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04-21-2021 Hearing Examiner Agenda
HEARING EXAMINER April 21, 2021 5:30 p.m. The Auburn City Hearing Examiner Meeting scheduled for Wednesday, April 21, 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/95279324579 Meeting ID: 952 7932 4579 One tap mobile 1 (253) 215-8782 Join from a PC, Mac, iPhone, iPad, or Android device I. Case No: SHL20-0001 and SHL20-0002 Applicant(s): Launce Goulet & Bruce Goulet 3226 S 198th St & 3722 S 198th St SeaTac, WA 98188 Agent: Heather Tatro Encompass Engineering & Surveying 165 NE Juniper St, Suite 201 Issaquah, WA 98027 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. . 1 of 519 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. Parcel Number(s): The King County parcel numbers are 3341000090, 3341000095, & 3341000100. 2 of 519 AGENDA BILL APPROVAL FORM HEARING EXAMINER Agenda Subject/Title: SHL20-0001 & SHL20-0002 Shoreline Conditional Use Permit Shoreline Substantial Dev. Permit Shoreline Variance Date: April 12, 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: Heather Tatro, Encompass Engineering & Surveying, 165 NE Juniper St, Suite 201, Issaquah, WA 98027 3 of 519 2019 Aerial Vicinity Map: Subject Site 104th Pl SE 4 of 519 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 519 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 519 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 is 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 December 18, 2020 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 for 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 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 2,121 square feet, Lot B to have a maximum building footprint of 1,751 square feet, and Lot C to have a maximum building footprint of 1,598 square feet. The residence proposed for Lot A will be setback 100 feet from the Green 7 of 519 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, one, 40-inch diameter at breast height (DBH), Big Leaf Maple, located more than 100 feet outside of the OHWM, but within the Urban Conservancy shoreline Environment designation, will be removed from Lot C. 7. The applicant provided a Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated April 10, 2020, revised October 28, 2020, confirming that the project will have “no net loss” in shoreline function. This includes Hydrologic, Vegetation, Hyporheic, and Habitat functions. The Critical Area Report is included as Exhibit 8. 8. To offset the loss minimum of the 100-foot stream buffer area that will be impacted on Lots B and C and the loss of the Big Leaf Maple on Lot C, 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 October 28, 2020, 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 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 8 of 519 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, as well as the sale price in 1985 to acquire two out of the three lots, City staff conclude that the three subject parcels are legal lots of records 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. 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 9 of 519 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. Also, 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 October 28, 2020, 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. 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, with the exception of one tree, the remaining existing trees outside of the 100 foot stream buffer area would be retained. 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. 21. 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. 22. 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. 23. 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 10 of 519 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 24. 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. 25. 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. 26. The existing land use surrounding the site includes single-family residences and open space. 27. 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 comments provided by the applicant, for a table containing the square footage and building footprint sizes of residences in the immediate area. Comprehensive Plan 28. The following City of Auburn Comprehensive Policies are relevant to the project: Volume 1, Land Use Element: 11 of 519 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 29. 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. 30. 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. 31. 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.” 32. 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. 12 of 519 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.” 33. 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.” 34. 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: 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 13 of 519 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.” 35. 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.” 36. 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.” 37. The City’s SMP contains the following policies related to Shoreline Vegetation Conservation: “4.4.2 Shoreline Vegetation Conservation 14 of 519 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.” 38. 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 39. 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). 40. 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. 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. 15 of 519 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. 41. 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. 42. 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. 43. 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. 44. 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. 45. 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: 16 of 519 “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 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, outsides 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 17 of 519 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 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; 18 of 519 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 one tree 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 removal 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. 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 19 of 519 current condition, in which invasive vegetation dominates the site, to a condition that will feature a dense mix of native vegetation plantings and wood 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 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 significantly 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 20 of 519 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. 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 21 of 519 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 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.” 22 of 519 “(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 the majority 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 one large tree within the building footprint area of Lot C. 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. 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 23 of 519 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 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. 24 of 519 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 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 25 of 519 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 December 18, 2020 (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 October 28, 2020 (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. 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. 26 of 519 8. With the exception of the 40-inch Big Leaf Maple within the southeast corner of Lot C, significant trees shall not be removed from the project site. Should the applicant need to remove any additional significant trees from the site, a 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 will be required either within 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, December 18, 2020 Exhibit 8 Critical Area Report, prepared by Evergreen Aquatic Resource Consultants, LLC, dated April 10, 2020, revised October 28, 2020 Exhibit 9 Shoreline Buffer Mitigation Plan, prepared by Evergreen Aquatic Resource Consultants, LLC, dated October 28, 2020 Exhibit 10 Geotechnical Study, prepared by Bergquist Engineering Services, dated November 4, 2020 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 27 of 519 666.7 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 28 of 519 166.7 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 29 of 519 30 of 519 31 of 519 32 of 519 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): 33 of 519 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 34 of 519 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 35 of 519 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. 36 of 519 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. 37 of 519 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 38 of 519 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. 39 of 519 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 40 of 519 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 41 of 519 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. 42 of 519 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] 43 of 519 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: 44 of 519 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). 45 of 519 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 46 of 519 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. 47 of 519 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 48 of 519 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 49 of 519 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 50 of 519 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 51 of 519 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 52 of 519 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. 53 of 519 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 54 of 519 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. 55 of 519 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- 56 of 519 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 57 of 519 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. 58 of 519 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. 59 of 519 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. 60 of 519 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. 61 of 519 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. 62 of 519 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. 63 of 519 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 64 of 519 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, 65 of 519 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. 66 of 519 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 67 of 519 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. 68 of 519 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 69 of 519 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 70 of 519 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. 71 of 519 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. 72 of 519 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. 73 of 519 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 74 of 519 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. 75 of 519 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. 76 of 519 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 77 of 519 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. 78 of 519 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 79 of 519 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 80 of 519 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. 81 of 519 82 of 519 83 of 519 84 of 519 85 of 519 86 of 519 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 October 28, 2020) Project Number 19046 87 of 519 WETLAND DELINEATION • MITIGATION DESIGN • COMPLIANCE MONITORING April 10, 2020 (revised October 28, 2020) 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 88 of 519 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 October 28, 2020) Project No. 19046 89 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page i April 10, 2020 (revised October 28, 2020) 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” ................................................................................................................................. 11 7.0 CONCLUSION ......................................................................................................................................... 12 8.0 REPORT LIMITATIONS .......................................................................................................................... 13 9.0 REFERENCES ........................................................................................................................................... 13 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 90 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 1 April 10, 2020 (revised October 28, 2020) 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 October 28, 2020). 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 project site is characterized by a moderately steep to 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. Topographic relief 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 91 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 2 April 10, 2020 (revised October 28, 2020) assessment was completed. The purpose of the assessment was to formally delineate and rate (classify) 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 92 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 3 April 10, 2020 (revised October 28, 2020) photographs as well as by observing conditions directly from the project site and/or from improved 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 site 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 during during a February 9, 2020 flood event revealed that flooding within the site is limited to the extreme western portions of the site when river flows are above the 93 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 4 April 10, 2020 (revised October 28, 2020) 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) are present in small patches. The limits of the OHWM were flagged “OHWM 1” through “OHWM 9”. Attachment 5 94 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 5 April 10, 2020 (revised October 28, 2020) to 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 effectively 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 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. 95 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 6 April 10, 2020 (revised October 28, 2020) 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. 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 may include, at a minimum, filter fabric (silt) fencing, temporary cover, and rock construction entrance best management practices (BMP’s). Permanent 96 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 7 April 10, 2020 (revised October 28, 2020) 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; 97 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 8 April 10, 2020 (revised October 28, 2020) 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 site, 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 within the buildable areas will be permanently stabilized. 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 October 20, 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 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. 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. 98 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 9 April 10, 2020 (revised October 28, 2020) Two years of temporary irrigation. Five years of maintenance and monitoring. Permanent preservation using a long-term protection notice on title. 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 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. 99 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 10 April 10, 2020 (revised October 28, 2020) 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). 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 manner. Existing plant species richness is low and dominant vegetation includes non-native species. Except for a few scattered trees, no significant habitat features or vegetation structure is present. Vegetation within the site is dominated by Himalayan blackberry, a Class C noxious weed, as well as a few scattered native trees and shrubs. Improved public right-of-way (104th Place SE) exists east of the site and the local vicinity supports single family residential development at a density greater than one dwelling unit (DU) per acre. The project site is located within the western hemlock (Tsuga heterophylla) 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 (Tsuga heterophylla), 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 100 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 11 April 10, 2020 (revised October 28, 2020) 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). 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. No work is proposed below the OHWM of the Green River and/or within associated flood hazard areas. 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 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. 101 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 12 April 10, 2020 (revised October 28, 2020) 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 (Tsuga heterophylla) forest zone of Washington State. 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. 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 102 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 13 April 10, 2020 (revised October 28, 2020) 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 (Tsuga heterophylla) forest zone as described by Franklin and Dyrness (1973). 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 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. 103 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 14 April 10, 2020 (revised October 28, 2020) 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. 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. 104 of 519 Critical Area Report: Wetlands & Streams Proposed Goulet Single Family Residences Page 15 April 10, 2020 (revised October 28, 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. 105 of 519 Attachment 1 Proposed Goulet Single Family Residences 04/10/2020 rev. 10/28/2020 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 Cros s 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 106 of 519 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. 10/28/2020107 of 519 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 108 of 519 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 109 of 519 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. 10/28/2020110 of 519 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 = 67.40' BASE FLOOD ELEVATION = 67.20' 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. 10/28/2020111 of 519 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. 10/28/2020112 of 519 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. 10/28/2020113 of 519 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 Green RiverRoad SE 104th Ave SELea Hill Rd SE8th ST NE 4th ST NE E a st M a i n ST West Main ST 14th ST NE 22nd ST NE Auburn Way NE ST NEM ST NER iv e r v ie 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 CrossST SE 112th PL SE105t h PL SEPROJECT 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 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. "CRITICAL AREA REPORT: WETLANDS AND STREAMS; PROPOSED GOULET SINGLE FAMILY RESIDENCES" BY EVERGREEN AQUATIC RESOURCE CONSULTANTS, LLC DATED 04/08/2020, REVISED OCTOBER 28, 2020. 2. "BOUNDARY & TOPOGRAPHIC SURVEY ‐ GOULET RESIDENCES" BY ENCOMPASS ENGINEERING & SURVEYING, DATED 10/16/2020. BASE DRAWINGS HAVE BEEN MODIFIED FROM THEIR ORIGINAL FORMAT TO ENHANCE VISUAL PRESENTATION AND/OR TO HIGHLIGHT SPECIFIC INFORMATION. 3. "CUP PLAN SET ‐ GOULET RESIDENCES" BY ENCOMPASS ENGINEERING & SURVEYING, DATED 10/22/2020. BASE DRAWINGS HAVE BEEN MODIFIED FROM THEIR ORIGINAL FORMAT TO ENHANCE VISUAL PRESENTATION AND/OR TO HIGHLIGHT SPECIFIC INFORMATION. 4. "SHORELINE VARIANCES PLAN SET LOT B & C ‐ GOULET RESIDENCES" BY ENCOMPASS ENGINEERING & SURVEYING, DATED 10/22/2020. BASE DRAWINGS HAVE BEEN MODIFIED FROM THEIR ORIGINAL FORMAT TO ENHANCE VISUAL PRESENTATION AND/OR TO HIGHLIGHT SPECIFIC INFORMATION. 5. "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). 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 PLAN10/28/201 114 of 519 OHWM9 OHWM1 OHWM2 OHWM3 OHWM4 OHWM5 OHWM6 OHWM7 OHWM8 CHANNEL MIGRATION ZONE 50' CHANNEL MIGRATION ZONE BUFFER 100 YEAR FLOODPLAIN (HATCHED AREA) 100' SHORELINE BUFFER N 7 4 °1 5 '2 4 "E 1 6 1 .3 1 ' N88°25'43"W 185.33' N 6 0 °1 2 '2 4 "E 1 4 9 .7 2 'N 6 0 °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 = 67.40' BASE FLOOD ELEVATION = 67.20' UTILITY EASEMENT RECORDING NUMBER 2000091000505 N29°47'36"W 90.00' 15' SEWER SETBACK (HATCHED AREA) 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 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 PLAN10/28/201 115 of 519 PROPOSED REDUCED SHORELINE BUFFER (WIDTH VARIES) PROPOSED SHORELINE BUFFER REDUCTION (HATCHED AREA) 40" BIGLEAF MAPLE. TREE TO BE REMOVED. LOGS SHALL BE SALVAGED DURING TREE REMOVAL FOR FUTURE USE IN BUFFER MITIGATION AREAS. 3 X 28" BIGLEAF MAPLE. SAVE TREES. INSTALL TREE PROTECTION ‐ SEE DETAIL 3‐2. 12" COTTONWOOD. SAVE TREE. INSTALL TREE PROTECTION ‐ SEE DETAIL 3‐2. INSTALL TEMPORARY STREAM BUFFER FENCING AT BUFFER LIMITS. SEE DETAIL 3‐1. 36" DOUGLAS‐FIR. SAVE TREE. INSTALL TREE PROTECTION ‐ SEE DETAIL 3‐2. 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 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. ALL TREES DESIGNATED TO BE SAVED SHALL BE PROTECTED BY FENCING, AS ILLUSTRATED. INSTALL TREE PROTECTION FENCE AT TREE DRIP LINE OR AT EDGE OF DISTURBED AREA, AS SHOWN ON PLANS, PRIOR TO START OF CONSTRUCTION. TREE PROTECTION FENCING SHALL BE MAINTAINED THROUGHOUT THE DURATION OF THE PROJECT AND SHALL NOT BE REMOVED UNTIL AUTHORIZED BY THE CITY OF AUBURN.DRIP LINE OR ASAPPROVED BY ARBORISTORANGE, UV RESISTANT HIGH TENSILE STRENGTH POLYETHYLENE LAMINAR BARRICADE FABRIC TREE PROTECTION DETAIL2 3 NO SCALE WOOD OR METAL POST 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 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 98188DRIP LINE OR ASAPPROVED BY ARBORISTREVISED PER NEW SITE PLAN10/28/201 LOT B BUILDABLE AREA = 2,597 SF LOT A BUILDABLE AREA = 2,834 SF LOT C BUILDABLE AREA = 2,322 SF 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% PROPOSED BUILDABLE AREA: PROPOSED PROPOSED 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 % 116 of 519 MITIGATION LEGEND: QUANTITY PER LOT DESCRIPTION LOT ALOT BLOT 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 222 LOG W/O ROOTWAD 222 CRITICAL AREA FENCE 92 LF 84 LF 91 LF CRITICAL AREA SIGN 111 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 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 ALOT BLOT C BIGLEAF MAPLE ACER MACROPHYLLUM FACU 2 GALLON CONTAINERIZED 80 26 26 28 BLACK COTTONWOOD POPULUS BALSAMIFERA FAC 2 GALLON CONTAINERIZED 51 17 17 18 DOUGLAS‐FIR PSEUDOTSUGA MENIESII FACU 2 GALLON CONTAINERIZED 29 10 9 10 WESTERN REDCEDAR THUJA PLICATA FAC 2 GALLON CONTAINERIZED 112 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. 15' MIN. NATIVE SOIL1/2 DIA MIN LOGS SHALL BE A 50%/50% MIX OF CONIFER AND DECIDUOUS SPECIES HAVING A MINIMUM DIAMETER OF 12 INCHES WITH BARK ATTACHED. 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 117 of 519 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: PLANT MATERIALS (includes labor cost for plant installation) Type Unit Price Unit Quantity Cost PLANTS: Container, 2 gallon, medium soil $20.00 Each 377.00 $ 7,540.00 PLANTS: Stakes (willow)$2.00 Each 42.00 $ 84.00 TOTAL $ 7,624.00 Type Unit Price Unit Cost Labor: Consultant, supervising $55.00 HR 5.00 $ 275.00 Irrigation - temporary $3,000.00 Acre 0.23 $ 690.00 TOTAL $ 965.00 ITEMS Unit Cost Unit Cost Logs, w/o root wads, 16"-24" diam., 30' long $245.00 Each 2.00 $ 490.00 Logs w/ root wads, 16"-24" diam., 30' long $460.00 Each 2.00 $ 920.00 * All costs include delivery and installation TOTAL $ 1,410.00 EROSION CONTROL ITEMS Unit Cost Unit Cost Mulch, by hand, wood chips, 6" deep $3.25 SY 1193.00 $ 3,877.25 TOTAL $ 3,877.25 GENERAL ITEMS ITEMS Unit Cost Unit Cost Fencing, split rail, 3' high (2-rail)$10.54 LF 92.00 $ 969.68 Fencing, temporary (NGPE)$1.20 LF 92.00 $ 110.40 TOTAL $ 1,080.08 $ 14,956.33 ITEMS Percentage of Construction Ct Unit Cost Mobilization 10%1 $ 1,495.63 Contingency 30%1 $ 4,486.90 TOTAL $ 5,982.53 MAINTENANCE AND MONITORING Maintenance, annual (by owner or consultant) Larger than 5,000 sq.ft. but < 1 acre -buffer mitigation only $ 360.00 EACH 5.00 $ 1,800.00 Monitoring, annual (by owner or consultant) Larger than 5,000 sq.ft. but < 1 acre with wetland or aquatic area impacts $ 900.00 EACH 5.00 $ 4,500.00 TOTAL $ 6,300.00 Subtotal $27,238.86 25%$6,809.72 TOTAL $34,048.58 (8 hrs @ 45/hr) Description NOTE: Projects with multiple permit requirements may be required to have longer monitoring and maintenance terms. This will be evaluated on a case-by- case basis for development applications. Monitoring and maintance ranges may be assessed anywhere from 5 to 10 years. (Construction Cost Subtotal) (10 hrs @ $90/hr) OTHER INSTALLATION COSTS ( LABOR, EQUIPMENT, & OVERHEAD) HABITAT STRUCTURES* BOND ESTIMATE ‐ LOT A1 5 PLANT MATERIALS (includes labor cost for plant installation) Type Unit Price Unit Quantity Cost PLANTS: Container, 2 gallon, medium soil $20.00 Each 344.00 $ 6,880.00 PLANTS: Stakes (willow)$2.00 Each 38.00 $ 76.00 TOTAL $ 6,956.00 Type Unit Price Unit Cost Labor: Consultant, supervising $55.00 HR 5.00 $ 275.00 Irrigation - temporary $3,000.00 Acre 0.21 $ 630.00 TOTAL $ 905.00 ITEMS Unit Cost Unit Cost Logs, w/o root wads, 16"-24" diam., 30' long $245.00 Each 2.00 $ 490.00 Logs w/ root wads, 16"-24" diam., 30' long $460.00 Each 2.00 $ 920.00 * All costs include delivery and installation TOTAL $ 1,410.00 EROSION CONTROL ITEMS Unit Cost Unit Cost Mulch, by hand, wood chips, 6" deep $3.25 SY 998.00 $ 3,243.50 TOTAL $ 3,243.50 GENERAL ITEMS ITEMS Unit Cost Unit Cost Fencing, split rail, 3' high (2-rail)$10.54 LF 84.00 $ 885.36 Fencing, temporary (NGPE)$1.20 LF 84.00 $ 100.80 TOTAL $ 986.16 $ 13,500.66 ITEMS Percentage of Construction Ct Unit Cost Mobilization 10%1 $ 1,350.07 Contingency 30%1 $ 4,050.20 TOTAL $ 5,400.26 MAINTENANCE AND MONITORING Maintenance, annual (by owner or consultant) Larger than 5,000 sq.ft. but < 1 acre -buffer mitigation only $ 360.00 EACH 5.00 $ 1,800.00 Monitoring, annual (by owner or consultant) Larger than 5,000 sq.ft. but < 1 acre with wetland or aquatic area impacts $ 900.00 EACH 5.00 $ 4,500.00 TOTAL $ 6,300.00 Subtotal $25,200.92 25%$6,300.23 TOTAL $31,501.16 (8 hrs @ 45/hr) Description NOTE: Projects with multiple permit requirements may be required to have longer monitoring and maintenance terms. This will be evaluated on a case-by- case basis for development applications. Monitoring and maintance ranges may be assessed anywhere from 5 to 10 years. (Construction Cost Subtotal) (10 hrs @ $90/hr) OTHER INSTALLATION COSTS ( LABOR, EQUIPMENT, & OVERHEAD) HABITAT STRUCTURES* PLANT MATERIALS (includes labor cost for plant installation) Type Unit Price Unit Quantity Cost PLANTS: Container, 2 gallon, medium soil $20.00 Each 319.00 $ 6,380.00 PLANTS: Stakes (willow)$2.00 Each 30.00 $ 60.00 TOTAL $ 6,440.00 Type Unit Price Unit Cost Labor: Consultant, supervising $55.00 HR 5.00 $ 275.00 Irrigation - temporary $3,000.00 Acre 0.19 $ 570.00 TOTAL $ 845.00 ITEMS Unit Cost Unit Cost Logs, w/o root wads, 16"-24" diam., 30' long $245.00 Each 2.00 $ 490.00 Logs w/ root wads, 16"-24" diam., 30' long $460.00 Each 2.00 $ 920.00 * All costs include delivery and installation TOTAL $ 1,410.00 EROSION CONTROL ITEMS Unit Cost Unit Cost Mulch, by hand, wood chips, 6" deep $3.25 SY 802.00 $ 2,606.50 TOTAL $ 2,606.50 GENERAL ITEMS ITEMS Unit Cost Unit Cost Fencing, split rail, 3' high (2-rail)$10.54 LF 91.00 $ 959.14 Fencing, temporary (NGPE)$1.20 LF 91.00 $ 109.20 TOTAL $ 1,068.34 $ 12,369.84 ITEMS Percentage of Construction Ct Unit Cost Mobilization 10%1 $ 1,236.98 Contingency 30%1 $ 3,710.95 TOTAL $ 4,947.94 MAINTENANCE AND MONITORING Maintenance, annual (by owner or consultant) Larger than 5,000 sq.ft. but < 1 acre -buffer mitigation only $ 360.00 EACH 5.00 $ 1,800.00 Monitoring, annual (by owner or consultant) Larger than 5,000 sq.ft. but < 1 acre with wetland or aquatic area impacts $ 900.00 EACH 5.00 $ 4,500.00 TOTAL $ 6,300.00 Subtotal $23,617.78 25%$5,904.44 TOTAL $29,522.22 OTHER INSTALLATION COSTS ( LABOR, EQUIPMENT, & OVERHEAD) HABITAT STRUCTURES* Description NOTE: Projects with multiple permit requirements may be required to have longer monitoring and maintenance terms. This will be evaluated on a case-by- case basis for development applications. Monitoring and maintance ranges may be assessed anywhere from 5 to 10 years. (Construction Cost Subtotal) (10 hrs @ $90/hr) (8 hrs @ 45/hr) 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 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 PLAN10/28/201 118 of 519 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 119 of 519 120 of 519 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. 121 of 519 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. 122 of 519 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). 123 of 519 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. 124 of 519 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. 125 of 519 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 126 of 519 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 127 of 519 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 128 of 519 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: 129 of 519 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 130 of 519 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. 131 of 519 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. 132 of 519 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 133 of 519 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. 134 of 519 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. 135 of 519 136 of 519 137 of 519 138 of 519 139 of 519 140 of 519 141 of 519 142 of 519 143 of 519 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 144 of 519 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 145 of 519 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 146 of 519 147 of 519 148 of 519 149 of 519 150 of 519 151 of 519 152 of 519 153 of 519 154 of 519 155 of 519 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. 156 of 519 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 519 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 519 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 519 160 of 519 161 of 519 162 of 519 163 of 519 164 of 519 165 of 519 166 of 519 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 167 of 519 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 168 of 519 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. 169 of 519 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 170 of 519 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. 171 of 519 172 of 519 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 173 of 519 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 174 of 519 Photo 2 – Green River from Site Looking North Photo 3 – Green River from SE 320th Street Bridge Looking North 175 of 519 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. 176 of 519 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. 177 of 519 2. Concentrated Flow Dispersion (BMP T5.11) or Sheet Flow Dispersion (BMP T5.12): No additional hard surfaces to mitigate. 178 of 519 179 of 519 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 180 of 519 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. 181 of 519 Appendix A Hydraulic/Hydrologic Analysis and Modeling Results 182 of 519 WWHM2012 PROJECT REPORT 183 of 519 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 184 of 519 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 185 of 519 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 186 of 519 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 5 Routing Elements Predeveloped Routing 187 of 519 WWHM Model_Lot A 3/3/2020 7:50:33 AM Page 6 Mitigated Routing 188 of 519 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 0.014 189 of 519 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 190 of 519 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 191 of 519 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 10192 of 519 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 193 of 519 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. 194 of 519 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. 195 of 519 WWHM Model_Lot A 3/3/2020 7:51:07 AM Page 14 LID Report 196 of 519 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. 197 of 519 WWHM Model_Lot A 3/3/2020 7:51:30 AM Page 16 Appendix Predeveloped Schematic 198 of 519 WWHM Model_Lot A 3/3/2020 7:51:33 AM Page 17 Mitigated Schematic 199 of 519 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 200 of 519 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 201 of 519 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 202 of 519 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 203 of 519 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 204 of 519 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 *** 205 of 519 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 206 of 519 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 207 of 519 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 26 Predeveloped HSPF Message File 208 of 519 WWHM Model_Lot A 3/3/2020 7:51:34 AM Page 27 Mitigated HSPF Message File 209 of 519 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 210 of 519 Appendix B Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 211 of 519 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 212 of 519 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 213 of 519 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 214 of 519 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. 215 of 519 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. 216 of 519 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). 217 of 519 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. 218 of 519 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. 219 of 519 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 220 of 519 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 221 of 519 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. 222 of 519 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: 223 of 519 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 224 of 519 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. 225 of 519 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. 226 of 519 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 227 of 519 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. 228 of 519 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. 229 of 519 230 of 519 231 of 519 232 of 519 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. 233 of 519 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. 234 of 519 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. 235 of 519 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. 236 of 519 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. 237 of 519 238 of 519 239 of 519 240 of 519 241 of 519 242 of 519 243 of 519 244 of 519 245 of 519 246 of 519 247 of 519 248 of 519 249 of 519 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. 250 of 519 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 519 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 519 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 519 254 of 519 255 of 519 256 of 519 257 of 519 258 of 519 259 of 519 260 of 519 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 261 of 519 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 262 of 519 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. 263 of 519 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 264 of 519 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. 265 of 519 266 of 519 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 267 of 519 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 268 of 519 Photo 2 – Green River from Site Looking North Photo 3 – Green River from SE 320th Street Bridge Looking North 269 of 519 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. 270 of 519 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. 271 of 519 2. Concentrated Flow Dispersion (BMP T5.11) or Sheet Flow Dispersion (BMP T5.12): No additional hard surfaces to mitigate. 272 of 519 273 of 519 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 274 of 519 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. 275 of 519 Appendix A Hydraulic/Hydrologic Analysis and Modeling Results 276 of 519 WWHM2012 PROJECT REPORT 277 of 519 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 278 of 519 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 279 of 519 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 280 of 519 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 5 Routing Elements Predeveloped Routing 281 of 519 WWHM Model_Lot B 3/3/2020 8:04:44 AM Page 6 Mitigated Routing 282 of 519 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 0.015 283 of 519 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 284 of 519 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 285 of 519 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 10286 of 519 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 287 of 519 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. 288 of 519 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. 289 of 519 WWHM Model_Lot B 3/3/2020 8:05:17 AM Page 14 LID Report 290 of 519 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. 291 of 519 WWHM Model_Lot B 3/3/2020 8:05:41 AM Page 16 Appendix Predeveloped Schematic 292 of 519 WWHM Model_Lot B 3/3/2020 8:05:43 AM Page 17 Mitigated Schematic 293 of 519 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 294 of 519 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 295 of 519 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 296 of 519 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 297 of 519 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 298 of 519 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 *** 299 of 519 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 300 of 519 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 301 of 519 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 26 Predeveloped HSPF Message File 302 of 519 WWHM Model_Lot B 3/3/2020 8:05:44 AM Page 27 Mitigated HSPF Message File 303 of 519 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. 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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 304 of 519 Appendix B Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 305 of 519 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 306 of 519 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 307 of 519 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 308 of 519 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. 309 of 519 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. 310 of 519 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). 311 of 519 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. 312 of 519 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. 313 of 519 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 314 of 519 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 315 of 519 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. 316 of 519 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: 317 of 519 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 318 of 519 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. 319 of 519 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. 320 of 519 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 321 of 519 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. 322 of 519 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. 323 of 519 324 of 519 325 of 519 326 of 519 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. 327 of 519 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. 328 of 519 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. 329 of 519 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. 330 of 519 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. 331 of 519 332 of 519 333 of 519 334 of 519 335 of 519 336 of 519 337 of 519 338 of 519 339 of 519 340 of 519 341 of 519 342 of 519 343 of 519 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. 344 of 519 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 519 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 519 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 519 348 of 519 349 of 519 350 of 519 351 of 519 352 of 519 353 of 519 354 of 519 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 355 of 519 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 356 of 519 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. 357 of 519 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 358 of 519 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. 359 of 519 360 of 519 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 361 of 519 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 362 of 519 Photo 2 – Green River from Site Looking North Photo 3 – Green River from SE 320th Street Bridge Looking North 363 of 519 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. 364 of 519 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. 365 of 519 2. Concentrated Flow Dispersion (BMP T5.11) or Sheet Flow Dispersion (BMP T5.12): No additional hard surfaces to mitigate. 366 of 519 367 of 519 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 368 of 519 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. 369 of 519 Appendix A Hydraulic/Hydrologic Analysis and Modeling Results 370 of 519 WWHM2012 PROJECT REPORT 371 of 519 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 372 of 519 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 373 of 519 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 374 of 519 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 5 Routing Elements Predeveloped Routing 375 of 519 WWHM Model_Lot C 3/3/2020 8:23:22 AM Page 6 Mitigated Routing 376 of 519 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 0.015 377 of 519 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 378 of 519 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 379 of 519 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 10380 of 519 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 381 of 519 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. 382 of 519 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. 383 of 519 WWHM Model_Lot C 3/3/2020 8:23:55 AM Page 14 LID Report 384 of 519 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. 385 of 519 WWHM Model_Lot C 3/3/2020 8:24:19 AM Page 16 Appendix Predeveloped Schematic 386 of 519 WWHM Model_Lot C 3/3/2020 8:24:21 AM Page 17 Mitigated Schematic 387 of 519 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 388 of 519 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 389 of 519 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 390 of 519 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 391 of 519 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 392 of 519 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 *** 393 of 519 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 *** # - #<------------------><---> 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 394 of 519 WWHM Model_Lot C 3/3/2020 8:24:22 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 395 of 519 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 26 Predeveloped HSPF Message File 396 of 519 WWHM Model_Lot C 3/3/2020 8:24:22 AM Page 27 Mitigated HSPF Message File 397 of 519 WWHM Model_Lot C 3/3/2020 8:24:22 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 398 of 519 Appendix B Critical Areas Report by Bergquist Engineering Services dated April 9, 2020 399 of 519 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 400 of 519 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 401 of 519 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 402 of 519 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. 403 of 519 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. 404 of 519 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). 405 of 519 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. 406 of 519 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. 407 of 519 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 408 of 519 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 409 of 519 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. 410 of 519 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: 411 of 519 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 412 of 519 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. 413 of 519 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. 414 of 519 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 415 of 519 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. 416 of 519 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. 417 of 519 418 of 519 419 of 519 420 of 519 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. 421 of 519 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. 422 of 519 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. 423 of 519 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. 424 of 519 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. 425 of 519 426 of 519 427 of 519 428 of 519 429 of 519 430 of 519 431 of 519 432 of 519 433 of 519 434 of 519 435 of 519 436 of 519 437 of 519 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. 438 of 519 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 519 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 519 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 519 442 of 519 443 of 519 444 of 519 445 of 519 446 of 519 447 of 519 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. 448 of 519 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) 449 of 519 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. 450 of 519 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.) 451 of 519 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. 452 of 519 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 453 of 519 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 454 of 519 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. 455 of 519 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. 456 of 519 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. 457 of 519 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. 458 of 519 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 459 of 519 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. 460 of 519 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. 461 of 519 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. 462 of 519 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. 463 of 519 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. 464 of 519 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. 465 of 519 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. 466 of 519 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 467 of 519 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 468 of 519 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). 469 of 519 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 470 of 519 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 471 of 519 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: 472 of 519 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 473 of 519 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. 474 of 519 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: 475 of 519 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 476 of 519 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: 477 of 519 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. 478 of 519 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. 479 of 519 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 480 of 519 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, 481 of 519 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. 482 of 519 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”. 483 of 519 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 484 of 519 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. 485 of 519 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. 486 of 519 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 487 of 519 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: 488 of 519 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. 489 of 519 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 490 of 519 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: 491 of 519 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. 492 of 519 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. 493 of 519 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. 494 of 519 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 495 of 519 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: 496 of 519 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. 497 of 519 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. 498 of 519 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: 499 of 519 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 500 of 519 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__________ 501 of 519 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) 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 503 of 519 Project Site 504 of 519 Proposed Site Plan (Draft) 505 of 519 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: 506 of 519 • 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: 507 of 519 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 508 of 519 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 509 of 519 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 510 of 519 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. 511 of 519 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. 512 of 519 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 513 of 519 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. 514 of 519 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 515 of 519 516 of 519 2/2/2021 Z (250×1016) data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAQCAwMDAgQDAwMEBAQEBQkGBQUFBQsICAYJDQsNDQ0LDAwOEBQRDg…1/1 517 of 519 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. 518 of 519 3/11/2021 9k= (250×958) data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAQCAwMDAgQDAwMEBAQEBQkGBQUFBQsICAYJDQsNDQ0LDAwOEBQRDg…1/1 519 of 519