubra), and bigleaf maple (Acer macrophyllum) along the riverbank. Lot B – King County Tax Parcel No. 334100-0095: Vegetation present within the buildable area on Lot B includes dense Himalayan blackberry (Rubus armeniacus) and four significant trees (three 28” dbh bigleaf maples [Acer macrophyllum] and a 36” dbh Douglas-fir [Pseudotsuga menziesii]). The balance of the site includes dense Himalayan blackberry with scattered red alder, bigleaf maple, redosier dogwood (Cornus sericea), salmonberry (Rubus spectabilis), common snowberry (Symhoricarpus albus), and willow (Salix sp.) along the riverbank. Lot C – King County Tax Parcel No. 334100-0100: Vegetation present within the buildable area on Lot C includes dense Himalayan blackberry (Rubus armeniacus) and two significant trees (a 12” dbh black cottonwood [Populus balsamifera] and a 40” dbh bigleaf maple [Acer macrophyllum]). The balance of the site includes dense Himalayan blackberry and a patchy distribution of red alder, redosier dogwood (Cornus sericea), salmonberry (Rubus spectabilis), common snowberry (Symhoricarpus albus), and willow (Salix sp.) along the riverbank. Scattered black locust trees exist near the southern property line. b. What kind and amount of vegetation will be removed or altered? Lot A – King County Tax Parcel No. 334100-0090: Vegetation to be removed from the buildable area on Lot A is limited to dense Himalayan blackberry (Rubus armeniacus). Lot B – King County Tax Parcel No. 334100-0095: Vegetation to be removed from the buildable area on Lot B is limited to dense Himalayan blackberry (Rubus armeniacus). 470 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 23 of 54 Lot C – King County Tax Parcel No. 334100-0100: Vegetation to be removed from the buildable area on Lot C is limited to dense Himalayan blackberry as well as a 40” dbh bigleaf maple (Acer macrophyllum). c. List threatened and endangered species known to be on or near the site. Lot A – King County Tax Parcel No. 334100-0090: There are no known threatened or endangered plant species located on or near Lot A. Lot B – King County Tax Parcel No. 334100-0095: There are no known threatened or endangered plant species located on or near Lot B. Lot C – King County Tax Parcel No. 334100-0100: There are no known threatened or endangered plant species located on or near Lot C. d. Proposed landscaping, use of native plants, or other measures to preserve or enhance vegetation on the site, if any: Lot A – King County Tax Parcel No. 334100-0095: Landscaping will be limited to the buildable area located within Lot A. A detailed stream buffer enhancement plan has been for the balance of the lot. The overall goal of the plan is to improve stream buffer functions and provide a no net loss in shoreline functioning by controlling non-native plant species and installing dense native plantings. Plants to be installed as part of the enhancement plan include four tree species and seven shrub species that are native to the Puget Sound lowland area of Washington State. Plants have been selected to match the specific environmental conditions present within Lot A. Prior to native plant installation, Himalayan blackberry (Rubus armeniacus) will be controlled. Lot B – King County Tax Parcel No. 334100-0090: Landscaping will be limited to the buildable area located within Lot B. A detailed stream buffer enhancement plan has been for the balance of the lot. The overall goal of the plan is to improve stream buffer functions and provide a no net loss in shoreline functioning by controlling non-native plant species and installing dense native plantings. Plants to be installed as part of the enhancement plan include four tree species and seven shrub species that are native to the Puget Sound lowland area of Washington State. Plants have been selected to match the specific environmental conditions present within Lot B. Prior to native 471 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 24 of 54 plant installation, Himalayan blackberry (Rubus armeniacus) will be controlled. Lot C – King County Tax Parcel No. 334100-0100: Landscaping will be limited to the buildable area located within Lot C. A detailed stream buffer enhancement plan has been for the balance of the lot. The overall goal of the plan is to improve stream buffer functions and provide a no net loss in shoreline functioning by controlling non-native plant species and installing dense native plantings. Plants to be installed as part of the enhancement plan include four tree species and seven shrub species that are native to the Puget Sound lowland area of Washington State. Plants have been selected to match the specific environmental conditions present within Lot C. Prior to native plant installation, Himalayan blackberry (Rubus armeniacus) will be controlled. e. List all noxious weeds and invasive species known to be on or near the site. Lot A – King County Tax Parcel No. 334100-0090: Himalayan blackberry (Rubus armeniacus), a Class C noxious weed, is present in Lot A and exists as generally a dense monotypic stand. Although control of Himalayan blackberry is not required in King County based on the noxious weed classification, control is recommended in protected wilderness areas and in natural lands that are being restored to native vegetation because of the invasive potential of this blackberry species. Lot B – King County Tax Parcel No. 334100-0095: Himalayan blackberry (Rubus armeniacus), a Class C noxious weed, is present in Lot B and exists as generally a dense monotypic stand. Although control of Himalayan blackberry is not required in King County based on the noxious weed classification, control is recommended in protected wilderness areas and in natural lands that are being restored to native vegetation because of the invasive potential of this blackberry species. Lot C – King County Tax Parcel No. 334100-0100: Himalayan blackberry (Rubus armeniacus), a Class C noxious weed, is present in Lot C and exists as generally a dense monotypic stand. Although control of Himalayan blackberry is not required in King County based on the noxious weed classification, control is recommended in protected wilderness areas and in natural lands that are being restored to native vegetation because of the invasive potential of this blackberry species. 5. Animals 472 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 25 of 54 a. List any birds and other animals which have been observed on or near the site or are known to be on or near the site. Examples include: birds: hawk, heron, eagle, songbirds, other: mammals: deer, bear, elk, beaver, other: fish: bass, salmon, trout, herring, shellfish, other ________ Lot A – King County Tax Parcel No. 334100-0090: The segment of the Green River adjacent to Lot A supports populations of most salmonid species native to the Puget Sound including chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), chum salmon (O. keta), pink salmon (O. gorbuscha), and steelhead trout (O. mykiss). On- site upland habitats likely provide limited seasonal foraging opportunities and escape cover for small mammals and passerine birds accustomed to suburban environments dominated by non-native species. Lot A is located within the home range of larger mammals; however, use of the project site by larger mammals is likely limited to non-existent because of existing plant community characteristics and the proximity and density of surrounding residential development. Lot B – King County Tax Parcel No. 334100-0095: The segment of the Green River adjacent to Lot B supports populations of most salmonid species native to the Puget Sound including chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), chum salmon (O. keta), pink salmon (O. gorbuscha), and steelhead trout (O. mykiss). On- site upland habitats likely provide limited seasonal foraging opportunities and escape cover for small mammals and passerine birds accustomed to suburban environments dominated by non-native species. Lot B is located within the home range of larger mammals; however, use of the project site by larger mammals is likely limited to non-existent because of existing plant community characteristics and the proximity and density of surrounding residential development. Lot C – King County Tax Parcel No. 334100-0100: The segment of the Green River adjacent to Lot C supports populations of most salmonid species native to the Puget Sound including chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), chum salmon (O. keta), pink salmon (O. gorbuscha), and steelhead trout (O. mykiss). On- site upland habitats likely provide limited seasonal foraging opportunities and escape cover for small mammals and passerine birds accustomed to suburban environments dominated by non-native species. Lot C is located within the home range of larger mammals; however, use of the project site by larger mammals is likely limited to non-existent because of existing plant community characteristics and the proximity and density of surrounding residential development. b. List any threatened and endangered species known to be on or near the site. Lot A – King County Tax Parcel No. 334100-0095: 473 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 26 of 54 The segment of the Green River located adjacent to Lot A is known to support and/or exists with the home range of the following species that are federally listed as “threatened” under the Endangered Species Act: • Chinook Salmon Puget Sound (Oncorhynchus tshawytscha) • Steelhead Puget Sound (Oncorhynchus mykiss) • Bull Trout (Salvelinus confluentus) Lot B – King County Tax Parcel No. 334100-0095: The segment of the Green River located adjacent to Lot A is known to support and/or exists with the home range of the following species that are federally listed as “threatened” under the Endangered Species Act: • Chinook Salmon Puget Sound (Oncorhynchus tshawytscha) • Steelhead Puget Sound (Oncorhynchus mykiss) • Bull Trout (Salvelinus confluentus) Lot C – King County Tax Parcel No. 334100-0100: The segment of the Green River located adjacent to Lot A is known to support and/or exists with the home range of the following species that are federally listed as “threatened” under the Endangered Species Act: • Chinook Salmon Puget Sound (Oncorhynchus tshawytscha) • Steelhead Puget Sound (Oncorhynchus mykiss) • Bull Trout (Salvelinus confluentus) c. Is the site part of a migration route? If so, explain. Lot A – King County Tax Parcel No. 334100-0090: The segment of the Green River located adjacent to Lot A serves as a migratory corridor for most salmonid species native to the Puget Sound including chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), chum salmon (O. keta), pink salmon (O. gorbuscha), and steelhead trout (O. mykiss). Lot B – King County Tax Parcel No. 334100-0095: The segment of the Green River located adjacent to Lot B serves as a migratory corridor for most 474 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 27 of 54 salmonid species native to the Puget Sound including chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), chum salmon (O. keta), pink salmon (O. gorbuscha), and steelhead trout (O. mykiss). Lot C – King County Tax Parcel No. 334100-0100: The segment of the Green River located adjacent to Lot C serves as a migratory corridor for most salmonid species native to the Puget Sound including chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), chum salmon (O. keta), pink salmon (O. gorbuscha), and steelhead trout (O. mykiss). d. Proposed measures to preserve or enhance wildlife, if any: Lot A – King County Tax Parcel No. 334100-0090: A detailed stream buffer mitigation plan has been prepared for Lot A. The overall goal of the proposed plan is to improve stream buffer functions and provide a no net loss in shoreline functioning by controlling non-native plant species as well as installing large woody debris and dense native plantings within the on-site buffers. Plants to be installed as part of the enhancement plan include four tree species and seven shrub species that are native to the Puget Sound lowland trough area of Washington State. Three logs will also be placed into the buffer. Lot B – King County Tax Parcel No. 334100-0095: A detailed stream buffer mitigation plan has been prepared for Lot B. The overall goal of the proposed plan is to improve stream buffer functions and provide a no net loss in shoreline functioning by controlling non-native plant species as well as installing large woody debris and dense native plantings within the on-site buffers. Plants to be installed as part of the enhancement plan include four tree species and seven shrub species that are native to the Puget Sound lowland trough area of Washington State. Three logs will also be placed into the buffer. Lot C – King County Tax Parcel No. 334100-0100: A detailed stream buffer mitigation plan has been prepared for Lot C. The overall goal of the proposed plan is to improve stream buffer functions and provide a no net loss in shoreline functioning by controlling non-native plant species as well as installing large woody debris and dense native plantings within the on-site buffers. Plants to be installed as part of the enhancement plan include four tree species and seven shrub species that are native to the Puget Sound lowland trough area of Washington State. Three logs will also be placed into the buffer. e. List any invasive animal species known to be on or near the site. 475 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 28 of 54 Lot A – King County Tax Parcel No. 334100-0090: There are no known populations of invasive animal species on or near Lot A. Lot B – King County Tax Parcel No. 334100-0095: There are no known populations of invasive animal species on or near Lot B. Lot C – King County Tax Parcel No. 334100-0100: There are no known populations of invasive animal species on or near Lot C. 6. Energy and Natural Resources a. What kinds of energy (electric, natural gas, oil, wood stove, solar) will be used to meet the completed project's energy needs? Describe whether it will be used for heating, manufacturing, etc. Lot A – King County Tax Parcel No. 334100-0090: During construction, the proposed project will utilize petroleum-based products (oil, gas, diesel fuels) during operation of combustion engine powered construction equipment as well as electricity to power construction tools. The completed project will utilize standard residential energy sources such as electricity and natural gas for lighting, heating, cooling, and ventilation. Lot B – King County Tax Parcel No. 334100-0095: During construction, the proposed project will utilize petroleum-based products (oil, gas, diesel fuels) during operation of combustion engine powered construction equipment as well as electricity to power construction tools. The completed project will utilize standard residential energy sources such as electricity and natural gas for lighting, heating, cooling, and ventilation. Lot C – King County Tax Parcel No. 334100-0100: During construction, the proposed project will utilize petroleum-based products (oil, gas, diesel fuels) during operation of combustion engine powered construction equipment as well as electricity to power construction tools. The completed project will utilize standard residential energy sources such as electricity and natural gas for lighting, heating, cooling, and ventilation. b. Would your project affect the potential use of solar energy by adjacent properties? If so, generally describe. Lot A – King County Tax Parcel No. 334100-0090: 476 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 29 of 54 The buildable area on Lot A will not affect the potential use of solar energy by adjacent properties because the building site is located at the base of hillside and will not block or overshadow adjacent properties. Lot B – King County Tax Parcel No. 334100-0095: The buildable area on Lot B will not affect the potential use of solar energy by adjacent properties because the building site is located at the base of hillside and will not block or overshadow adjacent properties. Lot C – King County Tax Parcel No. 334100-0100: The buildable area on Lot C will not affect the potential use of solar energy by adjacent properties because the building site is located at the base of hillside and will not block or overshadow adjacent properties. c. What kinds of energy conservation features are included in the plans of this proposal? List other proposed measures to reduce or control energy impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: Future residential development on Lot A will employ standard energy conservation measures by utilizing modern day design and construction practices as well as commercially available appliances, light and plumbing fixtures, and HVAC equipment that meets the minimum energy and building codes required by the City of Auburn as well as state and federal agencies. Lot B – King County Tax Parcel No. 334100-0095: Future residential development on Lot B will employ standard energy conservation measures by utilizing modern day design and construction practices as well as commercially available appliances, light and plumbing fixtures, and HVAC equipment that meets the minimum energy and building codes required by the City of Auburn as well as state and federal agencies. Lot C – King County Tax Parcel No. 334100-0100: Future residential development on Lot B will employ standard energy conservation measures by utilizing modern day design and construction practices as well as commercially available appliances, light and plumbing fixtures, and HVAC equipment that meets the minimum energy and building codes required by the City of Auburn as well as state and federal agencies. 7. Environmental Health 477 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 30 of 54 a. Are there any environmental health hazards, including exposure to toxic chemicals, risk of fire and explosion, spill, or hazardous waste, that could occur as a result of this proposal? If so, describe. 1) Describe any known or possible contamination at the site from present or past uses. Lot A – King County Tax Parcel No. 334100-0090: There are no known or possible contaminants on Lot A from present or past uses. Lot B – King County Tax Parcel No. 334100-0095: There are no known or possible contaminants on Lot B from present or past uses. Lot C – King County Tax Parcel No. 334100-0100: There are no known or possible contaminants on Lot C from present or past uses. 2) Describe existing hazardous chemicals/conditions that might affect project development and design. This includes underground hazardous liquid and gas transmission pipelines located within the project area and in the vicinity. Lot A – King County Tax Parcel No. 334100-0090: There are no known hazardous chemicals/conditions within or immediately adjacent to Lot A that might affect project development and design. Lot B – King County Tax Parcel No. 334100-0095: There are no known hazardous chemicals/conditions within or immediately adjacent to Lot B that might affect project development and design. Lot C – King County Tax Parcel No. 334100-0100: There are no known hazardous chemicals/conditions within or immediately adjacent to Lot C that might affect project development and design. 3) Describe any toxic or hazardous chemicals that might be stored, used, or produced during the project's development or construction, or at any time during the operating life of the project. Lot A – King County Tax Parcel No. 334100-0090: 478 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 31 of 54 There are no planned or anticipated hazardous chemicals that might be stored, used, or produced by construction or future residential use within Lot A. Lot B – King County Tax Parcel No. 334100-0095: There are no planned or anticipated hazardous chemicals that might be stored, used, or produced by construction or future residential use within Lot B. Lot C – King County Tax Parcel No. 334100-0100: There are no planned or anticipated hazardous chemicals/conditions that might be stored, used, or produced by construction or future residential use within Lot C. 4) Describe special emergency services that might be required. Lot A – King County Tax Parcel No. 334100-0090: No special emergency services are required for construction or future residential use within Lot A. Any required emergency medical, fire, or police services required will be consistent with those typical of standard of residential construction and single-family use. Lot B – King County Tax Parcel No. 334100-0095: No special emergency services are required for construction or future residential use within Lot B. Any required emergency medical, fire, or police services will be consistent with those typical of standard of residential construction and single-family use. Lot C – King County Tax Parcel No. 334100-0100: No special emergency services are required for construction or future residential use within Lot C. Any required emergency medical, fire, or police services will be consistent with those typical of standard of residential construction and single-family use. 5) Proposed measures to reduce or control environmental health hazards, if any: Lot A – King County Tax Parcel No. 334100-0090: Sound design and construction practices will be utilized to ensure a safe construction site and future residential structure within Lot A. No specialized measures to reduce or control environmental health hazards are proposed. 479 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 32 of 54 Lot B – King County Tax Parcel No. 334100-0095: Sound design and construction practices will be utilized to ensure a safe construction site and future residential structure within Lot B. No specialized measures to reduce or control environmental health hazards are proposed. Lot C – King County Tax Parcel No. 334100-0100: Sound design and construction practices will be utilized to ensure a safe construction site and future residential structure within Lot C. No specialized measures to reduce or control environmental health hazards are proposed. b. Noise 1) What types of noise exist in the area which may affect your project (for example: traffic, equipment, operation, other)? Lot A – King County Tax Parcel No. 334100-0090: There is no known noise within Lot A or local area that may affect the proposed lot development. Lot B – King County Tax Parcel No. 334100-0095: There is no known noise within Lot B or local area that may affect the proposed lot development. Lot C – King County Tax Parcel No. 334100-0100: There is no known noise within Lot C or local area that may affect the proposed lot development. 2) What types and levels of noise would be created by or associated with the project on a short-term or a long-term basis (for example: traffic, construction, operation, other)? Indicate what hours noise would come from the site. Lot A – King County Tax Parcel No. 334100-0090: Temporary construction noise will be present in the short term during normal working hours. Noise may be generated by motorized construction equipment such as dump trucks, excavators, or backhoes as well as pneumatic nailers, electric saws, etc. Long-term noise generated or associated with the completed project will be consistent with standard single- family residential development. 480 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 33 of 54 Lot B – King County Tax Parcel No. 334100-0095: Temporary construction noise will be present in the short term during normal working hours. Noise may be generated by motorized construction equipment such as dump trucks, excavators, or backhoes as well as pneumatic nailers, electric saws, etc. Long-term noise generated or associated with the completed project will be consistent with standard single- family residential development. Lot C – King County Tax Parcel No. 334100-0100: Temporary construction noise will be present in the short term during normal working hours. Noise may be generated by motorized construction equipment such as dump trucks, excavators, or backhoes as well as pneumatic nailers, electric saws, etc. Long-term noise generated or associated with the completed project will be consistent with standard single- family residential development. 3) Proposed measures to reduce or control noise impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: Construction and future use of Lot A for residential use will conform to applicable City of Auburn noise ordinances and related regulations. Lot B – King County Tax Parcel No. 334100-0095: Construction and future use of Lot B for residential use will conform to applicable City of Auburn noise ordinances and related regulations. Lot C – King County Tax Parcel No. 334100-0100: Construction and future use of Lot C for residential use will conform to applicable City of Auburn noise ordinances and related regulations. 8. Land and Shoreline Use a. What is the current use of the site and adjacent properties? Will the proposal affect current land uses on nearby or adjacent properties? If so, describe. Lot A – King County Tax Parcel No. 334100-0090: Lot A is currently undeveloped vacant land. Land use surrounding Lot A is residential in nature and comprises a mix of single-family residences and occasional undeveloped lots. Residential development along the west side of 104th Place SE extends back to the early 1900’s and existing 481 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 34 of 54 development generally includes one- or two-story single-family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th Street, most residences are of a conventional on-site stick-built construction type. Most residences are setback from the Green River and are located close to 104th Place SE. Lot B – King County Tax Parcel No. 334100-0095: Lot B is currently undeveloped vacant land. Land use surrounding Lot B is residential in nature and comprises a mix of single-family residences and occasional undeveloped lots. Residential development along the west side of 104th Place SE extends back to the early 1900’s and existing development generally includes one- or two-story single-family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th Street, most residences are of a conventional on-site stick-built construction. Most residences are setback from the Green River and are located close to 104th Place SE. Lot C – King County Tax Parcel No. 334100-0100: Lot C is currently undeveloped vacant land. Land use surrounding Lot C is residential in nature and comprises a mix of single-family residences and occasional undeveloped lots. Residential development along the west side of 104th Place SE extends back to the early 1900’s and existing development generally includes one- or two-story single-family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th Street, most residences are of a conventional on-site stick-built construction. Most residences are setback from the Green River and are located close to 104th Place SE. b. Has the project site been used as working farmlands or working forest lands? If so, describe. How much agricultural or forest land of long-term commercial significance will be converted to other uses as a result of the proposal, if any? If resource lands have not been designated, how many acres in farmland or forest land tax status will be converted to nonfarm or nonforest use? Lot A – King County Tax Parcel No. 334100-0090: Lot A does not contain agricultural or forest land of long-term commercial significance. Similarly, the lot does not maintain farmland or forest land tax status. Prior to 1936, Lot A was cleared of native vegetation and used as farmland. Around 1957, intensive agricultural use had ended. Since that time, Lot A has remained vacant and vegetation has been allowed to grow in a relatively uncontrolled manner. Lot B – King County Tax Parcel No. 334100-0095: Lot B does not contain agricultural or forest land of long-term commercial significance. Similarly, 482 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 35 of 54 the lot does not maintain farmland or forest land tax status. Prior to 1936, Lot B was cleared of native vegetation and used as farmland. Around 1957, intensive agricultural use had ended. Since that time, Lot B has remained vacant and vegetation has been allowed to grow in a relatively uncontrolled manner. Lot C – King County Tax Parcel No. 334100-0100: Lot C does not contain agricultural or forest land of long-term commercial significance. Similarly, the lot does not maintain farmland or forest land tax status. Prior to 1936, Lot C was cleared of native vegetation and used as farmland. Around 1957, intensive agricultural use had ended. Since that time, Lot C has remained vacant and vegetation has been allowed to grow in a relatively uncontrolled manner. 1) Will the proposal affect or be affected by surrounding working farm or forest land normal business operations, such as oversize equipment access, the application of pesticides, tilling, and harvesting? If so, how: Lot A – King County Tax Parcel No. 334100-0090: Development of Lot A will not affect or be affected by surrounding working farms and/or commercial forest land. There are no working farms or commercial forest land adjacent to Lot A. Lot B – King County Tax Parcel No. 334100-0095: Development of Lot B will not affect or be affected by surrounding working farms and/or commercial forest land. There are no working farms or commercial forest land adjacent to Lot B. Lot C – King County Tax Parcel No. 334100-0100: Development of Lot C will not affect or be affected by surrounding working farms and/or commercial forest land. There are no working farms or commercial forest land adjacent to Lot C. c. Describe any structures on the site. Lot A – King County Tax Parcel No. 334100-0090: There are no structures present on Lot A. Lot B – King County Tax Parcel No. 334100-0095: There are no structures present on Lot B. 483 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 36 of 54 Lot C – King County Tax Parcel No. 334100-0100: There are no structures present on Lot C. d. Will any structures be demolished? If so, what? Lot A – King County Tax Parcel No. 334100-0090: No structures will be demolished on Lot A. Lot B – King County Tax Parcel No. 334100-0095: No structures will be demolished on Lot B. Lot C – King County Tax Parcel No. 334100-0100: No structures will be demolished on Lot C. e. What is the current zoning classification of the site? Lot A – King County Tax Parcel No. 334100-0090: The current zoning designation for Lot A is “R-5” (residential; 5 dwelling units per acre). Lot B – King County Tax Parcel No. 334100-0095: The current zoning designation for Lot B is “R-5” (residential; 5 dwelling units per acre). Lot C – King County Tax Parcel No. 334100-0100: The current zoning designation for Lot C is “R-5” (residential; 5 dwelling units per acre). f. What is the current comprehensive plan designation of the site? Lot A – King County Tax Parcel No. 334100-0090: The current comprehensive plan designation for Lot A is “Single Family”. Lot B – King County Tax Parcel No. 334100-0095: The current comprehensive plan designation for Lot B is “Single Family”. 484 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 37 of 54 Lot C – King County Tax Parcel No. 334100-0100: The current comprehensive plan designation for Lot C is “Single Family”. g. If applicable, what is the current shoreline master program designation of the site? Lot A – King County Tax Parcel No. 334100-0090: The current shoreline master program designation for Lot A is “Urban Conservancy”. Lot B – King County Tax Parcel No. 334100-0095: The current shoreline master program designation for Lot B is “Urban Conservancy”. Lot C – King County Tax Parcel No. 334100-0100: The current shoreline master program designation for Lot C is “Urban Conservancy”. h. Has any part of the site been classified as a critical area by the city or county? If so, specify. Lot A – King County Tax Parcel No. 334100-0090: The following critical areas have identified within Lot A: Erosion Hazard, Groundwater Protection Zone 2, Landslide Hazard, Stream, Flood Hazard (100 year floodplain, channel migration zone). Lot B – King County Tax Parcel No. 334100-0095: The following critical areas have identified within Lot B: Erosion Hazard, Groundwater Protection Zone 2, Landslide Hazard, Stream, Flood Hazard (100 year floodplain, channel migration zone). Lot C – King County Tax Parcel No. 334100-0100: The following critical areas have identified within Lot C: Erosion Hazard, Groundwater Protection Zone 2, Landslide Hazard, Stream, Flood Hazard (100 year floodplain, channel migration zone). i. Approximately how many people would reside or work in the completed project? Lot A – King County Tax Parcel No. 334100-0090: Approximately 3 people will reside in the future residential structure to be constructed in Lot A. This 485 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 38 of 54 assumes 2.72 persons per household, which is the latest information available from the US Census Bureau for Auburn, Washington. Lot B – King County Tax Parcel No. 334100-0095: Approximately 3 people will reside in the future residential structure to be constructed in Lot B. This assumes 2.72 persons per household, which is the latest information available from the US Census Bureau for Auburn, Washington. Lot C – King County Tax Parcel No. 334100-0100: Approximately 3 people will reside in the future residential structure to be constructed in Lot C. This assumes 2.72 persons per household, which is the latest information available from the US Census Bureau for Auburn, Washington. j. Approximately how many people would the completed project displace? Lot A – King County Tax Parcel No. 334100-0090: The completed project in Lot A will not displace people. Lot B – King County Tax Parcel No. 334100-0095: The completed project in Lot B will not displace people. Lot C – King County Tax Parcel No. 334100-0100: The completed project in Lot C will not displace people. k. Proposed measures to avoid or reduce displacement impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: No measures are proposed to avoid or reduce displacement impacts. Lot B – King County Tax Parcel No. 334100-0095: No measures are proposed to avoid or reduce displacement impacts. Lot C – King County Tax Parcel No. 334100-0100: No measures are proposed to avoid or reduce displacement impacts. 486 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 39 of 54 L. Proposed measures to ensure the proposal is compatible with existing and projected land uses and plans, if any: Lot A – King County Tax Parcel No. 334100-0090: The proposed project conforms to existing and projected zoning and land use. Lot B – King County Tax Parcel No. 334100-0095: The proposed project conforms to existing and projected zoning and land use. Lot C – King County Tax Parcel No. 334100-0100: The proposed project conforms to existing and projected zoning and land use. m. Proposed measures to reduce or control impacts to agricultural and forest lands of long-term commercial significance, if any: Lot A – King County Tax Parcel No. 334100-0090: Does not apply. Agricultural or forest lands of long-term commercial significance are not present within the vicinity of Lot A. Lot B – King County Tax Parcel No. 334100-0095: Does not apply. Agricultural or forest lands of long-term commercial significance are not present within the vicinity of Lot B. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. Agricultural or forest lands of long-term commercial significance are not present within the vicinity of Lot B. 9. Housing a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low-income housing. Lot A – King County Tax Parcel No. 334100-0090: Development of Lot A will provide one (1) single-family residence. Design of the residence will target pricing as middle-income housing. 487 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 40 of 54 Lot B – King County Tax Parcel No. 334100-0095: Development of Lot B will provide one (1) single-family residence. Design of the residence will target pricing as middle-income housing. Lot C – King County Tax Parcel No. 334100-0100: Development of Lot A will provide one (1) single-family residence. Design of the residence will target pricing as middle-income housing. b. Approximately how many units, if any, would be eliminated? Indicate whether high, middle, or low-income housing. Lot A – King County Tax Parcel No. 334100-0090: Development of Lot A will not eliminate any housing units. Lot B – King County Tax Parcel No. 334100-0095: Development of Lot B will not eliminate any housing units. Lot C – King County Tax Parcel No. 334100-0100: Development of Lot C will not eliminate any housing units. c. Proposed measures to reduce or control housing impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: Does not apply. No housing impacts are anticipated. Lot B – King County Tax Parcel No. 334100-0095: Does not apply. No housing impacts are anticipated. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. No housing impacts are anticipated. 10. Aesthetics 488 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 41 of 54 a. What is the tallest height of any proposed structure(s), not including antennas; what is the principal exterior building material(s) proposed? Lot A – King County Tax Parcel No. 334100-0090: The future residence within Lot A will conform to the maximum allowed building height of 35 feet per R-5 zoning. Principle exterior building materials may include wood, fiber cement, brick, stone, concrete, or a combination thereof. Lot B – King County Tax Parcel No. 334100-0095: The future residence within Lot B will conform to the maximum allowed building height of 35 feet per R-5 zoning. Principle exterior building materials may include wood, fiber cement, brick, stone, concrete, or a combination thereof. Lot C – King County Tax Parcel No. 334100-0100: The future residence within Lot C will conform to the maximum allowed building height of 35 feet per R-5 zoning. Principle exterior building materials may include wood, fiber cement, brick, stone, concrete, or a combination thereof. b. What views in the immediate vicinity would be altered or obstructed? Lot A – King County Tax Parcel No. 334100-0090: Does not apply. No views within the immediate vicinity of Lot A would be altered or obstructed. Lot B – King County Tax Parcel No. 334100-0095: Does not apply. No views within the immediate vicinity of Lot B would be altered or obstructed. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. No views within the immediate vicinity of Lot C would be altered or obstructed. c. Proposed measures to reduce or control aesthetic impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: Does not apply. No aesthetic impacts are anticipated. Lot B – King County Tax Parcel No. 334100-0095: 489 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 42 of 54 Does not apply. No aesthetic impacts are anticipated. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. No aesthetic impacts are anticipated. 11. Light and Glare a. What type of light or glare will the proposal produce? What time of day would it mainly occur? Lot A – King County Tax Parcel No. 334100-0090: Anticipated light and glare produced by development of Lot A will be consistent with single-family residence uses and would be typically be present during the night or periods of low-level daylight. Exterior lighting will be shielded, directed down, and placed on timers as required by City of Auburn ordinance and codes. Lot B – King County Tax Parcel No. 334100-0095: Anticipated light and glare produced by development of Lot B will be consistent with single-family residence uses and would be typically be present during the night or periods of low-level daylight. Exterior lighting will be shielded, directed down, and placed on timers as required by City of Auburn ordinance and codes. Lot C – King County Tax Parcel No. 334100-0100: Anticipated light and glare produced by development of Lot C will be consistent with single-family residence uses and would be typically be present during the night or periods of low-level daylight. Exterior lighting will be shielded, directed down, and placed on timers as required by City of Auburn ordinance and codes. b. Could light or glare from the finished project be a safety hazard or interfere with views? Lot A – King County Tax Parcel No. 334100-0090: It is not anticipated that light and glare produced by development of Lot A will be a safety hazard or interfere with views. Exterior lighting will be shielded, directed down, and placed on timers as required by City of Auburn ordinance and codes. 490 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 43 of 54 Lot B – King County Tax Parcel No. 334100-0095: It is not anticipated that light and glare produced by development of Lot B will be a safety hazard or interfere with views. Exterior lighting will be shielded, directed down, and placed on timers as required by City of Auburn ordinance and codes. Lot C – King County Tax Parcel No. 334100-0100: It is not anticipated that light and glare produced by development of Lot C will be a safety hazard or interfere with views. Exterior lighting will be shielded, directed down, and placed on timers as required by City of Auburn ordinance and codes. c. What existing off-site sources of light or glare may affect your proposal? Lot A – King County Tax Parcel No. 334100-0090: There are no off-site sources of light or glare that may affect development of Lot A for residential use. Lot B – King County Tax Parcel No. 334100-0095: There are no off-site sources of light or glare that may affect development of Lot B for residential use. Lot C – King County Tax Parcel No. 334100-0100: There are no off-site sources of light or glare that may affect development of Lot C for residential use. d. Proposed measures to reduce or control light and glare impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: Does not apply. No aesthetic impacts are anticipated. Lot B – King County Tax Parcel No. 334100-0095: Does not apply. No aesthetic impacts are anticipated. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. No aesthetic impacts are anticipated. 12. Recreation 491 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 44 of 54 a. What designated and informal recreational opportunities are in the immediate vicinity? Lot A – King County Tax Parcel No. 334100-0090: Washington State Park access is located approximately 900 feet south of Lot A at the terminus of 104th Place SE, the Lea Hill Tennis Courts (32121 105th Place SE) are located approximately 950 feet east of Lot A, and Scoottie Brown Park (1403 Henry Road NE) is located approximately 1,300 feet west of Lot A. Lot B – King County Tax Parcel No. 334100-0095: Washington State Park access is located approximately 900 feet south of Lot B at the terminus of 104th Place SE, the Lea Hill Tennis Courts (32121 105th Place SE) are located approximately 950 feet east of Lot B, and Scoottie Brown Park (1403 Henry Road NE) is located approximately 1,300 feet west of Lot B. Lot C – King County Tax Parcel No. 334100-0100: Washington State Park access is located approximately 900 feet south of Lot C at the terminus of 104th Place SE, the Lea Hill Tennis Courts (32121 105th Place SE) are located approximately 950 feet east of Lot C, and Scoottie Brown Park (1403 Henry Road NE) is located approximately 1,300 feet west of Lot C. b. Would the proposed project displace any existing recreational uses? If so, describe. Lot A – King County Tax Parcel No. 334100-0090: Development of Lot A for residential use will not displace existing residential uses. Lot B – King County Tax Parcel No. 334100-0095: Development of Lot B for residential use will not displace existing residential uses. Lot C – King County Tax Parcel No. 334100-0100: Development of Lot C for residential use will not displace existing residential uses. c. Proposed measures to reduce or control impacts on recreation, including recreation opportunities to be provided by the project or applicant, if any: Lot A – King County Tax Parcel No. 334100-0090: 492 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 45 of 54 Does not apply. No impacts to existing designated or informal recreation opportunities are anticipated. Lot B – King County Tax Parcel No. 334100-0095: Does not apply. No impacts to existing designated or informal recreation opportunities are anticipated. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. No impacts to existing designated or informal recreation opportunities are anticipated. 13. Historic and cultural preservation a. Are there any buildings, structures, or sites, located on or near the site that are over 45 years old listed in or eligible for listing in national, state, or local preservation registers ? If so, specifically describe. Lot A – King County Tax Parcel No. 334100-0090: Residences located along 104th Place SE are of variable age ranging back to 1910, but most older residences have been upgraded or updated resulting in considerable change from their original style. No structures currently exist on the site. There are no historical sites or properties located on the project site or in its vicinity listed or identified by national, state or local preservation registers per the Department of Archaeology and Historical Preservation’s WISAARD mapping tool. Lot B – King County Tax Parcel No. 334100-0095: Residences located along 104th Place SE are of variable age ranging back to 1910, but most older residences have been upgraded or updated resulting in considerable change from their original style. No structures currently exist on the site. There are no historical sites or properties located on the project site or in its vicinity listed or identified by national, state or local preservation registers per the Department of Archaeology and Historical Preservation’s WISAARD mapping tool. Lot C – King County Tax Parcel No. 334100-0100: Residences located along 104th Place SE are of variable age ranging back to 1910, but most older residences have been upgraded or updated resulting in considerable change from their original style. No structures currently exist on the site. There are no historical sites or properties located on the project site or in its vicinity listed or identified by national, state or local preservation registers per the Department of Archaeology and Historical Preservation’s WISAARD mapping tool. 493 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 46 of 54 b. Are there any landmarks, features, or other evidence of Indian or historic use or occupation? This may include human burials or old cemeteries. Are there any material evidence, artifacts, or areas of cultural importance on or near the site? Please list any professional studies conducted at the site to identify such resources. Lot A – King County Tax Parcel No. 334100-0090: There are no known landmarks, features, or other evidence of Indian or historic use or occupation within or immediately adjacent to Lot A per WISAARD GIS tool. Lot B – King County Tax Parcel No. 334100-0095: There are no known landmarks, features, or other evidence of Indian or historic use or occupation within or immediately adjacent to Lot B per WISAARD GIS tool. Lot C – King County Tax Parcel No. 334100-0100: There are no known landmarks, features, or other evidence of Indian or historic use or occupation within or immediately adjacent to Lot C per WISAARD GIS tool. c. Describe the methods used to assess the potential impacts to cultural and historic resources on or near the project site. Examples include consultation with tribes and the department of archeology and historic preservation, archaeological surveys, historic maps, GIS data, etc. Lot A – King County Tax Parcel No. 334100-0090: No formal study completed; however, a general web search was completed for known cultural and historic resources on or near the project site was completed. WISAARD GIS tool was consulted to assess the impacts to cultural and historic resources. Lot B – King County Tax Parcel No. 334100-0095: No formal study completed; however, a general web search was completed for known cultural and historic resources on or near the project site was completed. WISAARD GIS tool was consulted to assess the impacts to cultural and historic resources. Lot C – King County Tax Parcel No. 334100-0100: No formal study completed; however, a general web search was completed for known cultural and historic resources on or near the project site was completed. WISAARD GIS tool was consulted to assess the impacts to cultural and historic resources. 494 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 47 of 54 d. Proposed measures to avoid, minimize, or compensate for loss, changes to, and disturbance to resources. Please include plans for the above and any permits that may be required. Lot A – King County Tax Parcel No. 334100-0090: Does not apply. No impacts to historic or cultural resources are anticipated. Lot B – King County Tax Parcel No. 334100-0095: Does not apply. No impacts to historic or cultural resources are anticipated. Lot C – King County Tax Parcel No. 334100-0100: Does not apply. No impacts to historic or cultural resources are anticipated. 14. Transportation a. Identify public streets and highways serving the site or affected geographic area and describe proposed access to the existing street system. Show on site plans, if any. Lot A – King County Tax Parcel No. 334100-0090: Access to Lot A is directly from 104th Place SE. Lot B – King County Tax Parcel No. 334100-0095: Access to Lot B is directly from 104th Place SE. Lot C – King County Tax Parcel No. 334100-0100: Access to Lot C is directly from 104th Place SE. b. Is the site or affected geographic area currently served by public transit? If so, generally describe. If not, what is the approximate distance to the nearest transit stop? Lot A – King County Tax Parcel No. 334100-0090: Lot A is located the Sound Transit Regional Transit Authority (RTA) taxing district. Metro bus route #181 makes regular stops less than 0.5 miles from Lot A on 8th Street NE as well as Lea Hill Road SE. 495 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 48 of 54 Lot B – King County Tax Parcel No. 334100-0095: Lot B is located the Sound Transit Regional Transit Authority (RTA) taxing district. Metro bus route #181 makes regular stops less than 0.5 miles from Lot B on 8th Street NE as well as Lea Hill Road SE. Lot C – King County Tax Parcel No. 334100-0100: Lot C is located the Sound Transit Regional Transit Authority (RTA) taxing district. Metro bus route #181 makes regular less than 0.5 miles from Lot C stops on 8th Street NE as well as Lea Hill Road SE. c. How many additional parking spaces would the completed project or non-project proposal have? How many would the project or proposal eliminate? Lot A – King County Tax Parcel No. 334100-0090: The residence proposed for Lot A will include a 2 car garage and 2 parking spaces on the proposed driveway. No parking spaces will be eliminated. Lot B – King County Tax Parcel No. 334100-0095: The residence proposed for Lot B will include a 2 car garage and 2 parking spaces on the proposed driveway. No parking spaces will be eliminated. Lot C – King County Tax Parcel No. 334100-0100: The residence proposed for Lot C will include a 2 car garage and 2 parking spaces on the proposed driveway. No parking spaces will be eliminated. d. Will the proposal require any new or improvements to existing roads, streets, pedestrian, bicycle or state transportation facilities, not including driveways? If so, generally describe (indicate whether public or private). Lot A – King County Tax Parcel No. 334100-0090: Street deferral SDR20-0008 was approved on 6/25/2020 to defer half street improvements along Lot A, with the following conditions/exceptions to be met prior to building permit approval: 1. The applicant must provide a minimum width of 20’ of pavement along the frontage with pavement tapers per AASHTO requirements. The road can be expanded on the west side of the road due to the steep slope located on the east side of 104th PL SE. 2. 104th PL SE is currently in poor condition. The applicant shall mill and overlay the minimum 496 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 49 of 54 width of 20’ of pavement across the frontage. 3. A Puget Sound Energy LED light shall be provided on the existing utility pole located along the frontage of the parcels. Lot B – King County Tax Parcel No. 334100-0095: Street deferral SDR20-0008 was approved on 6/25/2020 to defer half street improvements along Lot B, with the following conditions/exceptions to be met prior to building permit approval: 4. The applicant must provide a minimum width of 20’ of pavement along the frontage with pavement tapers per AASHTO requirements. The road can be expanded on the west side of the road due to the steep slope located on the east side of 104th PL SE. 5. 104th PL SE is currently in poor condition. The applicant shall mill and overlay the minimum width of 20’ of pavement across the frontage. 6. A Puget Sound Energy LED light shall be provided on the existing utility pole located along the frontage of the parcels. Lot C – King County Tax Parcel No. 334100-0100: Street deferral SDR20-0008 was approved on 6/25/2020 to defer half street improvements along Lot C, with the following conditions/exceptions to be met prior to building permit approval: 7. The applicant must provide a minimum width of 20’ of pavement along the frontage with pavement tapers per AASHTO requirements. The road can be expanded on the west side of the road due to the steep slope located on the east side of 104th PL SE. 8. 104th PL SE is currently in poor condition. The applicant shall mill and overlay the minimum width of 20’ of pavement across the frontage. 9. A Puget Sound Energy LED light shall be provided on the existing utility pole located along the frontage of the parcels. e. Will the project or proposal use (or occur in the immediate vicinity of) water, rail, or air transportation? If so, generally describe. Lot A – King County Tax Parcel No. 334100-0090: No. Lot A is located within an existing residential setting that is not served directly by water, rail, or water transportation. Lot B – King County Tax Parcel No. 334100-0095: No. Lot B is located within an existing residential setting that is not served directly by water, rail, or water transportation. Lot C – King County Tax Parcel No. 334100-0100: 497 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 50 of 54 No. Lot C is located within an existing residential setting that is not served directly by water, rail, or water transportation. f. How many vehicular trips per day would be generated by the completed project or proposal? If known, indicate when peak volumes would occur and what percentage of the volume would be trucks (such as commercial and nonpassenger vehicles). What data or transportation models were used to make these estimates? Lot A – King County Tax Parcel No. 334100-0090: Vehicular trips generated by a completed residential project on Lot A would be typical of single- family residential uses, would consist of typically passenger vehicles, and would likely be highest in the morning or evening hours. Lot B – King County Tax Parcel No. 334100-0095: Vehicular trips generated by a completed residential project on Lot B would be typical of single- family residential uses, would consist of typically passenger vehicles, and would likely be highest in the morning or evening hours. Lot C – King County Tax Parcel No. 334100-0100: Vehicular trips generated by a completed residential project on Lot C would be typical of single- family residential uses, would consist of typically passenger vehicles, and would likely be highest in the morning or evening hours. g. Will the proposal interfere with, affect or be affected by the movement of agricultural and forest products on roads or streets in the area? If so, generally describe. Lot A – King County Tax Parcel No. 334100-0090: Not applicable. Commercial agricultural or forest products are not routinely transported in the vicinity of Lot A. Lot B – King County Tax Parcel No. 334100-0095: Not applicable. Commercial agricultural or forest products are not routinely transported in the vicinity of Lot B. Lot C – King County Tax Parcel No. 334100-0100: Not applicable. Commercial agricultural or forest products are not routinely transported in the vicinity of Lot C. 498 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 51 of 54 h. Proposed measures to reduce or control transportation impacts, if any: Lot A – King County Tax Parcel No. 334100-0090: None proposed. Residential development on Lot A will not impact transportation within the local area. Lot B – King County Tax Parcel No. 334100-0095: None proposed. Residential development on Lot B will not impact transportation within the local area. Lot C – King County Tax Parcel No. 334100-0100: None proposed. Residential development on Lot C will not impact transportation within the local area. 15. Public Services a. Would the project result in an increased need for public services (for example: fire protection, police protection, public transit, health care, schools, other)? If so, generally describe. Lot A – King County Tax Parcel No. 334100-0090: Yes. Future residential development on Lot A includes one (1) single family residence and will present a slight increase in the potential for emergency services such as fire and police protection as well as other public services such as transit and schools. Lot B – King County Tax Parcel No. 334100-0095: Yes. Future residential on Lot B includes one (1) single family residence and will present a slight increase in the potential for emergency services such as fire and police protection as well as other public services such as transit and schools. Lot C – King County Tax Parcel No. 334100-0100: Yes. Future residential on Lot C includes one (1) single family residence and will present a slight increase in the potential for emergency services such as fire and police protection as well as other public services such as transit and schools. b. Proposed measures to reduce or control direct impacts on public services, if any. 499 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 52 of 54 Lot A – King County Tax Parcel No. 334100-0090: Applicable impact fees for public services will be paid by the project applicant prior to building permit issuance. Lot B – King County Tax Parcel No. 334100-0095: Applicable impact fees for public services will be paid by the project applicant prior to building permit issuance. Lot C – King County Tax Parcel No. 334100-0100: Applicable impact fees for public services will be paid by the project applicant prior to building permit issuance. 16. Utilities a. Circle utilities currently available at the site: electricity, natural gas, water, refuse service, telephone, sanitary sewer, septic system, other ___________ Lot A – King County Tax Parcel No. 334100-0090: The following utilities are present within 104th Avenue NE adjacent to Lot A: electricity, natural gas, refuse services, telephone services, and sanitary sewer. Lot B – King County Tax Parcel No. 334100-0095: The following utilities are present within 104th Avenue NE adjacent to Lot B: electricity, natural gas, refuse services, telephone services, and sanitary sewer. Lot C – King County Tax Parcel No. 334100-0100: The following utilities are present within 104th Avenue NE adjacent to Lot C: electricity, natural gas, refuse services, telephone services, and sanitary sewer. e. Describe the utilities that are proposed for the project, the utility providing the service, and the general construction activities on the site or in the immediate vicinity which might be needed. Lot A – King County Tax Parcel No. 334100-0090: 500 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 53 of 54 Temporary power will be provided to Lot A by Puget Sound Energy during construction phases and construction debris will be disposed of or recycled at a local commercial facility determined by the construction contractor. A future residence with Lot A will be connected to the following utility services: • Puget Sound Energy – electricity & natural gas • Xfinity (Comcast) – cable television/internet/telephone • CenturyLink – telephone/internet • City of Auburn – water and sanitary sewer • Trash/recycling – Waste Management (via City of Auburn billing) Lot B – King County Tax Parcel No. 334100-0095: Temporary power will be provided to Lot B by Puget Sound Energy during construction phases and construction debris will be disposed of or recycled at a local commercial facility determined by the construction contractor. A future residence with Lot B will be connected to the following utility services: • Puget Sound Energy – electricity & natural gas • Xfinity (Comcast) – cable television/internet/telephone • CenturyLink – telephone/internet • City of Auburn – water and sanitary sewer • Trash/recycling – Waste Management (via City of Auburn billing) Lot C – King County Tax Parcel No. 334100-0100: Temporary power will be provided to Lot C by Puget Sound Energy during construction phases and construction debris will be disposed of or recycled at a local commercial facility determined by the construction contractor. A future residence with Lot C will be connected to the following utility services: • Puget Sound Energy – electricity & natural gas • Xfinity (Comcast) – cable television/internet/telephone • CenturyLink – telephone/internet • City of Auburn – water and sanitary sewer • Trash/recycling – Waste Management (via City of Auburn billing) C. Signature 501 of 721 SEPA Environmental checklist (WAC 197-11-960) July 2016 Page 54 of 54 The above answers are true and complete to the best of my knowledge. I understand that the lead agency is relying on them to make its decision. Signature: ___________________________________________________ Name of signee _______Mariah Gill___________________________________________ Position and Agency/Organization _______Land Use Planner_______________________ Date Submitted: ___November 2020__________ 502 of 721 NOTICE OF APPLICATION (NOA) and DETERMINATION OF NON-SIGNIFICANCE (DNS) GOULET SINGLE-FAMILY RESIDENTIAL PROJECT SEP20-0009 The City of Auburn is issuing a Notice of Application (NOA) and Determination of Non-Significance (DNS) for the following described project. The permit applications and listed studies may be reviewed at the Auburn Department of Community Development at One E Main St., 2nd Floor, Customer Service Center, Auburn, WA 98001. Proposal: Shoreline Substantial Development Permit and Shoreline Conditional Use Permit to allow for the construction of three new single-family residences on three vacant parcels located within the Urban Conservancy Shoreline Designation. Additionally, two Shoreline Variances are requested to allow for the construction of the dwellings on Lots B and C to extend 5.5 and 10.5 feet into the required 100-foot setback from the Green River Ordinary High Water Mark (OHWM). Location: The site, comprised of three separate parcels, is located along the east bank of the Green River and directly to the west of 104th Pl SE, approximately 330 feet south of the SE 320th St and 104th Pl SE intersection. Notice of Application: February 5, 2021 Application Complete: June 15, 2020 Permit Application: May 14, 2020 File Nos. SEP20-0009 SHL20-0001 SHL20-0002 Applicant: Encompass Engineering & Surveying Heather Tatro, Associate Planner 165 NE Juniper Street, Suite 201 Issaquah, WA 98027 Property Owner: Bruce & Launce Goulet 3226 S 198th St SeaTac, WA 98188 Studies/Plans Submitted With Application: • Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated October 28, 2020 • Shoreline Buffer Mitigation Plan, prepared by Evergreen Aquatic Resource Consultants, LLC, dated October 28, 2020 • Critical Areas Report (geotechnical), prepared by Bergquist Engineering Services, dated November 4, 2020 • Environmental Checklist, prepared by Encompass Engineering & Surveying, dated November 2020 • Site Plan, prepared by Encompass Engineering & Surveying, dated November 9, 2020 Other Permits, Plans, and Approvals Needed: • Grading Permit, Shoreline Conditional Use Permit, Shoreline Var iance, Shoreline Substantial Development Permit, Building Permit(s) NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0009 (Continued) Page 2 of 4 Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and Public Works Design and Construction Standards. Lead Agency: City of Auburn The lead agency for this proposal has determined that it does not have probable significant adverse impact on the environment. An environmental impact statement (EIS) is not required under RCW 43.21C.030(2)(c). This decision was made after review of a completed environmental checklist and other information on file with the lead agency. This information is available to the public on request. Public Comment Period: This may be your only opportunity to comment on the environmental impact of the proposal. All persons may comment on this application. This DNS is issued under WAC 197-11-355; the lead agency will not act on this proposal for 15 days from the date issued below. Comments must be in writing and submitted by 5:00 pm on February 20, 2021 to the mailing address of 25 W Main ST, Auburn, WA, 98001 or emailed to the contact below. Any person wishing to become a party of record, shall include in their comments that they wish to receive notice of and participate in any hearings, if relevant, and request a copy of decisions once made. Any person aggrieved of the City's determination may file an appeal with the Auburn City Clerk at 25 West Main Street, Auburn, WA 98001- 4998 within 14 days of the close of the comment period, or by 5:00 p.m. on March 6, 2021. For questions regarding this project, please contact Dustin Lawrence, AICP, CFM, Senior Planner, at planning@auburnwa.gov or 253-931-3092. Public Hearing: The Public Hearing will be scheduled at a later time. RESPONSIBLE OFFICIAL: Jeff Tate POSITION/TITLE: Director, Department of Community Development ADDRESS: 25 West Main Street Auburn, Washington 98001 253-931-3090 DATE ISSUED: SIGNATURE: Note: This determination does not constitute approval of the proposal. Approval of the proposal can only be made by the legislative or administrative body vested with that authority. The proposal is required to meet all applicable regulations. February 5, 2021 504 of 721 NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0009 (Continued) Page 3 of 4 Project Site 505 of 721 NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0009 (Continued) Page 4 of 4 Proposed Site Plan (Draft) 506 of 721 NOTICE OF PUBLIC HEARING Goulet Single-Family Residential Project SHL20-0001 & SHL20-0002 The City of Auburn is issuing a Notice of Hearing for the following described project. The permit applications and listed studies may be reviewed at the Auburn Department of Community Development at 1 E Main ST, 2nd Floor, Customer Service Center, Auburn, WA 98001. Proposal: Shoreline Substantial Development Permit and Shoreline Conditional Use Permit to allow for the construction of three new single-family residences on three vacant parcels located within the Urban Conservancy Shoreline Designation. Additionally, two Shoreline Variances are requested to allow for the construction of the dwellings on Lots B and C to extend 5.5 and 10.5 feet into the required 100-foot setback from the Green River Ordinary High Water Mark (OHWM). Location: The site, comprised of three separate parcels, is located along the east bank of the Green River and directly to the west of 104th Pl SE, approximately 330 feet south of the SE 320th St and 104th Pl SE intersection. Notice of Application: February 5, 2021 Permit Application: June 15, 2020 Complete Application: May 14, 2020 File No. SEP20-0009 SHL20-0001 SHL20-0002 Applicant: Encompass Engineering & Surveying Heather Tatro, Associate Planner 165 NE Juniper Street, Suite 201 Issaquah, WA 98027 Owner: Bruce & Launce Goulet 3226 S 198th St SeaTac, WA 98188 Studies/Plans Submitted with Application: • Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated October 28, 2020 • Shoreline Buffer Mitigation Plan, prepared by Evergreen Aquatic Resource Consultants, LLC, dated October 28, 2020 • Critical Areas Report (geotechnical), prepared by Bergquist Engineering Services, dated November 4, 2020 • Environmental Checklist, prepared by Encompass Engineeri ng & Surveying, dated November 2020 • Site Plan, prepared by Encompass Engineering & Surveying, dated November 9, 2020 Other Permits, Plans, and Approvals Needed: 507 of 721 NOTICE OF PUBLIC HEARING SHL20-0001 & SHL20-0002 (Continued) Page 2 of 2 • Grading Permit, Shoreline Conditional Use Permit, Shoreline Variance, Shoreline Substantial Development Permit, Building Permit(s) Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and Design and Construction Standards. Public Comment Period: All persons may comment on this application. Comments must be in writing and received by the end of the comment period at 5:00 p.m. on April 21, 2021 to the mailing address of 25 W Main ST, Auburn, WA, 98001-4998. Any person wishing to become a party of record, shall include in their comments that they wish to receive notice of and participate in any hearings, if relevant, request a copy of decisions once made, and be made aware of appeal rights. For questions regarding this project, please contact Dustin Lawrence, AICP, Senior Planner, at planning@auburnwa.gov or (253) 931-3092. Public Hearing: The meeting of the City of Auburn Hearing Examiner scheduled for April 21, 2021 at 5:30 p.m. will be held virtually and telephonically. To attend the meeting virtually please enter the meeting ID into the ZOOM app or call into the meeting at the phone number listed below. Per the Governor’s Emergency Proclamation 20-28, the City of Auburn is prohibited from holding an in-person meeting at this time. All meetings will be held virtually and telephonically. City of Auburn is inviting you to a scheduled Zoom meeting. Join Zoom Meeting https://zoom.us/j/95279324579 Meeting ID: 952 7932 4579; One tap mobile +12532158782,,95279324579# US (Tacoma) +16699009128,,95279324579# US (San Jose) VICINITY MAP: 508 of 721 State of Washington • Department of Archaeology & Historic Preservation P.O. Box 48343 • Olympia, Washington 98504-8343 • (360) 586-3065 www.dahp.wa.gov February 12, 2021 Mr. Dustin Lawrence Senior Planner Department of Community Development City of Auburn 25 W Main St, Auburn, WA. 98001 In future correspondence please refer to: Project Tracking Code: 2021-02-00848 Property: City of Auburn_ Goulet Single-Family Residences Re: Survey Requested Dear Mr. Lawrence: Thank you for contacting the Washington State Historic Preservation Officer (SHPO) and Department of Archaeology and Historic Preservation (DAHP) and providing documentation regarding the above referenced project. A desktop review using our statewide predictive model has identified the proposed project area as having very high sensitivity for archaeological resources. The location of these parcels, occupying high ground above the Green River, gives this area particular sensitivity for archaeological resources. Further, the scale of the proposed ground disturbing actions would destroy any archaeological resources present. Identification during construction is not a recommended detection method because inadvertent discoveries often result in costly construction delays and damage to the resource. Therefore, we recommend a professional archaeological survey of the project area be conducted prior to ground disturbing activities. We also recommend consultation with the concerned Tribes' cultural committees and staff regarding cultural resource issues. These comments are based on the information available at the time of this review and on behalf of the SHPO in conformance with Washington State law. Should additional information become available, our assessment may be revised. Thank you for the opportunity to comment on this project and we look forward to receiving the survey report. Please ensure that the DAHP Project Number (a.k.a. Project Tracking Code) is shared with any hired cultural resource consultants and is attached to any communications or submitted reports. Should you have any questions, please feel free to contact me. Sincerely, Dennis Wardlaw Transportation Archaeologist (360) 485-5014 dennis.wardlaw@dahp.wa.gov 509 of 721 1 Dustin Lawrence From:Santiago, Railin (ECY) <RASA461@ECY.WA.GOV> Sent:Wednesday, February 24, 2021 3:26 PM To:Dustin Lawrence Subject:RE: SEP20-0009; SHL20-0001; SHL20-0002 Follow Up Flag:Follow up Flag Status:Flagged Hello Dustin, Thank you for the opportunity to comment on the Goulet SFR project (SHL20-001 & SHL 20-0002) which requires a Shoreline Conditional Use (SCUP) and Shoreline Variances (SVAR). Below are my comments. Ecology Shoreline Planner Comments: Can the building footprint on lot B & C be the same? If so, lot B shouldn’t need a variance. The proposed footprint of lot C looks like it could fit on lot B without a Shoreline Variance. The applicant should address SCUP and SVAR criteria under WAC 173-27-160 and 173-27-170. Please explain how this is the minimum necessary (why the residences cannot be any narrower between the road and buffer) and why a residence cannot be provided without extending into the setback/buffer. Per Geotech report “we recommend that the building design process includes appropriate subsurface exploration as described above and development of engineering recommendations for design of a foundation system or soils improvement methods that will mitigate the effects of liquefaction.” This should be a condition of the permit. A residence should not be allowed if a bulkhead would be required during the life of the structure. I don’t see a statement indicating a bulkhead would never be required for the structure. A bulkhead prohibition may need to be a condition of the permit or on the title. I hope you are having a great day! Sincerely, Railin Santiago Shoreline Planner | WA Department of Ecology | Shorelands & Environmental Assistance Northwest Region, 3160 160th Ave SE, Bellevue, WA 98008 cell: 425-301-6989 | railin.santiago@ecy.wa.gov This communication is public record and may be subject to disclosure as per the Washington State Public Records Act, RCW 42.56 . From: Dustin Lawrence <dlawrence@auburnwa.gov> Sent: Friday, February 12, 2021 3:40 PM To: Santiago, Railin (ECY) <RASA461@ECY.WA.GOV> Subject: RE: SEP20-0009; SHL20-0001; SHL20-0002 510 of 721 2 THIS EMAIL ORIGINATED FROM OUTSIDE THE WASHINGTON STATE EMAIL SYSTEM - Take caution not to open attachments or links unless you know the sender AND were expecting the attachment or the link Hi Railin, Of course, thank you for reaching out. Please visit this link: https://www.auburnwa.gov/cms/one.aspx?portalId=11470638&pageId=17402062 Let me know if you are able to find what you need. There is a section on this page with all of the studies/plans submitted with the application. Dustin Lawrence, AICP, CFM Senior Planner Department of Community Development City of Auburn | www.auburnwa.gov Office# 253-931-3092 | Cell# 253-561-2224 | dlawrence@auburnwa.gov Mailing Address: 25 W Main Street, Auburn, WA 98001 Permit Center Address: 1 E Main Street, Auburn, WA 98002 (Click Here for Map) Customer Service Survey | Application Forms | Zoning Maps From: Santiago, Railin (ECY) <RASA461@ECY.WA.GOV> Sent: Friday, February 12, 2021 3:31 PM To: Dustin Lawrence <dlawrence@auburnwa.gov> Subject: SEP20-0009; SHL20-0001; SHL20-0002 Hello Dustin, I see that the Goulet project (SEP20-0009; SHL20-0001; SHL20-0002) on the Green River is seeking a Shoreline Conditional Use permit and two Shoreline Variances. Are you able to send me the permit application materials, or maybe there is a link you can send me? I am interested in providing some SEPA comments. Thank you so much for your time and assistance. Sincerely, Railin Santiago Shoreline Planner | WA Department of Ecology | Shorelands & Environmental Assistance Northwest Region, 3160 160th Ave SE, Bellevue, WA 98008 cell: 425-301-6989 | railin.santiago@ecy.wa.gov This communication is public record and may be subject to disclosure as per the Washington State Public Records Act, RCW 42.56 . The information contained in this electronic communication is personal, privileged and/or confidential information intended only for the use of the individual(s) or entity(ies) to which it has been addressed. If you 511 of 721 3 read this communication and are not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication, other than delivery to the intended recipient is strictly prohibited . If you have received this communication in error, please immediately notify the sender by reply e-mail. Thank you. 512 of 721 Ecology Shoreline Planner Comments: Can the building footprint on lot B & C be the same? If so, lot B shouldn’t need a variance. The proposed footprint of lot C looks like it could fit on lot B without a Shoreline Variance. The footprint for lot C doesn't fit on lot B due to a much wider buildable area on Lot C. The width of the buildable area on Lot C somewhat makes up for the constraint on the depth of the buildable area that was removed from lot C. The width of Lot B is more than 10’ narrower than Lot C. In comparison Lot B is deeper than Lot C which allows for the building footprint to be slightly deeper. These lots are not uniform in shape or size and much consideration was taken to size the buildable area appropriately for the characteristics of each lot. Given the footprint of the neighboring house to the south, reducing the footprint depth of Lot B to match Lot C would decrease the enjoyment of the parcel drastically below that experienced by adjoining property owners. The applicant should address SCUP and SVAR criteria under WAC 173-27-160 and 173-27- 170. The criteria listed in WAC 173-27-160 and 173-27-170 was addressed in the last submittal with the following documents: Goulet Written Statement & Criterion Compliance for Shoreline Conditional Use Permit Rev. 1 Goulet Lot B Written Statement Shoreline Variance-Goulet Residences Rev. 1 Goulet Lot C Written Statement Shoreline Variance-Goulet Residences Rev. 1 In WAC 173-27-160 the purpose of a conditional use permit is to provide a system within the master program which allows flexibility in the application of use regulations in a manner consistent with the policies of RCW 90.58.020. Starting on page 3 of the written document noted above, the conditional use written statement addresses all criteria as necessary to show that it is consistent with the RCW and the City of Auburn Shoreline Master Program. In WAC 173-27-170 the purpose of a variance permit is strictly limited to granting relief from specific bulk, dimensional or performance standards set forth in the applicable master program where there are extraordinary circumstances relating to the physical character or configuration of property such that the strict implementation of the master program will impose unnecessary hardships on the applicant or thwart the policies set forth in RCW 90.58.020. The variance written statements noted above for lots B & C address the Shoreline Variance criterion as laid out in SMP 16.08.058 which should be in-line with the criteria listed in the WAC. Please explain how this is the minimum necessary (why the residences cannot be any narrower between the road and buffer) and why a residence cannot be provided without extending into the setback/buffer. 513 of 721 In the R-5 zone the minimum Front Setback is 10’ and the garage setback is 20’. In addition, there is a 15’ setback from the sewer line which runs in an easement along the East property line. All of these elements compress the depth of the buildable area away from the East property line. Adjustment of the footprints toward the street is not available due to an existing sewer easement that was recorded when the neighboring property was developed. The maximum lot coverage in the R-5 zone is 40% of the lot area. For Lot B that would be 5,440sf and 5,280sf for Lot C. While the property owner would have an expectation to build significantly larger structures on lots of this size, the proposed footprints for Lot B and C have an average lot coverage of 12.5%. The proposed footprints are well below typical allowances for lots this size. The minimum standard depth and width of a 2-car garage is 20’ x 20’. These dimensions would only be sufficient for car storage and would need to be larger to account for other utility storage or larger vehicles. For the safety of the residents and possible visitors, it is important that there is sufficient space on-site for a garage and surface parking. In particular, the depth of the Lot C building footprint cannot be reduced or there would not be sufficient space to build a minimum standard garage. This proposal allows for no accessory buildings as enjoyed by other single family uses in the area and therefore utility storage space must be accounted for within the footprint of the homes which would result in additional space in the garage for storage. The typical garage size in the neighboring homes is 600 SF or more. Single family residences have been constructed several parcels to the north and south of the site, the Amberview Apartments are located to the east of the site across 104th Avenue SE, and the Green River borders the site directly to the west. Residential development along the west side of 104th PL SE extends back to the early 1900’s and existing development generally includes one or two story single family residences with either attached or detached garages. Except for two mobile or manufactured homes located near SE 320th ST, most residences are of a conventional on-site stick-built construction averaging 2,510 SF (dwelling unit + accessory structures) in footprint. Most residences are setback from the Green River and are located close to 104 th PL SE. The properties to the south are on similarly sized lots as the subject proposal, but were built significantly closer to the River and the structures have much larger footprints than we are proposing. See attached spreadsheet, tabulating these properties. The proposal is striving to produce buildable areas on the parcels that protect the environmental function of the river and are consistent with the character and use enjoyed by the neighboring properties, some that were developed recently. The proposed buffer intrusion is quite minimal (5’-10’) and the amount of mitigation measures provided more than compensate for the encroachment and result in a “no net loss” of shoreline environment. Per Geotech report “we recommend that the building design process includes appropriate subsurface exploration as described above and development of engineering recommendations 514 of 721 for design of a foundation system or soils improvement methods that will mitigate the effects of liquefaction.” This should be a condition of the permit. The applicant does not disagree with this condition. A residence should not be allowed if a bulkhead would be required during the life of the structure. I don’t see a statement indicating a bulkhead would never be required for the structure. A bulkhead prohibition may need to be a condition of the permit or on the title. The current condition of the property does not require a bulkhead. River flows within the reach of the Green River, adjacent to the site have been regulated by the Howard Hansen Dam since about 1961. Per the Geotech report, flow regulation provided by the HHD has somewhat reduced river erosion and deposition of sediment onto the site. On maps dating back to 1888 and aerial photos dating back to 1936, they show the river in its current location which suggests a stable channel configuration. There is no evidence that historic or current channel migration exists on the site. In addition, there are no known bulkheads or similar structures that we are aware of on the adjacent properties, so no indication that a bulkhead would ever be desired or necessary. The project does not include shoreline access for any lots and all development is located outside of floodplains, channel migration hazards, and related buffers. To prohibit construction of a residence based on the unlikely need for a bulkhead during the “life of a structure”, is an unnecessary hardship or limitation given the environmental factors and site conditions. Although history indicates that channel migration is highly unlikely, a statement that a bulkhead may NEVER be constructed is an extreme measure. We strongly recommend against this being a condition of approval unless the prohibition is limited to a 3- year term. 515 of 721 Property Comparison of Surrounding Lots Property Address Parcel Number Total Lot Size (SF) # of floors # of bedrooms Structure Details: SF Footprint Sf Total Square Footage (house + garage)Year Built Lot Covg % Notes 1 32003 104th Pl SE 334100-0085 25,611 1 ? Mobile Home: 1848 Detached garage: 1300 3148 3148 1998 0.12 2 32013 104th Pl SE 334100-0086 19,491 1 ? Mobile Home: 1792 Detached garage: 720 2,512 2,512 0.13 3 32021 104th Pl SE 334100-0087 15,476 2 2 First Floor: 1275 Finished Basement: 910 Accessory structure: 353, 244 Deck: 160 2032 2942 1910 0.13 Multiple unpermitted structures 4 32149 104th Pl SE 334100-0125 11,700 2 4 First Floor: 2490 Second Floor: 940 Attached Garage: 740 Open Porch/Deck: 170, 110 3510 4450 2000 0.30 Adjacent to Lot C 5 32201 104th Pl SE 334100-0130 11,340 2 3 First Floor: 720 Attached Garage: 480 Deck: 360 1560 1560 1974 0.14 6 32211 104th Pl SE 334100-0135 12,760 2 2 First Floor: 2110 Basement: 650 Workshop: 725 Shed: 274 Open Porch: 640 3749 4399 1940 0.29 7 32267 104th Pl SE 334000-0145 9,919 2 3 First Floor: 1380 Second Floor: 910 Detached Garage: 1060 Open Porch: 70 2510 3420 2005 0.25 8 602 Riverview Dr NE 733190-0110 10,194 1 3 First Floor: 1410 Attached Garage: 500 1910 1910 1963 0.19 Across the river from Lot B 9 506 Riverview Dr NE 733190-0120 10,556 2 5 First Floor: 1140 Second Floor: 480 Basement: 800 Attached Garage: 480 Open Porch/Deck: 190, 140 1950 3230 1963 0.18 Across the river from Lot C Average 14,116 1.67 3.14 2,542 3,063 Indicates most recent developments 516 of 721 517 of 721 2/2/2021 Z (250×1016) data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAQCAwMDAgQDAwMEBAQEBQkGBQUFBQsICAYJDQsNDQ0LDAwOEBQRDg…1/1 518 of 721 AFFIDAVIT OF POSTING OF LEGAL NOTICE BY APPLICANT Application Number: SHL20-0001 & SHL20-0002 Applicant: Encompass Engineering & Surveying Heather Tatro, Associate Planner 165 NE Juniper Street, Suite 201 Issaquah, WA 98027 Owner: Bruce & Launce Goulet 3226 S 198th St SeaTac, WA 98188 Location: The site, comprised of three separate parcels, is located along the east bank of the Green River and directly to the west of 104th Pl SE, approximately 330 feet south of the SE 320th St and 104th Pl SE intersection, King County Parcels 3341000090, 3341000095, and 3341000100. Closing Date for Public Comments: April 21, 2021 I certify that on March 15, 2021 I did erect a land use posting board at the location above, which included a Notice of Application for the above referenced application, as required by Auburn City Code 1.27 and 16.06.090. The board was erected at least 15 days prior to the closing date for public comments noted above. I declare under penalty of perjury of the laws of the State of Washington that the foregoing is true and correct. Dustin Lawrence March 15, 2021 Name (please print or type) Date Signature NOTE This affidavit must be returned to the Department of Community Development at least one week prior to the closing date for public comments or review of the application may be postponed. 519 of 721 3/11/2021 9k= (250×958) data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAQCAwMDAgQDAwMEBAQEBQkGBQUFBQsICAYJDQsNDQ0LDAwOEBQRDg…1/1 520 of 721 LAYTON TREE CONSULTING, LLC It’s all about trees…… PO BOX 572, SNOHOMISH, WA 98291-0572 * 425-220-5711 * bob@laytontreeconsulting.com ARBORIST REPORT Goulet Auburn Project 320XX 104th Place SE King County Parcels: 334100-0090, -0095 & -0100 Auburn, WA Report Prepared by: Bob Layton Registered Consulting Arborist #670 Certified Arborist #PN-2714A May 12, 2021 521 of 721 Arborist Report – Goulet Auburn Project Page 2 Layton Tree Consulting LLC May 12, 2021 Table of Contents Summary ....................................................................................................................................................... 3 Assignment.................................................................................................................................................... 3 Description .................................................................................................................................................... 3 Methodology ................................................................................................................................................. 4 Judging Condition...................................................................................................................................... 4 Judging Retention Suitability .................................................................................................................... 4 Observations ................................................................................................................................................. 5 Discussion/Recommendations ...................................................................................................................... 6 Tree Protection Measures ............................................................................................................................ 6 Tree Replacement Requirements ................................................................................................................. 7 Arborist Disclosure Statement ...................................................................................................................... 7 Attachments Photos, pages 8 - 11 Tree Summary Table Tree Locator/Condition Map 522 of 721 Arborist Report – Goulet Auburn Project Page 3 Layton Tree Consulting LLC May 12, 2021 Summary The subject properties are vacant or undeveloped. The site appears to have been mostly cleared and mass-graded in the past. The properties contain very little significant tree cover overall. Invasive Himalayan blackberry has covered the entire site. A total of 35 trees were identified on the properties. 23 of these are considered ‘significant’ trees. The proposal is to remove trees adjacent to 104th Place SE to create three buildable lots. This will result in the removal of a small percentage of the existing significant trees. Only six significant trees are proposed for removal. The river buffer or channel migration buffer area is of very poor habitat quality. It is completely covered with invasive Himalayan blackberry. This area can be significantly enhanced by the removal of the invasive plant species and the planting of long-lived native evergreen tree species and native shrubs that can positively contribute to the landscape for decades to come. Assignment Layton Tree Consulting LLC was asked to conduct an assessment of the significant trees located on King County Parcels: 334100-0090, -0095 and -0100 in Auburn. A significant tree means a healthy evergreen tree, six inches or more in diameter measured four feet above grade, or a healthy deciduous tree four inches or more in diameter measured four feet above grade. Alders and cottonwoods are excluded from this definition. My assignment is to prepare a written report on the viability or feasibility of retaining trees at the site. The assessment will take into consideration the proposed clearing and grading of the site; installation of utilities; and future environmental factors that may have the potential to create hazardous tree conditions in the future. Date of Field Examination: May 11, 2021 Description 35 trees were identified and assessed at the site. Eight of these are non-significant red alder or black cottonwood. The study area is vacant property with sparse tree cover. The properties are abutted by 104th Place SE to the east and the Green River to the west. The entire site is densely covered with invasive plant species of Himalayan blackberry. Subject trees are shown on the attached map. Subject trees were identified with a numbered aluminum tag attached to the lower trunk. These tag numbers correspond with the numbers on the attached Tree Summary Table and map. There are no off-site or neighboring trees that would be impacted by the development of the subject parcels. 523 of 721 Arborist Report – Goulet Auburn Project Page 4 Layton Tree Consulting LLC May 12, 2021 Methodology Each tree in this report was visited. Tree diameters were measured by tape at DBH (diameter at breast height, 4 ½-feet above ground). The tree heights were measured using a Spiegel Relaskop. Each tree was visually examined for defects and vigor. The tree assessment procedure involves the examination of many factors: • The crown or canopy of the tree is examined for current vigor/health by examining the foliage for appropriate color and density, the vegetative buds for color and size, and the branches for structural form and annual shoot growth; and the overall presence of limb dieback and/or any disease issues. • The trunk or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting bodies of decay (conks or mushrooms), seams, insect pests, bleeding or exudation of sap, callus development, broken or dead tops, structural defects and unnatural leans. Structural defects can include but are not limited to excessive or unnatural leans, crooks, forks with V-shaped crotches, multiple attachments. • The root collar and exposed surface roots are inspected for the presence of decay, insect damage, as well as if they have been injured or wounded, undermined or exposed, or the original grade has been altered. Assessment tools used included a probe, mallet and binoculars. No invasive methods were utilized unless described in the sections below. Judging Condition The three condition categories are described as follows: Good – free of significant structural defects, no disease concerns, minor pest issues, no significant root issues, good structure/form with uniform crown or canopy, foliage of normal color and density, average or normal vigor, will be wind firm if isolated or left as part of a grouping or grove of trees, suitable for its location Fair – minor to moderate structural defects not expected to contribute to a failure in near future, no disease concerns, moderate pest issues, no significant root issues, asymmetric or unbalanced crown or canopy, average or normal vigor, foliage of normal color, moderate foliage density, will be wind firm if left as part of a grouping or grove of trees, cannot be isolated, suitable for its location Poor – major structural defects expected to cause fail in near future, disease or significant pest concerns, decline due to old age, significant root issues, asymmetric or unbalanced crown or canopy, sparse or abnormally small foliage, poor vigor, not suitable for its location The attached Tree Summary Table provides specific information on tree sizes and condition. Judging Retention Suitability Not all trees necessarily warrant retention. The three retention suitability categories as described in ANSI A300 Part 5 (Standard Practices for the Management of Trees During Site Planning, Site Development and Construction) are as follows: 524 of 721 Arborist Report – Goulet Auburn Project Page 5 Layton Tree Consulting LLC May 12, 2021 Good – trees are in good health condition and structural stability and have the potential for longevity at the site Fair – trees are in fair health condition and/or have structural defects that can be mitigated with treatment. These trees may require more intense management and monitoring, and may have shorter life-spans than those in the “good” category. Poor – trees are in poor health condition and have significant defects in structure that cannot be mitigated with treatment. These trees can be expected to decline regardless of management. The species or individual tree may possess characteristics that are incompatible or undesirable in landscape settings or be unsuited for the intended use of the site. Observations The site appears to have been mostly cleared and mass-graded many years ago. The subject trees are largely found in small groupings. Afterwards, the site regenerated to predominantly invasive Himalayan blackberry, which is prolific across the site and has smothered out almost all of the native vegetation. Other invasive plant species observed on the property include English ivy, morning glory and Japanese knotweed. Overall, the subject properties contain very sparse tree cover. There is a large grouping of semi-mature black locust (Robinia pseudoacacia) trees at the south end of the site. These are estimated at around 30 to 40 years of age. These 11 trees make up almost half of the significant trees found on the properties (Trees #16, #17 and #20 > #30). Condition is fair. They have developed typical form or architecture. many have suffered broken tops and large stem failures in the past. There is a moderate component of bigleaf maple (Acer macrophyllum). These include Trees #2, #11, #12, #14, #15, #18 and #31 > #35. These range from young specimens of less than 15 years of age to mature specimens of 80 to 100 years of age. The majority are stressed, evident by recent and older dieback of upper crown components. The cause of decline is likely associated with past summer drought conditions. Trees #15, #33 and #35 are rated as ‘poor’ condition with major top dieback and decline. These are in ultimate decline. Trees #1 and #10 are mature Douglas fir. Both are of fairly good vigor. #10 has some notable branch tip dieback. The lower trunks appear sound with no outward indicators of any internal decay issues. Both trees are surrounded by dense blackberry vines. There is a moderate component of non-significant black cottonwood (Trees #7, #8, #9 and #19) and red alder (Trees #3 > #6) on the property. These are mostly older specimens. The alder is in natural decline due to age. A few have recently died on the property and were not surveyed. The cottonwood has developed typical form. Tree #13 is a young to semi-mature cherry plum (Prunus cerasifera) that likely seeded in naturally at the site. It is of good vigor. Its form is more shrub-like. Condition is fair. 525 of 721 Arborist Report – Goulet Auburn Project Page 6 Layton Tree Consulting LLC May 12, 2021 Discussion/Recommendations The proposal is to remove trees adjacent to 104th Place SE to create three buildable lots. This will result in the removal of a small percentage of the existing significant trees. Only six significant trees are proposed for removal. The trees within the river buffer or channel migration buffer will not be impacted by the proposal. The placement of silt fencing or construction fencing at the river buffer edge will be adequate to protect the trees to remain at the site. The river buffer or channel migration buffer is of poor habitat quality. It is covered with dense invasive Himalayan blackberry. English ivy is also prolific along the south perimeter of the property, which has climbed the trunks of several trees in the area. This area can be significantly enhanced by the removal of the invasive plant species and the planting of long-lived native evergreen tree species and native shrubs that can positively contribute to the landscape for decades to come. Any mitigation plan shall incorporate native tree and shrub species suitable to the site. Western red cedar, shore pine, grand fir and Sitka spruce are the recommended tree species for the area. The proposed removal of the subject trees from the site is not expected to have any adverse impacts on trees to remain at the site, either on or off of the property. There are no off-site or neighboring trees that will be impacted by this proposal. Given the very small sizes of the proposed building lots, the retention of Trees #1, #10 and #34 is not feasible. The anticipated ground disturbance and grade changes within their critical root zones will compromise health and stability. Removal and replacement will be necessary. Tree #20 may also require removal in the future, depending on the site design of the lot. Tree Protection Measures The following general guidelines are recommended to ensure that the designated space set aside for the retained trees is protected and construction impacts are kept to a minimum. • Erect a tree protection barrier around any trees to be retained prior to moving any heavy equipment on site. Doing this will set clearing limits and avoid compaction of soils within root zones of retained trees. For this project, orange construction/silt fencing is appropriate. position fencing at 5-feet beyond the dripline edge. Fencing shall be securely positioned and not moved for the duration of the building project. • Excavation limits shall be laid out in paint on the ground to avoid unnecessary over-excavation. • To establish sub grade for foundations, and driveway sections near retained trees, soil shall be removed parallel to the roots and not at 90-degree angles to avoid breaking and tearing roots that lead back to the trunk within the drip-line. Any roots damaged during these excavations shall be exposed to sound/undamaged tissue and cut cleanly with a sharp saw. • Areas excavated near retained trees shall be thoroughly irrigated weekly during dry periods. 526 of 721 Arborist Report – Goulet Auburn Project Page 7 Layton Tree Consulting LLC May 12, 2021 • Preparations for final landscaping shall be accomplished by hand within the drip-lines of retained trees. Large equipment shall be kept outside of the tree protection zones at all times. Tree Replacement Requirements The number of required replacement trees will be determined by the City. All required replacement trees shall be planted within the property boundaries. The site is fully capable of supporting all required replacement trees. Replacement trees shall be primarily native and planted within the river buffer. Recommended species in this area would include Sitka spruce, Western red cedar, grand fir and shore pine. Arborist Disclosure Statement Arborists are tree specialists who use their education, knowledge, training and experience to examine and assess trees, recommend measures to enhance the beauty and health of trees, and attempt to reduce the risks associated with living near trees. Clients may choose to accept or disregard the recommendations of the arborist, or to seek additional advice. Arborists cannot detect every condition that could possibly lead to the structural failure of a tree. Trees are living organisms that grow, respond to their environment, mature, decline and sometimes fail in ways we do not fully understand. Conditions are often hidden within trees and below ground. Arborists cannot guarantee that a tree will be healthy and/or safe under all circumstances, or for a specified period of time. Likewise, remedial treatments, like any medicine, cannot be guaranteed. Treatment, pruning and removal of trees may involve considerations beyond the scope of the arborist’s services such as property boundaries, property ownership, site lines, disputes between neighbors, and other issues. Arborists cannot take such considerations into account unless complete and accurate information is disclosed to the arborist. An arborist should then be expected to reasonably rely upon the completeness and accuracy of the information provided. Trees can be managed, but they cannot be controlled. To live near trees is to accept some degree of risk. The only way to eliminate all risk associated with trees is to eliminate all trees. 527 of 721 Arborist Report – Goulet Auburn Project Page 8 Layton Tree Consulting LLC May 12, 2021 Photo Documentation North side of property, looking west from 104th PL SE, Tree #1 on left East side of property adjacent to 104th PL SE, Trees #7 > #10 in background 528 of 721 Arborist Report – Goulet Auburn Project Page 9 Layton Tree Consulting LLC May 12, 2021 South side of property, looking west from 104th PL SE, Trees #16, #17 & #19 in foreground Black locust grouping in southwest corner of site, English ivy infestation on south perimeter 529 of 721 Arborist Report – Goulet Auburn Project Page 10 Layton Tree Consulting LLC May 12, 2021 Middle of property, Tree #18 in foreground, #13 in background Tree #13 in foreground, #11, #12, #14 and #15 in background 530 of 721 Arborist Report – Goulet Auburn Project Page 11 Layton Tree Consulting LLC May 12, 2021 Upper crowns of black locust grouping Recent and older dead red alder trees in middle of property 531 of 721 Layton Tree Consulting LLC For:Goulet Site:320XX 104th PL SE - Auburn Tree Summary Table Date: Significant Tree/DBH Height Tree Retention Tag #Species (inches)(feet)Yes/No Condition Suitability Comments Proposal N S E W 1 Douglas fir 31 98 Yes 18 14 10 16 Good IBF sound, good vigor Remove 2 bigleaf maple 38 80 Yes NA NA NA NA Fair Good typical form, good vigor Leave 3 red alder 16 52 No NA NA NA NA Poor Fair in decline Leave 4 red alder 22 70 No NA NA NA NA Poor Fair over mature, top decline Leave 5 red alder 15 46 No NA NA NA NA Fair Fair heavy lean south,decent vigor Leave 6 red alder 12 38 No NA NA NA NA Fair Fair heavy lean south,decent vigor Leave 7 black cottonwood 36 132 No 20 6 8 14 Fair IBF natural lean north,mature Remove 8 black cottonwood 30 112 No 16 18 18 10 Fair IBF mature, natural lean west Remove 9 black cottonwood 41 128 No 12 22 8 20 Fair IBF mature, lean south, trunk covered with ivy Remove 10 Douglas fir 36 104 Yes 12 14 10 16 Good IBF minor branch dieback, appears sound Remove 11 bigleaf maple 16 52 Yes NA NA NA NA Fair Fair moderate top dieback, decline, stressed Leave 12 bigleaf maple 11 45 No NA NA NA NA Poor Fair major top dieback Leave 13 cherry plum 10 27 Yes NA NA NA NA Fair Fair some top decline, shrublike Leave 14 bigleaf maple 14 44 Yes NA NA NA NA Fair Fair moderate top dieback, decline, stressed Leave 15 bigleaf maple 14 40 No NA NA NA NA Poor Fair major top dieback Leave 16 black locust 13 59 Yes 12 6 7 12 Fair IBF forked top Remove 17 black locust 13,11,10,9 58 Yes 8 16 16 8 Fair IBF cluster, multiple past stem failures Remove 18 bigleaf maple 16 55 Yes 18 14 18 22 Fair IBF forked, poor structural form Remove 19 black cottonwood 34 130 Yes 22 18 14 18 Fair IBF mature, trunk surrounded by blackberry Remove 20 black locust 14,14,12 70 Yes NA NA NA NA Fair Fair cluster, trunk covered in ivy Retain if Possible 21 black locust 15,12 63 Yes NA NA NA NA Fair Fair typical Leave 22 black locust 14,12,10,8 60 No NA NA NA NA Poor Fair cluster, major lean west, low risk Leave 23 black locust 11 58 Yes NA NA NA NA Fair Fair typical Leave 24 black locust 12 64 Yes NA NA NA NA Fair Fair typical Leave 25 black locust 11 62 Yes NA NA NA NA Fair Fair typical Leave 26 black locust 15 70 Yes NA NA NA NA Fair Fair trunk covered in ivy Leave 27 black locust 14,12 66 Yes NA NA NA NA Fair Fair trunk covered in ivy Leave 28 black locust 14 70 Yes NA NA NA NA Fair Fair trunk covered in ivy Leave 29 black locust 16 72 Yes NA NA NA NA Fair Fair trunk covered in ivy Leave 30 black locust 16 72 Yes NA NA NA NA Fair Fair trunk covered in ivy Leave 31 bigleaf maple 18 56 Yes NA NA NA NA Fair Fair some top decline Leave 32 bigleaf maple 14 48 Yes NA NA NA NA Fair Fair forked top Leave 33 bigleaf maple 11 30 No NA NA NA NA Poor Fair suppressed, 90% dead Leave 34 bigleaf maple 30 78 Yes 20 22 18 26 Fair IBF top dieback, stressed Remove 35 bigleaf maple 11 32 No NA NA NA NA Poor IBF major top dieback Remove Dripline measurements from face of trunk IBF - in proposed building footprints Drip-Line (feet) 5/11/2021 532 of 721 533 of 721 534 of 721 AGENDA BILL APPROVAL FORM HEARING EXAMINER Agenda Subject/Title: SHL21-0002 Shoreline Conditional Use Permit Date: June 3, 2021 Department: Community Development DESCRIPTION: Request for Shoreline Conditional Use Permit to allow for the removal of rock located at the remnant upstream end of the TransCanada Levee. The project is located at River Mile 9.3, along the left bank of the White River. The site has as a ‘Natural’ Shoreline Environment Designation. ADMINISTRATIVE RECOMMENDATION: Hearing Examiner to conduct a public hearing and approve the Shoreline Conditional Use Permit. PROJECT SUMMARY: The applicant seeks to remove a portion rock along the face of the TransCanada Levee along the left bank of the White River within the City’s ‘Natural’ Shoreline Environment Designation. The purpose of the work is to restore riverine processes and functions in the Lower White River and its floodplain in order to enhance riparian habitat for salmonids and additional species. The site has a zoning designation of RC Residential Conservancy. LOCATION: The site is located along the left bank of the White River, at river mile 9.3, King County parcel number 2821059007 APPLICANT: Tom Bloxton, King County River and Floodplain Management, 201 S Jackson St, Suite 5600, Seattle, WA 98104 535 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 2 of 20 2019 Aerial Vicinity Map: Stuck River Dr SE Area of work 536 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 3 of 20 The Comprehensive Plan designation, Shoreline environment designation, zoning classification and current land uses of the site and surrounding properties are: Location Comprehensive Plan Designation Zoning Classification Shoreline Environment Designation Current Land Use Subject Site “Residential Conservancy” “Open Space” RC Residential Conservancy Natural Vacant North “Open Space” “Multiple Family” OS Open space RMHC Residential Manufactured Mobile Home Community Urban Conservancy White River Mobile Home Park South “Residential Conservancy” OS Open space N/A Vacant East “Open Space “Single Family” “Multiple Family” OS Open Space RMHC Residential Manufactured Mobile Home Community Natural Vacant White River West “Open Space” “Multiple Family” RMHC Residential Manufactured Mobile Home Community UNC Unclassified Use District Urban Conservancy White River Vacant 537 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 4 of 20 Excerpted Comprehensive Plan Designation Map: Moderate Density Residential Residential Conservancy Open Space Multiple Family Proposed Work 538 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 5 of 20 Excerpted Zoning Classification Map: RMHC Residential Manufactured/Mobile Home Community OS Open Space R-10 Residential, 10 dwelling units per acre Proposed Work 539 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 6 of 20 Excerpted Shoreline Environment Designations Proposed Work Urban Conservancy Natural Urban Conservancy 540 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 7 of 20 SEPA STATUS: A Mitigated Determination of Non-Significance (MDNS), referred to as a Programmatic SEPA, was issued by King County, Department of Natural Resources and Parks, on May 16, 2007. The MDNS covered a range of activities within flood prone areas in King County, including routine maintenance projects, flood damage repair projects, and projects involving removal of woody debris posing a threat to public health. An Addendum to this MDNS was issued on May 14, 2015, by King County. The Addendum included addressing impacts associated with acquisition of lands to alleviate flooding and included more flexibility for King County to provide routine maintenance and repair within flood prone areas. City of Auburn staff reviewed the MDNS, Addendum, and support information, such as the previously prepared environmental checklists, and determined that the proposed project falls within the activities outlined within the determination. Specifically, the project falls under “flood damage repair projects”, which include the removals of existing bank stabilization facilities where such actions will not adversely affect flood containment or the minimum freeboard performance currently provided by the facility. As such, a project specific threshold determination under SEPA was not required for the proposal. A copy of the MDNS (Programmatic SEPA), prepared by King County, dated May 16, 2007 and the Addendum is included as Exhibit 12. FINDINGS OF FACT: Proposal Description 1. Tom Bloxton, King County River and Floodplain Management, applied on February 22, 2021 for a Shoreline Conditional Use Permit (SCUP) to allow for removal of rock along the face of the TransCanada Levee, located in the Natural Shoreline Environment Designation. The work will be completed along the left bank of the White River, near River Mile 9.3. A copy of the Civil Plans, prepared by King County, Department of Natural Resources and Parks, dated February, 2021 are included as Exhibit 7. 2. Because the proposal involves the modification of a structural flood hazard reduction facility, it most closely fits within the “structural flood hazard reduction (dikes and levees) use”, which is a permitted activity in the Natural Shoreline Environment Designation, subject to issuance of a SCUP, per the City of Auburn’s Shoreline Master Program, Section 4.5. 3. The project also fits in with the use of “Shoreline Habitat and Natural Systems Enhancement Project”, as listed in Auburn SMP Section 4.6.7. However, given the possibility for potential impacts downstream due to the removal of existing rock, that a small portion of land area waterward of the existing levee could be reclaimed by the White River thereby functioning as a natural flood control element, and that the project is related to an existing flood control system, staff determined that the shoreline habitat and natural enhancement component of the use was secondary to the structural flood hazard reduction use. 541 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 8 of 20 4. The work will involve removing as much rock as possible from the levee facing using an excavator while protecting significant trees. The work will begin upstream at the eroded end of the levee and extend 400 feet downstream. Angular face rock from the eroded levee will be removed from the channel. Extensive excavation to locate buried riprap will not take place. Light regarding of the slope after riprap removal will take place at the direction of the project representative to help in the restoration and planting process. The disturbed areas of the site will be vegetated with a mix of native trees and shrubs. Any trees that need to be removed from the project will be placed in the riparian area to serve as terrestrial habitat. See Exhibit 7. 5. The proposed levee modifications will meet the requirements of the Auburn City Code (ACC), as applicable. The proposal will meet the flood hazard reduction standards outlined within the City’s Shoreline Master Program (SMP) 4.4.6. 6. In addition to the Shoreline program requirements, the site borders the White River, a Type S Stream and is subject to the city’s critical area regulations (ACC 16.10). A minimum 100-foot buffer, in which native vegetation is to be retained, is required for Type S streams (river). 7. The applicant provided a Critical Areas Report & Floodplain Habitat Impact Assessment, prepared by ESA, dated April, 2021. The report concluded that the project “will have no effect (NA)” on any Endangered Species Act (ESA) listed species or habitat elements. The Critical Areas Report is included as Exhibit 8. 8. In order to demonstrate compliance with the City’s Surface Water Management Manual, a Stormwater Site Plan, prepared by King County Department of Natural Resources and Parks, dated February 18, 2021, was provided as part of the review of the application. No new pollution generating surfaces would be created and surface water runoff conditions will generally remain the same. A copy of the Stormwater Site Plan is included as Exhibit 10. 9. In order to evaluate the geomorphic risks associated with the proposed rock removal, as well as identify the locations of the Channel Migration Zone (CMZ) from the White River and any landslide hazards that could result from the project, the applicant submitted a Geomorphic Risk Analysis, prepared by King County, Water and Land Resources Division, dated December 2, 2020. The Report concludes that whether or not the project is completed, the risks associated with channel migration along the left bank of the White River will generally remain the same. Further, the Report notes that risks associated with the downstream right bank of the White River have the potential to be reduced should the project be completed, as the hydraulic and hydrologic forces along the right bank within this portion of the River have the potential to be slightly alleviated. The Report is marked as Exhibit 9. 10. The applicant provided a written statement that describing the project. A copy of the Written Statement, prepared by Tom Bloxton, King County, dated April 7, 2021, is included as Exhibit 6. 542 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 9 of 20 Site Characteristics (General) 11. The project site is located along the left bank of the White River at River Mile 9.3. Specifically, the project area involves a Levee that was developed during the early 1900s that provides flood protection to areas directly to the south and west. The levee is located along the far northeast portion of the parcel. Because the White River abuts the site, the entire project area is located within 200 feet of the White River Ordinary High Water Mark and shoreline jurisdiction and is within the ‘Natural’ shoreline environment designation. 12. The project area and surrounding parcels along the left bank of the White River are undeveloped and generally, heavily vegetated. The White River channel has changed at various times, with portions of it running throughout this area. See Exhibit 2 for a copy of the vicinity map. 13. With the project being in close proximity to the White River, a Cultural Resources Review Memo, prepared by King County staff, was provided with the application to confirm the likelihood of discovery of culturally significant resources during construction. In summary, the memorandum concludes that there is a low likelihood of discovery, as the project area generally involves previously dredged material and involves a man- made levee system. A copy of the Cultural Resources Memo is included as Exhibit 11. Site Characteristics (Critical Areas & Shoreline Areas) 14. The White River, which abuts the site directly to the north and east, is a mapped floodway. While the project site and immediate area are not identified in a FEMA Flood Insurance Rate Map (FIRM), based on elevation data and the proximity of nearby mapped Special Flood Hazard Areas (SFHAs), staff confirmed that the area waterward of the levee is located within the SFHA. Additionally, as noted in the Geomorphic Risk Analysis provided by the applicant, this portion of the White River has Channel Migration Zone area that extends over the entire project site, meaning that this is an area susceptible to the river changing its course long term and diverging into this area. In addition, all of the area in which work is proposed is also located within a Riparian Buffer Zone (RBZ), a type of regulatory floodplain area per Chapter 15.68 ACC, “Floodplain Development Management”. See Exhibit 9 for a copy of the Geomorphic Risk Analysis. 15. In addition to being a Shoreline of the State, the White River is also classified by the City as regulated “Critical Area” and more specifically as a Type S Stream per ACC 16.10.080, “Classification and rating of critical areas”. As outlined in SMP 4.5, Table 1, Type S Streams within the Shoreline Residential Shoreline Environment Designation have a-100 foot setback from the OHWM. While defined as a setback within the SMP, the setback effectively acts as a 100 foot buffer. 16. The site is located in an area that may have Wildlife Habitat Area, as defined in ACC 16.10.080(E). This is due to the site being located along the White River, a Type S Stream system that provides habitat area for various species. Per the applicant’s Critical Areas Report, minor and temporary impacts will occur during the proposed rock removal. However, tree removals will be minimized and any trees that are removed, will be left within the project area. Further, habitat area will be enhanced by proposed rock removal 543 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 10 of 20 and incorporation of new plantings. See Exhibit 8 for a copy of the applicant’s Critical Areas Report. 17. The site is located within an Aquifer Recharge Area known as Type I, Groundwater Protection Zone 3, as defined in ACC 16.10.080(F). These areas have a critical recharging effect on aquifers used for potable water. Best management practices (BMP) will be required for any future development of the site. 18. The applicant provided a Critical Areas Report and Habitat Impact Assessment, prepared by ESA, dated April, 2021, in order to identify all wetlands, streams, and any associated buffers affecting the site. The Report concluded that there are no wetlands or associated buffers on the site and that the White River, a Type S stream is located along the eastern portion of the site. See Exhibit 8 for a Copy of the Critical Area Report. 19. The sites location along a Type S Stream also results in it being within a Riparian Buffer Zone. These areas contain habitat that may be used by federal or state listed threatened or endangered Fish species. As identified in the applicant’s Critical Areas Report and Habitat Impact Assessment, the project will have “not effect” in regards to potential impacts on endangered species. Native vegetation within the Protected Area, as defined in ACC 15.68.100(OO), will likely remain. Should any small trees need to be removed as a result of the rock removal, said trees will be added as woody debris and left within the project area. Further, new native vegetation plantings will be incorporated into the project site. See Exhibit 8 for a copy of the Critical Areas Report and Habitat Impact Assessment. 20. While the site does not contain any mapped landslide hazard areas, the Geomorphic Risk Analysis, prepared by King County, dated December 2, 2020, provided by the applicant, outlines any potential landslide hazards or erosion hazards that could occur as a result of the project. The report noted that future landslide risks that could result downstream will be negligible. Further, the report notes that should the project not occur, it is likely that over time the existing levee and rock proposed for removal would erode, thereby, resulting in similar conditions downstream regardless. See Exhibit 9 for a copy of the Geomorphic Risk Analysis. 21. The area within 200 feet of the Ordinary High Water Mark (OHWM) along the White River is within the “Natural” designation and thus, is within the jurisdiction of the Auburn Shoreline Master Program (Auburn SMP, Section 4.2.A). Unless otherwise exempt, activity associated with structure flood hazard reduction facilities in the ‘Natural’ designation will require a Shoreline Conditional Use Permit (SCUP). The language of this Section provides: “4.2 Applicability. 1. The provisions of this chapter shall apply to all shorelines, shorelands and associated wetland areas covered by the Shoreline Management Act of 1971 as follows: 544 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 11 of 20 1. All rivers and streams and their associated wetlands downstream from a point where the mean annual flow is 20 cubic feet per second or greater. 2. All lakes and their associated wetlands which are 20 surface acres in size or larger. 3. Shorelands and associated uplands extending 200 feet in all directions as measured on a horizontal plane from the ordinary high water mark; floodways and contiguous floodplain areas landward two hundred feet from such floodways; and all wetlands and river deltas associated with their streams, lakes, and tidal waters subject to the provisions of Chapter 90.58 RCW.” Characteristics of the Surrounding Area 22. The project and adjacent properties are located within the jurisdiction of the City of Auburn. 23. The surrounding areas have Comprehensive Plan designations of: “Multiple Family”, “Residential Conservancy”, and “Open Space”. The surrounding zoning designations include “RMHC” Residential Manufactured/Mobile Home Community and “RS” Residential Conservancy. 24. The existing land uses surrounding the site includes a mobile home park to the north (across the White River) and vacant, open space land surrounding the site along the left bank of the White River. Comprehensive Plan 25. The following City of Auburn Comprehensive Policies are relevant to the project: Imagine Auburn: City of Auburn Comprehensive Plan – Core Plan: Community Vision & Values (Page C3-5) We will protect the natural environment, preserve open space, and create safe and appropriate access. Shoreline Management Program 26. The City of Auburn currently uses its 2020 City of Auburn Shoreline Master Program (SMP) to regulate development and management of the City’s shoreline. Under the Shoreline Management Act, all development occurring within the shoreline jurisdiction area must be consistent with policies and regulations of the local Shoreline Management Program (SMP), as well as with the policies of the State Shoreline Management Act. While some policies, goals, and development regulations may be referenced as findings within this staff report, additional policies, goals, and development regulations of the SMP not explicitly referenced may be found by review of the City’s 2020 SMP document. 545 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 12 of 20 27. Because the project requires a Shoreline Conditional Development Permit, the Project must be found consistent with the criteria established in WAC 173-27-160 and City of Auburn SMP 6.1.8. 28. The City’s rules and procedures for shoreline permits are contained in the SMP; more specifically Section 6.0. The section provides the following general purpose and intent: “6.1.1 Chapter purpose and intent. It is the intention of the city council that the provisions of this chapter will promulgate and adopt a program for the administration and enforcement of a permit system that shall implement by reference the State Shoreline Management Act of 1971, Chapter 90.58 RCW; the State Department of Ecology regulations and guidelines adopted as Chapters 173-26 and 173-27 WAC; the Auburn shoreline master program attached to the ordinance codified in this chapter, together with amendments and/or additions thereto, and to provide for the implementation of the policy and standards as set forth in the aforesaid laws and regulations which are by reference made a part of this chapter with the force and effect as though set out in full in this chapter.” 29. Pursuant ACC 6.1.12, the Hearing Examiner shall hold at least one public hearing on the Shoreline Conditional Use Permit in accordance with the following: “6.1.12 Application – Hearing – Required. A. The hearing examiner shall hold at least one public hearing on each application for a shoreline substantial development permit, shoreline conditional use permit, or shoreline variance on shorelines within the city. The public hearing shall be held not less than 30 days following the final publication of the notice required by ACC 16.08.050. B. The notice and conduct of the public hearing shall be in accordance with Chapter 2.46 ACC.” 30. The City’s rules provide the following requirements for public notice: “6.1.6 Application – Notices. The director shall give notice of the application in accordance with the applicable provisions of ACC 14.07.040, no less than 30 days prior to permit issuance. The notices shall include a statement that any person desiring to present his view to the director with regard to the application may do so in writing to the director, and any person interested in the hearing examiner's action on an application for a permit may submit his views or notify the director of his interest within 30 days of the last date of publication of the notice. Such notification or submission of views to the director shall entitle said persons to a copy of the action taken on the application.” 31. The City’s SMP contains the following information regarding the “Natural” shoreline environment: 546 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 13 of 20 “3.4 Natural 3.4.1 Purpose: The purpose of the "Natural" environment is to protect those shoreline areas that are relatively free of human influence or that include intact or minimally degraded shoreline functions that would become irreversibly impaired as a result of human development and activity. These systems require that only very low intensity uses be allowed in order to maintain ecological functions and ecosystem-wide processes. Consistent with the policies of the designation, the City of Auburn should include planning for restoration of degraded shorelines within this environment. 3.4.2 Designation Criteria: The “Natural” environment designation should be assigned to shoreline areas if any of the following characteristics apply: (A) The shoreline is ecologically intact (as described in WAC 173-26-211(5)(a)(iii)) and therefore currently performing an important, irreplaceable function or ecosystem-wide process that would be damaged by human activity; (B) The shoreline is considered to represent ecosystems and geologic types that are of particular scientific and educational interest; or (C) The shoreline is unable to support new development or uses without significant adverse impacts to ecological functions or risk to human safety. 3.4.3 Management Policies: The following management policies should apply to all shoreline areas classified as Natural Environments: 1. Any use that would substantially degrade the ecological functions or natural character of the shoreline area should not be allowed. 2. The following new uses should not be allowed in the "Natural" environment: • Commercial uses. • Industrial uses. • Non-water-oriented recreation. • Roads, utility corridors, and parking areas that can be reasonably located outside of "Natural" designated shorelines. 3. Single-family residential use may be allowed on properties designated as "Natural" if the density and lot configuration can accommodate such use by maintaining portions of the property in shoreline jurisdiction in a natural condition, consistent with the purpose of the environment. 4. Scientific, historical, cultural, educational research uses, and low-intensity water- oriented recreational access uses may be allowed provided that no significant ecological impact on the area will result. 5. New development or significant vegetation removal that would reduce the capability of vegetation to perform normal ecological functions should not be allowed. Do not allow the subdivision of property in a configuration that, to achieve its intended purpose, will require significant vegetation removal or shoreline modification that adversely impacts ecological functions. That is, each new parcel must be able to support its intended development without significant ecological impacts to the shoreline ecological functions.” 547 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 14 of 20 32. The City’s SMP contains the following goals related to Shoreline Use: “2.5.1 Goals 1. Promote the best possible pattern of land and water uses that will be most beneficial to the natural and human environments. 2. Designated Shorelines of Statewide Significance are of value to the entire State and shall be managed consistent with this recognition. In order of preference the priorities are to: a. Recognize and protect the Statewide interest over local interest; b. Preserve the natural character of the shoreline; c. Result in long term over short term benefit; d. Protect the resources and ecology of the shoreline; and, e. Increase public access to publicly owned areas of the shorelines.” 33. City City’s SMP contains the following goals related to Flood Prevention/Critical Areas: “2.8.1 Goals 1. Continue to participate in a regional approach to flood protection issues, coordinating with the State of Washington, King County, Pierce County and other entities interested in reducing flood hazards on both the White and Green Rivers. 2. Continue to protect wetlands, streams, wildlife habitat, and groundwater and minimize geologic hazards in the shoreline environment in accordance with the Critical Areas Ordinance.” 34. The City’s SMP contains the following policies related to Shoreline Vegetation Conservation: “4.4.2 Shoreline Vegetation Conservation 1. Developments and activities in the City’s shoreline should be planned and designed to retain native vegetation or replace shoreline vegetation with native species to achieve no net loss of the ecological functions and ecosystem-wide processes performed by vegetation. 2. Woody debris should be left in the river corridors to enhance wildlife habitat and shoreline ecological functions, except where it threatens personal safety or critical infrastructure, such as bridge pilings. In such cases where debris poses a threat, it should be dislodged, but should not be removed from the river.” 35. The City’s SMP contains the following policies related to Flood Hazard Reduction: “4.4.6 Flood Hazard Reduction 1. The City should manage flood protection through the City’s Comprehensive Drainage Plan, Comprehensive Plan, stormwater regulations, and flood hazard areas regulations. 548 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 15 of 20 2. Discourage development within the floodplains associated with the City’s shorelines that would individually or cumulatively result in an increase to the risk of flood damage. 3. Non-structural flood hazard reduction measures should be given preference over structural measures. Structural flood hazard reduction measures should be avoided whenever possible. When necessary, they should be accomplished in a manner that assures no net loss of ecological functions and ecosystem-wide processes. Non- structural measures include setbacks, land use controls prohibiting or limiting development in areas that are historically flooded, stormwater management plans, or bioengineering measures. 4. Where possible, public access should be integrated into publicly financed flood control and management facilities. Public Notice, Comments and Procedures 36. A Mitigated Determination of Non-Significance (MDNS), referred to as a Programmatic SEPA, was issued by King County, Department of Natural Resources and Parks, on May 16, 2007. An Addendum to this MDNS was issued on May 14, 2015, by King County. The MDNS (Programmatic SEPA) and addendum are included as Exhibit 12. 37. City staff, including representatives with expertise in Utilities, Transportation, Building, Development Review, as well as the Valley Regional Fire Authority (VRFA) had an opportunity to review the proposal and provide comments. Based on the initial review of the project applications and support materials, none of the City staff or VRFA staff raised objections to the proposal. 38. The City issued the Notice of Hearing (NOH) on May 14, 2021. The notice was provided 30 days prior to the hearing date as required by SMP 6.1.6, “Application – Notices”. The notice was mailed to property owners within 300 feet of the project site, published in the newspaper, and posted on site (See Exhibit 13). At the time of the preparation of this report, no comments have been received in response to the NOH. 39. The contents of the case file for this project (SHL21–0002) are hereby incorporated by reference and made part of the record of this hearing. 40. The decision on SCUP shall be final with the Hearing Examiner and subject to the Washington State Dept. of Ecology review period as required by the following code section: “SMP 6.1.18 Grant or denial decision – Notifications. The director shall notify the following persons in writing of the hearing examiner’s final approval, disapproval or conditional approval of a substantial development permit, shoreline conditional use permit, or shoreline variance application within eight days of its final decision: A. The applicant; B. The State Department of Ecology; C. The State Attorney General; D. Any person who has submitted to the director written comments on the application; E. Any person who has written the director requesting notification.” 549 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 16 of 20 CONCLUSIONS: What follows is the criteria for decision-making provided in italics, followed by an analysis by staff of the project’s consistency with the criteria (in bold). Shoreline Conditional Use Permit 1. The Shoreline Master Program (SMP) provides the following review criteria for Shoreline Conditional Use Permits: “6.1.8 Application – Shoreline conditional use permit – Review criteria. A. Pursuant to WAC 173-27-210, the criteria below shall constitute the minimum criteria for review and approval of a shoreline conditional use permit. Uses classified as conditional uses, and not uses prohibited by the regulations of this SMP, may be authorized; provided, that the applicant can demonstrate all of the following: “1. That the proposed use will be consistent with the policies of RCW 90.58.020, the policies of this SMP, the city of Auburn comprehensive plan and other applicable plans, programs and/or regulations; The project has been reviewed for consistency with the goals, objectives, policies, and use regulations of the Auburn SMP. Specifically: • No net loss in shoreline functions will occur; • Modification of previously permitted flood control systems are proposed, with no new facility or expansion of said facility proposed; • The project meets the development standards, as applicable, of the Natural Shoreline Environment Designation 2. That the proposed use will not interfere with the normal public use or access to public shorelines; The project will not interfere with normal public use or access to the public shorelines. No new structures, roads, or utility systems are proposed. Any existing use or access available to the public along this portion of the shoreline will remain unchanged. 3. That the proposed use of the site and design of the project will be compatible with other permitted uses within the area and with uses planned for the area under the comprehensive plan and shoreline master program; The proposed use and site design will be compatible with other permitted uses within the area, as the area is predominately open space or vacant land susceptible to flooding due to the historic changes of the White River. The project is consistent with uses allowed in this area, including Flood Hazard Reduction and Shoreline Habitat and Natural Systems Enhancement. 4. That the proposed use will cause no unreasonably adverse effects to the shoreline, will not result in a net loss of ecological functions, and will not be incompatible with the environment designation or zoning classification in which it is to be located; 550 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 17 of 20 Based on the analysis provided by the applicant, including multiple reports addressing any downstream impacts that could occur, no adverse effects to the shoreline will result from the proposal. Further, the project involves removal of existing rock area, allowing for the White River to reclaim a small portion of area waterward of an existing levee system, thereby providing increased habitat area for protected salmonid species. Additionally, new native vegetation plantings will be incorporated into the project. Both the Shoreline environmental classification and zoning classification allow for the proposed use of a flood hazard reduction facility and for shoreline habitat and natural systems enhancement projects. 5. That the public interest suffers no substantial detrimental effect; The public interest will suffer no substantial detrimental effect, as demonstrated by the various reports and analysis provided by the applicant. The City is in agreement that the project will help contribute towards improving the shoreline habitat within this segment of the White River. Any detriment to the public interest would be due to the potential for impacts to occur downstream as a result of the rock removal. However, as noted from the geomorphic risk analysis provided by the applicant, such impacts downstream will be negligible. 6. That the proposed use is in the best interest of the public health, safety, morals or welfare; and The project involves modification of a flood hazard reduction facility and could be construed as a shoreline habitat and natural systems enhancement project, uses that are both either permitted or conditionally permitted per the City’s SMP. By meeting the requirements of the City’s SMP, the proposed use is in the best interest of the public health, safety, morals, and welfare. Further, as previously noted, the applicant provided an analysis supported by detailed reports confirming that impacts associated with the proposal will be negligible, if any at all. The City is in agreement with this analysis and the supporting reports. 7. That consideration of cumulative impacts resultant from the proposed use has occurred and has demonstrated that no substantial cumulative impacts are anticipated, consistent with WAC 173-27-160(4). No cumulative impacts are anticipated from a result of the proposed use. If the project were not to happen, the rock area proposed for removal would eventually erode, resulting in the same negligible impacts downstream and within the surrounding area. The City is unaware of any similar, recent projects that could contribute towards a larger cumulative impact. B. The director may attach conditions to the approval of permits as necessary to assure consistency of the proposal with the above criteria.” Staff finds that the proposal is consistent with the above criteria for a Shoreline Conditional Use Permit and the criteria outlined in WAC 173-27-160 551 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 18 of 20 Consistency with SMA & Local SMP 2. The Shoreline Management rules (WAC 173-27-140) set forth the following two criteria for all developments within the shoreline jurisdiction. “(A) No authorization to undertake use or development on shorelines of the state shall be granted by the local government unless upon review the use or development is determined to be consistent with the policy and provisions of the Shoreline Management Act and the master program.” “(B) No permit shall be issued for any new or expanded building or structure of more than thirty-five feet above average grade level on shorelines of the state that will obstruct the view of a substantial number of residences on areas adjoining such shorelines except where a master program does not prohibit the same and then only when overriding considerations of the public interest will be served.” The proposed project is consistent with the Shoreline Management Act and the City’s Shoreline Management Program (SMP). The City's program identifies the project area to be the “Natural” shoreline environment designation. The project will be consistent with the designation by allowing removal of rock on the face of an existing levee, thereby resulting in enhancements to shoreline habitat area. Minimal impacts are anticipated and public access to the shorelines will not be impacted or reduced. The proposed project is consistent with the SMP policies applicable to flood hazard reduction uses. The levee rock removal measures may potentially have a negligible impact to property downstream due to the changes in hydrology from the existing White River. However, with these impacts being negligible, and even likely to occur in the future if no action is taken, staff concludes that no further mitigation action is necessary to demonstrate consistency with the local SMP. Removal and disturbance of vegetation near the shoreline will be limited. Should any trees be damaged or need to be removed due to the rock removals, said trees will remain in place and act as woody debris within the shoreline area. Additionally, new plantings and vegetation will be incorporated into the project. The project will meet the recommendations provided within a Geomorphic Risk Analysis, which includes post project monitoring of the areas downstream. This will ensure that, in the event that unforeseen impacts do occur in the future, measures can be explored that will ensure the life, safety, and welfare of the surrounding residents is protected. No development will occur within the floodway, Special Flood Hazard Area, or Channel Migration Zone. City of Auburn staff believe the project is consistent with the criteria established in WAC 173-27-140. 3. The Shoreline Management rules in WAC 173-27-160 set forth the following criteria that must be met for approval of a Shoreline Conditional Use Permit. The project must be consistent with: 552 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 19 of 20 (1) Uses which are classified or set forth in the applicable master program as conditional uses may be authorized provided that the applicant demonstrates all of the following: (a) That the proposed use is consistent with the policies of RCW 90.58.020 and the master program; (b) That the proposed use will not interfere with the normal public use of public shorelines; (c) That the proposed use of the site and design of the project is compatible with other authorized uses within the area and with uses planned for the area under the comprehensive plan and shoreline master program; (d) That the proposed use will cause no significant adverse effects to the shoreline environment in which it is to be located; and (e) That the public interest suffers no substantial detrimental effect (2) In the granting of all conditional use permits, consideration shall be given to the cumulative impact of additional requests for like actions in the area. For example, if conditional use permits were granted for other developments in the area where similar circumstances exist, the total of the conditional uses shall also remain consistent with the policies of RCW 90.58.020 and shall not produce substantial adverse effects to the shoreline environment. (3) Other uses which are not classified or set forth in the applicable master program may be authorized as conditional uses provided the applicant can demonstrate consistency with the requirements of this section and the requirements for conditional uses contained in the master program. (4) Uses which are specifically prohibited by the master program may not be authorized pursuant to either subsection (1) or (2) of this section. As noted previously within the above analysis outlined within Conclusion 1, City of Auburn staff believe the project is consistent with the criteria established in WAC 173-27-160. STAFF RECOMMENDATION Based on the application, findings, and conclusions of the Staff report, Staff recommends that the Hearing Examiner APPROVE the Shoreline Conditional Use Permit, subject to the following conditions: 1. The future work associated with the subject Shoreline Conditional Use Permit shall be completed within two years from the effective date of the decision from the Department of Ecology, as specified in WAC 173-27-090. 2. The proposed work shall be substantially consistent with the Civil Plans, prepared by King County, dated February, 2021 (Exhibit 7). 3. The project shall implement the recommendations from the Geomorphic Risk Analysis, prepared by King County, dated December 2, 2020, requiring annual monitoring of the right valley wall downstream. Further, the area shall be monitored after any significant 553 of 721 Staff Member: Dustin Lawrence Date: June 3, 2021 Page 20 of 20 flood events. The findings of the monitoring shall be shared with the City of Auburn. (Exhibit 9). 4. All woody debris resulting from the project, including any trees that are removed but left on site as a result of the rock removals, shall be anchored by a method acceptable to the City’s Public Works Department. 5. The applicant shall secure the necessary floodplain development permit approval(s) from the City of Auburn, if applicable. Staff reserves the right to supplement the record of the case to respond to matters and information raised subsequent to the writing of this report. EXHIBIT LIST Exhibit 1 Staff Report Exhibit 2 Vicinity Map Exhibit 3 City of Auburn Critical Area Inventory Map Exhibit 4 Completed City of Auburn Land Use Application Form, dated February 4, 2021 Exhibit 5 Joint Aquatic Resources Permit Application (JARPA) form, King County, dated July 1, 2020 Exhibit 6 Written Statement, King County, dated April 7, 2021 Exhibit 7 Civil Plans, King County, Department of Natural Resources and Parks, dated February, 2021 Exhibit 8 Critical Areas Report & Floodplain Habitat Impact Assessment, prepared by ESA, dated April, 2021 Exhibit 9 Geomorphic Risk Analysis, prepared by King County, Water and Land Resources Division, dated December 2, 2020 Exhibit 10 Stormwater Site Plan, prepared by King County, dated February 18, 2021 Exhibit 11 Cultural Resources Review Memo, prepared by King County, Department of Natural Resources and Parks, dated May 22, 2020 Exhibit 12 Programmatic SEPA & Environmental Checklists, prepared by King County, dated May 16, 2007; Addendum dated May 14, 2015 Exhibit 13 Notice of Public Hearing (NOH), issued May 14, 2021 Exhibit 14 Public Notice Affidavits and Confirmation of Postings 554 of 721 666.7 NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet Feet666.7333.30 eGIS CDPW 6/1/2021Printed Date: Map Created by City of Auburn eGIS Imagery Date: May 2015 Information shown is for general reference purposes only and does not necessarily represent exact geographic or cartographic data as mapped. The City of Auburn makes no warranty as to its accuracy. 555 of 721 666.7 NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet Feet666.7 Notes Type any additional notes- delete text to leave blank Legend 333.30 1:4,000 eGIS CDPW 1 in =333.3 ft 6/1/2021Printed Date: Map Created by City of Auburn eGIS Imagery Date: May 2015 Information shown is for general reference purposes only and does not necessarily represent exact geographic or cartographic data as mapped. The City of Auburn makes no warranty as to its accuracy. Scale Channel Migration Area (CMA) Riparian Habitat Zones (RHZ) 1995 FIRM Special Flood Hazard Areas (SFHA) 1995 FIRM Floodway Wetlands Priority Habitats and Species Elk Riparian Zones Roosevelt Elk Urban Natural Open Space Waterfowl Concentrations Wetlands Erosion Prone Landslide Hazard 556 of 721 Form Updated: June 2019 MASTER LAND USE APPLICATION FORM Date Received: Physical Address: Auburn City Hall Annex, 2nd Floor 1 E Main St Mailing Address: 25 W Main St Auburn, WA 98001 Webpage & Application Submittal: www.auburnwa.gov applications@auburnwa.gov Phone and Email: 253-931-3090 permitcenter@auburnwa.gov Project Name: Parcel Number(s): APPLICANT Check Box if Primary Contact OWNER Check Box if Primary Contact Name: Name: Title: Title: Company: Company: Email: Email: Address: Address: City: State: Zip: City: State: Zip: Phone: Phone: Signature: Signature: (Signature Required) (Signature Required) AGENT Check Box if Primary Contact ARCHITECT / ENGINEER Check Box if Primary Contact Name: Name: Title: Title: Company: Company: Email: Email: Address: Address: City: State: Zip: City: State: Zip: Phone: Phone: Signature: Signature: (Signature Required) (Signature Required) Brief Description: LAND USE APPROVALS BEING APPLIED FOR UNDER THIS APPLICATION (Check all That Apply) Administrative Appeal Director’s Interpretation Short Plat (Subdivision 9 Lots or Less) Administrative Use Permit Landscape Plan Alteration / Tree Removal Preliminary Administrative Variance Master Sign Plan (New or Adjustment) Final Architectural and Site Design Review Plat (Subdivision Greater Than 9 Lots) Site Plan Approval (Outlet Collection) Multi-Family / Mixed-Use Preliminary Site Plan Approval (Lakeland PUD) DUC Design Review Final Sign Area Deviation Binding Site Plan Adjustment (Major) Special Exception Preliminary Adjustment (Minor) Special Home Occupation Final Extension Temporary Use Permit (See Checklist) Boundary Line Adjustment Real Estate Tax Exemption Type I Boundary Line Elimination SEPA Environmental Review Type II Comp. Plan Map Amendment Special Event Comp. Plan Text Amendment Exemption Variance Conditional Use Permit Substantial Development Zoning Code Text Amendment Critical Areas Variance Zoning Map Amendment (Rezone) Exemption Reasonable Use Variance Shoreline Determination / Study Review Feb. 2020 557 of 721 ORIA-revised 02/2020 Page 1 of 16 AGENCY USE ONLY Date Received: Agency reference #: . Tax Parcel #(s): . . . WASHINGTON STATE Joint Aquatic Resources Permit Application (JARPA) Form 1,2 [help] USE BLACK OR BLUE INK TO ENTER ANSWERS IN THE WHITE SPACES BELOW. Part 1 - Project Identification 1. Project Name (A name for your project that you create. Examples: Smith's Dock or Seabrook Lane Development) [help] Stuck River Drive Revetment Repair and TransCanada Levee Rock Removal Part 2 - Applicant The person and/or organization responsible for the project. [help] 2a. Name (Last, First, Middle) Bloxton, Tom 2b. Organization (if applicable) King County DNRP, River and Floodplain Management Section 2c. Mailing Address (Street or PO Box) 201 S Jackson St, Suite 600 2d. City, State, Zip Seattle, WA 98104-3854 2e. Phone (1) 2f. Phone (2) 2g. Fax 2h. E-mail ( 206 ) 263-6870 ( 206 ) 316-0876 ( ) tbloxton@kingcounty.gov ¹Additional forms may be required for the following permits: • If your project may qualify for Department of the Army authorization through a Regional General Permit (RGP), contact the U.S. Army Corps of Engineers for application information (206) 764-3495. • If your project might affect species listed under the Endangered Species Act, you will need to fill out a Specific Project Information Form (SPIF) or prepare a Biological Evaluation. Forms can be found at http://www.nws.usace.army.mil/Missions/CivilWorks/Regulatory/PermitGuidebook/EndangeredSpecies.aspx. • Not all cities and counties accept the JARPA for their local Shoreline permits. If you need a Shoreline permit, contact the appropriate city or county government to make sure they accept the JARPA. ²To access an online JARPA form wth [help] screens, go to http://www.epermitting.wa.gov/site/alias__resourcecenter/jarpa_jarpa_form/9984/jarpa_form.aspx. For other help, contact the Governor's Office for Regulatory Innovation and Assistance at (800) 917-0043 or help@oria.wa.gov. 558 of 721 ORIA-revised 02/2020 Page 2 of 16 Part 3 - Authorized Agent or Contact Person authorized to represent the applicant about the project. (Note: Authorized agent(s) must sign 11b of this application.) [help] 3a. Name (Last, First, Middle) Bloxton, Tom 3b. Organization (if applicable) King County DNRP, River and Floodplain Management Section 3c. Mailing Address (Street or PO Box) 201 S Jackson St, Suite 600 3d. City, State, Zip Seattle, WA 98104-3854 3e. Phone (1) 3f. Phone (2) 3g. Fax 3h. E-mail ( 206 ) 263-6870 ( 206 ) 316-0876 ( ) tbloxton@kingcounty.gov Part 4 - Property Owner(s) Contact information for people or organizations owning the property(ies) where the project will occur. Consider both upland and aquatic ownership because the upland owners may not own the adjacent aquatic land. [help] Same as applicant. (Skip to Part 5.) Repair or maintenance activities on existing rights-of-way easements. (Skip to Part 5.) There are multiple upland property owners. Complete the section below and fill out JARPA Attachment A for each additional property owner. Your project is on Department of Natural Resources (DNR)-managed aquatic lands. If you don't know, contact the DNR at (360) 902-1100 to determine aquatic land ownership. If yes, complete JARPA Attachment E to apply for the Aquatic Use Authorization. 4a. Name (Last, First, Middle) Backus, Nancy 4b. Organization (if applicable) City of Auburn 4c. Mailing Address (Street or PO Box) 25 West Main St. 4d. City, State, Zip Auburn, WA 98001 4e. Phone (1) 4f. Phone (2) 4g. Fax 4h. E-mail ( 253 ) 931-3041 ( ) ( ) 559 of 721 ORIA-revised 02/2020 Page 3 of 16 Part 5 - Project Location(s) Identifying information about the property or properties where the project will occur. [help] There are multiple project locations (e.g. linear projects). Complete the section below and use JARPA Attachment B for each additional project location. 5a. Indicate the type of ownership of the property. (Check all that apply.) [help] Private Federal Publicly owned (state, county, city, special districts like schools, ports, etc.) Tribal Department of Natural Resources (DNR) - managed aquatic lands (Complete JARPA Attachment E) 5b. Street Address (Cannot be a PO Box. If there is no address, provide other location information in 5p.) [help] 5c. City, State, Zip (If the project is not in a city or town, provide the name of the nearest city or town.) [help] Auburn, WA 5d. County [help] King 5e. Provide the section, township, and range for the project location. [help] ¹/₄ Section Section Township Range SW 1/4 29 21 N 05 E 5f. Provide the latitude and longitude of the project location. [help] ● Example: 47.03922 N lat. / -122.89142 long. (Use decimal degrees - NAD 83) 47.276 / -122.203 5g. List the tax parcel number(s) for the project location. [help] ● The local county assessor's office can provide this information. 292105HYDR, 2921059069 5h. Contact information for all adjoining property owners. (If you need more space, use JARPA Attachment C.) [help] Name Mailing Address Tax Parcel # (if known) 560 of 721 ORIA-revised 02/2020 Page 4 of 16 5i. List all wetlands on or adjacent to the project location. [help] 5j. List all waterbodies (other than wetlands) on or adjacent to the project location. [help] 5k. Is any part of the project area within a 100-year floodplain? [help] Yes No Don't know 5l. Briefly describe the vegetation and habitat conditions on the property. [help] 5m. Describe how the property is currently used. [help] 5n. Describe how the adjacent properties are currently used. [help] 5o. Describe the structures (above and below ground) on the property, including their purpose(s) and current condition. [help] 5p. Provide driving directions from the closest highway to the project location, and attach a map. [help] From Auburn City Center: - Head south on A St SE toward 1st St SE for 1.7 mi - Turn left onto 29th St SE and drive 1.0 mi - Turn right onto R St SE and drive 0.6 mi - Turn left onto Stuck River Dr and drive 0.2 mi 561 of 721 ORIA-revised 02/2020 Page 5 of 16 Part 6 - Project Description 6a. Briefly summarize the overall project. You can provide more detail in 6b. [help] Stuck River Site: In Year 1 (2020), repair up to 210 lineal feet of an existing rock revetment along Stuck River Drive on the White River, between river mile 7.8 and 7.9. Erosion of rock during high flows damaged the existing revetment, compromising its function and integrity. Up to four trees may need to be cut in order to repair the revetment – this will be determined during construction. The proposed trees to be removed are two 4 inch diameter deciduous, a 6 inch diameter conifer and a multi- stemmed conifer with two 4 inch diameter stems (see sheet 3 of the drawings). Some of the larger trees on the project site may be limbed partially by an arborist to allow excavator access for rock placement. Up to 290 cubic yards of rock (four- or five-man and light loose riprap) will be placed below OHW to stabilize discontinuous toe rock, repair bank armor, and fill voids. Some light loose riprap (up to 40 CY) will also be placed where necessary above OHW, as directed by the Engineer. The revetment will be repaired within its original footprint with no waterward or landward expansion. One or two rows of native willows will be planted above OHW with a spacing of no more than 18 inches. Up to thirty-one native trees and 158 shrubs will also be planted within the project site with a spacing of 8-10 feet for trees and 4-6 feet for shrubs. A minimum of 80% survival of native trees and shrubs will be maintained for at least three years. Willow stakes will not be included in survival counts. Invasive plants and large pieces of concrete will be removed from the project site to improve riparian habitat conditions. An excavator will be used to break up the concrete pieces to facilitate transport away from the site. TransCanada Site: The TransCanada Rock Removal project is located at the remnant upstream end of the TransCanada Levee, approximately River Mile (RM) 9.3. The goal at this site is to restore riverine processes and functions in the Lower White River and its floodplain in order to enhance riparian habitat for salmonids and additional species. In Year 2 (2021), the project will remove as much rock as possible from the levee face while protecting the significant trees. The project will extend from the upstream, eroded end of the levee and conclude approximately 400 feet downstream. As practical operating from the bank, angular face rock from the eroded levee will be removed from the channel. Extensive excavation to locate buried riprap will not take place. Light regrading of the slope after riprap removal will take place at the direction of the project representative to help in the restoration planting process. The trees have been identified in three tiers: Tier 1 – Do not remove, establish a buffer area around the tree within which rock removal is very selective and will not damage tree, Tier 2 – Do not remove tree, no buffer area, extensive rock removal without complete destabilization of the trees, and Tier 3 – Remove as much rock as possible including potential to push over trees and leave onsite if needed for access or rock removal. If possible, these Tier 3 trees will be left standing but rock removal around them is the primary goal. Generally the largest trees are identified as Tier 1 and the smallest being Tier 3, however the large trees at the upstream end closest to the river will be pushed over to remove as much rock as possible to facilitate access for in-channel riprap removal. Both Sites: More rock will be exported from both sites combined than will be imported to the Stuck River Site. Calculations based on tonnage will be made to determine amount of rock imported/exported to/from the Stuck River Site in Year 1. In Year 2, tonnage calculations will be made to determine amount of rock exported from TransCanada. To compensate for the one year temporal lag between projects, King County will export at least 20% more rock overall than is imported to Stuck River. 6b. Describe the purpose of the project and why you want or need to perform it. [help] 562 of 721 ORIA-revised 02/2020 Page 6 of 16 6c. Indicate the project category. (Check all that apply.) [help] Commercial Residential Institutional Transportation Recreational Maintenance Environmental Enhancement 6d. Indicate the major elements of your project. (Check all that apply.) [help] Aquaculture Culvert Float Retaining Wall Bank Stabilization Dam / Weir Floating Home (upland) Boat House Dike / Levee / Jetty Geotechnical Survey Road Boat Launch Ditch Land Clearing Scientific Boat Lift Dock / Pier Marina / Moorage Measurement Device Bridge Dredging Mining Stairs Bulkhead Fence Outfall Structure Stormwater Facility Buoy Ferry Terminal Piling / Dolphin Swimming Pool Channel Modification Fishway Raft Utility Line Other: 6e. Describe how you plan to construct each project element checked in 6d. Include specific construction methods and equipment to be used. [help] ● Identify where each element will occur in relation to the nearest waterbody. ● Indicate which activities are within the 100-year floodplain. 563 of 721 ORIA-revised 02/2020 Page 7 of 16 All project elements occur within or just outside of the 100-year floodplain and are within, or immediately adjacent to, the White River. General Construction Notes: 1) The drive mechanisms (wheels, tracks, tires, etc.) shall not enter or operate waterward of the wetted perimeter. 2) All gas and oil containers for small equipment will be stored securely in utility vehicles. 3) All toe rock placed shall be clean fractured 4-5 man rock. 4) Fill all voids with light loose riprap or quarry spalls as directed by the engineer. 5) All fill is to be placed within pre-damage levee footprint, within 1.5H:1V levee slope below existing crest as shown in drawings. Construction Sequencing Notes: 1) Attend pre-construction meeting and notify permit authorities before starting construction. 2) Implement the TESC plan. See drawings. 3) Remove guardrail in Stuck River project area for machinery access. Remove (grub) invasive vegetation and dispose in landfill. 4) Using excavator, place clean 4-5 man rock (as shown in the drawings) at Stuck River damage sites. Engineer will field direct the placement of the toe rock. Do not extend the toe into the channel beyond the toe alignment staked by the engineer. 5) Using excavator, place toe rock with longest dimension parallel to the river and minimize potential for rolling. Embed the toe rock into riverbank to stabilize. 6) Place light loose riprap bedding for 4-5 man rock and fill voids with light loose riprap. 7) Place light loose riprap with willow stakes from OHW to transition to intact upper slope. 8) Disturbed upper areas shall be backfilled with native material or common borrow with topsoil, and native plant stakes installed where vegetation was removed at the direction of the field engineer. 9) Match repaired bank to the slope of the adjacent undamaged portions of the revetment at upstream and downstream ends. 10) Following construction, remove TESC features and seed disturbed areas. 11) Restore guardrail and trail to original condition. 12) Tree and shrub planting at both sites to be completed by others, following construction. 6f. What are the anticipated start and end dates for project construction? (Month/Year) [help] ● If the project will be constructed in phases or stages, use JARPA Attachment D to list the start and end dates of each phase or stage. Start Date: . End Date: . See JARPA Attachment D 6g. Fair market value of the project, including materials, labor, machine rentals, etc. [help] 6h. Will any portion of the project receive federal funding? [help] ● If yes, list each agency providing funds. Yes No Don't know Part 7 - Wetlands: Impacts and Mitigation Check here if there are wetlands or wetland buffers on or adjacent to the project area. (If there are none, skip to Part 8) [help] 7a. Describe how the project has been designed to avoid and minimize adverse impacts to wetlands. [help] Not applicable 564 of 721 ORIA-revised 02/2020 Page 8 of 16 7b. Will the project impact wetlands? [help] Yes No Don't know 7c. Will the project impact wetland buffers? [help] Yes No Don't know 7d. Has a wetland delineation report been prepared? [help] ● If Yes, submit the report, including data sheets, with the JARPA package. Yes No 7e. Have the wetlands been rated using the Western Washington or Eastern Washington Wetland Rating System? [help] ● If Yes, submit the wetland rating forms and figures with the JARPA package. Yes No Don't know 7f. Have you prepared a mitigation plan to compensate for any adverse impacts to wetlands? [help] ● If Yes, submit the plan with the JARPA package and answer 7g. ● If No, or Not applicable, explain below why a mitigation plan should not be required. Yes No Not applicable 7g. Summarize what the mitigation plan is meant to accomplish, and describe how a watershed approach was used to design the plan. [help] 7h. Use the table below to list the type and rating of each wetland impacted, the extent and duration of the impact, and the type and amount of mitigation proposed. Or if you are submitting a mitigation plan with a similar table, you can state (below) where we can find this information in the plan. [help] 565 of 721 ORIA-revised 02/2020 Page 9 of 16 Activity (fill, drain, excavate, flood, etc.) Wetland Name¹ Wetland type and rating category² Impact area (sq. ft. or Acres) Duration of Impact³ Proposed mitigation type⁴ Wetland mitigation area (sq. ft. or acres) ¹ If no official name for the wetland exists, create a unique name (such as “Wetland 1”). The name should be consistent with other project documents, such as a wetland delineation report. ² Ecology wetland category based on current Western Washington or Eastern Washington Wetland Rating System. Provide the wetland rating forms with the JARPA package. ³ Indicate the days, months or years the wetland will be measurably impacted by the activity. Enter “permanent” if applicable. ⁴ Creation (C), Re-establishment/Rehabilitation (R), Enhancement (E), Preservation (P), Mitigation Bank/In-lieu fee (B) Page number(s) for similar information in the mitigation plan, if available: . 7i. For all filling activities identified in 7h, describe the source and nature of the fill material, the amount in cubic yards that will be used, and how and where it will be placed into the wetland. [help] 7j. For all excavating activities identified in 7h, describe the excavation method, type and amount of material in cubic yards you will remove, and where the material will be disposed. [help] Part 8 - Waterbodies (other than wetlands): Impacts and Mitigation In Part 8, “waterbodies” refers to non-wetland waterbodies. (See Part 7 for information related to wetlands.) [help] Check here if there are waterbodies on or adjacent to the project area. (If there are none, skip to Part 9.) 8a. Describe how the project is designed to avoid and minimize adverse impacts to the aquatic environment. 566 of 721 ORIA-revised 02/2020 Page 10 of 16 [help] Not applicable Erosion and sedimentation controls will be installed prior to ground disturbing activities, as needed. TESC Notes: 1) Work shall be done in accordance with all applicable permits, including a consistent schedule with hydraulic project approval conditions. 2) In-water work will be limited to placement and stabilization of toe rock. The only excavation that will occur in- water will be manipulating existing rock in order to place new rock. Some of the existing rock will be moved higher on the bank as light loose riprap. 3) Only clean fractured rock will be placed in water. 4) The following materials shall be on-site or readily accessible during all construction activities: straw bales for slope mulching, high visibility fence, and straw wattles. 5) The TESC measures must be installed and maintained in such a manner to ensure that sediment laden water does not enter the river or violate applicable water quality standards. 6) When possible, native vegetation shall be left in place and care shall be taken to minimize damage to established vegetation. 7) Provide and maintain a spill cleanup kit for fuel and hydraulic oil spills. 8) Any area of exposed soils that will not be disturbed for two days during the wet season or seven days during the dry season shall be immediately stabilized with approved TESC cover methods. 9) All equipment working at or below OHW shall be equipped with biodegradable hydraulic fluids. 10) Protect all trees unless marked for removal, per Engineer’s direction. A turbidity curtain will not be used as an erosion and sedimentation control since flows are too deep/fast adjacent to the repair site for turbidity curtain installation, and the only excavation that will occur below OHW is manipulation of existing rock described in number 2 above. The drive mechanisms of heavy construction equipment (excavator) will remain landward of the OHW mark. The upper part of the Stuck River repair will have live willow stakes and other trees/shrubs planted and covered with mulch. The portion of the repair closest to the road will also be seeded with native grasses to minimize future erosion. This is anticipated to produce a more ecologically beneficial riparian condition than a standard rock revetment. The disturbed areas of the TransCanada site will have native trees/shrubs planted after rock removal. All trees removed for this project will be placed in the riparian area to serve as terrestrial habitat. 8b. Will your project impact a waterbody or the area around a waterbody? [help] Yes No 8c. Have you prepared a mitigation plan to compensate for the project’s adverse impacts to non-wetland waterbodies? [help] ● If Yes, submit the plan with the JARPA package and answer 8d. ● If No, or Not applicable, explain below why a mitigation plan should not be required. Yes No Not applicable Mitigation for the Stuck River revetment repair will be provided both on-site and off-site at the TransCanada Site. At Stuck River, we will remove large riprap from the upper bank and establish a willow buffer and enhance riparian vegetation with the addition of native trees and shrubs along the revetment as described in the project drawings. This will help enhance shade, leaf litter, and large wood input to the river over time. Removed trees will be placed in the river to be transported downstream as potential habitat elements. Where feasible, the rootwad will be kept intact. If a tree must be cut and produce a stump, the stump and root wad will be placed in the river separately during the revetment repair. These cut trees will not be anchored or backfilled in the river in any way. 567 of 721 ORIA-revised 02/2020 Page 11 of 16 Invasive species, such as Himalayan blackberry, will be removed as a part of this project. The establishment of native willows and other trees and shrubs will discourage future growth of invasive species. Various large portions of concrete that were placed on the revetment in the past will be removed as they are not needed for the function of the revetment and their removal will improve natural riparian habitat conditions. The large riprap removed from the upper bank may be reused in part below OHWM for the toe repair. The TransCanada project will provide additional (off-site) mitigation for the Stuck River Repair. Levee rock extending up to 400 feet of length will be removed to facilitate return of natural riverine processes. While the decision was made to leave some rock in place that is associated with large riparian trees (Tier 1 trees), a significant amount of rock within this length will be removed. Once this rock is removed, planting of native trees and shrubs will occur in an area currently void of an understory due to presence of large rock. 8d. Summarize what the mitigation plan is meant to accomplish. Describe how a watershed approach was used to design the plan.[help] ● If you already completed 7g you do not need to restate your answer here. [help] 8e. Summarize impact(s) to each waterbody in the table below. [help] Activity (clear, dredge, fill, pile drive, etc.) Waterbody name¹ Impact location² Duration of impact³ Amount of material (cubic yards) to be placed in or removed from waterbody Area (sq. ft. or linear ft.) of waterbody directly affected ¹ If no official name for the waterbody exists, create a unique name (such as “Stream 1”) The name should be consistent with other documents provided. ² Indicate whether the impact will occur in or adjacent to the waterbody. If adjacent, provide the distance between the impact and the waterbody and indicate whether the impact will occur within the 100-year flood plain. ³ Indicate the days, months or years the waterbody will be measurably impacted by the work. Enter “permanent” if applicable. 8f. For all activities identified in 8e, describe the source and nature of the fill material, amount (in cubic yards) you will use, and how and where it will be placed into the waterbody. [help] At Stuck River, up to 190 cubic yards of four- or five-man rock will be imported to the site and placed along the river bank as bank armoring. Up to 140 cubic yards of light loose riprap and/or quarry spalls will be imported to bed the revetment face armoring. Up to 80 cubic yards of topsoil and mulch may be imported to improve growing substrate in the willow buffers and upper slope planting areas. These fill materials will likely be imported from a nearby quarry. 8g. For all excavating or dredging activities identified in 8e, describe the method for excavating or dredging, type and amount of material you will remove, and where the material will be disposed. [help] 568 of 721 ORIA-revised 02/2020 Page 12 of 16 A large excavator will be used to remove, transport and place materials as needed. The material staging area will be on the existing public trail and portion of the road, atop the revetment at Stuck River. The only excavation that will take place below the OHW elevation is the manipulation of existing rock to facilitate placement of new rock at the bottom of the slope. Material contaminated with invasive species will be segregated and hauled to an approved upland disposal site. Large rock removed TransCanada will be transported at an approved upland facility. Part 9 - Additional Information Any additional information you can provide helps the reviewer(s) understand your project. Complete as much of this section as you can. It is ok if you cannot answer a question. 9a. If you have already worked with any government agencies on this project, list them below. [help] Agency Name Contact Name Phone Most Recent Date of Contact ( ) ( ) ( ) 9b. Are any of the wetlands or waterbodies identified in Part 7 or Part 8 of this JARPA on the Washington Department of Ecology’s 303(d) List? [help] ● If Yes, list the parameter(s) below. ● If you don’t know, use Washington Department of Ecology’s Water Quality Assessment tools at: http://www.ecy.wa.gov/programs/wq/303d/. Yes No 9c. What U.S. Geological Survey Hydrological Unit Code (HUC) is the project in? [help] ● Go to http://cfpub.epa.gov/surf/locate/index.cfm to help identify the HUC. 9d. What Water Resource Inventory Area Number (WRIA #) is the project in? [help] ● Go to http://www.ecy.wa.gov/services/gis/maps/wria/wria.htm to find the WRIA #. 9e. Will the in-water construction work comply with the State of Washington water quality standards for turbidity? [help] 569 of 721 ORIA-revised 02/2020 Page 13 of 16 ● Go to http://www.ecy.wa.gov/programs/wq/swqs/criteria.html for the standards. Yes No Not Applicable 9f. If the project is within the jurisdiction of the Shoreline Management Act, what is the local shoreline environment designation? [help] ● If you don’t know, contact the local planning department. ● For more information, go to: http://www.ecy.wa.gov/programs/sea/sma/laws_rules/173-26/211_designations.html. Rural Urban Natural Aquatic Conservancy Other: 9g. What is the Washington Department of Natural Resources Water Type? [help] ● Go to http://www.dnr.wa.gov/BusinessPermits/Topics/ForestPracticesApplications/Pages/fp_watertyping.aspx for the Forest Practices Water Typing System. Shoreline Fish Non-Fish Perennial Non-Fish Seasonal 9h. Will this project be designed to meet the Washington Department of Ecology’s most current stormwater manual? [help] ● If No, provide the name of the manual your project is designed to meet. Yes No Name of manual: 9i. Does the project site have known contaminated sediment? [help] ● If Yes, please describe below: Yes No 9j. If you know what the property was used for in the past, describe below. [help] 9k. Has a cultural resource (archaeological) survey been performed on the project area? [help] ● If Yes, attach it to your JARPA package. Yes No 9l. Name each species listed under the federal Endangered Species Act that occurs in the vicinity of the project area or might be affected by the proposed work. [help] 570 of 721 ORIA-revised 02/2020 Page 14 of 16 9m. Name each species or habitat on the Washington Department of Fish and Wildlife’s Priority Habitats and Species List that might be affected by the proposed work. [help] Part 10 - SEPA Compliance and Permits Use the resources and checklist below to identify the permits you are applying for. • Online Project Questionnaire at http://apps.oria.wa.gov/opas/. • Governor’s Office for Regulatory Innovation and Assistance at (800) 917-0043 or help@oria.wa.gov. • For a list of addresses to send your JARPA to, click on agency addresses for completed JARPA. 10a. Compliance with the State Environmental Policy Act (SEPA). (Check all that apply.) [help] • For more about SEPA, go to www.ecy.wa.gov/programs/sea/sepa/e-review.html A copy of the SEPA determination or letter of exemption is included with this application. A SEPA determination is pending with King County Water and Land Resources Division (lead agency). The expected decision date is 05/28/2020 . I am applying for a Fish Habitat Enhancement Exemption. (Check the box below in 10b) [help] This project is exempt (choose type of exemption below). Categorical Exemption. Under what section of the SEPA administrative code (WAC) is it exempt? . Other: SEPA is pre-empted by federal law. 10b. Indicate the permits you are applying for. (Check all that apply.) [help] LOCAL GOVERNMENT 571 of 721 ORIA-revised 02/2020 Page 15 of 16 Local Government Shoreline permits: Substantial Development Conditional Use Variance Shoreline Exemption Type (explain): . Other City/County permits: Floodplain Development Permit Critical Areas Ordinance STATE GOVERNMENT Washington Department of Fish and Wildlife: Hydraulic Project Approval (HPA) Fish Habitat Enhancement Exemption - Attach Exemption Form Washington Department of Natural Resources: Aquatic Use Authorization Complete JARPA Attachment E and submit a check for $25 payable to the Washington Department of Natural Resources. Do not send cash. Washington Department of Ecology: Section 401 Water Quality Certification Non-Federally Regulated Waters FEDERAL AND TRIBAL GOVERNMENT United States Department of the Army permits (U.S. Army Corps of Engineers): Section 404 (discharges into waters of the U.S.) Section 10 (work in navigable waters) United States Coast Guard: For projects or bridges over waters of the United States, contact the U.S. Coast Guard at: d13-pf-d13bridges@uscg.mil Bridge Permit Private Aids to Navigation (or other non-bridge projects) United States Environmental Protection Agency: Section 401 Water Quality Certification (discharges into waters of the U.S.) on tribal lands where tribes do not have treatment as a state (TAS) Tribal Permits: (Check with the tribe to see if there are other tribal permits, e.g., Tribal Environmental Protection Act, Shoreline Permits, Hydraulic Project Permits, or other in addition to CWA Section 401 WQC) Section 401 Water Quality Certification (discharges into waters of the U.S.) where the tribe has treatment as a state (TAS). 572 of 721 ORIA-revised 02/2020 Page 16 of 16 Part 11 - Authorizing Signature Signatures are required before submitting the JARPA package. the JARPA package includes the JARPA form, project plans, photos, etc. [help] 11a. Applicant Signature (required) [help] I certify that to the best of my knowledge and belief, the information provided in this application is true, complete, and accurate. I also certify that I have the authority to carry out the proposed activities, and I agree to start work only after I have received all necessary permits. I hereby authorize the agent named in Part 3 of this application to act on my behalf in matters related to this application. (Initial) By initialing here, I state that I have the authority to grant access to the property. I also give my consent to the permitting agencies entering the property where the project is located to inspect the project site or any work related to the project. (Initial) Tom Bloxton 7/1/2020 Applicant Printed Name Applicant Signature Date I certify that to the best of my knowledge and belief, the information provided in this application is true, complete, and accurate. I also certify that I have the authority to carry out the proposed activities and I agree to start work only after all necessary permits have been issued. Tom Bloxton 7/1/2020 Authorized Agent Printed Name Authorized Agent Signature Date 11c. Property Owner Signature (if not applicant). [help] Not required if project is on existing rights-of-way or easements. I consent to the permitting agencies entering the property where the project is located to inspect the project site or any work. These inspections shall occur at reasonable times and, if practical, with prior notice to the landowner. Nancy Backus Property Owner Printed Name Property Owner Signature Date 18 U.S.C 1001 provides that: Whoever, in any manner within the jurisdiction of any department of agency of the United States knowingly falsifies, conceals, or covers up any trick, scheme, or devise a material fact or makes any false, fictitious, or fraudulent statements or representations or makes or uses any false writing or document knowing same to contain any false, fictitious, or fraudulent statement or entry, shall be fined not more than $10,000 or imprisoned not more than 5 years or both. If you require this document in another format, contact the Governor's Office for Regulatory Innovation and Assistance (ORIA) at (800) 917-0043. People with hearing loss can call 711 for Washington Relay Service. People with a speech disability can call (877) 833-6341. ORIA publication number: ENV-019-09 rev. 09/2015 573 of 721 Written Statement for TransCanada Levee Rock Removal Project: 1. The shoreline designation for the TransCanada Levee project site is Natural. 2. The water body at the project site is the White River. 3. The project will remove as much rock as possible from the levee face using an excavator while protecting the significant trees. The project will extend from the upstream, eroded end of the levee and conclude approximately 400 feet downstream. As practical operating from the bank with an excavator, angular face rock from the eroded levee will be removed from the channel. Extensive excavation to locate buried riprap will not take place. Light regrading of the slope after riprap removal will take place at the direction of the project representative to help in the restoration planting process. The trees have been identified in three tiers: Tier 1 – Do not remove, establish a buffer area around the tree within which rock removal is very selective and will not damage tree, Tier 2 – Do not remove tree, no buffer area, extensive rock removal without complete destabilization of the trees, and Tier 3 – Remove as much rock as possible including potential to push over trees and leave onsite if needed for access or rock removal. If possible, these Tier 3 trees will be left standing but rock removal around them is the primary goal. Generally the largest trees are identified as Tier 1 and the smallest being Tier 3, however the large trees at the upstream end closest to the river will be pushed over to remove as much rock as possible to facilitate access for in-channel riprap removal. The disturbed areas of the TransCanada site will have native trees/shrubs planted after rock removal. All trees removed for this project will be placed in the riparian area to serve as terrestrial habitat. Levee rock extending up to 400 feet of length will be removed to facilitate return of natural riverine processes. While the decision was made to leave some rock in place that is associated with large riparian trees (Tier 1 trees), a significant amount of rock within this length will be removed. Once this rock is removed, planting of native trees and shrubs will occur in an area currently void of an understory due to presence of large rock. Large rock removed TransCanada will be transported at an approved upland facility. 4. The TransCanada Levee Rock Removal project is located at the remnant upstream end of the TransCanada Levee, approximately River Mile (RM) 9.3 on, parcel 282105-9007. This parcel is owned by King County River and Floodplain Management and is located within the boundaries of both the Muckleshoot Indian Tribe (MIT) reservation and the City of Auburn. The levee extends from RM 8.2 to 9.3 and was constructed in the late 1950’s. The current levee alignment restricts the river to a channelized section pushed up against the bluff to the north. The waterward side of the levee is composed of riprap and naturally-colonized trees and shrubs including Douglas-fir, black cottonwood, bigleaf maple, snowberry, swordfern, and various mosses. There are no buildings or improved structures on the levee. 5. Within 1,000 feet of the project area little development and the habitat is primarily mature riparian forest with dirt roads used for access by Tribal members. To the northeast there is a residential housing area across the river atop the bluff approximately 500 feet from the levee. 574 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38VICINITY MAP AND SHEET INDEX1SHEET INDEXVICINITY MAPAUBURNPROJECTAREASHEETDESCRIPTIONTRANSCANADA LEVEE ROCK REMOVALLAT: 47.28, LONG: -122.18WHITE RIVER RM 9.3ASSOCIATED PROJECT PERMITS:EARTHWORK QUANTITIESOWNER CONTACT INFORMATION:LEGAL AND SURVEY DESCRIPTION:CITY OF AUBURN GENERAL CONSTRUCTION NOTES:’“” ’’’“” HAUL ROUTE NOTES:CONSTRUCTION SEQUENCE NOTES:STORM SYSTEM DEVELOPMENT CHARGESTORM PERMITCITY OF AUBURN PERMITS:CITY OF AUBURN APPROVALS575 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38ACCESS AND TRAFFIC CONTROL PLAN2NOTE:ACCESS AND TRAFFIC CONTROL NOTES:LEGEND:576 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38EXISTING CONDITIONS AND TESC PLAN3LEGEND:TEMPORARY EROSION AND SEDIMENT CONTROL (TESC)NOTES:BASEMAP NOTES:577 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38PROPOSED DESIGN PLAN4B 6 GENERAL CONSTRUCTION NOTES:CONSTRUCTION SEQUENCING NOTES:LEGEND:A6 578 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38PROPOSED GRADING PLAN5GENERAL GRADING NOTES:LEGEND:579 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38TYPICAL SECTIONS6NOTES:580 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38TESC DETAILS7STRAW WATTLE NOTES:TEMPORARY CONSTRUCTION ENTRANCE NOTES:581 of 721 T T T T T T TTTTT TT T T T T T T T TT T T T T T T T T TT T T T T T T T T T T T T T T T T T T T T T TT TTTTTTTTTTTTTTTTTTTTTTT TKnow what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANSCANADA LEVEE ROCK REMOVALWHITE RIVER RM 9.38PLANTING PLAN8GENERAL PLANTING NOTES:T LEGENDPLAN VIEW582 of 721 KING COUNTY TRANSCANADA LEVEE ROCK REMOVAL Critical Areas Report and Floodplain Habitat Impact Assessment Prepared for April 2021 King County Water and Land Resources Contract: E00673E20 583 of 721 584 of 721 KING COUNTY TRANSCANADA LEVEE ROCK REMOVAL Critical Areas Report and Floodplain Habitat Impact Assessment Prepared for April 2021 King County Water and Land Resources Contract: E00673E20 5309 Shilshole Avenue NW Suite 200 Seattle, WA 98107 206.789.9658 esassoc.com Bend Camarillo Delray Beach Destin Irvine Los Angeles Oakland Orlando Pasadena Petaluma Portland Sacramento San Diego San Francisco San Jose Santa Monica Sarasota Seattle Tampa 585 of 721 586 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal i ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 TABLE OF CONTENTS Critical Areas Report and Floodplain Habitat Impact Assessment Page 1.0 PROJECT AUTHORIZATION, SCOPE OF WORK, AND QUALIFICATIONS .............. 1 2.0 PROJECT OVERVIEW AND DESCRIPTION ................................................................. 2 2.1 Site Description ....................................................................................................... 2 2.2 Project Description .................................................................................................. 2 3.0 EXISTING DOCUMENTATION ....................................................................................... 3 3.1 Wetlands ................................................................................................................. 3 3.2 Streams ................................................................................................................... 3 3.3 Wildlife Habitat ........................................................................................................ 4 3.4 Aquifer Recharge Areas .......................................................................................... 5 3.5 Flood Hazard Areas ................................................................................................ 5 4.0 RESULTS OF FIELD INVESTIGATION .......................................................................... 6 4.1 Streams ................................................................................................................... 6 4.2 Wildlife Habitat ........................................................................................................ 6 5.0 Project Impacts ............................................................................................................... 7 5.1 Stream Impacts ....................................................................................................... 8 5.2 Wildlife Habitat Impacts .......................................................................................... 8 6.0 LIMITATIONS ................................................................................................................ 14 7.0 REFERENCES AND BIBLIOGRAPHY ......................................................................... 15 Appendices A. Design Sheets .............................................................................................................. A-1 B. USFWS and NMFS Species Lists ............................................................................... B-1 List of Figures Figure 1 Vicinity Map Figure 2 Ordinary High Water Mark, Shoreline Jurisdiction, Stream Buffer, and Riparian Habitat Zone List of Tables Table 1. Listed Fish Species Potentially Present in the Project Vicinity ................................... 5 587 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanda Levee Rock Removal ii ESA / D202000663.03 Critical Areas and Report and Floodplain Habitat Impact Assessment April 2021 588 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 1 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 KING COUNTY TRANSCANADA LEVEE ROCK REMOVAL Critical Areas Report and Floodplain Habitat Impact Assessment 1.0 PROJECT AUTHORIZATION, SCOPE OF WORK, AND QUALIFICATIONS King County (County) is proposing to remove riprap from a portion of levee located along the White River as it flows through City of Auburn, Washington. At the request of the County, Environmental Science Associates (ESA) delineated wetland and stream ordinary high water mark boundaries, assessed habitat and the floodplain, and prepared this technical report for the proposed project. This Critical Areas Report and Floodplain Habitat Impact Assessment is organized to meet the requirements of the City of Auburn (City) Municipal Code (AMC), Chapter 16.10 – Critical Areas and Chapter 15.68 – Flood Hazard Areas. This report was primarily authored by Scott Olmsted. Scott meets the requirements of a “qualified consultant” to conduct stream and floodplain investigations as defined under AMC 16.10.020. He holds a Master’s degree in Urban Horticulture and has worked on wetlands, streams, and wildlife habitat projects in western Washington for over 14 years. Jessica Redman accompanied Scott during the field investigation and did not observe wetlands onsite. Jessica is registered with the Society of Wetland Scientists as a Professional Wetland Scientist (PWS) and has documented wetland, stream, and wildlife habitat for over 13 years. 589 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 2 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 2.0 PROJECT OVERVIEW AND DESCRIPTION King County’s River and Floodplain Management Section is planning to remove levee riprap to restore riverine processes and functions in the White River and its floodplain in order to enhance riparian habitat for salmonids and other species. The project will occur on King County Tax Parcel 2821059007, which is located north of Stuck River Drive on the Muckleshoot Indian Reservation (Figure 1). The project area is located within the White River Watershed, in the northwestern portion of WRIA 10 (Puyallup-White) (see Figures 1 and 2 for project area). The County anticipates the project to require several state and local permits including, Hydraulic Project Approval issued by the Washington State Department of Fish and Wildlife (WDFW) and Floodplain Development Permit and Shoreline Conditional Use Permit issued by the City of Auburn. 2.1 Site Description The project area is located within Auburn city limits on the Muckleshoot Indian Tribe reservation. The property is undeveloped and composed primarily of coniferous forest and deciduous riparian forest (Figure 2 and Photos). A dirt, vehicle access road on top of the TransCanada levee roughly parallels the river alignment. The earthen, left bank levee is armored with 1 to 2-foot diameter rock and forested with Douglas-fir (Pseudotsuga menziesii) and Western hemlock (Tsuga heterophylla). 2.2 Project Description The TransCanada Levee Rock Removal project is located at the remnant upstream end of the TransCanada Levee at approximately River Mile (RM) 9.3. The project will extend from the upstream, eroded end of the levee and conclude approximately 400 feet downstream as shown on the project design sheets (Appendix A). In 2021, the project will remove rock as shown on the design sheets from the levee face while protecting mature trees; tree removal is discussed in detail under Section 5.2—Wildlife Habitat Impacts. Limited regrading of the levee slope after riprap removal will take place at the direction of the project representative to help in the restoration planting process. Downed trees will be retained onsite and native woody plants will be installed within the project area. The project also proposes to remove a limited number of rocks that have fallen into the river channel at the eastern end of the project area. For this work, equipment will operate from outside the wetted channel to remove angular rock and will be limited to discrete locations where rock has fallen into the channel; extensive excavation to locate buried riprap will not take place. 590 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 3 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 3.0 EXISTING DOCUMENTATION Wetlands, streams (and rivers)1, wildlife habitat, aquifer recharge areas, and geologically hazardous areas are regulated by the City through their critical areas ordinance, AMC 16.10. Flood hazard areas are regulated separately under AMC 15.68. Geologically hazardous areas are not mapped in the study area and are not discussed further (City of Auburn, 2019 and King County, 2020, respectively) (see Figure 2 for the study area). 3.1 Wetlands Prior to conducting a field investigation on November 8, 2020, Environmental Science Associates reviewed National Wetlands Inventory (NWI) maps, soils maps from the Natural Resources Conservation Service (NRCS), and County critical area inventories to obtain an initial indication of site conditions. The NWI map shows a seasonally flooded, riverine wetland located between the levee and the river (USFWSa, 2020). Natural Resources Conservation Service mapped one non-hydric soil type in the study area (NRCS, 2020). The area southwest of the levee is mapped as Mixed Alluvial Land, which is a well-drained soil. King County’s iMap does not map any wetlands in the study area (King County, 2020) and no City wetland mapping was available for review. 3.2 Streams The White River is the only mapped stream in the study area (Figure 2) and flows from south to north/northwest through the study area. White River is classified as a stream of statewide significance and the river’s shoreline designation is Natural (City of Auburn, 2020). The proposed project, a restoration project of a degraded shoreline, is consistent with the policies of the designation. A U.S. Geological Survey river staff gage is located approximately 1.7 miles downstream from the project area at the R Street bridge in the City of Auburn. Discharge and gage height data that includes the 7 days prior to the field visit show that flows and river stage generally increased as the week progressed. Flows increased from about 1,500 cubic feet per second (CFS) to just over 2,000 CFS. The median daily statistic (10 years) for this time period shows discharge rates increased from about 1,200 to 1,500 CFS, indicating that river flows were slightly higher than normal preceding and during the site visit (USGS, 2020). 1 The City of Auburn Critical Area Code defines streams as those areas where surface waters produce a defined channel or bed that demonstrates clear evidence of the passage of water and includes, but is not limited to, bedrock channels, gravel beds, sand and silt beds and defined-channel swales. For purposes of this report the terms stream and river are used synonymously. 591 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 4 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 3.3 Wildlife Habitat Per AMC 16.10.080 wildlife habitat must be classified as critical, secondary, or tertiary. Critical habitat is defined as including: The documented presence of species or habitat listed by federal or state agencies as “endangered,” “threatened,” or “sensitive”; or The presence of unusual nesting or resting sites such as heron rookeries; Category I wetlands, as defined in these regulations; or Type S streams, as defined in these regulations. Based on existing documentation, habitat within the project area would be considered “critical” for the following reasons: there is documented presence of species and habitat listed by federal or state agencies as “endangered”, “threatened”, or “sensitive” within the White River and the White River, a shoreline of statewide significance, is a Type S stream in the study area. According to AMC 15.68.100, “riparian habitat zone” is defined as the waterbody and adjacent land areas that are likely to support aquatic and riparian habitat” and includes the lands 250 feet, measured from the ordinary high water mark, on either side of fish bearing streams. The White River and associated riparian habitat zone located within the study area are shown on Figure 2. Both the National Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS) provide listings of those threatened and endangered species listed under the Endangered Species Act that under their jurisdiction (Table 1; Appendix B). The current listings indicate the potential presence of three federally listed salmon species in the general vicinity of the project: The Puget Sound Evolutionary Significant Unit (ESU) of Chinook salmon (Oncorhynchus tshawytscha), the Puget Sound Distinct Population Segment (DPS) of steelhead (O. mykiss) and the Coastal-Puget Sound DPS bull trout (Salvelinus confluentus) (NMFS, 1999, 2007; USFWS, 1999). Washington Department of Fish and Wildlife map bull trout and fall Chinook presence within the study area and spawning for winter steelhead (WDFW, 2020a and 2020b). In addition to these listed fish species, multiple other salmonids are mapped within the study area, including: spring Chinook, fall chum, pink (odd year), sockeye, cutthroat trout, and coho (WDFW, 2020a and 2020b). Designated critical habitat for Puget Sound Chinook salmon (NMFS, 2005), Puget Sound steelhead (NMFS, 2016) and Coastal-Puget Sound bull trout (USFWS, 2010) is present within, upstream, and downstream of the study area in the mainstem White River. Essential Fish Habitat (EFH) for the Pacific salmon fishery occurs in the study area, specifically EFH for coho salmon, pink salmon, and chum salmon all of which have documented presence in the study area (WDFW, 2020a and 2020b). 592 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 5 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 In addition to these fish species, there are three threatened wildlife species that could potentially occur in the project vicinity: marbled murrelet (Brachyramphus marmoratus), streaked horned lark (Eremophila alpestris strigata) and yellow-billed cuckoo (Coccyzus americanus), as well as a proposed endangered species gray wolf (Canis lupis) (USFWSb, 2020). These species are either not historically distributed within the study area or the study area does not contain suitable habitat features to support the species. The project will have no effect on these species as documented under Section 5.2.1—Floodplain Habitat Assessment. TABLE 1. FEDERALLY LISTED FISH SPECIES POTENTIALLY PRESENT IN THE PROJECT VICINITY1 Common Name Scientific Name ESA Status* Jurisdiction Critical Habitat in Study Area? Coastal-Puget Sound DPS Bull Trout Salvelinus confluentus Threatened USFWS Yes Puget Sound Chinook Salmon Evolutionarily Significant Unit (ESU) Oncorhynchus tshawytscha Threatened NMFS Yes Puget Sound Steelhead DPS O. mykiss Threatened NMFS Yes Marbled Murrelet Brachyramphus marmoratus Threatened USFWS No Streaked Horned Lark Eremophilia alpestris strigata Threatened USFWS No Yellow-billed Cuckoo Coccyzus americanus Threatened USFWS No Gray Wolf Canis lupis Proposed Endangered USFWS No 1USFWSb, 2020 and NMFS, 2020. 3.4 Aquifer Recharge Areas The study area is mapped within the boundary of a Zone 3 groundwater protection area, which AMC 16.10.80(F)(1)(c) defines as a Type I aquifer recharge area. Specific land uses and activities located within these areas, which have a critical recharging effect on aquifers used for potable water, are prohibited by local code. The riprap removal and restoration project is considered an allowed activity according to AMC 16.10.100(D) and the critical area will not be discussed further. 3.5 Flood Hazard Areas The study area is mapped as Zone X, Area of Minimal Flood Hazard (FEMA, 2020) meaning the area is mapped outside of the regulatory floodplain (i.e., above the 500-year flood level and protected by levee from the 100-year flood). However, due to floodway and floodplain mapping both upstream and downstream of the study area (FEMA maps the regulatory floodway and Zone AE floodplain approximately 0.35-mile downstream of the study area and a Zone A floodplain about 0.70-mile upstream of the study area) and after discussions with City of Auburn, King County conservatively assumes the entire project area is located within the regulatory floodplain for the purpose of permitting (T. Bloxton, personal communication, 12/8/2020). 593 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 6 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 City regulations require water quality and aquatic and riparian habitat impacts assessments for developments within the regulatory floodplain. Development, such as grading, excavation, and filling within the area of special flood hazard, is regulated under AM 15.68 and while there is no mapped regulatory floodplain in the study area, the County has conservatively assumed a regulated floodplain exists. 4.0 RESULTS OF FIELD INVESTIGATION The following sections describe the results of the field investigation conducted by ESA biologists on November 18, 2020. The White River is the only critical area (i.e., stream and wildlife habitat) identified during the field visit; no wetlands were delineated within the study area nor observed adjacent to the study area. 4.1 Streams Within the study area, the observed wetted width of the White River measured about 60 to 120 feet wide and a large, left bank gravel bar with established vegetation was located between OHWM flags 7 to 16 as shown on Figure 2. Vegetation on the bar appears to be affected by river movements and flood events. Plants become well-established between flood events and then are scoured out by high flows. Landward of the levee, coniferous forest (primarily Douglas-fir and Western hemlock), with a native shrub understory (dominated by salal [Gaultheria shallon] and snowberry [Symphoricarpos albus]), cover much of the study area. A large cleared area located at the northwest part of the study area is dominated by moss and evergreen huckleberry (Vaccinium ovatum). Waterward of the levee, the gravel bar primarily contains red alder (Alnus rubra) with an understory of Scotch broom and bare sand/gravel. Scattered native shrubs are also established on the gravel bar. The White River channel substrate is dominated by cobbles, gravel, and sand, with boulders scattered throughout. Limited wracking was observed adjacent to the river’s wetted perimeter. Near continuous left bank erosion extends throughout the study area, with some portions of the bank undercut. Limited large woody debris was observed on the left bank and in the channel proximate to the bank. The ordinary high water mark (OHWM) was delineated according to the Washington State Department of Ecology’s (Ecology) Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State, (October 2016 Final Review, Publication No. 16-06-029) (Ecology, 2016). The OHWM was flagged in the field and recorded using a GPS unit that provided sub-meter accuracy (Figure 2). 4.2 Wildlife Habitat Limited wildlife was observed during the field visit; however, the coniferous and deciduous forests with a moderately dense shrub understory provide structural complexity for wildlife use. Bird species present during field visits include Steller’s jay (Cyanocitta stelleri), black-capped chickadee (Poecile atricapillus), American robin (Turdus migratorius), and song sparrow 594 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 7 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 (Melospiza melodia). Sign of raccoon (Procyon lotor) was observed at multiple locations on the gravel bar. No unusual nesting or resting sites or wetlands were identified within the study area. 4.2.1 Wildlife Habitat within the Floodplain Stands of Douglas-fir, Western hemlock, and red alder are present landward and waterward of the levee, respectively, within the floodplain of the White River. A dense shrub understory, albeit primarily comprised of an invasive species, provides cover and low quality habitat for wildlife species waterward of the levee. 5.0 Project Impacts The rock removal project was designed to avoid and minimize impacts to the White River and associated riparian buffer in accordance with federal, state, and local mitigation sequence requirements: 1. Avoiding the impact altogether by not taking a certain action or parts of an action. 2. Minimizing impacts by limiting the degree or magnitude of the action and its implementation, by using appropriate technology or by taking affirmative steps, such as project redesign, relocation, or timing, to avoid or reduce impacts. 3. Rectifying the impact to the critical area by repairing, rehabilitating, or restoring the affected environment to the conditions existing at the time of the initiation of the project. 4. Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action. 5. Compensating for the impact by replacing, enhancing, or providing substitute resources or environments. 6. Monitoring the hazard or other required mitigation and taking remedial action when necessary. Impacts to critical areas will be avoided and minimized during construction by locating staging areas and construction access points away from the stream and associated buffer to the greatest extent possible, and by using construction best management practices (BMPs). Best management practices include erosion and water quality control measures, such as installation of straw wattles and development of a temporary erosion and sediment control plan, to prevent negative impacts to the stream and buffer. Construction access points will use existing dirt roads to the greatest extent possible and construction equipment working near water will be equipped exclusively with biodegradable hydraulic fluids. In-water rock removal will occur during the in-water work window. Despite these measures, there will be unavoidable, temporary impacts during construction of the restoration project. The County intends to install native, riparian plantings and downed trees in place of the rock to mitigate for temporary impacts associated with rock removal. 595 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 8 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 5.1 Stream Impacts The majority of rock removal will occur landward of the OHWM and in most locations, greater than 90-feet from the river boundary. The notable exception to this is the eastern project area where the levee rock extends to the river OHWM and where the face of the left bank has eroded and resulted in sloughing of rock into the river channel. At this far eastern end of the project area, limited in-water work is proposed to remove levee rock that has fallen into the river channel. An excavator will operate from outside of the wetted width of the channel and will reach down into the river with a bucket and thumb to extract angular rock that is not embedded into the stream channel. Rock that is partially buried will be left in place to avoid impacts to the river channel. Extracted rock will be placed in a waiting dump truck or temporarily stockpiled for export with other levee rock. In-water impacts will be temporary and limited. 5.2 Wildlife Habitat Impacts The County intends to avoid impacts to wildlife and riparian habitat to the greatest extent possible while conducting the restoration project. Removal of levee rock in uplands will temporarily result in unavoidable impacts to the White River’s 200-foot stream buffer, 200-foot shoreline jurisdiction, and 250-foot riparian buffer zone, which are measured from the river’s OHWM. The area of temporary impacts is expected to total 12,500 square feet, with approximately 790 cubic yards of cut and 120 cubic yards of fill (net export of 670 cubic yards) within the floodplain. The County will minimize tree removal along the levee by designating specific treatment tiers as follows: Tier 1 – Tree remains and a buffer area is established within which rock removal is very selective and will not damage tree; Tier 2 – Tree remains but no buffer area is established; extensive rock removal will occur without complete destabilization of the trees, and Tier 3 – Remove as much rock as possible including potential to push over trees and leave onsite if needed for access or rock removal. If possible, Tier 3 trees will be left standing but rock removal around them is the primary goal. Generally, the largest trees are identified as Tier 1 and the smallest being Tier 3; however, the large trees at the upstream end of the project area, closest to the river, will be pushed over to remove as much rock as possible to facilitate access for in-water rip-rap removal. After rock is removed, downed trees will be placed within the footprint of rock removal and native, woody plants will be installed to restore the area temporarily disturbed by the project. 5.2.1 Floodplain Habitat Assessment The National Marine Fisheries Service’s (NMFS) Biological Opinion (BiOp) on the implementation of the National Flood Insurance Program (NFIP) in Puget Sound (dated 596 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 9 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 September 22, 2008) requires local communities that do not have BiOp-complaint floodplain management ordinances to require and review a Habitat Assessment (HA) before approving a floodplain permit, in order to demonstrate project compliance with the ESA. Development of a HA is a requirement per AMC 15.68.135 to obtain a permit for construction or development within the floodplain. This HA has been developed using the guidance of the FEMA Puget Sound BiOp Floodplain Habitat Assessment Worksheet (FEMA, 2017) and FEMA’s Floodplain Habitat Assessment and Mitigation: Regional Guidance Manual (FEMA, 2013). According to AMC 15.68.135, the floodplain habitat assessment includes an analysis of several habitat elements that address the habitat factors required by the BiOp to assist jurisdictions in considering aquatic impacts and impacts to ESA-listed fish species as a result of the project. A brief discussion of each habitat variable and the anticipated effect of the project on each is presented below. Primary Constituent Elements When a Species is Listed as Threatened or Endangered Designated critical habitat for Puget Sound Chinook salmon (NMFS, 2005), Puget Sound steelhead (NMFS, 2016) and Coastal-Puget Sound bull trout (USFWS, 2010) is present within, upstream, and downstream of the study area in the mainstem White River. As part of the designation of critical habitat, NMFS (2005, 2016) and USFWS (2010) have defined specific primary constituent elements (PCEs) for Chinook salmon, steelhead, and bull trout. Primary Constituent Elements (PCEs) are specific elements of physical or biological features that provide for a species’ life-history processes and are essential to the conservation of the species and used to define the presence or absence of critical habitat. Within freshwater sites, examples of these include freshwater spawning sites, freshwater rearing sites, and freshwater migration corridors. Specific PCEs, applicable to the proposed action in freshwater, as defined by NMFS for Chinook salmon, are: PCE 1 - Freshwater spawning sites with water quantity and quality conditions and substrate supporting spawning, incubation and larval development. There is no documented Chinook spawning within the study area. PCE 2 – Freshwater rearing sites with water quantity and floodplain connectivity to form and maintain physical habitat conditions that support juvenile growth and mobility; water quality and forage supporting juvenile development; and natural cover such as shade, submerged and overhanging large wood, logjams and beaver dams, aquatic vegetation, large rocks and boulders, side channels, and undercut banks. PCE 3 – Freshwater migration corridors free of obstruction, with water quantity and quality conditions and natural cover such as submerged and overhanging large wood, aquatic vegetation, large rocks and boulders, side channels, and undercut banks supporting juvenile and adult mobility and survival. 597 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 10 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 Specific PCEs, applicable to the proposed action in freshwater, as defined by NMFS for steelhead, are: PCE 1 - Freshwater spawning sites with water quantity and quality conditions and substrate supporting spawning, incubation and larval development. PCE 2 - Freshwater rearing sites with water quantity and floodplain connectivity to form and maintain physical habitat conditions and support juvenile growth and mobility; water quality and forage supporting juvenile development; and natural cover such as shade, submerged and overhanging large wood, log jams and beaver dams, aquatic vegetation, large rocks and boulders, side channels, and undercut banks. PCE 3 - Freshwater migration corridors free of obstruction with water quantity and quality conditions and natural cover such as submerged and overhanging large wood, aquatic vegetation, large rocks and boulders, side channels, and undercut banks supporting juvenile and adult mobility and survival. USFWS has identified nine PCEs for Coastal-Puget Sound bull trout critical habitat: PCE 1 - Springs, seeps, groundwater sources, and subsurface water connectivity (hyporehic flows) to contribute to water quality and quantity and provide thermal refugia. PCE 2 – Migration habitats with minimal physical, biological, or water quality impediments between spawning, rearing, overwintering, and freshwater and marine foraging habitats, including but not limited to permanent, partial, intermittent, or seasonal barriers. PCE 3 – An abundant food base, including terrestrial organisms of riparian origin, aquatic macroinvertebrates, and forage fish. PCE 4 – Complex river, stream, lake, reservoir, and marine shoreline aquatic environments, and processes that establish and maintain these aquatic environments, with features such as large wood, side channels, pools, undercut banks and unembedded substrates, to provide a variety of depths, gradients, velocities, and structure. PCE 5 – Water temperatures ranging from 2oC to 15oC (36oF to 59oF), with adequate thermal refugia available for temperatures that exceed the upper end of this range. Specific temperatures within this range will depend on bull trout life-history stage and form; geography; elevation; diurnal and seasonal variation; shading, such as that provided by riparian habitat; streamflow; and local groundwater influence. PCE 6 - Substrates of sufficient amount, size, and composition to ensure success of egg and embryo overwinter survival, fry emergence, and young-of-the-year and juvenile survival. A minimal amount (e.g., less than 12 percent) of fine substrate less than 0.85 mm (0.03 in.) in diameter and minimal embeddedness of these fines in larger substrates are characteristic of these conditions. PCE 7 - A natural hydrograph, including peak, high, low, and base flows within historic and seasonal ranges or, if flows are controlled, they minimize departures from a natural hydrograph. PCE 8 – Sufficient water quality and quantity such that normal reproduction, growth, and survival are not inhibited. 598 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 11 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 PCE 9 – Sufficiently low levels of nonnative predatory species (e.g., lake trout, walleye, northern pike, smallmouth bass); interbreeding species (e.g., brook trout [Salvelinus fontinalis]); or competing (e.g., brown trout [Salmo trutta]) species that, if present, are adequately temporally and spatially isolated from bull trout. The proposed project elements will have no negative effects on any PCEs for ESA-listed fish species critical habitat. The project will not affect flow, water temperature, prey base, or fish migration. Rock removal will be temporary and limited and will not result in negative effects to water quality. The project will not negatively affect the quality or quantity of habitat, including spawning, rearing, and migration habitat. It will not decrease stream complexity or result in a reduction of habitat features. Removal of in-water rip-rap will have a very slight beneficial effect on substrate and removal of the levee will result in a slight to moderate improvement of floodplain functions at larger (> 2 year) flood events, where the local floodplain will become at least partially engaged, versus existing conditions where the levee serves to disconnect the floodplain in the project area. Based on the fact the proposed action is a restoration project, which will improve salmon habitat and floodplain functions, the project will have no adverse effect on designated critical habitat, or any of the associated PCEs, for Chinook, steelhead, and bull trout as it will result in some improvements to instream and floodplain habitat quality within the project area. Essential Fish Habitat Designated by NMFS Essential Fish Habitat (EFH) is defined by NMFS as “those waters and substrate necessary to fish for spawning, breeding, feeding or growth to maturity” (U.S.C 180-1884) and includes all types of aquatic environments such as wetlands and streams. In compliance with the Magnuson-Stevens Act, EFH was assessed for the proposed project. The EFH designation for the Pacific salmon fishery includes all those streams, lakes, ponds, wetlands, and other water bodies, currently or historically accessible to salmon in Washington, Oregon, Idaho, and California, except above the impassable barriers identified by Pacific Fishery Management Council (1999). Essential Fish Habitat for the Pacific salmon fishery occurs in the study area, specifically EFH for coho salmon, pink salmon, and chum salmon all of which have documented presence in the study area (WDFW, 2020a and 2020b). Effects on EFH for Pacific salmon are similar to those analyzed above for PCEs. Based on the fact the proposed action will have limited impact to the river resulting from rock removal and because the project will reconnect the river to the floodplain, the project will have no adverse effect on EFH for Pacific Salmon. Wildlife Habitat The White River is critical wildlife habitat in the study area. Work within the river to extract levee rock that has fallen into the stream will result in temporary and limited project impacts to the stream. Use of an excavator with bucket and thumb at the eastern portion of the project area where significant left bank erosion has occurred will extract rock that is located on top of the channel bed, while buried levee rock will be left in-place to minimize substrate disturbance In- water rock removal will not impact fish migration, as work will not create any barriers to fish 599 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 12 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 movement, the construction will occur during the in-water work window, and the limited work will have no effect on ESA-listed species. Vegetation Communities and Habitat Structures The red alder overstory that dominates the gravel bar between the levee and stream contains and understory of Scotch broom, with scattered native shrubs. Limited downed wood was observed on the gravel bar and no additional habitat structures, such as snags, were observed onsite. Coniferous trees that are established within the levee rip-rap have been classified in three tiers for purposes of construction as discussed in Section 5.2. After rock has been removed, downed trees will be installed in the project area and native woody material will be planted to stabilize the soils in the project area, outcompete invasive species, and enhance habitat structure within the floodplain. Therefore, no effects to vegetation communities and habitat structures suitable for ESA-listed species are anticipated from the project. Water Quality The White River is on Ecology’s 303(d) list for temperature and pH within the study area, and upstream and downstream of the study area (Ecology, 2020). Levee rock removal will primarily occur landward of the OHWM and in the dry; however, a limited number of rock pieces have fallen below the OHWM and will be removed. The County will operate an excavator with bucket and thumb from outside of the wetted river channel and only extract angular rock that can be removed with minimal disturbance to the stream substrate (i.e., rock that is not buried). In-water levee rock removal will result in temporary and limited turbidity impacts to the stream and will not affect stream temperature or pH. Additionally, project BMPs, such as installation of straw wattles around the work area and a TESC, will be applied that include erosion and water quality control measures to prevent negative impacts to downstream areas. Water Quantity The project will not result in the addition of any new impervious surface, nor will it negatively affect flood storage. Overall, the project will export approximately 670 cubic yards of material. The removal of rock and associated improved connection of the stream with its floodplain will facilitate the conveyance of higher flows through the study area and allow some flows to disperse into the adjacent uplands, providing low-velocity areas for fish during flood flows and allowing flood waters to encounter areas with hydraulic roughness. These dynamics would be expected to benefit ESA-listed fish in the river by maintaining or slightly improving river hydraulics during larger flood flows, thus helping maintain or improve localized habitat functions. Channel Migration Processes The channel migration zone is defined as the lateral extent of likely movement along a stream reach with evidence of active channel migration or avulsions over the past 100 years (WFPB, 2000 as cited in Kerwin and Nelson, 2000). There is no channel migration hazard area mapped in the study area or upstream or downstream of the study area (King County, 2020) 600 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 13 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 Spawning Substrate The White River is mapped with documented winter steelhead spawning within the study area (WDFW, 2020a and 2020b). Rock removal, using an excavator with bucket and thumb and operated from the outside the wetted width of the river, would occur at the far eastern project area. Rock removal activities would be temporary and limited and would only remove rock that is located on top of the stream bed; buried rock will be left in-place to avoid sediment disturbance. Therefore, the project is anticipated to have no negative impacts to spawning habitat, with possibly a minor, localized improvement of such habitat for ESA-listed species. Floodplain Refugia Floodplains generally contain side-channels and other features that provide important rearing habitat, spawning habitat, and refugia during high flows. However, the floodplain located within the study area is dominated by Scotch broom and red alder trees less than 20 years old and does not contain high-functioning refugia. Rock removal proposed by the project would increase the stream’s engagement with the floodplain, remove invasive plant species, plant native woody plants, and install downed wood. Because floodplain refugia is currently degraded for ESA-listed species, a benefit to floodplain refugia is anticipated as a result of the project. 5.2.2 Effects Analysis Direct and Indirect Effects The only in-water work proposed for the project is limited removal of rip-rap below the OHWM of the White River. The project will not result in a degradation or loss of any of instream habitat features (e.g., large woody debris), and will not degrade riparian conditions. In addition, the project does not involve the additional of any new impervious surface in the project area. The lack of project effects on individual ecological functions and processes is detailed in the sections above and the project will not result in any changes to development patterns or rates. Based on this analysis, the project will result in no negative effects to listed species or their habitats. Interrelated and Interdependent Actions No interrelated or interdependent actions will occur that would negatively impact ESA-listed species as a result of the project. No future development of the site is currently known and any future phases of levee rock removal would undergo independent effects analyses to determine possible effects on ESA-listed species. Additionally, there is no other action or project that will have an independent use or effect as a result of the proposed action and therefore, the proposed action will have no interdependent effects. Cumulative Effects The project, in conjunction with other current actions or reasonably foreseeable future actions, would not impact ESA-listed species. The majority of project area does not support ESA-listed species, and due to the relatively limited level of development in the vicinity of the project, there is low potential for cumulative effects in the foreseeable future. 601 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 14 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 6.0 LIMITATIONS Within the limitations of schedule, budget, scope-of-work, and seasonal constraints, we warrant that this investigation was conducted in accordance with generally accepted environmental science practices, including the technical guidelines and criteria in effect at the time this investigation was performed. The results and conclusions of this report represent the authors’ best professional judgment, based on information provided by the project proponent in addition to that obtained during the course of this study. No other warranty, expressed or implied, is made. 602 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal 15 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 7.0 REFERENCES AND BIBLIOGRAPHY City of Auburn. 2020. Auburn Shoreline Master Program. Available: https://www.auburnwa.gov/UserFiles/Servers/Server_11470554/File/City%20Hall/Commu nity%20Development/Zoning%20and%20Land%20Use/Shoreline%20Master%20Program/ SMP%20Adopted%20May%207%202020.pdf. Accessed: December 2020. City of Auburn. 2019. Critical Areas Ordinance Update – Aquifer Recharge Areas Memo. Available: https://www.auburnwa.gov/UserFiles/Servers/Server_11470554/File/City%20Hall/Commu nity%20Development/Zoning%20and%20Land%20Use/Shoreline%20Master%20Program/ August%202019/August%207th.pdf. Accessed: December 2020. Ecology (Washington State Department of Ecology). 2016. Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State. Publication Number 16-06-029. Available: https://fortress.wa.gov/ecy/publications/documents/1606029.pdf. Accessed: December 2020. Ecology. 2020. Water Quality Atlas online mapper. Available: https://fortress.wa.gov/ecy/waterqualityatlas/map.aspx. Accessed: December 2020. FEMA (Federal Emergency Management Agency). 2008. Endangered Species Act Section 7 Formal Consultation and Magnuson-Stevens Fishery Conservation and Management Act Essential Fish Habitat Consultation for the on-going National Flood Insurance Program carried out in the Puget Sound area in Washington State. HUC 17110020 Puget Sound. Available: https://www.fema.gov/media-library-data/20130726-1900-25045- 9907/nfip_biological_opinion_puget_sound.pdf. Accessed: December 2020. FEMA. 2013. Regional Guidance for Floodplain Habitat Assessment and Mitigation in the Puget Sound Basin. Produced by FEMA - Region 10. August 2013. FEMA. 2017. FEMA Puget Sound BiOp Floodplain Habitat Assessment Worksheet. Version 1.6. Available: https://www.fema.gov/media-library-data/1521082188266- 40651225e6d536a82c5b995a9d4723d2/Floodplain-Habitat-Assessment- Worksheet_v1_6_Revised_508.pdf. Accessed: December 2020. FEMA. 2020. FEMA Flood Map Service Center. Flood Map 53033C1261G. Effective 8/19/2020. Available: https://msc.fema.gov/portal/search?AddressQuery=auburn%20wa#searchresultsanchor. Accessed: December 2020. Kerwin, J. and T.S. Nelson (Editors). 2000. Habitat limiting factors and reconnaissance assessment report, Green/Duwamish and Central Puget Sound watersheds (WRIA 9 and Vashon Island). King County. 2020. iMap – online mapping. Available: https://gismaps.kingcounty.gov/iMap/. Accessed: December 2020. 603 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 16 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 NRCS (Natural Resources Conservation Service). 2020. Web Soil Survey online soils mapping. Available: http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm. Accessed: December 2020. NMFS (National Marine Fisheries Service). 1999. Endangered and threatened species; threatened status for three Chinook salmon evolutionarily significant units (ESUs) in Washington and Oregon, and endangered status for one Chinook salmon ESU in Washington. Final Rule. March 24, 1999. Federal Register 64(56):14308-14328. NMFS. 2005. Endangered and threatened species; designation of critical habitat for 13 evolutionarily significant units of Pacific salmon (Oncorhynchus spp.) and steelhead (O. mykiss) in Washington, Oregon, and Idaho; Final Rule. September 2, 2005. Federal Register 70(170):52630–52858. NMFS. 2007. Endangered and Threatened Species: Final Listing Determination for Puget Sound Steelhead. May 11, 2007. Federal Register 72(91): 26722–26735. NMFS. 2016. Endangered and Threatened Species; Designation of Critical Habitat for Lower Columbia River Coho Salmon and Puget Sound Steelhead; Final Rule. Federal Register 81(36):9252–9325. February 24, 2016. NMFS. 2020. Status of ESA Listings and Critical Habitat Designations for West Coast Salmon and Steelhead. Updated July 2016. PFMC (Pacific Fishery Management Council). 1999. Amendment 14 to the Pacific Coast Salmon Plan. Appendix A: Description and Identification of Essential Fish Habitat, Adverse Impacts, and Recommended Conservation Measures for Salmon. Pacific salmon Management Council. USFWS (United States Fish and Wildlife Service). 1999. Endangered and threatened wildlife and plants; determination of threatened status for bull trout in the coterminous United States. Final rule November 1, 1999. Federal Register 64(210):58910-58933. USFWS. 2010. Endangered and Threatened Wildlife and Plants; Revised Designation of Critical Habitat for Bull Trout in the Coterminous United States; Final Rule. October 18, 2010. U.S. Fish and Wildlife Service. Federal Register 75(200):63898–64070. USFWS. 2020a. National Wetlands Inventory – online wetlands mapping. Available: http://www.fws.gov/wetlands/Data/Mapper.html. Accessed: December 2020. USFWS. 2020b. List of threatened and endangered species that may occur in your proposed project location, and/or may be affected by your proposed project. Consultation Code: 01EWFW00-2021-SLI-0283. Event Code: 01EWFW00-2021-E-00543. December 4, 2020. USGS (United State Geological Survey). 2020. National Water Information System: Web Interface. USGS 12100490 White River at R Street Near Auburn, Washington. Available: https://nwis.waterdata.usgs.gov/wa/nwis/uv?cb_00060=on&cb_00065=on&format=gif_def ault&site_no=12100490&period=&begin_date=2020-11-11&end_date=2020-11-22. Accessed: December 2020. 604 of 721 Critical Areas Report and Floodplain Habitat Impact Assessment King County TransCanada Levee Rock Removal. 17 ESA / D202000663.03 Critical Areas Report and Floodplain Habitat Impact Assessment April 2021 WDFW (Washington Department of Fish and Wildlife). 2020a. Priority Habitats and Species online mapping. Available: http://wdfw.wa.gov/mapping/phs/. Accessed: December 2020. WDFW (Washington Department of Fish and Wildlife). 2020b. SalmonScape fish database and mapping application. Available: http://wdfw.wa.gov/mapping/salmonscape/index.html. Accessed: December 2020. 605 of 721 606 of 721 FiguresESA January 2021 FIGURES 607 of 721 608 of 721 Maple DrDogwood Dr SEElmStSEPoplar St SE14thSt SE 18th St SE Fir St SE21st St SE 19th St SE 17th St SE 15th St SE 22n d StSE Nobl eCtSE16th St SE 20th St SEHemlockDrSE GinkoStSEDogwood St SEHemlock St SES ce nic Dr Stuck River D r SE Gr e e n V a l l e y R d Auburn WayS Study Area Path: U:\GIS\GIS\Projects\2020xxx\D202000663.03_KCWLRD_On-Call_WO#3_TransCanada_Levee\03_MXDs_Projects\VicinityMap.mxd, mmccart 12/8/2020SOURCE: King County, 2017; ESA, 2020 KCWLRD On-Call TransCanada Levee Figure 2Vicinity MapAuburn, Washington Kent Tacoma Renton Seattle Olympia Everett Bellevue MapArea WhiteRiver 609 of 721 !( !( !( !( !(!( !( !( !( !( !( !(!( !( !( !( !( !( !( !( !( !( !( !( !( !( !( 1 2 3 45 6 7 8 910 11 1213 14 15161718192021222324252627 Project Area Study Area Ordinary High Water Mark Shoreline Jurisdiction and Stream Buffer Riparian Habitat Zone White R i v e r Path: U:\GIS\GIS\Projects\2020xxx\D202000663.03_KCWLRD_On-Call_WO#3_TransCanada_Levee\03_MXDs_Projects\Figure1_OHWM.mxd, mmccart 12/14/2020SO URCE: King County, 2017; ESA, 2020 N0200 Feet KCWLRD On-Call TransCanada Levee Figure 2 Ordinary High Water Mark, Shoreline Jurisdiction, Stream Buffer, and Riparian Habitat Zone Auburn, Washington610 of 721 PhotosESA January 2021 SITE PHOTOGRAPHS 611 of 721 612 of 721 King County TransCanada Levee Rock Removal December 2020 Photo 1. Upstream end of the project area, looking downstream at the left bank. Photo 2. End of levee dirt road with rock sloughing down the bank; looking upstream at the left bank. 613 of 721 King County TransCanada Levee Rock Removal December 2020 Photo 3. Bare area on gravel bar, looking upstream on the left bank. Photo 4. Cobble and sand on left bank with invasive vegetation, looking upstream. 614 of 721 King County TransCanada Levee Rock Removal December 2020 Photo 5. Left bank vegetation looking downstream. 615 of 721 King County TransCanada Levee Rock Removal December 2020 Photo 6. Left bank erosion, looking downstream. 616 of 721 King County TransCanada Levee Rock Removal December 2020 Photo 7. Gravel bar adjacent to the levee. Photo 8. Upland, cleared area landward of the levee. 617 of 721 King County TransCanada Levee Rock Removal December 2020 Photo 9. Upland forested area landward of the levee. 618 of 721 Appendix A ESA January 2021 APPENDIX A: TRANSCANADA LEVEE ROCK REMOVAL DESIGN SHEETS 619 of 721 620 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37VICINITY MAP AND SHEET INDEX1SHEET INDEXVICINITY MAPAUBURNPROJECTAREASHEETDESCRIPTIONTRANSCANADA LEVEE ROCK REMOVALLAT: 47.28, LONG: -122.18WHITE RIVER RM 9.3ASSOCIATED PROJECT PERMITS:EARTHWORK QUANTITIESOWNER CONTACT INFORMATION:LEGAL AND SURVEY DESCRIPTION:CITY OF AUBURN GENERAL CONSTRUCTION NOTES:’“” ’’’“” HAUL ROUTE NOTES:CONSTRUCTION SEQUENCE NOTES:STORM SYSTEM DEVELOPMENT CHARGESTORM PERMITCITY OF AUBURN PERMITS:CITY OF AUBURN APPROVALS621 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37ACCESS AND TRAFFIC CONTROL PLAN2NOTE:ACCESS AND TRAFFIC CONTROL NOTES:LEGEND:622 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37EXISTING CONDITIONS AND TESC PLAN3LEGEND:TEMPORARY EROSION AND SEDIMENT CONTROL (TESC)NOTES:BASEMAP NOTES:623 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37PROPOSED DESIGN PLAN4A 5 GENERAL CONSTRUCTION NOTES:CONSTRUCTION SEQUENCING NOTES:LEGEND:624 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37TYPICAL SECTIONS5NOTES:625 of 721 Know what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37TESC DETAILS6STRAW WATTLE NOTES:TEMPORARY CONSTRUCTION ENTRANCE NOTES:626 of 721 T T T T T T TTTTT TT T T T T T T T TT T T T T T T T T TT T T T T T T T T T T T T T T T T T T T T T TT TTTTTTTTTTTTTTTTTTTTTTT TKnow what's below.RCall before you dig.Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionTRANS CANADA ROCK REMOVALWHITE RIVER RM 9.37PLANTING PLAN7GENERAL PLANTING NOTES:T LEGENDPLAN VIEW627 of 721 628 of 721 Appendix B ESA January 2021 APPENDIX B:USFWS and NMFS SPECIES LISTS 629 of 721 630 of 721 ! ! ^ ! ! ! ! ! ! ! ! ^ ! ! ! ! ! ! ! ! ! ! ^ ! ^ C o lum biaColumbiaSna k e Pocatello Spokane Wenatchee Walla WallaYakima Boise Bend Medford Eugene Salem Astoria Olympia Bellingham Redding Sacramento San Francisco Santa Cruz Fresno Santa Barbara San Diego Los Angeles Seattle Portland Salmon CoosBay Eureka DeschutesWillametteRog ue Umpqu a K l a m athTrinity Ee l Rus si a n S a c r a mentoSan J o a quin Salin as SantaAnaSa l m on Snake United StatesUnited StatesCanadaCanada United StatesUnited States MexicoMexico 0 200Miles O R E G O N W A S H I N G T O N I D A H O C A L I F O R N I A Status of ESA Listings & Critical Habitat Designationsfor West Coast Salmon & Steelhead Updated July 2016 Recovery DomainPuget SoundInterior Columbia Oregon Coast North-Central California Coast Central Valley North-Central California Coast and Central Valley Overlap So. OR / No. CA Coast and North-Central CA Coast Overlap Southern OR / Northern CA Coast Willamette / Lower Columbia and Interior Columbia OverlapWillamette / Lower Columbia South-Central / Southern CA Coast Evolutionarily Significant Unit / Distinct Population Segment ESA Status Date of ESA Listing Date of CH Designation Hood Canal Summer-run Chum Salmon T 3/25/1999 9/2/2005 Ozette Lake Sockeye Salmon T 3/25/1999 9/2/2005 Puget Sound Chinook Salmon T 3/24/1999 9/2/2005 Puget Sound Steelhead T 5/11/2007 2/24/2016 Middle Columbia River Steelhead T 3/25/19991/5/2006 9/2/2005 Snake River Fall-run Chinook Salmon T 4/22/1992 12/28/1993 Snake River Spring / Summer-run Chinook Salmon T 4/22/1992 10/25/1999 Snake River Sockeye Salmon E 11/20/1991 12/28/1993 Snake River Steelhead T 8/18/19971/5/2006 9/2/2005 Upper Columbia River Spring-run Chinook Salmon E 3/24/1999 9/2/2005 Upper Columbia River Steelhead T 8/18/19971/5/2006 9/2/2005 Columbia River Chum Salmon T 3/25/1999 9/2/2005 Lower Columbia River Chinook Salmon T 3/24/1999 9/2/2005 Lower Columbia River Coho Salmon T 6/28/2005 2/24/2016 Lower Columbia River Steelhead T 3/19/19981/5/2006 9/2/2005 Upper Willamette River Chinook Salmon T 3/24/1999 9/2/2005 Upper Willamette River Steelhead T 3/25/19991/5/2006 9/2/2005 Oregon Coast Coho Salmon T 2/11/2008 2/11/2008 Southern OR / Northern CA Coasts Coho Salmon T 5/6/1997 5/5/1999 California Coastal Chinook Salmon T 9/16/1999 9/2/2005 Central California Coast Coho Salmon E 10/31/1996 (T) 6/28/2005 (E)4/2/2012 (RE)5/5/1999 Central California Coast Steelhead T 8/18/19971/5/2006 9/2/2005 Northern California Steelhead T 6/7/20001/5/2006 9/2/2005 California Central Valley Steelhead T 3/19/19981/5/2006 9/2/2005 Central Valley Spring-run Chinook Salmon T 9/16/1999 9/2/2005 Sacramento River Winter-run Chinook Salmon E 11/5/1990 (T) 1/4/1994 (E)6/16/1993 South-Central California Coast Steelhead T 8/18/19971/5/2006 9/2/2005 Southern California Steelhead E 8/18/19975/1/2002 (RE)1/5/2006 9/2/2005 ESA = Endangered Species Act, CH = Critical Habitat, RE = Range ExtensionE = Endangered, T = Threatened, Willamette / Lower Columbia Recovery Domain Interior Columbia Recovery Domain Puget Sound Recovery Domain Oregon Coast Recovery Domain North-Central California Coast Recovery Domain Central Valley Recovery Domain South-Central / Southern California Coast Recovery Domain Southern Oregon / Northern California Coast Recovery Domain 631 of 721 Critical Habitat Rules Cited • 2/24/2016 (81 FR 9252) Final Critical Habitat Designation for Puget Sound Steelhead and Lower Columbia River Coho Salmon • 2/11/2008 (73 FR 7816) Final Critical Habitat Designation for Oregon Coast Coho Salmon • 9/2/2005 (70 FR 52630) Final Critical Habitat Designation for 12 ESU's of Salmon and Steelhead in WA, OR, and ID • 9/2/2005 (70 FR 52488) Final Critical Habitat Designation for 7 ESU's of Salmon and Steelhead in CA • 10/25/1999 (64 FR 57399) Revised Critical Habitat Designation for Snake River Spring/Summer-run Chinook Salmon • 5/5/1999 (64 FR 24049) Final Critical Habitat Designation for Central CA Coast and Southern OR/Northern CA Coast Coho Salmon • 12/28/1993 (58 FR 68543) Final Critical Habitat Designation for Snake River Chinook and Sockeye Salmon • 6/16/1993 (58 FR 33212) Final Critical Habitat Designation for Sacramento River Winter-run Chinook Salmon ESA Listing Rules Cited • 4/2/2012 (77 FR 19552) Final Range Extension for Endangered Central California Coast Coho Salmon • 2/11/2008 (73 FR 7816) Final ESA Listing for Oregon Coast Coho Salmon • 5/11/2007 (72 FR 26722) Final ESA Listing for Puget Sound Steelhead • 1/5/2006 (71 FR 5248) Final Listing Determinations for 10 Distinct Population Segments of West Coast Steelhead • 6/28/2005 (70 FR 37160) Final ESA Listing for 16 ESU's of West Coast Salmon • 5/1/2002 (67 FR 21586) Range Extension for Endangered Steelhead in Southern California • 6/7/2000 (65 FR 36074) Final ESA Listing for Northern California Steelhead • 9/16/1999 (64 FR 50394) Final ESA Listing for Two Chinook Salmon ESUs in California • 3/25/1999 (64 FR 14508) Final ESA Listing for Hood River Canal Summer-run and Columbia River Chum Salmon • 3/25/1999 (64 FR 14517) Final ESA Listing for Middle Columbia River and Upper Willamette River Steelhead • 3/25/1999 (64 FR 14528) Final ESA Listing for Ozette Lake Sockeye Salmon • 3/24/1999 (64 FR 14308) Final ESA Listing for 4 ESU's of Chinook Salmon • 3/19/1998 (63 FR 13347) Final ESA Listing for Lower Columbia River and Central Valley Steelhead • 8/18/1997 (62 FR 43937) Final ESA Listing for 5 ESU's of Steelhead • 5/6/1997 (62 FR 24588) Final ESA Listing for Southern Oregon / Northern California Coast Coho Salmon • 10/31/1996 (61 FR 56138) Final ESA Listing for Central California Coast Coho Salmon • 1/4/1994 (59 FR 222) Final ESA Listing for Sacramento River Winter-run Chinook Salmon • 4/22/1992 (57 FR 14653) Final ESA Listing for Snake River Spring/summer-run and Snake River Fall Chinook Salmon • 11/20/1991 (56 FR 58619) Final ESA Listing for Snake River Sockeye Salmon • 11/5/1990 (55 FR 46515) Final ESA Listing for Sacramento River Winter-run Chinook Salmon 632 of 721 December 04, 2020 United States Department of the Interior FISH AND WILDLIFE SERVICE Washington Fish And Wildlife Office 510 Desmond Drive Se, Suite 102 Lacey, WA 98503-1263 Phone: (360) 753-9440 Fax: (360) 753-9405 http://www.fws.gov/wafwo/ In Reply Refer To: Consultation Code: 01EWFW00-2021-SLI-0283 Event Code: 01EWFW00-2021-E-00543 Project Name: TransCanada Levee Rock Removal Subject:List of threatened and endangered species that may occur in your proposed project location, and/or may be affected by your proposed project To Whom It May Concern: The enclosed species list identifies threatened, endangered, and proposed species, designated and proposed critical habitat, and candidate species that may occur within the boundary of your proposed project and/or may be affected by your proposed project. The species list fulfills the requirements of the U.S. Fish and Wildlife Service (Service) under section 7(c) of the Endangered Species Act (Act) of 1973, as amended (16 U.S.C. 1531 et seq.). New information based on updated surveys, changes in the abundance and distribution of species, changed habitat conditions, or other factors could change this list. The species list is currently compiled at the county level. Additional information is available from the Washington Department of Fish and Wildlife, Priority Habitats and Species website: http://wdfw.wa.gov/ mapping/phs/ or at our office website: http://www.fws.gov/wafwo/species_new.html. Please note that under 50 CFR 402.12(e) of the regulations implementing section 7 of the Act, the accuracy of this species list should be verified after 90 days. This verification can be completed formally or informally as desired. The Service recommends that verification be completed by visiting the ECOS-IPaC website at regular intervals during project planning and implementation for updates to species lists and information. An updated list may be requested through the ECOS-IPaC system by completing the same process used to receive the enclosed list. The purpose of the Act is to provide a means whereby threatened and endangered species and the ecosystems upon which they depend may be conserved. Under sections 7(a)(1) and 7(a)(2) of the Act and its implementing regulations (50 CFR 402 et seq.), Federal agencies are required to utilize their authorities to carry out programs for the conservation of threatened and endangered species and to determine whether projects may affect threatened and endangered species and/or designated critical habitat. 633 of 721 12/04/2020 Event Code: 01EWFW00-2021-E-00543 2 ▪ A Biological Assessment is required for construction projects (or other undertakings having similar physical impacts) that are major Federal actions significantly affecting the quality of the human environment as defined in the National Environmental Policy Act (42 U.S.C. 4332(2) (c)). For projects other than major construction activities, the Service suggests that a biological evaluation similar to a Biological Assessment be prepared to determine whether or not the project may affect listed or proposed species and/or designated or proposed critical habitat. Recommended contents of a Biological Assessment are described at 50 CFR 402.12. If a Federal agency determines, based on the Biological Assessment or biological evaluation, that listed species and/or designated critical habitat may be affected by the proposed project, the agency is required to consult with the Service pursuant to 50 CFR 402. In addition, the Service recommends that candidate species, proposed species, and proposed critical habitat be addressed within the consultation. More information on the regulations and procedures for section 7 consultation, including the role of permit or license applicants, can be found in the "Endangered Species Consultation Handbook" at: http://www.fws.gov/endangered/esa-library/pdf/TOC-GLOS.PDF Please be aware that bald and golden eagles are protected under the Bald and Golden Eagle Protection Act (16 U.S.C. 668 et seq.). You may visit our website at http://www.fws.gov/pacific/ eagle/for information on disturbance or take of the species and information on how to get a permit and what current guidelines and regulations are. Some projects affecting these species may require development of an eagle conservation plan: (http://www.fws.gov/windenergy/ eagle_guidance.html). Additionally, wind energy projects should follow the wind energy guidelines (http://www.fws.gov/windenergy/) for minimizing impacts to migratory birds and bats. Also be aware that all marine mammals are protected under the Marine Mammal Protection Act (MMPA). The MMPA prohibits, with certain exceptions, the "take" of marine mammals in U.S. waters and by U.S. citizens on the high seas. The importation of marine mammals and marine mammal products into the U.S. is also prohibited. More information can be found on the MMPA website: http://www.nmfs.noaa.gov/pr/laws/mmpa/. We appreciate your concern for threatened and endangered species. The Service encourages Federal agencies to include conservation of threatened and endangered species into their project planning to further the purposes of the Act. Please include the Consultation Tracking Number in the header of this letter with any request for consultation or correspondence about your project that you submit to our office. Related website: National Marine Fisheries Service: http://www.nwr.noaa.gov/protected_species/species_list/ species_lists.html Attachment(s): Official Species List 634 of 721 12/04/2020 Event Code: 01EWFW00-2021-E-00543 1 Official Species List This list is provided pursuant to Section 7 of the Endangered Species Act, and fulfills the requirement for Federal agencies to "request of the Secretary of the Interior information whether any species which is listed or proposed to be listed may be present in the area of a proposed action". This species list is provided by: Washington Fish And Wildlife Office 510 Desmond Drive Se, Suite 102 Lacey, WA 98503-1263 (360) 753-9440 635 of 721 12/04/2020 Event Code: 01EWFW00-2021-E-00543 2 Project Summary Consultation Code:01EWFW00-2021-SLI-0283 Event Code:01EWFW00-2021-E-00543 Project Name:TransCanada Levee Rock Removal Project Type:LAND - RESTORATION / ENHANCEMENT Project Description:The project proposes to remove up to 400 linear feet of the bank armoring at the upstream end of the TransCanada levee on the left bank of the White River at approximately RM 9.35 on property owned by King County. The TransCanada levee is on the left bank of the White River and has eroded upstream of the project location in recent years. At the upstream limit of the project location the river is currently up against the levee. However, further downstream within the project area the wetted channel is up to 180 feet from the levee as a result of channel position changes in recent years. The levee is composed of large angular rock on the waterward side and a Douglas-fir and black cottonwood forest with an understory of western red cedar, swordfern, and snowberry has colonized the levee slopes. The top of the levee is an access road used for hunting, fishing, and recreational activities Project Location: Approximate location of the project can be viewed in Google Maps: https:// www.google.com/maps/place/47.282975588150585N122.17968148661132W Counties:King, WA 636 of 721 12/04/2020 Event Code: 01EWFW00-2021-E-00543 3 1. Endangered Species Act Species There is a total of 5 threatened, endangered, or candidate species on this species list. Species on this list should be considered in an effects analysis for your project and could include species that exist in another geographic area. For example, certain fish may appear on the species list because a project could affect downstream species. IPaC does not display listed species or critical habitats under the sole jurisdiction of NOAA Fisheries , as USFWS does not have the authority to speak on behalf of NOAA and the Department of Commerce. See the "Critical habitats" section below for those critical habitats that lie wholly or partially within your project area under this office's jurisdiction. Please contact the designated FWS office if you have questions. NOAA Fisheries, also known as the National Marine Fisheries Service (NMFS), is an office of the National Oceanic and Atmospheric Administration within the Department of Commerce. Mammals NAME STATUS Gray Wolf Canis lupus Population: Western Distinct Population Segment No critical habitat has been designated for this species. Proposed Endangered Birds NAME STATUS Marbled Murrelet Brachyramphus marmoratus Population: U.S.A. (CA, OR, WA) There is final critical habitat for this species. Your location is outside the critical habitat. Species profile: https://ecos.fws.gov/ecp/species/4467 Threatened Streaked Horned Lark Eremophila alpestris strigata There is final critical habitat for this species. Your location is outside the critical habitat. Species profile: https://ecos.fws.gov/ecp/species/7268 Threatened Yellow-billed Cuckoo Coccyzus americanus Population: Western U.S. DPS There is proposed critical habitat for this species. Your location is outside the critical habitat. Species profile: https://ecos.fws.gov/ecp/species/3911 Threatened 1 637 of 721 12/04/2020 Event Code: 01EWFW00-2021-E-00543 4 Fishes NAME STATUS Bull Trout Salvelinus confluentus Population: U.S.A., conterminous, lower 48 states There is final critical habitat for this species. Your location overlaps the critical habitat. Species profile: https://ecos.fws.gov/ecp/species/8212 Threatened Critical habitats There is 1 critical habitat wholly or partially within your project area under this office's jurisdiction. NAME STATUS Bull Trout Salvelinus confluentus https://ecos.fws.gov/ecp/species/8212#crithab Final 638 of 721 Water and Land Resources Division Department of Natural Resources and Parks King Street Center 201 South Jackson Street, Suite 600 Seattle, WA 98104-3855 206-477-4800 Fax 206-296-0192 TTY Relay: 711 December 2, 2020 TO: Chris Brummer, White River Basin Supervising Engineer, Water and Land Resources (WLRD), River and Floodplain Management Section (RFMS) Stephanie Shelton, Supervising Ecologist, WLRD RFMS Linda Bartolini Venegas, Stuck River Drive Project Manager, WLRD RFMS FM: Judi Radloff, Engineering Geologist, WLRD RFMS Luke Russell, Engineer 1, WLRD RFMS RE: Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal, White River, Stuck River Drive Revetment Repair Mitigation This memorandum summarizes the results of an analysis of the geomorphic risks associated with a project (the Project) that proposes to remove face and toe rock from a portion of the TransCanada levee located on the left bank of the White River near river mile (RM) 9.3. The Project is located on property owned by King County and is proposed as a companion project to the repair of the Stuck River Drive revetment located approximately 1.5 miles downstream of the project area. The purpose of the Project is to pre-emptively remove face and toe rock from the eroding levee, resulting in locally restored fluvial processes and improved aquatic and riparian habitat in the reach. This analysis evaluates existing geologic and geomorphic hazards present in the project area, the risks those hazards pose to private property in the project area, and whether additional risk is likely to result from the Project. Background The TransCanada levee was constructed in the 1950s and originally consisted of an approximately 2.4 mile-long earthen levee revetted with angular rock riprap. It protected property planned for residential development and a pipeline owned by the TransCanada pipeline company. Beginning in the 1970s, the White River breached the levee in several places, and the facility is no longer continuous. King County manages the remaining portion of intact levee that extends from RM 8.2 to 9.3. King County owns property behind the existing and former levee between RM 8.9 and 9.5 (see Figure 1). King County purchased the property with the intent of preserving open space and providing for salmon habitat restoration while 639 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 2 reducing flood risk through a future levee setback project (King County 2011). About 2,160 feet of intact levee remain on the King County property. Four levee setback alternatives were evaluated in a feasibility study (FS) for the TransCanada levee segment situated on the King County property under a Salmon Recovery Funding Board grant (King County 2011). The FS evaluated flood and erosion hazards (including channel migration) and sediment delivery changes for the four alternatives. Alternative 2, which was identified in the FS as the preferred alternative, included levee face and toe rock removal along approximately 0.4 miles of levee, no levee prism removal, and construction of four engineered log jams (ELJs) and a buried revetment at the downstream end of the site. A 30 percent design of Alternative 2 was presented in an appendix to the feasibility study. Data and analyses from the feasibility study are still relevant today because site conditions have changed very little since 2009 when flood flows on the White River were severely curtailed by reduced releases from Mud Mountain Dam. The proposed Project is most similar to Alternative 2 as presented in the FS (King County 2011), although reduced in length and without the ELJs or the downstream buried revetment. The Project similarly proposes to remove up to 400 linear feet of face and toe rock from the upstream end of the levee (as compared to over 2,000 feet removed by FS Alternative 2). The levee prism, trees and other woody vegetation in the project area will be left intact as much as possible to allow for natural recruitment by the river through channel migration processes. Restoration of these processes is expected to improve aquatic habitat conditions. Site Characterization This section describes the existing physical conditions including geology and geomorphic processes active at the project site and surrounding area, as well as some of the history of recent geomorphic change. The White River flows from southeast to northwest through the project area, entering a large radius, left meander bend with the apex at the downstream end of the King County property at about RM 9.1 (Figure 1). Topography in the project area consists of a broad floodplain that is between 2,500 and 3,000 feet wide, about 200 feet elevation above sea level and bordered by steep valley walls that are up to 150 feet high. The White River currently flows along the far right side of the valley and floodplain and is in contact with the toe of the right valley slope between RM 8.2 (at the Auburn Wall diversion structure) and RM 9.3. Site Geology Surficial geology was mapped at a scale of 1:24,000 for the Auburn Quadrangle in 1965 by the USGS (Mullineaux, 1965) and is shown in Figure 2. Site reconnaissance completed by King County River and Floodplain Management Section (RFMS) geologists in January and March 2020 focused on identifying and characterizing the geologic materials that are exposed on the steep valley wall that is also the right bank of the river from RM 9.3 to 9.1. Because the bluffs are very steep, photographs of a typical section is a good supplement to the geologic map to illustrate the geologic composition of the bluffs. Geologic characteristics of the right bank 640 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 3 bluffs are shown in Figures 3 through 5. Contacts between units are highlighted in Figures 3 and 4, and additional weathering and erosion characteristics are shown in Figure 5. Geologic units that comprise the site materials consist of Quaternary age glacial and fluvial sediments. The following descriptions, from oldest to youngest, are summarized from Mullineaux, 1965 and include the interpreted locations of each unit as observed during 2020 site visits: Qid – Quaternary Intermediate Drift: Includes clayey till sheets deposited by older, pre-Fraser Puget glacial lobe, separated by and locally overlain by lacustrine sand, silt, and clay, and relatively thin, lenticular deposits of fluvial sand and gravel. Maximum known thickness is about 300 feet. Outcrop areas on valley walls are characterized by many small and some large landslides. This unit is present at the toe of the right valley slope in the project area at the river’s water line (see Figures 3 and 4). Fresh exposures are gray in color and the glacially- overridden sediment is hard, highly cohesive, has very low permeability and weathers prominently with a massive to blocky fracture pattern. Larger failures consist of small gravity slab or block failures. Qss – Quaternary Salmon Springs Drift (correlated to Qpf, pre-Fraser glacial deposits): Chiefly fluvial sand and gravel and a lense of till deposited by the pre-Fraser Puget glacial lobe, and thin [interglacial?] beds of silt, clay, and peat. Partly well sorted, locally contains tight silt and clay matrix. Thickness generally is 50 feet. This unit overlies the Intermediate Drift and occurs midslope on the right valley wall. Some bedding was observed in the sand and gravel layers which are stained darker where groundwater is seeping out of the slope. Much of the unit is cohesive and fresh exposures are dark gray. The sediment is very dense/hard, having been glacially overridden, and it holds very steep slopes. Slope failures are more fluid than the Intermediate Drift and smaller debris flow failures contain silty sand and gravel with boulder-sized blocks of silt/clay material. Qg – Quaternary undifferentiated Vashon Glacial Drift: Outwash sand and gravel, and till. A discontinuous sheet of till underlain and overlain by discontinuous layers of outwash sand and gravel. In the project area, this unit consists of hard gray glacial till that comprises the top of the right valley slope. The till is highly cohesive and holds a very steep slope, weathers prominently and has similar, blocky slab-like failure characteristics as the older Intermediate Drift. Qpv – Quaternary Vashon Stade Proglacial (Recessional) Outwash: Mostly well- sorted, sandy pebble-and-cobble gravel deposited along and beyond retreating front of Puget glacial lobe by large ice-marginal stream that included melt water from Puget lobe and discharge from rivers draining the Cascade Range. Virtually unweathered. 641 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 4 Linear, terraced, cut-and-fill deposits formed in troughs in ground moraine and outwash plain beyond ice front. Generally 10 to 50 feet thick and grades westward to delta deposits. This material overlies glacial till on the right valley slope downstream of the project area at RM 9.1. The steeply sloped, unconformable contact (see Figure 3) between this unit and the underlying older glacial units is a cut-and-fill trough described above by Mullineaux (1965). Granular and non-cohesive with bedding visible, this material holds a shallower slope than the glacial materials, close to 30 or 35 degrees. Landsliding in this unit forms large, arcuate failures with rills, gullies and debris chutes well-developed (Figure 3). Groundwater perches at the base of this unit at the contact with underlying low-permeability till. Qom – Quaternary Osceola Mudflow: unsorted and unstratified sand to cobbles in clayey matrix from 5,600 year old lahar originating on Mt. Rainier. This unit is present on the plateau above the right valley slope and is shown in Figure 2 but it was not observed on the slopes within the study area. Qaw – Quaternary alluvium, White River: Bouldery cobble and pebble-cobble gravel and sand deposited by White River. Contains glassy volcanic material. This material comprises the left floodplain and the bed and bars within the active channel. Slope Processes Geomorphic slope processes are active on the steep, right valley wall above the right bank of the White River (see Figure 6). The slope is about 150 feet high and slope estimates range from 71 percent to over 100 percent in some areas (based on LiDAR measurements). Slope profiles from four locations along the project reach are shown in Figure 7 and include approximate locations of the geologic materials that comprise the slope. Slope processes observed include colluvial development, raveling, rilling, gullying, and mass wasting. Mass wasting includes shallow debris slides and debris flows within the project area. One larger, deep-seated landslide identified by King County in 2016 as part of the river corridor mapping study is mapped upstream of the project area from about RM 9.4 to 9.65, as shown in Figures 1 and 2 (King County 2016). The geologic materials at the location of the mapped, deep-seated landslide are similar to those at the project site but slope conditions are different, including river-slope interactions. Slope failures at the toe of the slope in contact with the White River are shallow debris slides. Based on a review of the regional geologic mapping by Mullineaux (1965) and the site visits, the geologic materials that are most exposed to river erosion at the toe of the right valley slope throughout the project area and downstream consist of hard/very dense, cohesive glacial silts and clays with minor sand and gravel in the matrix. This material has been glacially overridden and has very low permeability and high strength under unsaturated conditions. It erodes by weathering and gravity failure that originates along small fractures formed parallel to the steep bank face; failures are characteristically small and blocky. Although riverine processes 642 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 5 continually wet the surface of this material, its low permeability allows it to maintain bulk cohesion and strength. Two other types of slope failure were observed to be active in the project reach (see Figures 3 and 5). Small, shallow colluvial debris slides that consist of sloughing of surface soil, debris and vegetation including large trees, are common on the slope. Colluvial debris slides are gravity-induced and occur on a planar surface parallel to the slope where the accumulation of surface material overlies a stronger substrate. Shallow debris flow slides are very similar to colluvial debris slides and the material is more fluid, concentrates in a flow-path or gully, and the deposit spreads out as it exits the flow path. Debris flow slides may include a surface or groundwater component in slide initiation. Debris flow slides were observed originating from the mid and upper slopes in geologic units that include a mixture of granular (sand and gravel) and finer material. The largest of these types of failures was observed at RM 9.1 where a large thickness of non-cohesive outwash sediment overlies glacial till. Groundwater seeps at the contact between the two units may contribute to sliding but based on visual observations, the slide scarps are located at either the slope top or midslope. Slope processes interact with fluvial processes at the base of the slope. Sediment from slope failures that is delivered to the river channel is either carried away by seasonal high flows or accumulates in lateral bars that become stabilized by vegetation. At RM 9.2, a right lateral bar has developed at the base of the slope and collects sediment and woody material from both river and slope processes (see Figures 1, 5 and 6). Based on a review of aerial photographs between 1998 and 2019, this bar has been present during most of this period. Between 2002 and 2005, a failure resulted in some bank-top recession and loss of large trees at the top of the slope. The bar has been present in some form since 2012 and has grown upstream and appears to be accumulating fluvial material. Between RM 9.35 and 9.7 (Figure 1), a large right lateral bar has been growing since about 2002 and stabilized as vegetation became established. This bar also is at the toe of an active landslide slope with a side ravine and deep-seated landslide characteristics (King County 2016). The establishment of these bars on the right bank provides some protection to the slope, both from toe erosion by the river and serving as a buttressing feature that stabilizes the slope. Overall, these bluffs were found to contribute a minimal volume of sediment to the river (bedload) between 2004 and 2016 (King County 2019). An examination of two LiDAR data sets taken 10 years apart (2009 and 2019) indicates that bluff retreat at the top of the slope is within the error of measurement and georeferencing of the two data sets and is 3 feet horizontal or less. Fluvial Geomorphic Processes The White River in the project area occupies a broad alluvial valley flanked by tall, steep valley walls and is often referred to as the lower portion of the Canyon Reach (King County 2019). It has a steep channel gradient (average about 0.7 percent slope), a meandering to braided planform, and carries a high sediment load. The river forms a wide meander bend, flowing northwest at the head of the reach and into the project area, bends west and then southwest to exit the Canyon Reach onto the White River alluvial fan at about RM 8. The TransCanada levee has confined the river since the 1950s to a much narrower active channel area than it 643 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 6 occupied prior to levee construction. As a result of natural channel response to the 1906 White River avulsion located downstream at the Auburn Wall diversion structure that shortened and steepened the river’s course, a knickpoint from the avulsion node has been migrating upstream. This knickpoint migration or headcut has resulted in channel bed incision of up to 16 feet since the 1906 avulsion (4 to 5 meters; King County 2019). The incision has disconnected the active channel from the left bank floodplain, which now forms a forested terrace that locks the river against the steep right bank and the TransCanada levee. In the project reach, the TransCanada levee is situated on top of recent alluvium and forms the river’s left bank. The steep valley wall composed of glacial materials forms the right bank. At the upstream end of the extant TransCanada levee at about RM 9.3, large angular rock boulders eroded from the failed portion of the levee form a 350-foot long boulder cascade that is spread across the 125 to 150-foot-wide channel. The boulders provide grade control on the channel bed and have scoured a deep pool (estimated to be at least 12 feet deep) at the downstream end that is up against the right valley wall. Another boulder cascade formed by remnant levee toe and face rock can be seen in the channel at about RM 9.5, but the cascade has been reduced to a riffle as the channel has widened, flow has spread across a larger area, and sediment has deposited. Across from the pool a point bar is developed on the left bank on the waterward side of the TransCanada levee. Emergent and woody vegetation are establishing on the bar, and the channel between the bar edge (at 1,000 cubic feet per second flow) is only about 35 feet wide. At the time of our March 2020 site visit, recent sand deposits were observed on the point bar and large turbulent upwelling cells were observed in the pool. A small surface water drainage channel is cut into the right valley wall at the current impingement location at RM 9.3. Because of the presence of this drainage, this area has possibly the highest vulnerability of any location on the right bank within the project area because the slope is eroding from both surface runoff from above and river forces below. Downstream of the pool the river transitions to a riffle-glide bed morphology with additional small pools developed downstream of bars and natural large wood jams. Successive TransCanada levee breaches and left bank erosion occurring since about 1975 have resulted in the widening of the active channel. The active channel includes the wetted channel, banks, side and back channels, and seasonally vegetated sediment bars. Figure 1 shows channel traces from 2002 through 2009 and highlights the major changes in channel configuration that have impacted the morphology of the active channel prior to 2002 and following the 2006 and 2009 flood events. Geomorphic analysis for the TransCanada levee setback Feasibility Study (King County 2011) determined that channel expansion or widening is the dominant channel migration mode in the reach, versus lateral meander bend growth, translation or avulsion. Channel expansion after the 2006 and 2009 flood events that eroded approximately 500 feet and 300 feet of levee prism length, respectively, added about 100 feet of active channel width (King County 2011). Levee breaching in this reach began prior to 2002, probably in the 1970s, when a 580 foot-long levee segment eroded in the vicinity of RM 9.6. The maximum active channel width measured in 1955 before the levee was constructed is about 580 feet (King 644 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 7 County 2011). The current active channel width downstream of RM 9.3 where the levee is still intact ranges between about 150 to 215 feet. In addition to left bank lateral erosion, lateral bars along the right bank experienced downstream and waterward growth, resulting in overall channel expansion following levee breaching. The channel positions shown in Figure 1 show that as left lateral bank erosion progressed downstream, right lateral bar growth also progressed downstream and riparian vegetation expanded on the bars. Channel Migration The City of Auburn has requested an analysis confirming no impacts from channel migration will occur downstream resulting from the proposed Project. A channel migration zone (CMZ) has not been formally delineated for the White River in the project area. In the absence of CMZ analysis, in accordance with ACC 15.68.141 (D), the channel migration zone may be designated either as the Special Flood Hazard Area or in accordance with Regional Guidance for Hydrologic and Hydraulic Studies in Support of the Model Ordinance for Floodplain Management under the National Flood Insurance Program and Endangered Species Act (FEMA Region X, 2010). This Regional Guidance document and the Biological Opinion recommends using methods outlined in A Framework for Delineating Channel Migration Zones (Rapp and Abbe, 2003) as the basis for determining the location of the CMZ. The King County CMZ mapping methodology, adopted through a public rule process and codified under King County Code chapter 21A-24 uses the Framework and other Ecology guidance for the preparation of CMZ mapping. The King County public rule also specifies methods to delineate severe and moderate channel migration hazard areas. These CMZ hazard areas are critical areas under King County’s land-use regulations. King County conducted an analysis of natural channel movement for the TransCanada Levee Setback Feasibilty Study (King County, 2011). The analysis described channel migration modes and characteristics and calculated lateral bank erosion rates but did not produce the mapping of the CMZ hazard areas. The purpose of the analysis was to estimate the expected channel width if the proposed TransCanada levee setback project was constructed. The channel migration analysis is summarized here and a copy of Appendix B that describes the full analysis is attached to this memo for reference. The methods used in these analyses of the TransCanada levee setback feasibility study and the currently proposed face and toe rock removal project both are consistent with the methods outlined in Rapp and Abbe (2003). The project area is within a reach of the White River that tends to migrate first by channel expansion followed by lateral bank migration. Migration by avulsion is less common in this river reach, based on the available historical record, and avulsions were common on the alluvial fan reach downstream of about RM 8 prior to construction of the Auburn Wall in the early 1900s. Based on measurements made at transects within the project reach (between about RM 8 and RM 10.6), the average annual lateral channel migration rate ranges between 16 and 30 feet per year. Between 1944 and 1955, the period after Mud Mountain Dam was built and before the TransCanada levee was in place, the average later migration rate was 21 feet/year and 25 to 30 feet/year in the period following levee construction. The lowest measured rate was 16 feet/year for the time period 2000-2009, and the river experienced large, episodic channel expansion 645 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 8 along several transects in 2006 and 2009 of 255 and 75 feet, respectively. Average channel migration rates in the unconstrained reach immediately upstream of the project reach range up to 40 feet per year. Estimating the location of the CMZ using the reach average annual migration rates requires a “design life” or period for which the CMZ is calculated. Reviewing the Regional Guidance (FEMA 2010) and the Framework (Rapp and Abbe 2003), the CMZ includes the historical migration zone (HMZ) plus an erosion hazard area (EHA), the area the channel could occupy for the next 100 years. Avulsion hazard areas where the river could jump its bank and occupy a new area, and disconnected migration areas – those areas separated from the CMZ by man- made structures that prevent channel movement – should also be considered. Finally, the Regional Guidance (FEMA 2010) recommends using only the severe hazard area that is designated by the regulating community, plus an additional 50 feet. The HMZ for the historical record that is post-construction of Mud Mountain Dam and was developed for the Feasibility Study (Figure B-2; King County 2011) is shown in Figure 8. Using the lowest reach average lateral migration rate of 16 feet/year and adding 50 feet per the Regional Guidance (FEMA 2010), the landward boundary of the severe CMZ hazard area at the project site would be approximately 450 feet landward of the current active channel boundary which is located approximately at the TransCanada levee toe. Based on this rough estimate, the entire project area is within the severe CMZ as are shoreline areas on the left bank downstream of the Project. Geomorphic Process Discussion and Project Implications Based on the observations described in the preceding sections, both slope and fluvial geomorphic processes are dynamic and interact within the project area. River engagement of the slope toe on the steep right bank will affect slope stability and may accelerate some active slope processes while other slope processes are unaffected by river forces. The loss of channel confinement following the breaching of the TransCanada levee has allowed channel migration to occur through floodplain erosion, bar deposition, and overall widening of the active channel area. This response to the TransCanada levee breaching beginning in the 1970s may be used to predict the geomorphic response to the proposed Project. The base of the right valley wall is very steep and unvegetated at the water line, indicating continuous scour that does not allow vegetation to establish. Failures observed from across the river on the slope face within the project area included debris flows and shallow debris slides. Based on site observations, the shallow debris slides consist of colluvial failures that appear to originate at the top or midslope as the veneer of vegetation and colluvium or weathered soil slides over the stronger, underlying parent material. Surface water runoff that carves rills and gullies on the slope transports material downslope. The slope toe appears to protrude prominently in the slope profile relative to the upper slope, indicating that the material that comprises the slope toe is stronger and more resistant to weathering than material that comprises the upper slope. Material from small debris slides originating at the toe of the slope 646 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 9 accumulate at the base of the slope and exhibit a blocky morphology that is resistant to river erosion. Changes in sediment storage within the active channel impacts channel migration. Material that accumulates at the base of the right bank slope protects the slope from toe erosion, induces more sediment deposition and woody material accumulation due to reduced velocities, and contributes to channel migration toward the opposite bank. Removing the levee toe and face rock while leaving the levee prism,which appears to be constructed of native alluvial materials, would prevent the development of the boulder cascades that hold the channel in place. Based on measurements of channel width prior to TransCanada levee construction and after the levee was breached, the proposed Project also is likely to cause active channel area expansion. Expansion of the active channel area from the current width of 200 feet to about 600 feet may be expected in areas following removal of the levee constriction (face and toe rock only). The levee prism would remain in the project area and the river would expend energy and shear stress eroding the alluvial materials that comprise the levee prism. Based on reach-average, measured channel migration rates, and depending on the actual flow events that occur following levee face and toe rock removal and subsequent erosion of the levee prism material, it is estimated that it will take between 9 and 15 years to reach the maximum channel width after completion of the Project (King County 2011). This process should help to alleviate channel incision as stream power is directed toward left bank erosion and sediment mobilization and transport. Arrows placed on Figure 1 that have the same color as the corresponding channel year trace indicate the point of maximum impingement by river flow on the right bank. The points of impingement follow the downstream progression of the left lateral erosion and right lateral bar growth, leaving a wider active channel upstream. The dark red arrow near RM 9.35 is the current point of impingement where the steep, boulder cascade formed by the rock rip rap from the failed TransCanada levee is helping to hold the river bed in place, focusing river flow and energy that has formed a deep scour pool at the base of the slope. Removing the toe and face rock from the levee will facilitate left bank erosion that will dissipate hydraulic energy, recruit sediment and wood to the channel, allow channel expansion, and allow the river to migrate downstream of the steep boulder cascade. The light blue arrow on Figure 1 indicates the approximate location of the point of impingement in the years following levee rock removal. As left lateral river bank erosion progresses downstream, river impingement on the right bank will be spread out, erosive forces will be reduced, and the channel morphology will evolve to a wider active channel with increased sediment storage. The rate that the point of impingement migrates downstream will depend on the magnitude of seasonally high flows after completion of the Project. Landslide Risk Analysis The primary goal of this risk assessment is to determine potential impacts to areas downstream of the proposed Project that plans to remove up to 400 linear feet of levee face and toe rock. Of particular concern is understanding if the proposed rock removal could cause changes to the direction of hydraulic forces beyond those currently evident in this reach that would increase 647 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 10 toe erosion of the right valley slope, resulting in mass wasting and potentially increasing the level of risk to properties and structures located at the top of the slope. The existing risk is first summarized and then an assessment of potential future risk to right bank property with structures situated on top of the valley slope is described. Existing Risk Based on review of the analyses conducted for the 2011 TransCanada Levee Setback Feasibility Study, recent site visits, and other pertinent information, the high right bank slope currently is subject to slope stability hazards that pose a risk to property and structures situated at the top of the steep slope. The hazards on the right valley slope include slope failure from debris slides and debris flows, raveling, and rill and gully development. Previous studies have found the rate of bank retreat (as measured from the top of the valley slope) to be low (King County 2019; 2011). The distance from top of bluff to the nearest structures is about 120 feet at the current point of impingement. The rate of bluff retreat has not been measured but appears to be small in the areas upstream of RM 9.1. At RM 9.1 and downstream, highly erodible geologic materials underlie the slope and bluff retreat in this area is faster than in upstream areas. An analysis of topographic point data from six LiDAR surveys between 2009 and 2019 at four locations on the right bank bluff revealed no measurable bluff retreat upstream of RM 9.1 (Figure 7). The presence of failed levee rock in the channel maintains an ongoing erosion hazard directed at the right bank. As noted above, structures situated at the top of the slope in this area appear to be set back about 120 feet from the bluff edge at this location and the rate of bluff retreat, although not specifically known, appears to be low. Therefore, the existing risk from landslide hazards to these structures at the top of the bluff also is low. Future Risk with Built Project If the Project is completed, the river will gradually migrate downstream and set up a new point of impingement against the right bank. The nearest structure at the top of the slope is about 72 feet from the bluff edge at the potential new point of impingement if the Project is built. The presence of very dense and cohesive material at the base of the slope at this location is anticipated to inhibit toe erosion and maintain the current slope configuration. Based on review of the analyses conducted for the TransCanada Levee Setback Feasibility Study, the recent site visits, and other pertinent information, it is expected that the future risk to right bank private property and structures due to slope failures related to the Project is very low or negligible and will not increase with respect to current risk. If the channel responds to the 648 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 11 Project as expected, the overall risk to right bank property and structures could be reduced as hydraulic forces spread out over the wider floodplain, reducing their impact on the right bank. The current trend of downstream meander bend migration without associated slope failures is expected to continue in this area because geologic and geomorphic conditions are the same as upstream areas where the levee has breached. Future Risk, No Action River forces associated with significant flood events between 1975 and 2009 were sufficient to breach the levee, laterally erode the bank behind the former levee, and progress downstream over time. If levee face and toe rock removal are not conducted, it is likely that the river will eventually erode away the levee prism and allow the river meander and point of impingement on the right bank to migrate downstream. The point of impingement could be focused on the right bank by additional angular face and toe rock deposited in the channel. Therefore, future risk to right bank structures should be expected to increase over time in a downstream direction over current risk. Right bank structures at the current point of impingement should experience a slight decrease in risk as the point of impingement migrates downstream and the right lateral gravel bar also builds downstream and protects the slope toe. Note that flows high enough to erode the levee may not occur until after the current flow control manual deviation for Mud Mountain Dam operations has been reversed. Channel Migration Risk Analysis The current Project and areas downstream within approximately 450 feet of the left bank of the active channel currently are at severe risk of erosion by channel migration. The TransCanada levee is not structurally capable of preventing channel migration of the White River as indicated by breaches that occurred in the 1970s, 2006, and 2009. The levee does not protect a sole-source access road, railroad, or state highway, other common criteria for identifying areas landward of a flood protection structure as disconnected migration areas. Construction of the Project will not change the location of the severe channel migration zone as estimated using common, industry standard methods (Rapp and Abbe 2003; FEMA 2010; King County Public Rule 21A-24). Consequently, the Project will not increase the risk to property downstream from channel migration over existing conditions. The Project is small (removal of 400 feet of the remaining 2,100 foot long revetment) and impacts will be limited to the King County parcel within the severe channel migration time frame (approximately 25-50 years). In addition, flows out of Mud Mountain Dam would need to be restored in order to return to flood conditions allowed in the 1970s and the 2006-2009 time frames that breached and eroded the TransCanada levee. This should be expected to occur sometime in the near future and likely restoration of pre-2009 operating conditions at Mud Mountain Dam will be stepped up incrementally, allowing time for monitoring and adaptive management if unexpected conditions or flood events occur. Conclusions and Recommendations The existing risk from channel migration and landslide hazards to private property and structures on the right bank is low based on the results of this analysis. Property on the left bank, including the project site and property immediately downstream on the left bank 649 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 12 currently are subject to severe channel migration risk. If the Project is not built (no action alternative), the future risk is about the same as the existing risk to these properties and structures. Risk to right bank property may increase if the levee is left in place and the river continues to erode it slowly while the remainder of the river remains confined by the facility. If the Project is built, the future risk to right bank private property and structures will remain low and may be less than the existing risk as the river is allowed to access the left floodplain for channel migration processes and flooding, reducing the pressure on the right bank. Channel migration risk to property on the left bank remains the same as current if the Project is constructed. The uncertainty about changes in the landslide and channel migration hazards and the risks posed to property in the project area and downstream should be monitored post- project. Post-project monitoring should document the channel response following construction and consider any adaptive management actions if risks appear to be higher than expected. Monitoring should include annual reviews of available aerial photographs and annual site visits to document slope conditions on the right valley wall for the first several years and at least once after any significant flood events. Potential adaptive management measures should be developed to evaluate and address any unforeseen slope stability and/or channel migration issues. Adaptive management may include removing additional levee material to allow the river to migrate away from the right bank, removing additional levee face and toe rock to allow downstream channel migration of the meander bend apex (point of impingement), or capital project development to reduce flood and flood-related risks to downstream areas. 650 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 13 References FEMA 2010. Regional Guidance for Hydrologic and Hydraulic Studies in support of the Model Ordinance for Floodplain Management under the National Flood Insurance Program and the Endangered Species Act. Produced by FEMA – Region 10, Draft January 2010. King County 2011.TransCanada Levee Setback Feasibility Study. King County Department of Natural Resources and Parks Water and Land Resources Division. King County 2016. Mapping of Potential Landslide Hazards along the River Corridors of King County, Washington, Technical Report. King County Department of Natural Resources and Parks Water and Land Resources Division. King County 2019. Coarse Sediment Dynamics in the White River Watershed. Prepared by Scott Anderson and Kris Jaeger, United States Geological Survey, Washington Water Science Center, for King County Department of Natural Resources and Parks Water and Land Resources Division. Mullineaux, D. 1965. Geologic map of the Auburn Quadrangle, King and Pierce Counties, Washington. United States Geologic Survey GQ 406. Scale 1:24,000. Rapp, C. and T. Abbe 2003. A Framework for Delineation of Channel Migration Zones. Washington State Department of Ecology Publication 03-06-027. Attachments: Figures 1 and 2 and Appendix B from King County 2011. 651 of 721 RM 9 RM 9.5 RM 9.1 RM 9.6 RM 9.7 RM 9.2 RM 9.3 RM 9.8 RM 8.9 RM 9.4 Tr a n s - C a n a d a L e v e e IMAGE_Ortho2017KCNAT LEGEND 2017 Channel Position 2009 Channel Position 2007 Channel Position 2002 Channel Position Deep-seated Landslide* Shallow Landslide Trans Canada Levee Partial Rock Removal Project River facilities RFMS owned parcel Parcel Lines Muckleshoot Indian Tribe Reservation 0 250 500125 Feet ±Basemap: 2017 Aerial Figure 1: Geomorphic changes inthe White River valley ^_ IMAGE_Ortho2017KCNAT City of Auburn Stuck River Drive Revetment Repair Project 1,500 0 1,500 Feet 2009 - 2017 2007 2002 After rock removal Approximate flow direction *from the King County2016 Landslide Map 652 of 721 E E E E E E E E¶¶Figure 4 Figure 3 Qaw Qpv Qg Qom Qom Qss Qid Qid Qss Qaw Qgt RM 9 RM 9.5 RM 9.1 RM 9.6 RM 9.7 RM 9.2 RM 9.3 RM 9.4 Tr a n s - C a n a d a L e v e e LEGEND River facilities Trans Canada Levee Partial Rock Removal Project Deep-seated Landslide* Shallow Landslide ¶Location of photographs Geologic Units Alluvium Osceola Mudflow Vashon Recessional Outwash Vashon Glacial Till Undifferentiated Vashon Drift Salmon Springs Drift Intermediate Drift 0 250 500125 Feet ± Figure 2:Surface Geology ofthe White River valley ^_ King County City of Auburn Stuck River Drive Revetment Repair Project 1,500 0 1,500 Feet Geologic descriptions and polygons adapted from: Geologic map of the Auburn quadrangle, King and Pierce Counties, Washington: U.S. Geol. Survey. Mullineaux 1965 Qaw Qaw Qom Qpv Qgt Qid Qg Qss *from the King County 2016 Landslide Map 653 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 14 Figure 3: Right valley slope geology at RM 9.1. River flow is from right to left. 654 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 15 Figure 4: Right valley slope geology at RM 9.3. River flow is from Right to left. Dark, linear patches in Qss are emergent groundwater in sandier layers. 655 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 16 Figure 5: River flow direction from right to left. Right valley slope failure types at RM 9.2. Colluvial debris flow at right; debris flow with fan and blocky failure at center right; slab erosion center left. Right lateral bar with woody material accumulated at toe of slope, providing erosion protection and minor buttressing to the slope. Structures visible on horizon at slope top. 656 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 17 Figure 6: View upstream along right valley slope showing steep profile of in-place geologic materials, flow coming toward viewer. Right lateral bar at the slope toe with accumulated woody material and emergent vegetation is visible in the top center left to center right. 657 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 18 Figure 7. Slope profiles over 10 years of LiDAR topographic data collection at four locations. Note no vertical exaggeration in profiles, vertical scale = horizontal scale. Profile 1 illustrates prominent profile of erosion-resistant glacial material at slope toe. Profile 4 illustrates bank top recession of highly-erodible glacial outwash sand and gravel at upper slope. This material is not present in the other three slope profiles. Qpv: Recessional Outwash Qid: Silt and clay Qss: Till with sand/gravel lenses Qg: Vashon till Qid: Silt and clay Qid: Silt and clay Qid: Silt and clay Qg: Vashon till Qg: Vashon till Qss: Till with sand/gravel lenses Qss: Till with sand/gravel lenses 658 of 721 Geomorphic Risk Analysis of TransCanada Levee Face and Toe Rock Removal December 2, 2020 19 Figure 8. Historical channel zone (also called historical migration zone, HMZ) for the project reach and upstream. Reproduced Figure B-2 from King County, 2011. Yellow star is project site location and approximate extent. 659 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 60 Appendix B: Natural Channel Movement (channel migration) Analyses B.1 METHODS Existing information was used to describe likely channel migration modes and characteristics sufficient for the feasibility-level analyses and evaluations in this study. No comprehensive Channel Migration Zone (CMZ) study was prepared for this feasibility study. The potential for additional, more detailed channel migration analyses to be prepared subsequent to this feasibility study is discussed in this appendix. The main modes of channel migration that may affect the project area and the adjoining upstream and downstream White River reaches include lateral channel migration, channel expansion and channel avulsion. The primary method by which to quantify existing channel migration extents and rates along the project area and the adjoining reaches is to document historical channel locations and their changes through time. Lateral channel migration Historical channel locations on the Lower White River from approximate River Mile (RM) 5.5 to RM 29 have been georeferenced and plotted by Collins and Sheikh (2004) in a Geographic Information System (GIS) and lateral rates of channel migration were calculated at time intervals of approximately every 5 to 10 years based on aerial photos from 1931 through 2000, plus early maps dating to the 1860s. The river mileage system used by Collins and Sheikh (2004) differs, by about a half mile, from the river mileage system used in this report, which is based on Northwest Hydraulic Consultants (2009). Collins and Sheikh (2004) identified six river segments within their overall study length that proceed upstream from the upstream end of the White River alluvial fan at about RM 7.6. White River Segments 1 and 2 are relevant to this feasibility study. The TransCanada site resides within Segment 1, which includes about three RMs from near the R Street Bridge (RM 7.6) to the Williams pipeline crossing (RM 10.6). Segment 2, which includes about 0.8 miles of the once-leveed reach from RM 10.6 to about RM 11.4, also provides information relevant for this TransCanada feasibility study (Figure B-1). The methods of Collins and Sheikh (2004) were used in this study to document, in GIS, the channel locations in 2005, 2007 and 2009 through White River Segments 1 and 2. Lateral average annual channel migration rates were calculated for the periods 2000-2005, 2005-2007, 2007-2009 and 2000-2009 in Segment 1. Lateral channel migration rates that occurred during flow conditions and channel constraints similar to those likely to exist after completion of a TransCanada levee removal project would be most representative for use in this evaluation, e.g., after completion of the Mud Mountain Dam in 1948 and whenever levees are not in place (either before their construction or after their breach). 660 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 61 Figure B-1. Lower White River along TransCanada site showing River Segments 1 and 2 and valley transects (from Collins and Sheikh 2004). River Segment 1 River Segment 2 661 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 62 Channel expansion Lateral channel migration may be less relevant for this project site, based on evidence of channel expansion in response to removal or loss of confining levees. Channel expansion is a form of natural channel movement or channel migration. The White River channel has expanded markedly in the past when unconstrained by levees in river Segments 1 and 2, after which the river has assumed a braided or multi-thread channel morphology. Therefore, in addition to considering lateral channel migration extents and rates, it also is necessary characterize the area that may be affected by channel expansion under post-project conditions. On the site scale, relevant information is gleaned from the recent channel expansion erosion episodes that occurred in the 2005-2007 and 2007-2009 periods at the cross section at RM 9.477 within the TransCanada project site. Aerial photographs bracketing these periods allow measurement of the down-valley and lateral dimensions of areas eroded during these episodes. A channel expanding episode would occur abruptly, likely during one flood event. The rate of channel expansion would be very high over a short period of time, as opposed to a uniform average annual lateral migration rate. On the river reach (or segment) scale, the Active Channel Width (ACW) in any given photo year can be measured at each of the cross-valley transects of Collins and Sheikh (2004) and averaged for that year. For a potential levee removal project at the TransCanada site, the ACWs in Segments 1 and 2 in the year 1955 should be representative of conditions after a TransCanada levee modification project is in place because the 1955 ACW post-dates dam completion in 1948 and pre-dates levee construction. The TransCanada levee is estimated as being constructed by 1959. Similarly, all five photo-years from 1980 to 2000 in Segment 2 should be representative because the Segment 2 left bank levees were breached during that period. Channel avulsion An avulsion is an abrupt shift of the main channel flow, partly or entirely, to a different location. The avulsion route typically is an existing former channel, side channel, or floodplain channel or slough. Multiple side channels and floodplain sloughs are documented in the lower White River through the TransCanada project area (Collins and Sheikh 2004) and abrupt channel shifting is common in a braided channel morphology. Channel migration zone (CMZ) mapping methods currently used in King County CMZ studies and maps assume an existing side channel to be a likely avulsion route if the side channel has a direct connection to the main channel, diverges in a downstream direction from the main channel, and allows access of flow by frequent flood events through the side channel (Perkins 1996). These same criteria are used in evaluating the likelihood of avulsion for the TransCanada project alternatives. Rapp and Abbe (2003) recommend consideration of similar characteristics in assessing the potential for avulsion. Historical Channel Zone The White River channel has assumed a braided or multi-channel morphology following channel expansion in recent examples near to the TransCanada site, including in Segment 2 since the 1980s. Recognizing that channel migration will continue after initial channel expansion, an indication of future channel migration of the braided channel can be inferred from past movement of the active channel by considering the Historical Channel Zone, or HCZ (Collins and Sheikh 2004). The HCZ is a planview composite of active channel outlines from different 662 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 63 historical times, drawn either from historical aerial photos or maps. The HCZ is nearly identical to the Historical Migration Zone (HMZ) of Rapp and Abbe (2003) and the Historical Channel Occupation Tract (HCOT) of GeoEngineers (2003). While the most complete HCZ would be based on channels mapped from all available historical sources, such an HCZ on the White River would depict some periods that are not representative of conditions after a levee removal project. B.2. RESULTS Lateral channel migration: Average annual lateral channel migration rates during various time periods are summarized in Table B-1. The average annual lateral channel migration rate through all of Segment 1 from 1944-1959, which is at least partly post-dam and pre-levee, was 25 ft/yr. The average annual lateral channel migration rate within Segment 1 along only the TransCanada site from 1944-1959 was 21 ft/yr. The average annual lateral channel migration for Segment 2 from 1980 to 2000 (i.e., from when the levees were breached to the last year of the Collins and Sheikh study) was 40 ft/yr. Therefore, a range for the average annual lateral channel migration rate that could be considered representative of post-project conditions on the TransCanada site is between 25 ft/yr and 40 ft/yr. The Segment 1 average annual rate from 2000-2009 was 16 ft/yr. However, the levees in Segment 1 during this time were largely intact, so this rate likely would not be considered representative of conditions after removal of the TransCanada levee. Table B-1. Lower White River channel migration rates relevant to the TransCanada site, including calculated average annual rates of lateral channel migration and estimated episodic erosion rates by channel expansion. Average annual lateral channel migration rate White Episodic erosion: River [Note A] [Note B] Average Average Average channel expansion Segment 1944- 1955 1955- 1959 1944- 1959 1980- 2000 2000- 2009 2005- 2007 2007- 2009 or RM (ft/yr) (ft/yr) (ft/yr) (ft/yr) (ft/yr) feet Feet Segment 1 21 30 25 16 Segment 2 32 22 23 40 TransCanada RM 8.9-9.6 10 31 21 Xsection at RM 9.477 255 75 Notes: A: Mud Mountain Dam was completed in 1948. B: 1959 is the first aerial photo year in which levee is visible in Segments 1 and 2. RM 8.9-9.6 River Miles along TransCanada site. RM 9.477 Cross section within TransCanada site at which episodic erosion occurred. 663 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 64 Channel expansion Channel expansion from 2005-2007 and 2007-2009 at cross section 9.477 provides recent and local information relevant to potential future channel expansion within the project site, with an increase in ACW of about 255 feet and 75 feet in the two periods, respectively (Table B-1). ACWs both on the river reach (segment) scale and site scale in Segments 1 and 2 during representative timeframes are summarized in Table B-2. In 1955 (post-dam and pre-levee), the average ACW was 624 feet in Segment 1 and 561 feet in Segment 2. In the 1980-2009 period in Segment 2, where the left bank levee had breached, the ACW ranged from 581 feet to 830 feet. The Segment 2 average of ACWs during that period was 678 feet and the 2009 ACW of Segment 2 in 2009 was about 600 feet. The 2009 ACW was 607 feet at cross section 9.477 (in Segment 1), which is where channel expansion episodes had occurred during 2005-2007 and 2007-2009 periods within the TransCanada site (Figure 4-1). Table B-2. Lower White River Active Channel Widths (ACWs) relevant to an unconfined TransCanada site White River Segment or RM 1955 ACW (ft) 1980 ACW (ft) 1985 ACW (ft) 1989 ACW (ft) 1995 ACW (ft) 2000 ACW (ft) 2009 ACW (ft) Average of values from 1980-2000 (ft) Segment 1 624 Segment 2 561 713 830 672 673 581 601 678 TransCanada RM 8.9-9.6 435 Xsec at RM 9.477 607 These various measurements suggest the potential range of an unconfined ACW in this part of the White River. An ACW of about 600 feet could be representative of a post-project unconfined condition (i.e. levee prism and rock armor removed) along TransCanada because that is the width that formed most recently at cross section 9.477 and that is the ACW of the most recent measurements throughout Segment 2. The average ACW measured from the year 2000 active channel outline (Collins and Sheikh (2004), not shown here) through all of Segment 1, where most levees were intact, including along the TransCanada site, was about 230 feet. The difference between an unconfined ACW of 600 feet and a confined, leveed ACW of 230 feet is about 370 feet. The following calculations are based on assumptions that migration proceeds at a uniform average annual rate of 25 ft/yr to 40 ft/yr (per Table B-1) and furthermore that the channel moves by lateral migration. If Alternative 2 were implemented and only the face rock was removed it would take about nine to 15 years to migrate through the remaining 370-foot distance of width from the present 230-foot ACW to an unconfined ACW of 600 feet. If Alternative 3 were implemented, its excavation of about 90 feet landward into the floodplain would result in an average ACW of 330 feet at project completion. The remaining 270 feet of a 600-foot unconfined ACW could be traversed in as little as seven years to as 664 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 65 much as 11 years, at the average lateral migration rate of 25 ft/yr to 40 ft/yr. Another perspective is that the levee prism excavation component of Alternative 3 essentially would jumpstart the lateral migration process by as little as about two years to as much as four years compared to Alternative 2. Historic Channel Zone (HCZ): The composite of historical channel locations in Segments 1 and 2, i.e., the HCZ, was assembled through different timeframes to provide information regarding potential future channel migration. HCZs are shown in the following figures and their average widths are summarized in Table B-3. HCZs covering different periods have different levels of relevance regarding a levee removal project along the TransCanada site. While the 1959-2009 period (Figure B-2) is entirely post-dam, it also includes levees in place through most of the period in Segment 1. The 1980- 2009 period (Figure B-3) in Segment 2 is post-dam with breached levees, so it may be most relevant to the TransCanada project. The 1931-2009 HCZ (Figure B-4) encompasses periods and conditions not representative to this analysis (i.e., both pre-dam and intact levee conditions), but is included for comparison purposes. Similarly, multiple channels that apparently flowed across and split the TransCanada site, evident in historic maps from mid-1800s to early 1900s but not shown here, would not represent current conditions relevant to this analysis. Table B-3. Lower White River Historical Channel Zone (HCZ) widths from time periods that may inform consideration of channel migration along an unconfined TransCanada site. Historical Channel Zone width (feet) Segment 1 Segment 2 Segment 1&2 Period (n=20) (n=5) (n=25) Comment 1959-2009 mean 465 1197 612 Post-dam, with levees in place. median 509 1129 530 1980-2009 mean 404 1187 561 Post-dam. Levee breaches in Segment 2. median 410 1077 506 1931-2009 mean 1063 1574 1165 Full photo period. Both pre-dam and post-dam. median 1134 1570 1162 Note: n = the number of locations at which the HCZ width was measured in each Segment. 665 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 66 Figure B-2. Lower White River Historical Channel Zone (HCZ) based on historical channels from 1959 through 2009. Average HCZ width through River Segments 1 and 2 is approximately 600 feet. River Segment 1 River Segment 2 666 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 67 Figure B-3. Lower White River Historical Channel Zone (HCZ) based on historical channels from 1980 through 2009. Average HCZ width through Segment 2 is approximately 1200 feet. River Segment 1 River Segment 2 667 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 68 Figure B-4. Lower White River Historical Channel Zone (HCZ) based on historical channels from 1931 through 2009. Average HCZ width through Segments 1 and 2 is approximately 1165 feet. River Segment 1 River Segment 2 668 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 69 Discussion Existing information from sources including recent channel expansion and ACWs from relevant timeframes suggest a width of 600 feet as a potential extent of channel expansion following removal of confining levees, within White River Segments 1 and 2. The 612- foot average (Table B-3) width of the 1959-2009 HCZ in Segment 1 and 2 is similar to that dimension, but the widespread existence of intact levees suggests that it is not a representative of conditions absent levees. The 1187-foot average width of the 1980- 2009 Segment 2 HCZ (Table B-3) may be more representative of unconfined conditions after a levee removal project at the TransCanada project site. But in order to make a specific prediction of future channel migration along the TransCanada project site, other controlling factors (e.g., geology, soils, channel gradient, valley confinement, etc.), as well as potential migration beyond the HCZ, would need to be considered on the river reach scale in both Segment 1 and Segment 2. Until such a comprehensive analysis is conducted, the extent of future channel migration on the TransCanada site cannot be specifically delineated. Future channel migration Future channel migration may occur beyond a representative ACW or HCZ. It may be necessary for a more specific characterization of future channel migration to be conducted as part of subsequent design phases for this project. Information that should be considered when characterizing future channel migration (in addition to historical channel locations and movement) should recognize or include the following: Existing site, reach and basin-scale conditions that may affect channel migration, including: Geology and soils Sediment trends in the area Vertical relationship between channel and adjacent lands Connectivity of channel to floodplain Degree of and trends in channel incision Large wood occurrence and flux Basin-scale controls on or alterations to sediment and flow regimes, and their potential changes through time Cumulative likely future channel migration by various modes, including: Lateral channel migration Potential geotechnical or slope stability conditions relevant to channel migration Channel expansion Channel avulsion Migration of the entire braided channel corridor 669 of 721 TransCanada Levee Setback Feasibility Study June 2011 Page 70 References Collins, B. D., and A. J. Sheikh. 2004. Historical channel locations of the White River, RM 5 - RM 28, King County, Washington. Prepared for King County Department of Natural Resources and Parks, Water and Land Resources Division, Flood Hazard Reduction Services Section, Seattle, Washington. GeoEngineers. 2003. Geomorphic evaluation and channel migration zone analysis, Puyallup, Carbon and White Rivers. Report prepared for Pierce County Public Works and Utilities Environmental Services, Water Programs Division, June 2003. Northwest Hydraulic Consultants. 2009. Floodplain Mapping Study for White River Zone 2 (RM 5.6 to RM 10.6). Prepared for King County Department of Natural Resources and Parks, Water and Land Resources Division, River and Floodplain Management Section, Seattle, Washington. Perkins, S. J. 1996. Channel migration in the Three Forks area of the Snoqualmie River. King County Department of Natural Resources, Surface Water Management Division, Seattle, Washington. Rapp, C. F., and T. B. Abbe. 2003. A framework for delineating channel migration zones. Washington State Department of Ecology and Washington State Department of Transportation. Final draft report. 670 of 721 Permit Number(s): N/A Applicant: King County River and Floodplain Management Section Phone: 206-263-6870 Email: tbloxton@kingcounty.gov This project does not disturb more than an acre of soil and has not triggered coverage under the NPDES Construction Stormwater General Permit. Section 1 – Project Overview Scope of Work The proposed TransCanada Levee Rock Removal Project includes removal of levee armor rock from the remnant, eroding, TransCanada levee with the goal to restore the project riverine processes and functions in the Lower White River and its floodplain in order to enhance riparian habitat for salmonids and additional species. The project is on the White River, 2.3 miles upstream of R Street Bridge, in the City of Auburn. The project is funded by the King County Flood Control District. Site Description The TransCanada Levee Rock Removal Project is located on the White River in the City of Auburn (Figure 1). The project includes modifications along approximately 400 feet linear along the left bank of the White River at approximately River Mile (RM) 9.3, approximately 2.3 miles upstream from the R Street Bridge. King County manages the TransCanada Levee, an earthen berm levee with a riprap armor face that stretches between RM 8.2 and 9.3. The existing levee composition includes variable sizes of riprap face rock placed over an alluvium fill prism. The levee has variable amounts of vegetation with large trees growing on and into the levee face. The properties immediately landward of the levee are owned by King County and the Muckleshoot Indian Tribe and are undeveloped. The levee historically extended upriver to RM 10.6, but the riprap armor has overtime eroded and launched into the river channel. The proposed TransCanada Rock Removal Project includes removal of levee armor rock from the remnant, eroding, TransCanada levee. The native alluvium levee prism remaining after removal of the armor rock will be left in place. This proposal is limited in scope and much smaller than the large-scale setback of the TransCanada levee that was evaluated by King County previously (2011 King County TransCanada Feasibility Study) and does not preclude a later setback of the remaining levee elements. 671 of 721 Figure 1: TransCanada Levee Vicinity Map Project Description The project will remove as much rock as possible from the levee face while avoiding impacts to wildlife and riparian habit to the greatest extent possible. The project will extend from the upstream, eroded end of the levee and conclude approximately 400 feet downstream. An excavator working from the bank will retrieve small amounts of angular face rock from the river channel that were eroded from the levee. Extensive excavation to locate buried riprap will not take place. Once the armor rock of the levee is removed the slope will be smoothed and light regrading of the slope will take place at the direction of the project representative to facilitate planting. Wood mulch will be spread on the slope to stabilize the area from stormwater runoff. Tree removal along the levee has been categorized in a three-tier system: • Tier 1 – Do not remove, establish a buffer area around the tree within which rock removal is very selective and will not damage tree • Tier 2 – Do not remove tree, no buffer area, extensive rock removal without complete destabilization of the trees, and 672 of 721 • Tier 3 – Remove as much rock as possible including potential to push over trees and leave onsite if needed for access or rock removal. Save standing trees if possible. Generally, the largest trees are identified as Tier 1 and the smallest being Tier 3, however the large trees at the upstream end closest to the river, will be pushed over to remove as much rock as possible to facilitate equipment access for the riprap removal from the channel. In order to allow for substantial rock removal without removing all the benefits of the large trees in the area trees will be left behind on the river bank. Rock removed from the levee face will be exported from the project area by truck. Trees removed during the work will be placed on the levee face and the disturbed areas planted with native trees and shrubs as an ecological benefit. The attached site and project plans show the project boundaries, existing conditions, and proposed site development. The total project area is approximately 0.84 acres with approximately 400 lineal feet of levee armor removal. 26 trees are planned to be removed and several of the larger trees will be limbed to facilitate construction but left in place. A temporary staging area on the access road totaling approximately 14300 square feet. Armor rock removal along the levee face will disturb a total of approximately 12500 square feet. The total impervious surface area of the completed project will be reduced, due to the armor rock removal, compared to existing conditions. These project elements will enhance riparian habitat and allow for more natural river processes. Construction will be completed within the fish window defined by Washington Department of Fish and Wildlife (WDFW): July 1-August 31 and during the dry season (May 1 – September 30). The levee top road is mostly sloping to the back of the levee and drains to the vegetated area. Surface Water Considerations The levee face drains to the vegetated area in front of the levee. The levee was built before current levee standards and few engineering records exist. Aerial photography from the 1930’s document the river in the area, and the exposed soil under the rock armoring indicates that river alluvium was used to build up the area. The current levee face is approximately at a 2:1 slope, with a few steeper areas. In-water work will be planned to minimize increase of turbidity to the White River. However, short-term releases (pulses) of turbid water may occur during the construction activities near the toe of the revetment at the upstream end only. Turbidity levels are highly variable and generally higher than other regional rivers because of the glacial nature of the White River and extremely high turbidity is common during summer low flow water conditions. Fish window (July 1 – August 31) turbidity levels in the White River at the R Street Bridge USGS gage ranged from 50 to 600 NTU’s in 2019. 673 of 721 Excavation in the channel will be limited and will take place with the excavator operating from the riverbank and only removing angular riprap that does not require digging into the river bed. The majority of the project is away from the river on the levee face that has a vegetated buffer between the river and the levee. The levee face disturbed area will be mulched with wood mulch. Areas potentially running off or onto the disturbed area will have straw wattles applied. Permits Permits required from the City of Auburn include: Clearing and Grading permit, Floodplain Development Permit and Shoreline Conditional Use Permit. A Hydraulic Project Approval is also needed from WDFW. Section 2 – Site Analysis A site analysis was performed by the King County River and Floodplain Management Section (RFMS). The project was deemed to be a restoration action that would not change the stormwater runoff properties of the area. Water directly infiltrates into much of the site currently, and any additional sheet flows from the dirt levee top road generally flow landward into the vegetated backside of the levee. Further geotechnical investigations were not performed. The OHW elevation is approximately 167 feet. There are no existing utilities in the project area and no other paved or developed areas exist. The levee is located on RFMS property and the hydro layer, with part of it in the river and most of it within the floodplain. There was no evidence of drainage issues entering/leaving the project area. The dirt road exits onto the gravel road portion of Stuck River Drive. 674 of 721 Section 3 – Minimum Requirements Per the City of Auburn Surface Water Management Manual, the project is required to meet minimum requirements #1 through #5 based on the total hard surface area being built. The following describes how the project will meet these requirements: • MR #1 Stormwater Site Plan Report – This document satisfies the requirement for a complete Stormwater Site Plan report except for items k-m. For item k, the final grade of the project will not change the flow path for stormwater runoff and there are no pipes, catch basins, ditches, or other conveyance systems in the project, therefore, final grade contours and proposed surface water flow directions will not be shown in the site plan. For item l, there are no ditches, swales, culverts, or pipes to show grades, dimensions, and/or direction of flow for within the project. For item m, there are no dewatering systems within the project to show in the plan site. • MR #2 Construction Stormwater Pollution Prevention Plan (SWPPP) – The attached City of Auburn Construction SWPPP Short Form and temporary erosion and sediment control (TESC) plan outlines the erosion and sediment control plan for construction of the project and satisfies this minimum requirement. The site plan and SWPPP short form do not have representation for requirements 3, 7, 10, and 13. For requirement #3 – Control Flow Rates, there is no concentrated flow to control on site, stormwater runoff from the project site is dispersed through sheet flow and direct infiltration. For requirement #7 – Protect Drain Inlets, there are no drainage inlets within the project site or downstream of the project site. For requirement #10 – Control Dewatering, a dewatering system will not be implemented during this project. For requirement #13 – Protect Low Impact Development BMPs, there are no bioretention areas within the project area to be protected. • MR #3 Source Control of Pollution – The project is the removal of riprap from an existing facility and will not have any significant commercial or industrial pollution generating activities following construction. This requirement has been considered and no further action is required. • MR #4 Preservation of Natural Drainage Systems and Outfalls – The existing site has been analyzed, runoff is currently to the surrounding natural area and will not change. The project will not create new discharge from the site and will not cause significant adverse impact to downstream receiving waters and properties. • MR #5 On – Site Stormwater Management – The applicant chooses to meet this requirement with the List Option. No BMPs were found to be infeasible. The project will satisfy this requirement in the following ways: Levee Face - The area of rock face infiltrates into the levee below and any additional runoff into the vegetated area at the toe. The rock area will be greatly reduced and disturbed area will be mulched and planted. The areas of retained native vegetation are exempt from BMP T5.13. 675 of 721 King County Historic Preservation Program Cultural Resources Review _____________________________________________________________________________ Request Number: 20-156 Project Name: Stuck River Revetment Repair Project Combination Code: 0049652 Date Requested: 05/05/2020 Reviewer(s): Philippe LeTourneau; Todd Scott Review Date: 05/22/2020 Federal Undertaking? : No State Undertaking? : No Department/Division/Section: DNRP/WLRD/RFMS Contact: JoAnn Whited Project Location Street Address: The Stuck River Revetment repair project site is located on the left bank of the White River at River Mile 7.9. Across the road is Icon Materials 4020 Kersey Way SE, Auburn, WA 98092. The companion Parcels: 292105HYDR, 2821059007 Summary Project Description T 21N, R 5E, sections 28 and 29. The Stuck River Revetment repair will be an in-kind repair of approx. 180 ft of damaged revetment. Large rock will be placed at toe within existing footprint and bank will not be regraded due to constraints of proximity of trail and road and need to keep mature trees. Live willow stakes will be planted on the repaired surface and trees and shrubs will be planted on the upper slope. Ground disturbance: live stakes will be driven to depths of 1.5 feet and trees and shrubs will be planted in 2-foot- diameter holes at depths of 1.5 feet. All ground disturbance for planting and live staking will be in dredged river sediments used in constructing the revetment. The companion action at TransCanada Levee will remove 200-400 feet of rock starting at the top end of the levee and minimize removal of large trees to the extent possible. Known Cultural Resources Within or Adjacent to Project Area Historic Res. Inventory: None. Archaeological Sites: None. Burke Museum Reported Sites: None. Ethnographic Places: None. GLO Map Features: None (1867, 1868 maps). Other DAHP Sites (cemeteries, etc.): None. Above-Ground Historic Resources: Both the Stuck River Drive Revetment and the Trans Canada Levee are of sufficient age to be considered historic. However, both are standard hydraulic solutions from the 1960s and not exceptional, and the work to the revetment is considered minimal repair. Work on the levee is more significant, but is still a small portion of levee removal over a much longer resource, so there is no adverse effect to the resource as a whole. 676 of 721 Information from Historic Maps, Aerial Photographs, Other Sources: The 1907-1908 King County Assessor's Timber Cruiser's report shows a trail crossing the TransCanada Levee project area and a "siwash" house 80 m to the west. Siwash is Chinook jargon for Indian, from the French "sauvage" (wild, savage). According to WLRD, the Stuck River Revetment is constructed of dredged river sediments (a mix of boulders, gravels, and sands). The TransCanada project area is within the Muckleshoot Indian reservation and is used for fishing and hunting purposes by tribal members. Comments: There are no archaeological sites in or adjacent to the project areas. Cultural Resources Surveys Within or Adjacent to Project Area: Above ground: none known. There have been no archaeological surveys in or adjacent to the project areas. DAHP GIS Predictive Model Classification: Very High Risk Environmental Conditions Landform: Holocene floodplain (aggrading) Distance to Water: 0 m Water Source: White River Slope: < 1 % Information from Historic Maps, Aerial Photographs, Other Sources: The 1907-1908 King County Assessor's Timber Cruiser's report shows the Stuck River Revetment project area on the right (north) bank of the Stuck River and the TransCanada Levee project area on the right (north) bank of the White River. 1936 aerial photographs show the Stuck River revetment project area in the White River channel and the Trans Canada Levee project area on a gravel bar in the White River. The 1949-1967 USGS Auburn 1:24,000 topographic quadrangles show the Stuck River Revetment project area on the right bank (north) side of the White River and the TransCanada Levee project area in its current position. The 1969-2017 USGS Auburn 1:24,000 topographic quadrangles show both project areas in their current positions. Comments: None. King County CRPP GIS Model Classification: The project areas have a Low Probability of containing archaeological resources because both were in the White River in 1936 and both are on dredged fill or other recent sediments. Even disturbed archaeological sites, if present, would necessitate that WLRD consult with DAHP and the Affected Indian Tribes about the need to obtain a state archaeological excavation permit. Comments: None. Recommendations Action: Yes 677 of 721 Arch. Survey: No Arch. Monitoring: No DAHP Excavation Permit: No Other Recommendation: Yes Comments: Above ground: no action required. No archaeological investigations are necessary as long as work crews have been trained in recognizing archaeological materials and in the appropriate procedures they should follow in the event any such materials are discovered during the project. Related Reviews: None. Tribal Contact/Consultation: We've been working with MIT and PTI and both have had site visits to the repair location. A collaboration with MIT is how the companion project was created as they requested that we look to restore natural geomorphic processes within the reach however due to the pandemic we have not had a site visit to the TransCanada rock removal location. Both tribes are aware of the project status' and are supportive. WLRD should forward HPP's review to the Tribes and keep them updated as to upcoming project activities. NOTE: This information is confidential and must not be released to the public. Site locations must be summarized without specific details in SEPA checklists and other public documents. Confidentiality of archaeological site information is protected under RCW 42.56.300. 678 of 721 King County Environmental ChecklistRFMS Prosrammatic SEPAt{¡KingCountyETvIRoNMENTAL GHecKLIST ADDEN DUMKing County Flood Protection Facility Maintenance andFlood Damage Repair Program Programmatic SEPANOTE: Bold text contains new information that varÍes from the original SEPA EnvironmentalChecklist. Non-bold, strike-through text contains the responses to questions in the originalEnvironmental Checklist. Only background information and those questions to which theânswers have changed as a result of this addendum are presented here; answers to questionsnot shown here are unchanged from the original Environmental Checklist.A. BACKGROUNDL Name of the proposed project, if applicable:King County Flood Protection Facility Maintenance and Flood Damage Repair ProgramProgrammatic SEPA2. Name of Applicant:Keny BaumanKing County Department of Natural Resources and Parks'Water and Land Resources DivisionAddress and phone number of applicant and contact personKing County'Water and Land Resources Division201 South Jackson Street, Suite 600Seattle, V/A 98 104-3855Phone: 206-477-4637Fax: 206-205-5134Date checklist prepared:May 15, 2007;Revised 05104t2015(Questions A.lln A.l2,and 8.1 have been revised)Agency r e que s ting che c kl i s.t :King County Department of Natural Resources and ParksV/ater and Land Resources DivisionaJ45Ii :\forms\environmental checklist.doc0s/14/L5679 of 721 King County Environmental ChecklistRFMS Programmatic SEPA6. Proposed timing or schedule (include phasing, if applicable):This checklist describes ongoing routine maintenance and flood damage repair of KingCounty levees and revetments and all appurtenances, as needs and funding warrant.10. List any government approvals or permits that will be neededfor your proposal, if lwtown.Regulatory permits typically required for King County Rivers and Floodplain ManagementProgram routine maintenance and flood damage repair projects covered under thisChecklist are listed below:National Marine Fisheries Service and U.S. Fish and Wildlife Service - EndangeredSpecies Act Section 7 Consultation. The Army Corps of Engineers typically conducts theseconsultations prior to issuance of Clean V/ater Act, Section 404Individual and NationwidePermit.aU.S. Army Corps of Engineers -- Clean V/ater Act, Section4}4,NationwidePermits. In the past most of these projects havê been conducted followingissuance of Nationwide Permit #3 9maintenance) and, less frequently, NationwidePermit #13 (Bank Stabilization) and #27 (Aquatic Habitat Restoration,Establishment, and Enhancement Activities).Washington Department of Fish and Wildlife - Hydraulic Project Approval (HPA)Chapter 77.55 Revised Code of V/ashington (RCW).Washington Department of Ecology - Clean V/ater Act, Section 4011402 Permits,Water Quality Standards (Turbidity Mixing Zone), Chapter 173-201A V/AC(Typically applied for during Army Corps 404 Permit process).Washington Department of Ecology - Letter of Authorization for Surface V/aterV/ithdrawal for Vegetation Plantings. (Typically applied for and issued annually,to cover all King County projects).King County Department of Development and Environmental Services - ShorelineSubstantial Development Permit (SSDP) Exemption. (Previous exemptions basedon criteria for routine maintenance or repair set forth in the Shorelinesmanagement Act of I97l: chapter 90.58 RCV/ and Title 173 V/AC; andconsistency with requirements of the king County Shoreline Master Program andKing County Title 25).King County Department of Development and Environmental Services - Clearingand Grading Permit (King County Code chapter 16.82, Clearing and Grading andKing County Code chapter 21A.24, Critical Areas. No Clearing and GradingPermit is required for maintenance or repair conducted under the regional RoadMaintenance ESA Program Guidelines if there is no extension of the length of thefacility or waterward extension and there is three-year monitoring).aaaai:Vorms\environmental checklist.doc05/t4t1s2680 of 721 King Countv Environmental ChecklistRFMS Proqrammatic SEPAProjects located within incorporated cities must meet Cities' correspondingrequirements (including and ESA-related updates) for shorelines and gradingpermit exemptions.King County River and Floodplain Management Program staff will be working inclose cooperation with the various WRIA groups to ensure that routine facilitymaintenance and flood damage repair activities will be mutually compatible withfuture WRIA salmon recovery plans and goals.I L Give a brief, complete description of your proposal, including the proposed uses andthe size of the project and site. There are several questions later in this checklist that askyou to describe certain aspects ofyour proposal. You do not need to repeat those answerson thís page. (Lead agencies may modify thisform to include additional specfficinformation on proj e ct de s øiption).The purpose of the projects described under this proposal is the repair and maintainexisting levees and revetments within and landward of the original footprint of theexisting facility, and relocation or removal of woody debris. These projects can bedivided into tåree five broad categories: (1) routine maintenance projects, (2) flooddamage repair projects, aad (3) relocation of limited amounts of large woody debriswhere they pose a threat to public safety, public infrastructure, developed publicproperty, private structures, or significant natural resources, (4) acquisition of lands toalleviate flooding, and (5) mitigation for routine maintenance, flood damage repair,relocation or removal of hazardous large wood, or other action authorized by thisProgrammatic SEPA. Mitigation will occur in the same river basin in areas thatmay or may not have an existing levee, rev-etment, or other flood protection facility."Routine maintenance projects - include (a) repair of existing gates and access roads; (b)installation of beneficial native shrubs along the face and landward sides of existingrevetments; (c) removal of undesirable non-native vegetation such as blackberries onexisting levee and revetment surfaces and access roads by hand or mechanical means suchas mowing; (d) mechanical removal of stumps left after tree or shrub cutting as part ofvegetation maintenance, and (d) (e) repair of interior drainage channels, flap gates,culverts and other already existing levee and revetment appurtenances.Flood damage repair projects - entail reconstruction of flood damaged levee andrevetment segments using the fish-friendly, bioengineering approaches laid out in the1993 Guidelines for Bank Stabilization Projects, or more recent best practices, andmitigation required for flood damage repairs. These include installing acombination of large toe rock (which is sometimes completely buried within the toe ofthe slope) and large coniferous logs with intact rootwads at or below the ordinary highwater mark (OHWM), which may be anchored to timber piles, boulders, or similarinstalled in the riverbed or bank, and native vegetation and biodegradable geotextilefabric above the OHWM, occasionally in combination with rock facing. Such projectsaIJi :\forms\environmental checklist. doc0s/14/t5681 of 721 King County Environmental ChecklistRFMS Programmatic SEPAare intended to stabilize eroding or slumping riverbanks and provide fish habitatbenefits within the flood protection facilities and adjacent floodplains.Flood damage repairs also include setbacks and removals of existing bank stabilizationfacilities where such actions will not adversely affect flood containment or theminimum freeboard performance cunently provided by the facility. Whereverpracticable, the top ofthe bank or undeveloped portions ofthe adjacent riparian zonewill be revegetated with native riparian plant species to provide additional riparianhabitat for fish and wildlife.This proposal does not cover construction of any new levees and revetments, nor doesit cover projects that entail addition to existing facilities such as levee raising andrevetment extensions. A separate, individual SEPA checklist will be prepared for suchprojects.2. Relocation or removal of large woody debris - may be conducted where it poses asubstantial threat to public health and safety, public infrastructure, developed publicproperty, private structures or significant natural resources. The volumes of materialsrelocated or removed are generally limited to the minimum amount needed to alleviatethe risk. For example, a small portion of a floodborne tree that is deflectingfloodwater onto a levee, a revetment, or a bridge abutment may be removed in order toredirect flow away from the threatened facility, or a log that is deflecting floodwatertoward a facility may be repositioned parallel to the bank or relocated a short distancedownstream in order to alleviate the risk. In some cases large wood may be addedas mitigation for removal or repositioning of hazard wood; mitigation wood willbe located and placed in a way that minimizes the potential for future hazard.River and stream channels are dynamic systems that continuously transport largewoody debris and sediments from their upper reaches to lower elevations. Thesematerials are integral parts of the natural ecology and geomorphology of the river orstreams, and are particularly vital in the life cycle of salmon and trout. However, insome circumstanses, significant accumulations of these materials can increaseflooding or erosion risks to public health and safety, public property, privatestructures, and significant natural resourcest.In accordance with policies set forth in the 2006 King County Flood hazardManagement Plan (Policies RCM-I and RCM-2), King County may reposition,relocate, or remove portions of large woody debris. Each Complaint by a landowner,l Threats to public health and safety include threats to critical facilities (e.g., hospitals, schools, nursing homes, andemergency response facilities) or health-related infrastructure (e.g., water supply systems, sewer lines). Thepresence of deep, high-velocity flows carrying debris through populated areas also constitute a threat to life andlimb. Public infrastructure and developed public property includes but is not limited to roads, bridges, utilitysystems, public buildings parks, and property for which King County has acquired development rights (e.g.,agricultural land). Private structures refers to residential and non-residential structures. Significant natural'resources are defined to include fish and wildlife species and their habitats that are considered significant to thelower Puget Sound Region, or which are listed as threatened or endangered under the federal Endangered SpeciesAct (ESA).4i :\forms\environmental checklist.doc05/14/15682 of 721 King County Environmental ChecklistRFMS Programmatic SEPAcitizen, or public agency staff member of large rwoody debris will be promptlyinspected in the field by technical and ecological staff of the king County River andFloodplain management Program to determine whether such materials pose animminent threat to public safety, public property, private structures, or naturalresources. The potential for such materials to provide beneficial fish and wildlifehabitat will also be evaluated. Accumulations of large woody debris are removed onlyif they pose a direct, imminent threat to public safety, public infrastructure anddeveloped public property, private structures or significant natural resources. Seefurther discussion on removal of large woody debris when it impacts river recreationin Section 8.12.d).During a "routine" no-floodingyear, at current funding levels, two to five levee orrevetment maintenance or repair projects are undertaken. Following a year withserious flooding and related increased federal flood disaster funding, the number ofprojects may increase to between five and ten. Individual projects may extend from100ft. to 2,000ft. along one side of the riverbank, with projects in the 200 to 500 ft.range being the most coÍtmon. Projects have been implemented using designapproaches involving bioengineering bank stabilization methods, and includedinstallation of large woody debris (mostly large coniferous trunks with intactrootwads).12. Location of the proposal. Give sfficient informationfor a person to understønd theprecise location ofyour proposed project, including a street address, tf any, and section,township, and range, if lwtown. If a proposal would occur over a range of areas, providethe range or boundøries of the site(s). Provide a legal desøiption, site plan, vicinity map,and topographic map, if reasonably available. Ií¡hile you should submit any plans requiredby the agency, you are not required to duplicate maps or detailed plans submitted with anypermit applications related to this checklist.The proposal covers routine maintenance and flood repair of exis+ing King County floodprotection facilities -- (those akeady included in the King County Rivers and FloodplainManagement Program river facilities inventory --), repositioning or removal ofhazardous large wood, and mitigation sites for routine maintenance and flood repairof King County flood protection facilities, on segments of the South Fork of theSkykomish River and its main tributaries including the Tye, Foss and Miller Rivers; theSnoqualmie River and its main tributaries, including the Tolt and the Raging Rivers, andthe North, Middle, and South Forks; the Sammamish River; the Cedar River, includingIssaquah Creek; the Green River, and the V/hite River, including the Greenwater River. Alisting of King County river facilities is included in Appendix E of the 2006 King CountyFlood Hazard Management Plan. The 2006 Plan is available at:http:i/www.kinecounty.gov/envirorunent/waterandland/floodins/dosuments/flood-hazard-management-plan.aspx5i :\forms\environmental checklist. doc05/t4/15683 of 721 King County Environmental ChecklistRFMS Programmatic SEPAB. ENVIRONMENTALELEMENTS1. Earthh. Proposed measures to restore or control erosion, or other impacts to the earth, f anyLower Slope and Toe Reconstruction BMPsWhere necessary, toe buttress rocks will be placed to firmly secure the large woodydebris in place, and to secure the entire toe buttress against undercutting erosion. Insome cases large wood may be anchored to timber piles, boulders, or similarinstalled in the riverbed or bank.C. SIGNATUREThe øbove answers are true and complete ta the best of my lcnowledge. I understand thatthe lead agency is relying on them to make its decision6Signature:Title:Date Submitted:tlv\n,-t I l ,2,ot6.Ii:\forms\environmental checklist.doc05t14ns6684 of 721 685 of 721 686 of 721 687 of 721 688 of 721 689 of 721 690 of 721 691 of 721 692 of 721 693 of 721 694 of 721 695 of 721 696 of 721 697 of 721 698 of 721 699 of 721 700 of 721 701 of 721 702 of 721 703 of 721 704 of 721 705 of 721 706 of 721 707 of 721 708 of 721 709 of 721 710 of 721 711 of 721 712 of 721 713 of 721 714 of 721 715 of 721 NOTICE OF PUBLIC HEARING TransCanada Levee Removal Project SHL21-0002 The City of Auburn is issuing a Notice of Hearing for the following described project. The permit applications and listed studies may be reviewed at the Auburn Department of Community Development at 1 E Main ST, 2nd Floor, Customer Service Center, Auburn, WA 98001. Proposal: Shoreline Conditional Use Permit to allow for removal of portion of existing levee along the left bank of the White River for the purposes of restoring riverine processes and functions. The site is located in the Natural Shoreline Environment Designation. Location: King County Parcel Number 2821059007, River Mile 9.3, White River. Notice of Application: May 14, 2021 Permit Application: February 22, 2021 Complete Application: March 22, 2021 File No. SHL21-0002 Applicant: Tom Bloxton King County 201 S Jackson St, Suite 5600 Seattle, WA 98104 Owner: King County River and Floodplain Management 201 S Jackson St, Suite 5600 Seattle, WA 98104 Studies/Plans Submitted with Application: • Critical Area Report and Habitat Impact Assessment, prepared by ESA, dated January, 2021 • Geomorphic Risk Analysis, prepared by King County, dated December 2, 2020 • Civil Plans, prepared by King County, dated February 17, 2021 • Joint Aquatic Resource Permit Application, prepared by King County, dated April 7, 2021 • Stormwater Site Plan, prepared by King County • Programmatic SEPA, prepared by King County, dated May 16, 2007 and revised May 14, 2015 Other Permits, Plans, and Approvals Needed: • Grading Permit, Shoreline Conditional Use Permit Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and Design and Construction Standards. Public Comment Period: All persons may comment on this application. Comments must be in writing and received by the end of the comment period at 5:00 p.m. on June 16, 2021 to the mailing address of 25 W Main ST, Auburn, WA, 98001-4998. Any person wishing to become a party of record, shall include in their comments that they wish to receive notice of and participate in any hearings, if relevant, request a copy of decisions once made, and be made 716 of 721 NOTICE OF PUBLIC HEARING SHL21-0002 (Continued) Page 2 of 2 aware of appeal rights. For questions regarding this project, please contact Dustin Lawrence, AICP, Senior Planner, at planning@auburnwa.gov or (253) 931-3092. Public Hearing: The meeting of the City of Auburn Hearing Examiner scheduled for June 16, 2021 at 5:30 p.m. will be held virtually and telephonically. To attend the meeting virtually please enter the meeting ID into the ZOOM app or call into the meeting at the phone number listed below. Per the Governor’s Emergency Proclamation 20-28, the City of Auburn is prohibited from holding an in-person meeting at this time. All meetings will be held virtually and telephonically. City of Auburn is inviting you to a scheduled Zoom meeting. Join Zoom Meeting https://zoom.us/j/96943444864 Meeting ID: 969 4344 4864 One tap mobile +12532158782,,96943444864# US (Tacoma) +13462487799,,96943444864# US (Houston) VICINITY MAP: 717 of 721 718 of 721 719 of 721 1 Dustin Lawrence From:Legals <legals@seattletimes.com> Sent:Wednesday, May 12, 2021 3:21 PM To:Dustin Lawrence Subject:RE: 10291 - Land Use Notice - May 14th Hi Dustin, This notice is scheduled to publish on 5/14, the total is $281.87. Thank you, Holly Botts Legal Advertising Representative p: (206) 652-6604 e: hbotts@seattletimes.com 720 of 721 2 From: Dustin Lawrence <dlawrence@auburnwa.gov> Sent: Wednesday, May 12, 2021 2:43 PM To: Legals <legals@seattletimes.com> Subject: 10291 - Land Use Notice - May 14th Hello, Please see the attached land use notice for May 14 th. Thank you, Dustin Lawrence, AICP, CFM Senior Planner Department of Community Development City of Auburn | www.auburnwa.gov Office# 253-931-3092 | Cell# 253-561-2224 | dlawrence@auburnwa.gov Mailing Address: 25 W Main Street, Auburn, WA 98001 Permit Center Address: 1 E Main Street, Auburn, WA 98002 (Click Here for Map) Customer Service Survey | Application Forms | Zoning Maps The information contained in this electronic communication is personal, privileged and/or confidential information intended only for the use of the individual(s) or entity(ies) to which it has been addressed. If you read this communication and are not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication, other than delivery to the intended recipient is strictly prohibited. If you have received this communication in error, please immediately notify the sender by reply e-mail. Thank you. CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. ”footer”" style="”background-color:" #ffeb9c;="" width:="" 100%;="" border:="" 1px="" solid="" #FFEB9C;="" padding:="" 2pt;="" border-style:="" solid;="" border-color:="" #9C6500;?=""> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. 721 of 721