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Home My WebLink About05-19-2021 Hearing Examiner Agenda1 of 336 HEARING EXAMINER May 19, 2021 5:30 p.m. The Auburn City Hearing Examiner Meeting scheduled for Wednesday, May 19, 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/98766513075 Meeting ID: 987 6651 3075 One tap mobile (253) 215-8782 I. Case No: SHL20-0004 Shoreline Substantial Dev. Permit Applicant(s): Seth Amrhein King County River and Floodplain Management Section, KSC-NR-0600, 201 S Jackson St, Seattle, WA 98104 Request: Request for Shoreline Substantial Development Permit to allow for additional fill to be placed on three segments of an existing levee in order to provide additional flood protection to nearby property. The area, located along the left bank of the Green River, has a ‘Shoreline Residential’ Shoreline Environment Designation. . 2 of 336 Project Location: The site is located along the left bank of the Green River, between river mile 29.5 and 30.9. Regarding the project’s location in relation to public roads, it is located between 26th St NE and8th St NE. The project site includes a combination of private and public property. Page 2 AGENDA BILL APPROVAL FORM HEARING EXAMINER Agenda Subject/Title: SHL20-0004 Shoreline Substantial Dev. Permit Date: May 5, 2021 Department: Community Development DESCRIPTION: Request for Shoreline Substantial Development Permit to allow for additional fill to be placed on three segments of an existing levee in order to provide additional flood protection to nearby property. The area, located along the left bank of the Green River, has a ‘Shoreline Residential’ Shoreline Environment Designation. ADMINISTRATIVE RECOMMENDATION: Hearing Examiner to conduct a public hearing and approve the Shoreline Substantial Development Permit. PROJECT SUMMARY: The applicant seeks to make improvements to the existing Dykstra Levee at three separate locations along the left bank of the Green River within the City’s ‘Shoreline Residential’ Shoreline Environment Designation. The site has zoning designations of R-5 Residential Zone, Five Dwelling Units Per Acre, R-7 Residential, Seven Dwelling Units Per Acre, R-20 Residential Zone, Twenty Dwelling Units Per Acre, I Institutional Zone, and OS Open Space. LOCATION: The site is located along the left bank of the Green River, between river mile 29.5 and 30.9. Regarding the project’s location in relation to public roads, it is located between 26th St NE and 8th St NE. The project site includes a combination of private and public property. APPLICANT: Seth Amrhein, King County River and Floodplain Management Section, KSC-NR-0600, 201 S Jackson St, Seattle, WA 98104 3 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 2 of 20 2019 Aerial Vicinity Map: Area A Area B 22nd St NE Riverview Drive NE 4 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 3 of 20 2019 Aerial Vicinity Map (continued): Area C Pike St NE 5 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 4 of 20 The Comprehensive Plan designation, Shoreline environment designation, zoning classification and current land uses of the site and surrounding properties are: Location Comprehensive Plan Designation Zoning Classification Shoreline Environment Designation Current Land Use Subject Site “Institutional” “Single Family” “Multiple Family” “Open Space” I Institutional Zone R-5 Residential, 5 du per acre R-7 Residential, 7 du per acre R-20 Residential, 20 du per acre OS Open Space Shoreline Residential Levee North “Open Space” “Single Family” OS Open space R-1 Residential, 1 du per acre R-5 Residential, 5 du per acre Urban Conservancy Park Single Family Green River South “Open Space” “Single Family” OS Open space R-1 Residential, 1 du per acre R-5 Residential, 5 du per acre Urban Conservancy Vacant Single Family Green River East “Open Space “Single Family” “Institutional” OS Open Space R-1 Residential, 1 du per acre Urban Conservancy Vacant Single Family Green River West “Single Family” “Multiple Family” R-5 Residential, 5 du per acre R-7 Residential, 7 du per acre R-20 Residential, 20 du per acre N/A Single Family Multi-Family 6 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 5 of 20 Excerpted Comprehensive Plan Designation Map: Institutional Single-Family Single-Family Multiple-Family Single-Family Open Space Institutional Multiple Family Area A Area B Area C 7 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 6 of 20 Excerpted Zoning Classification Map: R-20 Residential, 20 dwelling units per acre Open Space R-7 Residential Zone, 7 dwelling units per acre R-1 Residential Zone, 1 dwelling unit per acre Area A Area B Area C RMHC Residential Manufactured/Mobile Home Community 8 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 7 of 20 Excerpted Shoreline Environment Designations Area A Urban Conservancy Area B Area C Urban Conservancy Shoreline Residential Shoreline Residential 9 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 8 of 20 SEPA STATUS: A Determination of Non-Significance (DNS) was issued under City File No. SEP20-0008 on July 16, 2020. The comment period ended July 31, 2020 and the appeal period ended August 14, 2020. During the comment period, the Muckleshoot Indian Tribe (MIT) raised concerns regarding the lack of native vegetation incorporated into the proposal. As a result, the applicant requested the DNS be withdrawn. Subsequently, the applicant provided an updated submittal that included incorporating native vegetation plantings within one of the project areas in an effort to address the MIT’s comments. As a result, a revised DNS was issued on February 26, 2021. The comment period ended March 13, 2021. The appeal period ended March 27, 2021. No appeal of the SEPA decision was received. Comments received in response to the revised DNS were limited to questions about the project, with no concerns identified. Additional information regarding the comments received in response to the DNS is included within the below Findings of Fact section. A copy of the Revised SEPA Environmental Checklist, prepared by King County, dated January 26, 2021 and the Revised DNS issued by the City of Auburn are included as Exhibits 12 and 13, respectively. FINDINGS OF FACT: Proposal Description 1. Seth Amrhein, King County, applied on May 14, 2020 for a Shoreline Substantial Development Permit (SSDP) to allow for flood control related improvements to the existing Dykstra levee, located in the Shoreline Residential Environment Designation. The work will be completed within three separate segments of the levee between Green River miles 29.5 and 30.9. A copy of the Civil Plans, prepared by King County, Department of Natural Resources and Parks, dated May, 2020 are included as Exhibit 7. 2. Because the proposal involves the rehabilitation an existing levee, it most closely fits within the “structural flood hazard reduction use”, which is a permitted activity in the Shoreline Residential Shoreline Environment Designation, subject to issuance of a SSDP, per the City of Auburn’s Shoreline Master Program, Section 4.5. 3. The proposal involves three separate segments. The work will involve stripping away the existing levee top surface of grass down to a stable substrate, which will be followed by adding suitable fill material to bring the levee height up to the appropriate elevation. The side slopes of the added fill will be contoured to match the existing slopes of the face and back of the levee. Some minor adjustments of the face of the existing levee may be needed to match the slop added materials. In three locations, block retaining walls up to 30 feet long may be needed to support added fill on the landward side of the levee to avoid impacts to yards and existing homes. All disturbed areas will be revegetated with a native grass seed mix to establish the grass ground cover that currently exists on the levee. See Exhibit 8. 4. Area A, which is approximately 960 linear feet and located along the left bank of the Green River, will incorporate enough fill that will result in the existing levee being raised up to three additional feet. Area A includes King County parcels 0721059038, 8944150000, and 8944130000. 10 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 9 of 20 5. Area B, which is approximately 600 linear feet and located along the left bank of the Green River, will incorporate enough fill that will result in the existing levee being raised up to one additional foot. Area B includes King County parcels 7349400540, 7349400550, 7349400560, 7349400570, 7349400580, 7349100590, and 734900600. 6. Area C, which is approximately 400 linear feet and located along the left bank of the Green River, will incorporate enough fill that will result in the existing levee being raised up to one additional foot. Area C includes King County parcels 7349400350, 734900360, 7349400370, 7349400380, 7349400390, and 7349400400. 7. In addition to the levee modifications, a 35,590 square foot area along the waterward side of the levee, located within Area A, currently dominated by invasive reed canary grass, will be revegetated with native trees and shrubs to improve the currently degraded riparian habitat conditions. See Exhibit 8. 8. The proposed levee modifications will meet the requirements of the Auburn City Code (ACC), as applicable. The proposal will meet the flood hazard reduction standards outlined within the City’s Shoreline Master Program (SMP) 4.4.6. 9. In addition to the Shoreline program requirements, the site borders the Green River, a Type S Stream and is subject to the city’s critical area regulations (ACC 16.10). A minimum 100-foot buffer, in which native vegetation is to be retained, is required for Type S streams (river). 10. The applicant provided a Critical Areas Report & Habitat Impact Assessment, prepared by Seth Amrhein, King County Department of Natural Resources and Parks, dated January 6, 2021. The report concluded that the project “May Affect, Not Likely to Adversely Affect (NLAA)” any Endangered Species Act (ESA) listed species or habitat elements. The Critical Areas Report is included as Exhibit 8. 11. In order to demonstrate compliance with the City’s Surface Water Management Manual, a Stormwater Site Plan Report, prepared by King County Department of Natural Resources and Parks, dated November 23, 2020, was provided as part of the review of the application. The report notes that stormwater will be managed through having the top of the levee slope 1 to 2% towards the Green River. This will allow stormwater that doesn’t infiltrate to sheet flow towards the river and away from existing development on the landward side of the levee. No new pollution generating surfaces would be created. A copy of the Stormwater Site Plan Report is included as Exhibit 10. 12. In order to confirm that all fill proposed for the project will be above the base flood elevation and that no increase in flood levels would occur, the applicant prepared a Hydraulic and Hydrologic Analysis Report, prepared by King County, dated September 22, 2020. The Report is marked as Exhibit 11. 13. The applicant provided a written statement that describing the project. A copy of the Written Statement, prepared by Seth Amrhein, King County, dated January 26, 2021, is included as Exhibit 6. Site Characteristics (General) 11 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 10 of 20 14. The project site is divided into three separate sections that all abut the Green River. Each section of the project contains portions of an existing levee that currently provides flood protection along the left bank of the Green River, between river mile 29.5 and 30.9. Because the Green River abuts the site, the entire project area is located within 200 feet of the Green River Ordinary High Water Mark and shoreline jurisdiction and is within the ‘Shoreline Residential’ shoreline environment designation. The levee is dominated by lawn grass, with some ornamental shrubs planted by nearby property owners. 15. The applicant provided copies of easements confirming that King County has access to and ability to maintain the levee that is the subject of this permit. Copies of the easement documents are included as Exhibit 18. 16. Area A is predominately developed with multi-family uses and contains the waterward area that will be enhanced with native vegetation plantings. Areas B and C are developed with individual single-family residential uses. See Exhibit 7 for a copy of the Civil Plans showing the location of these uses in relation to the proposed levee work. Site Characteristics (Critical Areas & Shoreline Areas) 17. The Green River, which abuts the site directly to the east, is a mapped floodway. With the exception of the portion of Area A that will have additional native vegetation plantings, no portion of the floodway extends onto any portion of the site proposed for development. Generally, the Special Flood Hazard Area (SFHA) and Floodway only extend to the waterward portion of the existing levee areas. 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 reed canary grass or residential landscaped lawn areas. 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. 18. In addition to being a Shoreline of the State, the Green River is also classified by the City as regulated “Critical Area” and more specifically as a Type S Stream per ACC 16.10.080, “Classification and rating of critical areas”. As outlined in SMP 4.5, Table 1, Type S Streams within the Shoreline Residential Shoreline Environment Designation have a-100 foot setback from the OHWM. While defined as a setback within the SMP, the setback effectively acts as a 100 foot buffer. 19. Also, a small portion of the site (Area C) is located in an area that may have Wildlife Habitat Area, as defined in ACC 16.10.080(D). This is due to a portion of this Area C possibly having wetland habitat provided along this portion of the Green River. Per the applicant’s Critical Areas Report however, no regulated wetlands are located on the project site. See Exhibit 3 for a Copy of the City’s Critical Area Inventory map. 20. The site is located within an Aquifer Recharge Area known as Groundwater Protection Zone 4, as defined in ACC 16.10.080(F). These areas have a critical recharging effect 12 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 11 of 20 on aquifers used for potable water. Best management practices (BMP) will be required for any future development of the site. 21. The applicant provided a Critical Areas Report and Habitat Impact Assessment, prepared by Seth Amrhein, King County, dated January 6th, 2021, in order to identify all wetlands, streams, and any associated buffers affecting the site. Further, the report provides more detail regarding the native vegetation plantings proposed within Area A. 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 eastern portion of the site. See Exhibit 8 for a Copy of the Critical Area Report. 22. The sites location along a Type S Stream also results in it being within a Riparian Buffer Zone. These areas contain habitat that may be used by federal or state listed threatened or endangered Fish species. As identified in the applicant’s Critical Areas Report and Habitat Impact Assessment, the project “may affect, not likely to adversely affect” in regards to potential impacts on endangered species. No native vegetation within the Protected Area, as defined in ACC 15.68.100(OO), would be removed. Further, new native vegetation plantings and the removal of existing reed canary grass will occur within a section of Area A. See Exhibit 8 for a copy of the Critical Areas Report and Habitat Impact Assessment. 23. While the site does not contain any mapped landslide hazard areas or erosion prone areas, the applicant provided a Geotechnical Investigation, prepared by King County, Department of Local Services, dated November 5, 2020, addressing any stability concerns related to adding additional fill to the existing levee. The report noted that the existing levee profile will be able to be raised while meeting the conditions for long term and rapid drawdown stability. Further, the report noted that raised sections of the levee be inclined at no steeper than 2H:1V and that a small block wall, up to 2 feet in height, may be required on portions of the landside of the levee to keep fill within the levee easement area. See Exhibit 9 for a copy of the Geotechnical Investigation. 24. The area within 200 feet of the Ordinary High Water Mark (OHWM) along the Green River is within the “Shoreline Residential” designation and thus, is within the jurisdiction of the Auburn Shoreline Master Program (Auburn SMP, Section 4.2.A). Unless otherwise exempt, the rehabilitation of structure flood hazard reduction facilities in the ‘Shoreline Residential’ designation will requires a Shoreline Substantial Development Permit (SSDP). 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. 13 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 12 of 20 3. Shorelands and associated uplands extending 200 feet in all directions as measured on a horizontal plane from the ordinary high water mark; floodways and contiguous floodplain areas landward two hundred feet from such floodways; and all wetlands and river deltas associated with their streams, lakes, and tidal waters subject to the provisions of Chapter 90.58 RCW.” Characteristics of the Surrounding Area 25. The project and adjacent properties are located within the jurisdiction of the City of Auburn. All proposed work will occur above the OHWM and on public and private property. No in-water work is proposed. 26. Properties along the left bank of the Green River benefit from the flood protection that the Dykstra Levee currently provides. 27. The surrounding areas have Comprehensive Plan designations of: “Single Family”, “Multiple Family”, “Institutional”, and “Open Space”. The surrounding zoning designations include “R-5” Residential Zone, “R-7” Residential Zone, “R-20” Residential Zone, “I” Institutional Zone, and “OS” Open Space. 28. The existing land uses surrounding the site includes, multiple-family, single-family residences, public parks, and open space. Comprehensive Plan 29. The following City of Auburn Comprehensive Policies are relevant to the project: Imagine Auburn: City of Auburn Comprehensive Plan – Core Plan: Community Vision & Values (Page C3-5) We will protect the natural environment, preserve open space, and create safe and appropriate access. Shoreline Management Program 30. The City of Auburn currently uses its 2020 City of Auburn Shoreline Master Program (SMP) to regulate development and management of the City’s shoreline. Under the Shoreline Management Act, all development occurring within the shoreline jurisdiction area must be consistent with policies and regulations of the local Shoreline Management Program (SMP), as well as with the policies of the State Shoreline Management Act. While some policies, goals, and development regulations may be referenced as findings within this staff report, additional policies, goals, and development regulations of the SMP not explicitly referenced may be found by review of the City’s 2020 SMP document. 31. Because the project requires a Shoreline Substantial Development Permit, the Project must be found consistent with the criteria established in WAC 173-27-150 and City of Auburn SMP 6.1.7. 14 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 13 of 20 32. The City’s rules and procedures for shoreline permits are contained in the SMP; more specifically Section 6.0. The section provides the following general purpose and intent: “6.1.1 Chapter purpose and intent. It is the intention of the city council that the provisions of this chapter will promulgate and adopt a program for the administration and enforcement of a permit system that shall implement by reference the State Shoreline Management Act of 1971, Chapter 90.58 RCW; the State Department of Ecology regulations and guidelines adopted as Chapters 173-26 and 173-27 WAC; the Auburn shoreline master program attached to the ordinance codified in this chapter, together with amendments and/or additions thereto, and to provide for the implementation of the policy and standards as set forth in the aforesaid laws and regulations which are by reference made a part of this chapter with the force and effect as though set out in full in this chapter.” 33. Pursuant ACC 6.1.12, the Hearing Examiner shall hold at least one public hearing on the Shoreline Substantial Development Permit in accordance with the following: “6.1.12 Application – Hearing – Required. A. The hearing examiner shall hold at least one public hearing on each application for a shoreline substantial development permit, shoreline conditional use permit, or shoreline variance on shorelines within the city. The public hearing shall be held not less than 30 days following the final publication of the notice required by ACC 16.08.050. B. The notice and conduct of the public hearing shall be in accordance with Chapter 2.46 ACC.” 34. The City’s rules provide the following requirements for public notice: “6.1.6 Application – Notices. The director shall give notice of the application in accordance with the applicable provisions of ACC 14.07.040, no less than 30 days prior to permit issuance. The notices shall include a statement that any person desiring to present his view to the director with regard to the application may do so in writing to the director, and any person interested in the hearing examiner's action on an application for a permit may submit his views or notify the director of his interest within 30 days of the last date of publication of the notice. Such notification or submission of views to the director shall entitle said persons to a copy of the action taken on the application.” 35. The City’s SMP contains the following information regarding the “Shoreline Residential” shoreline environment: “3.2 Shoreline Residential 3.2.1 Purpose: 15 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 14 of 20 The purpose of the “Shoreline Residential” environment is to accommodate residential development and appurtenant structures that are consistent with this chapter. An additional purpose is to provide appropriate public access and recreational uses. 3.2.2 Designation Criteria: The Shoreline Residential environment designation is appropriate for those areas of the City’s shorelines that are characterized predominantly by single-family or multi-family residential development or are planned and platted for residential development. 3.2.3 Management Policies: The following management policies should apply to all shorelines in the Shoreline Residential Environment: Standards for density or minimum frontage width, setbacks, lot coverage limitations, buffers, shoreline stabilization, vegetation conservation, critical area protection, and water quality shall be set to maintain no net loss of shoreline ecological functions. Proposed projects should be reviewed for consistency with the no net loss policy, taking into account 1) the environmental limitations and sensitivity of the shoreline area, 2) proposed mitigation for anticipated impacts, 3) the level of infrastructure and services available, and 4) other comprehensive planning considerations. Multi-family and multi-lot residential and recreational developments should provide public access and joint use for community recreational facilities where appropriate. Access, utilities, and public services should be available and adequate to serve existing needs and/or planned future development.” 36. The City’s SMP contains the following goals related to Shoreline Use: “2.5.1 Goals 1. Promote the best possible pattern of land and water uses that will be most beneficial to the natural and human environments. 2. Designated Shorelines of Statewide Significance are of value to the entire State and shall be managed consistent with this recognition. In order of preference the priorities are to: a. Recognize and protect the Statewide interest over local interest; b. Preserve the natural character of the shoreline; c. Result in long term over short term benefit; d. Protect the resources and ecology of the shoreline; and, e. Increase public access to publicly owned areas of the shorelines.” 37. City City’s SMP contains the following goals related to Flood Prevention/Critical Areas: “2.8.1 Goals 1. Continue to participate in a regional approach to flood protection issues, coordinating with the State of Washington, King County, Pierce County and other entities interested in reducing flood hazards on both the White and Green Rivers. 16 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 15 of 20 2. Continue to protect wetlands, streams, wildlife habitat, and groundwater and minimize geologic hazards in the shoreline environment in accordance with the Critical Areas Ordinance.” 38. The City’s SMP contains the following policies related to Shoreline Vegetation Conservation: “4.4.2 Shoreline Vegetation Conservation 1. Developments and activities in the City’s shoreline should be planned and designed to retain native vegetation or replace shoreline vegetation with native species to achieve no net loss of the ecological functions and ecosystem-wide processes performed by vegetation. 2. Woody debris should be left in the river corridors to enhance wildlife habitat and shoreline ecological functions, except where it threatens personal safety or critical infrastructure, such as bridge pilings. In such cases where debris poses a threat, it should be dislodged, but should not be removed from the river.” 39. The City’s SMP contains the following policies related to Flood Hazard Reduction: “4.4.6 Flood Hazard Reduction 1. The City should manage flood protection through the City’s Comprehensive Drainage Plan, Comprehensive Plan, stormwater regulations, and flood hazard areas regulations. 2. Discourage development within the floodplains associated with the City’s shorelines that would individually or cumulatively result in an increase to the risk of flood damage. 3. Non-structural flood hazard reduction measures should be given preference over structural measures. Structural flood hazard reduction measures should be avoided whenever possible. When necessary, they should be accomplished in a manner that assures no net loss of ecological functions and ecosystem-wide processes. Non- structural measures include setbacks, land use controls prohibiting or limiting development in areas that are historically flooded, stormwater management plans, or bioengineering measures. 4. Where possible, public access should be integrated into publicly financed flood control and management facilities. Public Notice, Comments and Procedures 40. A Determination of Non-Significance (DNS) was issued under City File No. SEP20-0008 on July 16, 2020, with an associated 15-day comment period. The notice was mailed to property owners within 300 feet of the project site, published in the newspaper and posted on site The comment period ended July 31, 2020 and the appeal period ended August 14, 2020. The DNS is included as Exhibit 13. 41. During the comment period, the Muckleshoot Indian Tribe (MIT) raised concerns that the project did not incorporate recommendations from the King County Council approved 2019 Green River System Wide Improvement Framework (SWIF) Report. Specifically, 17 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 16 of 20 there was little or no mention of restoration or enhancements of existing riparian vegetation. The MIT’s comments are included as Exhibit 15. 42. In addition to the comments from MIT, a group of neighboring property owners provided comments indicating they wanted to be included on any future correspondence regarding the project. Additionally, multiple concerns were raised regarding a planned park along the right bank of the Green River, unrelated to the subject project. The neighborhood comments are included as Exhibit 15. 43. As a result of the comments received from the MIT, the applicant requested the DNS be withdrawn, as the project would need to be modified to address the MIT’s concerns. The Withdrawn DNS is included as Exhibit 13. 44. Subsequently, the applicant provided an updated submittal that included incorporating native vegetation plantings within one of the project areas in an effort to address the MIT’s comments. The applicant worked with MIT staff to arrive at a solution acceptable to both parties. As a result, a revised DNS was issued on February 26, 2021. The comment period ended March 13, 2021. The appeal period ended March 27, 2021. No appeal of the revised SEPA was received. The Revised DNS is included as Exhibit 13 and a response letter from the applicant is included as Exhibit 16. 45. 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. 46. The City issued the Notice of Hearing (NOH) on April 2, 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 14). At the time of the preparation of this report, no comments have been received in response to the NOH. 47. The contents of the case file for this project (SHL20–0004 & SEP20-0008) are hereby incorporated by reference and made part of the record of this hearing. 48. The decision on SSDP shall be final with the Hearing Examiner and subject to the Washington State Dept. of Ecology review period as required by the following code section: “SMP 6.1.18 Grant or denial decision – Notifications. The director shall notify the following persons in writing of the hearing examiner’s final approval, disapproval or conditional approval of a substantial development permit, shoreline conditional use permit, or shoreline variance application within eight days of its final decision: A. The applicant; B. The State Department of Ecology; C. The State Attorney General; D. Any person who has submitted to the director written comments on the application; 18 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 17 of 20 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; • No in-water work is proposed • Repair of existing, previously permitted flood control systems are proposed • The project meets the development standards, as applicable, of the Shoreline Residential Shoreline Environment Designation 2. Auburn Comprehensive Plan and Municipal Code; and The project modifications and rehabilitation of an existing, permitted, levee structure in zoning districts that allows for such. Additionally, various City staff experts and the VRFA have reviewed the proposal and have raised no objections. It should be noted that future permit approvals will be required to meet various City, State, and Federal regulations. Through meeting the Auburn City Code requirements, 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 19 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 18 of 20 Consistency with SMA & Local SMP 2. The Shoreline Management rules (WAC 173-27-140) set forth the following two criteria for all developments within the shoreline jurisdiction. “(A) No authorization to undertake use or development on shorelines of the state shall be granted by the local government unless upon review the use or development is determined to be consistent with the policy and provisions of the Shoreline Management Act and the master program.” “(B) No permit shall be issued for any new or expanded building or structure of more than thirty-five feet above average grade level on shorelines of the state that will obstruct the view of a substantial number of residences on areas adjoining such shorelines except where a master program does not prohibit the same and then only when overriding considerations of the public interest will be served.” The proposed project is consistent with the Shoreline Management Act and the City’s Shoreline Management Program (SMP). The City's program identifies the project area to be the “Shoreline Residential” shoreline environment designation. The project will be consistent with the designation by allowing rehabilitation of an existing levee which will have minimal impact on the surrounding properties. Public access to the shorelines will not be impacted or reduced. The proposed project is consistent with the SMP policies applicable to flood hazard reduction uses. No in- or overwater work is proposed. The levee rehabilitation measures would not cause impacts to other properties or public improvements. Removal and disturbance of vegetation near the shoreline will be limited to the removal of existing non-native lawn grass on the surface of the levee. Such grasses will be replaced, with an area of the project incorporating new native vegetation plantings for the purposes of restoring shoreline ecological functions. The project will meet the recommendations provided within a Geotechnical Report that will ensure the life, safety, and welfare of the surrounding residents is protected. No development will occur within the floodway, Special Flood Hazard Area, or Channel Migration Zone. City of Auburn staff believe the project is consistent with the criteria established in WAC 173-27-140. 3. The Shoreline Management rules in WAC 173-27-150 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; 20 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 19 of 20 (b) The provisions of this regulation; and (c) The applicable master program adopted or approved for the area. Provided, that where no master program has been approved for an area, the development shall be reviewed for consistency with the provisions of chapter 173-26 WAC, and to the extent feasible, any draft or approved master program which can be reasonably ascertained as representing the policy of the local government. (2) Local government may attach conditions to the approval of permits as necessary to assure consistency of the project with the act and the local master program. As noted previously within the above analysis outlined within Conclusion 1, City of Auburn staff believe the project is consistent with the criteria established in WAC 173-27-150. 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, subject to the following conditions: 1. The future work associated with the subject Shoreline Substantial Development Permit shall be completed within two years from the effective date of the decision from the Department of Ecology, as specified in WAC 173-27-090. 2. The levee rehabilitation shall be substantially consistent with the Civil Plans, prepared by King County, dated May 8, 2020 (Exhibit 7). 3. The project shall be developed to be substantially consistent with the native vegetation plan within Area A, outlined within the Critical Areas Report and Habitat Impact Assessment, prepared by King County, dated January 6, 2021 (Exhibit 8). 4. The applicant shall secure the necessary floodplain development permit approval(s) from the City of Auburn, if applicable. Staff reserves the right to supplement the record of the case to respond to matters and information raised subsequent to the writing of this report. EXHIBIT LIST Exhibit 1 Staff Report Exhibit 2 Vicinity Map Exhibit 3 City of Auburn Critical Area Inventory Map Exhibit 4 Completed City of Auburn Land Use Application Forms, Received May 14, 2020 Exhibit 5 Joint Aquatic Resources Permit Application (JARPA) form, King County, dated April 14, 2020 Exhibit 6 Written Statement, King County, dated May 14, 2020 Exhibit 7 Civil Plans, King County, dated May 8, 2020 Exhibit 8 Critical Areas Report and Habitat Impact Assessment, prepared by King County, dated January 6, 2021 21 of 336 Staff Member: Dustin Lawrence Date: May 5, 2021 Page 20 of 20 Exhibit 9 Geotechnical Report, prepared by King County, dated November 5, 2020 Exhibit 10 Stormwater Site Plan, prepared by King County, dated November 23, 2020 Exhibit 11 Hydraulic and Hydrologic Analysis, King County, dated September 22, 2020 Exhibit 12 SEPA Environmental Checklist (revised), prepared by King County, dated January 2021 Exhibit 13 Notice of Application (NOA) and Determination of Non-Significance (DNS), issued July 16th, 2020, SEPA Withdrawal Notice, issued, August 14, 2020, and Revised DNS, issued February 26, 2021 Exhibit 14 Notice of Public Hearing (NOH), issued April 2, 2021 Exhibit 15 Public Comments Received Exhibit 16 Response Comments to MIT, King County, dated January 1, 2021 Exhibit 17 Public Notice Affidavits and Confirmation of Postings Exhibit 18 Easement Documents 22 of 336 1,333.3 NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet Feet1,333.3666.70 eGIS CDPW 5/3/2021Printed 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. 23 of 336 1,333.3 NAD_1983_StatePlane_Washington_North_FIPS_4601_Feet Feet1,333.3 Notes Legend 666.70 1:8,000 City Critical Area Inventory Map 1in =667 ft 4/26/2021Printed 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. Channel Migration Area (CMA) 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 Erosion Prone Streams Landslide Hazard Parcel Boundaries 24 of 336 1 25 of 336 2 Dykstra Levee Improvement Project Property Owner and Infromation Area “A”: Owner: COA Address: 25 W MAIN ST, Auburn, WA, 98001 Assessor’s Parcel ID# 0721059038 Lot size (sq.ft.): 77600 Zoning District: INSTITUTIONAL USE DISTRICT Existing Use of Site: City park Owner: N/A Address: 1519 22ND ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 8944150000 Lot size (sq.ft.): 94300 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: multi-family residence Owner: N/A Address: 1741 22ND ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 8944150000 Lot size (sq.ft.): 336600 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: multi-family residence Area “B” Owner: LOUISE CHRISTINE AMIA Address: 1544 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400540 Lot size (sq.ft.): 9,257 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: GILBERT MICHAEL A+FIINA M Address: 1602 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400550 Lot size (sq.ft.): 10,569 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: SATA YURIKO K Address: 1604 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400560 Lot size (sq.ft.): 10,883 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence 26 of 336 3 Owner: KING COUNTY-WLRD RFMS Address: N/A, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400570 Lot size (sq.ft.): 12,012 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: BIRO CHASE+RACHEL Address: 1614 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400580 Lot size (sq.ft.): 14,480 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: ROSETTIE MARK EDWARD Address: 1620 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400590 Lot size (sq.ft.): 14,479 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: CARLSON JUSTIN A Address: 1624 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400600 Lot size (sq.ft.): 14,080 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Area “C” Owner: TSAI MICHAEL N+ELISABETH A Address: 1226 PIKE ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400350 Lot size (sq.ft.): 10,541 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: ROBERTS RANDY+ARLEEN Address: 1234 PIKE ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400360 Lot size (sq.ft.): 9,946 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence 27 of 336 4 Owner: TACHERON PAUL H+LUCY A Address: 1302 PIKE ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400370 Lot size (sq.ft.): 10,226 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: FRITZ RODGER H Address: 1306 PIKE ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400380 Lot size (sq.ft.): 10,871 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: ROSSICK JOHN D+CATHLEEN J Address: 1314 PIKE ST NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400390 Lot size (sq.ft.): 14,113 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence Owner: ZARLENGO CHRISTOPHER Address: 1404 RIVERVIEW DR NE, Auburn, WA, 98002 Assessor’s Parcel ID#: 7349400400 Lot size (sq.ft.): 12,949 Zoning District: RESIDENTIAL 20 DU/ACRE Existing Use of Site: single-family residence 28 of 336 5 J. WRITTEN STATEMENT ❑ 1. The shoreline designation according to the Shoreline Master Program; Residential Shoreline Environment ❑ 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; Three segments along the Dykstra Levee in the City of Auburn have been found to be below the elevation needed to provide a uniform flood containment of 12,000 cubic feet per second (the modelled 100-year discharge) plus an additional 3 feet of freeboard. These sections, identified as Areas A, B, and C, are approximately 960, 600, and 400 feet long, respectively. The Green River Dykstra Levee Improvement Project will raise the deficient sections up to 2.75 feet from their current elevations to provide a uniform level of protection along the length of the levee. The work will involve stripping away the existing levee top surface of grass down to a stable substrate, followed by adding suitable fill material to bring the levee height up to the appropriate elevation in the three areas. The side slopes of the added fill will be contoured to match the existing slopes of the face and back of the levee. After the earthwork, all disturbed areas will be revegetated with a native grass seed mix to reestablish the grass ground cover that currently exists on the levee. ❑ 4. A general description of the property’s existing physical characteristics, improvements, and structures; The work will occur on an existing levee along the Green River that was constructed in the 1960s. Please see provided Critical Area Report and Habitat Impact Assessment for additional details. ❑ 5. A general description of adjacent (within 1,000 feet in all directions) use, structures, improvements, intensity of development, and physical characteristics. The work area is a levee along the left bank of the Green River. The levee provides protection for single- and multi-family homes landward of the levee. Please see provided Critical Area Report and Habitat Impact Assessment for additional details and aerial photographs of the project area and surroundings. 29 of 336 Page: 1 of 5 WASHINGTON STATE AGENCY USE ONLY Date Received: 2020-04-15 Application ID :21226 Online Submission Application submitted with attachments and fee Standard Hydraulic Project 01. Application Information * Application Type: Standard 02. Project Identification * Project Name (A name for your project that you create. Examples: Smith’s Dock or Seabrook Lane Development) Green River Dykstra Levee Improvement * NonSimplified Project Type(s) (check all that apply): Other * Others: Flood control 03. Applicant * Business Name (if applicable) King County DNRP, River and Floodplain Management Section * First Name Seth * Last Name Amrhein * Address 1 201 S Jackson St * Address 2 KSC-NR-0600 * City Seattle * State/Province WA * Zip Code (12345 or 12345-1234) 98104-3854 * Country United States * Primary Phone No (555-555-5555 Ext.) 2062636923 * Mobile Phone No (555-555-5555) 2068173771 * Email 30 of 336 Page: 2 of 5 seth.amrhein@kingcounty.gov 04. Applicant Account Type * Please select one applicant account type Government – County 05. Authorized Agent or Contact * No agent will be acting on behalf of the Applicant Yes * Business Name (if applicable) King County DNRP, River and Floodplain Management Section * First Name Seth * Last Name Amrhein * Address 1 201 S Jackson St * Address 2 KSC-NR-0600 * City Seattle * State/Province WA * Zip Code (12345 or 12345-1234) 98104-3854 * Country United States * Primary Phone No (555-555-5555 Ext.) 2062636923 * Mobile Phone No (555-555-5555) 2068173771 * Email seth.amrhein@kingcounty.gov 06. Property Owner(s) * Check here if Property Owner is the same as Applicant Yes * Business Name (if applicable) King County DNRP, River and Floodplain Management Section * First Name Seth * Last Name Amrhein * Address 1 201 S Jackson St 31 of 336 Page: 3 of 5 * Address 2 KSC-NR-0600 * City Seattle * State/Province WA * Zip Code (12345 or 12345-1234) 98104-3854 * Country United States * Primary Phone No (555-555-5555 Ext.) 2062636923 * Mobile Phone No (555-555-5555) 2068173771 * Email seth.amrhein@kingcounty.gov 07. Project Location * Location Site Name: Green River Dykstra Levee Work Start Date: August 1, 2020 Work End Date: September 30, 2021 Address: 1610 RIVERVIEW DR NE, Auburn, King, WA 98002, United States Latitude: 47.321 Longitude: -122.205 Township: 21 N Range: 08 E Section: 5 Quarter Section: SW 1/4 WRIA: 9 Stream Number: 0183 Stream Name: Green River Parcel No: 0721059038; 8944150000; 8944130000; 7349400540; 7349400550; 7349400560; 7349400570; 7349400580; 7349400590; 7349400600; 7349400350; 734900360; 7349400370; 7349400380; 7349400390; 7349400400 100 Year Flood: No Drive Direction: From I-5: https://goo.gl/maps/Y3z98PepshLrvkcu8 -------------------------------------------------------------------------------------------- 08. Project Description * Will you be operating equipment in water? Yes * Type of equipment used For the Dysktra Levee improvement project, an excavator and bulldozer will operate from the top of the levee to place fill material delivered by dumptrucks. A standard 10 -yard dump truck will be used to haul materials to and from the site. Basic hand tools will be used to install, maintain, and remove erosion control BMPs. * Summarize the overall project. Three segments along the Dykstra Levee in the City of Auburn have been found to be below the height needed to provide flood containment of 12,000 cubic feet per second (the modelled 100 -year discharge) plus an additional 3 feet of freeboard. The three sections of the Dykstra Levee that do not meet this requisite elevation are approximately 400, 600, and 960 feet long. These sections need to be raised up to 32 of 336 Page: 4 of 5 approximately 3 feet from their current elevation to meet this protection level. The work will involve stripping away the existing levee top surface of grass down to a stable substrate, followed by adding suitable fill material to bring the levee height up to the appropriate elevation. The side slopes of the added fill will be contoured to match the existing slopes of the face and back of the levee. Some minor adjustments of the face of the existing levee may be needed to match the slope added material. * Describe how you plan to construct each project element. Include specific construction methods and equipment to be used. Identify where each element will occur in relation to the nearest waterbody. Indicate which activities are within the 100-year flood plain. Specific construction activities planned for construction of the Green River Dykstra Levee improvement project include: • Installation of a temporary erosion and sediment control measures in compliance with City of Auburn and Washington State water quality protection standards. • Construction of a temporary construction accesses off Riverview Dr NE for each of the three levee improvement sites. Establishing temporary staging areas and access routes to support construction and marking non - disturbance areas with construction fencing as necessary. • A tracked excavator and bulldozer operating from the top of the levee will distribute and compact fill material delivered with dump trucks. • After completing the earthwork, temporary erosion control measures will be removed. All disturbed areas will be revegetated with a native grass seed mix, as shown on the landscape plan sheet in the provided plan set. • All work is above the 100-year floodplain. Work will be in compliance with the City of Auburn’s critical areas, shoreline, and floodplain development regulations. * Requested Project Start Date: 08/01/2020 * Requested Project End Date: 09/30/2021 09. Waterbodies (other than wetlands): Impacts and Mitigation * Describe how the project is designed to avoid and minimize adverse impacts to the aquatic environment. We are only improving the minimum segments of the deficient levee needed to provide the desired level of flood protection. This will minimize construction disturbance adjacent to the Green River. We have avoided removal of native trees and shrubs and all work is within the existing footprint of the levee. Construction will be in the dry season and the site will be revegetated after construction to minimize erosion and sedimentation, which could impact water quality. Erosion control BM Ps will also be used to protect water quality. * Will your project impact a waterbody or the area around a waterbody? Yes * Describe how your project will impact a waterbody or the area around a waterbody. The Dykstra Levee improvement project will have minimal impacts to the Green River. It involves spot improvements in three sections of the levee of an existing levee constructed in the 1960s to provide a uniform level of flood protection along its length. This disturbed area surface is currently comprised of grass and compacted gravel. No trees or shrubs will need to be removed. No in water work will be conducted and all disturbances will be at least 20 feet landward of the ordinary high-water mark. The construction disturbance will be temporary, and impacts are limited to potential degradation of water quality from potential erosion of exposed soils. However, the risk will be greatly reduced by completing the project in the dry season and using temporary erosion control measures in compliance with City of Auburn development regulations. Installation and maintenance of these best management practices will be supervised by a Washington Certified Erosion and Sedimentation Control Lead. 33 of 336 Page: 5 of 5 * Describe impact(s) that cannot be avoided through project design and implementation. For each location, please include the following:General location description where the impact(s) will occur(e.g. stream bank, beach front, 2-foot strip from bank, portion of gravel bar, etc.)Provide length, quantities, and/or area of impact The Dykstra Levee improvement project will have minimal impacts to the Green River. It involves spot improvements to the top of three sections of an existing levee constructed in the 1960s to provide a uniform level of flood protection along its length. This disturbed area surface is currently comprised of grass and compacted gravel. No trees or shrubs will need to be removed. No in water work will be conducted and all disturbances will be at least 20 feet landward of the ordinary high -water mark. The construction disturbance will be temporary, and impacts are limited to potential degradation of water quality from potential erosion of exposed soils. However, this risk will be greatly reduced by completing the project in the dry season a nd using temporary erosion control measures in compliance with City of Auburn development regulations. Installation and maintenance of these best management practices will be supervised by a Washington Certified Erosion and Sedimentation Control Lead. * Have you prepared a mitigation plan to compensate for the project’s adverse impacts to non - wetland waterbodies? No * Have you prepared a mitigation plan to compensate for the project’s adverse impacts to non- wetland waterbodies? We have not prepared a separate mitigation plan. We have assembled a suite of construction actions with best management practices that do not warrant mitigation. * Describe the source and nature of any fill material, amount (in cubic yards) you will use, and how and where it will be placed into the waterbody. No fill will be placed in any waterbody. * For all excavating or dredging activities, descr ibe the method for excavating or dredging type and amount of material you will remove, and where the material will be disposed. No excavating in a waterbody will occur. A small volume of sod and soil will be stripped from the surface of the levee and disposed of at a permitted topsoil disposal facility. 10. SEPA Compliance * Compliance with the State Environmental Policy Act (SEPA). For more information about SEPA, go to "http://www.ecy.wa.gov/programs/sea/sepa/e- review.html" A SEPA determination is pending. "SEPA determination is pending with City of Auburn" "Expected date for SEPA determination is 08/01/2020" 34 of 336 5 J. WRITTEN STATEMENT ❑ 1. The shoreline designation according to the Shoreline Master Program; Residential Shoreline Environment ❑ 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; Three segments along the Dykstra Levee in the City of Auburn have been found to be below the elevation needed to provide a uniform flood containment of 12,000 cubic feet per second (the modelled 100-year discharge) plus an additional 3 feet of freeboard. These sections, identified as Areas A, B, and C, are approximately 960, 600, and 400 feet long, respectively. The Green River Dykstra Levee Improvement Project will raise the deficient sections up to 2.75 feet from their current elevations to provide a uniform level of protection along the length of the levee. The work will involve stripping away the existing levee top surface of grass down to a stable substrate, followed by adding suitable fill material to bring the levee height up to the appropriate elevation in the three areas. The side slopes of the added fill will be contoured to match the existing slopes of the face and back of the levee. After the earthwork, all disturbed areas will be revegetated with a native grass seed mix to reestablish the grass ground cover that currently exists on the levee. ❑ 4. A general description of the property’s existing physical characteristics, improvements, and structures; The work will occur on an existing levee along the Green River that was constructed in the 1960s. Please see provided Critical Area Report and Habitat Impact Assessment for additional details. ❑ 5. A general description of adjacent (within 1,000 feet in all directions) use, structures, improvements, intensity of development, and physical characteristics. The work area is a levee along the left bank of the Green River. The levee provides protection for single- and multi-family homes landward of the levee. Please see provided Critical Area Report and Habitat Impact Assessment for additional details and aerial photographs of the project area and surroundings. 35 of 336 36 of 336 37 of 336 38 of 336 39 of 336 40 of 336 41 of 336 42 of 336 43 of 336 44 of 336 45 of 336 46 of 336 47 of 336 48 of 336 49 of 336 50 of 336 51 of 336 52 of 336 53 of 336 54 of 336 STA. 10+50FENCESTA. 11+00FENCE CROSS SECTIONS - STA. 10+50-11+0020LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:16:13 PM, _AutoCAD PDF (General Documentation).pc3 55 of 336 STA. 12+00STA. 11+50FENCE CROSS SECTIONS - STA. 11+50-12+0021LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:17:28 PM, _AutoCAD PDF (General Documentation).pc3 56 of 336 STA. 13+00STA. 12+50CROSS SECTIONS - STA. 12+50-13+0022LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:18:12 PM, _AutoCAD PDF (General Documentation).pc3 57 of 336 STA. 13+50STA. 14+00CROSS SECTIONS - STA. 13+50-14+0023LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:18:58 PM, _AutoCAD PDF (General Documentation).pc3 58 of 336 STA. 14+50STA. 15+00FENCECROSS SECTIONS - STA. 14+50-15+0024LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:19:43 PM, _AutoCAD PDF (General Documentation).pc3 59 of 336 STA. 15+50BUILDINGSTA. 16+00BUILDINGCROSS SECTIONS - STA. 15+50-16+0025LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:20:28 PM, _AutoCAD PDF (General Documentation).pc3 60 of 336 STA. 16+50BUILDINGSTA. 17+00BUILDINGCROSS SECTIONS - STA. 16+50-17+0026LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:21:13 PM, _AutoCAD PDF (General Documentation).pc3 61 of 336 STA. 17+50BUILDINGSTA. 18+00BUILDINGCROSS SECTIONS - STA. 17+50-18+0027LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:21:58 PM, _AutoCAD PDF (General Documentation).pc3 62 of 336 STA. 18+50BUILDINGSTA. 19+00BUILDINGPATIOCROSS SECTIONS - STA. 18+50-19+0028LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:22:43 PM, _AutoCAD PDF (General Documentation).pc3 63 of 336 STA. 19+50BUILDINGPATIOSTA. 20+00BUILDINGCROSS SECTIONS - STA. 19+50-20+0029LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:23:28 PM, _AutoCAD PDF (General Documentation).pc3 64 of 336 STA. 20+50BUILDINGPATIOSTA. 21+00BUILDINGPATIOCROSS SECTIONS - STA. 20+50-21+0030LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:24:13 PM, _AutoCAD PDF (General Documentation).pc3 65 of 336 STA. 21+50STA. 22+00BUILDINGPATIOCROSS SECTIONS - STA. 21+50-22+0031LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:25:38 PM, _AutoCAD PDF (General Documentation).pc3 66 of 336 STA. 22+50STA. 23+00CROSS SECTIONS - STA. 22+50-23+0032LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:27:03 PM, _AutoCAD PDF (General Documentation).pc3 67 of 336 STA. 47+50FENCESTA. 48+00FENCE CROSS SECTIONS - STA. 47+50-48+0033LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:28:23 PM, _AutoCAD PDF (General Documentation).pc3 68 of 336 STA. 48+50FENCESTA. 49+00FENCE CROSS SECTIONS - STA. 48+50-49+0034LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:29:48 PM, _AutoCAD PDF (General Documentation).pc3 69 of 336 STA. 49+50FENCEGATESTA. 50+00FENCE CROSS SECTIONS - STA. 49+50-50+0035LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:31:13 PM, _AutoCAD PDF (General Documentation).pc3 70 of 336 STA. 50+50FENCESTA. 51+00CONSTRUCTIONENTRANCECROSS SECTIONS - STA. 50+50-51+0036LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:32:38 PM, _AutoCAD PDF (General Documentation).pc3 71 of 336 STA. 51+50STA. 52+00FENCEGATE CROSS SECTIONS - STA. 51+50-52+0037LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:34:03 PM, _AutoCAD PDF (General Documentation).pc3 72 of 336 STA. 52+50FENCESTA. 53+00FENCE CROSS SECTIONS - STA. 52+50-53+0038LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:35:23 PM, _AutoCAD PDF (General Documentation).pc3 73 of 336 STA. 53+50FENCE CROSS SECTIONS - STA. 53+5039LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:36:47 PM, _AutoCAD PDF (General Documentation).pc3 74 of 336 STA. 63+00CONSTRUCTIONENTRANCESTA. 63+50FENCE CROSS SECTIONS - STA. 63+00-63+5040LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:37:43 PM, _AutoCAD PDF (General Documentation).pc3 75 of 336 STA. 64+00STA. 64+50CROSS SECTIONS - STA. 64+00-64+5041LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:39:08 PM, _AutoCAD PDF (General Documentation).pc3 76 of 336 STA. 65+00STA. 65+50BUILDINGCROSS SECTIONS - STA. 65+00-65+5042LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:40:38 PM, _AutoCAD PDF (General Documentation).pc3 77 of 336 STA. 66+00FENCE BUILDINGSTA. 66+50FENCE BUILDINGGATE CROSS SECTIONS - STA. 66+00-66+5043LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:42:03 PM, _AutoCAD PDF (General Documentation).pc3 78 of 336 STA. 67+00BUILDINGFENCE STA. 67+50CROSS SECTIONS - STA. 67+00-67+5044LEGEND (SECTION):DYKSTRA LEVEERIVER MILE 29.5 TO RIVER MILE 30.9111188944PROGRESS COPY5/6/2020Christie True, DirectorWater and Land Resources DivisionDepartment of Natural Resources and ParksRiver and FloodplainManagement SectionKnow what's below.RCall before you dig.PROJECT REF:THESE PLANS AREA APPROVED FORCONFORMANCE WITH THE CITY OF AUBURN'SENGINEERING REQUIREMENTS.DEV. REVIEW ENGINEER:DATE APPROVED:I:\1-RIVERS CAD SUPPORT\1111889_DYKSTRA_Levee\DWG\1111889_DYKSTRA_XSEC2.dwg, 5/6/2020 9:43:18 PM, _AutoCAD PDF (General Documentation).pc3 79 of 336 Critical Areas Report and Habitat Impact Assessment Green River Dykstra Levee Improvement Project Submitted to: City of Auburn Department of Planning and Development 25 West Main Street Auburn, WA 98001 Prepared by: Seth Amrhein, Environmental Scientist III King County Department of Natural Resources and Parks Water and Land Resources Division River and Floodplain Management Section 201 South Jackson Street, Suite 600 Seattle, WA 98104 January 6th, 2021 80 of 336 2 Table of Contents Introduction .................................................................................................................................................. 3 Project Description........................................................................................................................................ 3 Project Areas ................................................................................................................................................. 5 Site Analysis .................................................................................................................................................. 6 Habitat Impact Analysis ................................................................................................................................ 9 Measures to Avoid or Minimize Potential Adverse Effects .................................................................... 13 Effect Determination .............................................................................................................................. 14 Monitoring .................................................................................................................................................. 14 Facility performance ........................................................................................................................... 14 References .................................................................................................................................................. 16 Appendix A: Galli-Dykstra wetland and ordinary high water mark reconnaissance .................................. 17 81 of 336 3 Introduction In 2013 the City of Auburn developed an elevation profile of the Galli, Dykstra, and Lone’s Addition levees to analyze where freeboard deficits exist . The City then asked the King County Flood Control District to undertake work to evaluate and address identified low points in the levee system in Auburn. The 2019 Green River System Wide Improvement Framework (SWIF) recommended addressing identified low areas along the levee system as an interim risk reduction measure (IRRM). The goal of the Galli’s-Dykstra Feasibility and Repair Project is to evaluate and address low areas that compromise the level of flood risk reduction afforded by the levee system. Initial feasibility work identified three areas along the Dykstra levee in the City of Auburn where corrective action is needed to address low spots so that the levee will provide a uniform level of flood risk reduction to residential areas in Auburn . Levee improvements made to the Dykstra levee segment will raise the height of the levee prism to contain flood flows of 12,000 cfs (1% annual chance exceedance or a 100-year flood event) plus sufficient levee height to account for uncertainty in containing flood flows (referred to as freeboard). The purpose of this report is to demonstrate that the Green River Dykstra Levee Improvement Project complies with the City of Auburn’s Critical Areas code (ACC 16.10) and provide supporting documentation for the Shoreline Substantial Development Permit and Floodplain Development Permit Application, including the Habitat Impact Assessment required by ACC 15.68.135(J). Project Description The goal of the Galli’s-Dykstra Feasibility and Repair Project is to evaluate and address low areas that compromise the level of flood risk reduction afforded by the levee system between river mile 29.5 and 30.8. Earthen levee raising projects are recommended as an Interim Risk Reduction Measure in the 2019 Green River Systemwide Improvement Framework (SWIF). Three segments along the Dykstra Levee in the City of Auburn have been found to be below the elevation needed to provide a uniform flood containment of 12,000 cubic feet per second (the modelled 100-year discharge) plus an additional 3 feet of freeboard. These sections, identified as Areas A, B, and C, are approximately 960, 600, and 400 feet long, respectively. The Green River Dykstra Levee Improvement Project will raise the deficient sections up to 2.75 feet from their current elevations to provide a uniform level of flood protection along the length of the levee. The work will involve stripping away the existing levee top surface of grass down to a stable substrate, followed by adding suitable fill material to bring the levee height up to the appropriate elevation in the three areas. The side slopes of the added fill will be contoured to match the existing slopes of the face and back of the levee. After the earthwork, all disturbed areas will be revegetated with a native grass seed mix to reestablish the grass ground cover that currently exists on the levee. In conjunction with the work on the levee, an established 82 of 336 4 bench along the toe of the levee will be revegetated with native trees and shrubs to improve riparian habitat. Key project components of the project include: • Installation of a temporary erosion and sediment control measures in compliance with City of Auburn and Washington State water quality protection standards. • Preparation of temporary construction accesses off Riverview Dr NE for each of the three levee improvement sites. • Establishment temporary staging areas and access routes to support construction and marking non-disturbance areas with construction fencing as necessary. • Use of a tracked excavator and bulldozer operating from the top of the levee to distribute and compact fill material delivered with dump trucks. • Removal of temporary erosion control measures after completing the earthwork. • Revegetation of all areas disturbed by construction with a native grass seed mix, as shown on the landscape plan sheet in the provided plan set. • Revegetation of an approximately 35,590 square-foot area along the waterward side of the levee that is currently dominated by invasive reed canary grass with native trees and shrubs to improve the currently degraded riparian habitat conditions. 83 of 336 5 Figure 1. Vicinity map locating each of the three work areas, “A,” “B,” and “C.” Project Areas Area A Area A is an approximately 970-foot long segment of the Dykstra Levee at the north end of the Dykstra Levee along the left bank of the Green River. In this area up to 2.75 feet of fill will be imported to raise the elevation of the levee to provide the requisite level of protection. The area of added fill is approximately 11,518 square feet. Approximately 2.22 cubic yards of sod and surface material will need to be scraped away before the importation of approximately 589 cubic yards of levee fill material. Equipment will access the levee and work area through a gravel access path in City of Auburn street right of way at the eastern terminus of 22 nd St NE. The existing surface of the levee that will be disturbed is predominantly grass. No trees, shrubs, or other riparian vegetation will be removed. All proposed work on the levee is at least 14 feet from the ordinary high water mark of the Green River, which was determined by King County Senior Ecologist, Thomas Bannister, PWS, on April 20 th, 2020 (report in Appendix A). The approximately 35,590 square-foot riparian revegetation area is on bench along the waterward side of Area A (see figures 3 and 4). 84 of 336 6 Figure 2. Aerial photo showing Area A, the City of Auburn proposed Floodway and Special Flood Hazard Area, Moderate Channel Migration Area, ordinary high water mark, and temporary construction access. 85 of 336 Figure 3. Riparian revegetation plan. Additional details are in project plan set. 86 of 336 Figure 4. Proposed revegetation area along toe of levee (left side of picture; summer 2020). Figure 5. Photograph of Area A. Area B Area B is an approximately 600-foot long segment of the Dykstra Levee near the midpoint of this facility. Up to 1 foot of fill will be imported to raise the elevation of the levee to provide the requisite level of protection. The area of added fill is approximately 7,200 square feet. 87 of 336 3 Approximately 2.55 cubic yards of sod and surface material will need to be scraped away before the importation of approximately 147.17 cubic yards of levee fill material. Equipment will access the levee and work area through a property (tax ID # 7349400570) owned by King County. The existing surface of the levee that will be disturbed is grass. No trees, shrubs, or other riparian vegetation will be removed. All proposed work is at least 13 feet from the ordinary high water mark of the Green River. Figure 6. Aerial photo showing Area A, the City of Auburn proposed Floodway and Special Flood Hazard Area, Moderate Channel Migration Area, ordinary high water mark, and temporary construction access. 88 of 336 4 Figure 7. Photograph of Area B. Area C Area C is an approximately 400-foot long segment of the Dykstra Levee near the upstream end of this facility. Up to 1 foot of fill will be imported to raise the elevation of the levee to provide the requisite level of protection. The area of added fill is approximately 4,800 square feet. Approximately 0.87 cubic yards of sod and surface material will need to be scraped away before the importation of approximately 120.67 cubic yards of levee fill material. Equipment to access the levee will access the levee and work area through a tract parcel (734940TR-A) in which King County holds an access easement. The existing surface of the levee that will be disturbed is grass. No trees, shrubs, or other riparian vegetation will be removed. All proposed work is at least 14 feet from the ordinary high water mark of the Green River. 89 of 336 5 Figure 8. Aerial photo showing Area A, the City of Auburn proposed Floodway and Special Flood Hazard Area, Moderate Channel Migration Area, ordinary high water mark, and temporary construction access. 90 of 336 6 Figure 9. Photograph of Area C. Site Analysis This section includes a description of critical areas regulated under ACC 16.10.080 and protected areas regulated under ACC 15.68. The Shoreline Environment designated in the City of Auburn Shoreline Master Program is also identified. Shoreline Designation All proposed work in Areas A, B, and C is in the Residential Shoreline Environment, as designated in the City of Auburn Shoreline Master Program. Replacement or rehabilitation of existing levees is a permitted use within the Residential Shoreline Environment (per the Permitted Use Table 1 in the Auburn Shoreline Master Program) . The proposed approximately 35,590 square-foot revegetation component to enhance the riparian habitat within Residential Shoreline Environment is permitted as a shoreline habitat and natural systems enhancement project (per the Permitted Use Table 1 in the Auburn Shoreline Master Program). 91 of 336 7 Wetlands A wetland investigation was conducted by King County Senior Ecologist, Thomas Bannister, PWS, on April 20th, 2020. Mr. Bannister determined that no wetlands or wetland buffers are present within the project work area. The report documenting these find ings in provided in Appendix A. Streams The only stream within the project area is the Green River. The stream reach within the project area has been channelized following levee construction on the left bank. The Green River is a fish-bearing, perennial stream that is classified as a Type S shoreline of the state (ACC 16.10.080.D.1). The City of Auburn requires a 100-foot protective buffer for Type S streams in the Residential Shoreline Environment. The buffer is to extend landward from the ordinary high water mark, which was determined by King County Senior Ecologist, Thomas Bannister, PWS (see Appendix A). All proposed work in Areas A, B, and C is within this 100-foot buffer. Structures or improvements permitted under the City’s adopted shoreline master program are permitted in stream buffers (ACC 16.090.E.2.c.). As noted above, the City’s Shoreline Master Program permits replacement or rehabilitation of existing levees within the Residential Shoreline Environment. Therefore, the proposed work on the Dykstra Levee is permitted within the stream buffer. Wildlife Habitat The Green River is designated as “critical habitat” (ACC 16.10.020) due to the presence of salmonids listed as threatened under the federal Endangered Species Act. Puget Sound Chinook (Oncorhynchus tshawytscha) were listed as threatened in 1999 (March 24, 1999 64FR 14307). This listing was later amended (June 28, 2005 70FR 37160). Puget Sound steelhead (Oncorhynchus mykiss) were listed as threatened (May 11, 2007 72 FR 26722). Bull trout (Salvelinus confluentus) are listed as threatened in the lower 48 United States (November 1, 1999 64 FR 58909). Common Name Scientific Name Priority Area Sockeye Salmon Oncorhynchus nerka Breeding Area Coast Resident Cutthroat Oncorhynchus clarki Occurrence/Migration Steelhead Trout Oncorhynchus mykiss Breeding Area/Occurrence Chum Salmon Oncorhynchus keta Occurrence/Migration Bull Trout Salmo confluentus Occurrence/Migration Coho Salmon Oncorhynchus kisutch Breeding Area/Occurrence Pink Salmon Oncorhynchus gorbuscha Breeding Area Chinook Salmon Oncorhynchus tshawytscha Breeding Area/Occurrence Wetlands Aquatic Habitat Riverine Aquatic Habitat Table 1. WDFW Priority Habitat and Species information in the Green River adjacent to Dykstra Levee. 92 of 336 8 Flood Hazard Areas Protected areas, as defined in ACC 15.68.060.BB, within the project area include the Special Flood Hazard Area (SFHA)/100-Year Regulatory Floodplain, the Floodway, the Riparian Habitat Zone (RHZ), and the Channel Migration Area (CMA). A very small portion of the Dykstra Levee in Area A falls within the regulatory boundary of the SFHA and Floodway, as depicted on the FEMA Flood Insurance Rate Map (FIRM; Map # 53033C1254). However, the FIRM panel depicts the levee as being outside of the SFHA and Floodway (see figure 10). The elevation of the water surface elevation of the regulatory base flood elevations (BFE) provided in Volume 2 of the 2010 FEMA Flood Insurance Study for King County was plotted against a longitudinal profile of the top of the Dykstra Levee. This complete profile is provided in the project construction plan set and demonstrates that the existing levee top is above the regulatory BFE (i.e., 100-year floodplain) and Floodway and that all proposed added fill is outside of these areas. Areas B and C are completely outside of the SFHA and Floodway, based on the locations of the work area on the Flood Insurance Rate Map and the surveyed elevation of the top of the levee relative to the regulatory BFE and Floodway elevations provided in the 2010 Flood Insurance Study. A hydraulic and hydrologic analyses report, which provides documentation that all proposed fill is above 100-year floodplain, has been included with the permit application package. Areas A, B, and C are completely within the Riparian Habitat Zone, which extends 250 feet landward from the ordinary high water mark of the Green River. Approximately one-half of Area A is within the mapped Moderate Channel Migration Area. Areas B and C are partly in the mapped Severe Channel Migration Area. The proposed approximately 35,590 square-foot revegetation component to enhance the riparian habitat is within the SFHA/Floodway and riparian habitat zone. Projects to enhance natural functions are permitted in this area under ACC 15.68.380. 93 of 336 9 Figure 10. FEMA Flood Insurance Rate Map of project vicinity. Note levee is drawn landward of Special Flood Hazard Area/Floodway. Habitat Impact Analysis The proposed project meets the definition of “development,” as defined under ACC 15.68.060.G. When development is proposed in a “protected area,” which includes Special Flood Hazard Areas (SFHA), floodways, the riparian habitat zone, and channel migration areas (ACC 15.68.060.BB), a habitat impact analysis is required to evaluate the impact of the project on water quality and aquatic and riparian habitat (ACC 15.68.135.J). As discussed above, the proposed construction will occur on the top of a levee within the riparian habitat zone and channel migration area. In conjunction with this work, an approximately 35,590 square-foot area along toe of the levee will be revegetated with native trees and shrub to enhance riparian functions. The purpose of this assessment is to determine the impact of the project on the habitat of species protected under the Endangered Species Act (ESA). ACC 15.68.135.J.4 requires that the assessment be prepared in accordance with Regional Guidance for Floodplain Habitat Assessment and Mitigation, FEMA Region X, 2010. This guidance requires analysis of 94 of 336 10 impacts the following elements, per ACC 15.68.135.J.4, including direct, indirect, interdependent, interrelated, or cumulative effects. Primary constituent elements (PCEs) of critical habitat for ESA-listed species In freshwater systems primary constituent elements (PCEs) of critical habitat for ESA-listed species include: adequate water quality, water quantity, and substrate (free of fine sediments) for spawning, incubation, and larval development; adequate water quality and floodplain connectivity for rearing; and stream channels free of man-made obstructions (due to physical, water temperature, or chemical barriers) (FEMA 2013). As discussed above, all construction is landward of the ordinary high water mark of the Green River in a riparian habitat zone. The only impact to the identified PCEs from the proposed work in this area is the potential for temporary degradation of water quality from erosion of exposed soils during earthwork. However, this risk will be minimized to the greatest extent possible by using temporary erosion and sedimentation control measures, constructing during the dry season, and employing careful site management to minimize the amount of exposed, erodible soils on the site at any given time. Erosion control best management practices will be inspected regularly by a Certified Erosion and Sedimentation Control Lead. If any measure is observed to not be functioning to fully control sediment from entering the Green River, construction would be halted, and the failure would be remedied with appropriate best management practices (e.g., covering bare soils, repairing failing silt fencing or straw wattles). Immediately after construction, all disturbed soils will be revegetated to provide permanent soil stabilization. In conjunction with the construction on the levee, an approximately 35,590 square-foot area along the waterward side of the levee that is currently dominated by invasive reed canary grass will be revegetated with native trees and shrubs to improve the currently deg raded riparian habitat conditions. This action is identified as a key opportunity for habitat restoration and enhancement in this reach in the Green River SWIF Current Conditions Report, Aquatic, Floodplain and Riparian Habitat Technical Memorandum. This planting area is also identified as critical for shade importance based on the Muckleshoot Tribe sun exposure model, as reported in the SWIF. The incorporation of the revegetation component is expected to improve stream buffer/riparian management area functions by addressing several habitat limiting factors identified in the SWIF, including creating shade that may help moderate water temperatures, increasing future large word recruitment, and increasing insect and detrital inputs into the aquatic food web. Essential fish habitat designated by the National Marine Fisheries Service The Green River provides Essential Fish Habitat for anadromous and resident salmonid populations. The project has been designed to avoid direct and indirect impacts to the Green River by ensuring all construction is as far away from the stream as possible. No construction on 95 of 336 11 the levee is proposed closer than 13 feet from the ordinary high water mark of the Green River. As noted above, the proposed work will occur in the stream buffer/riparian habitat zone. Stream buffers may provide critical function to an adjacent waterbody, including shading, input of organic debris and course sediments, uptake of nutrients, stabilization of banks, interception of fine sediments, protection from disturbance by humans and domestic animals, and maintenance of wildlife habitat. Disruption of the stream buffer has the potential to adversely impact the adjacent waterbody. The areas of proposed construction are within the top of a constructed levee with a surface of grass and gravel, which precludes or greatly limits the buffer from fully performing these functions. After construction, the surface of the buffer will be returned to its pre-construction condition of grass surface cover by seeding all disturbed areas with native grasses. The post-construction stream buffer/riparian habitat zone functions in the levee work areas will be equivalent to the pre-construction functions. Therefore, the proposed project will cause no long-term direct or indirect effects on Essential Fish Habitat in the Green River. However, short-term temporary indirect impacts from construction disturbance, limited to minor degradation of water quality in the Green River from potential erosion of exposed soils, is possible. This risk will be greatly minimized by completing the project in the dry season and using temporary erosion control measures in compliance with City of Auburn development regulations. Installation, maintenance, and monitoring of these best management practices will be supervised by a Washington Certified Erosion and Sedimentation Control Lead. Fish and wildlife habitat conservation areas As noted above, the Green River is designated as “critical habitat” for federally listed salmonids and supports Priority Species designated by the WDFW. This project has been designed to avoid direct and indirect construction impacts to the Green River, which is designated as critical habitat due to the presence of threatened salmonids. All ground-disturbing actions will occur landward and above the ordinary high water mark (OHWM) of the Green River. As described above, construction is proposed within the stream buffer/riparian habitat zone area along the Green River, which could cause impacts to the critical habitat in the river if buffer functions were disrupted. However, the area of construction is with an existing levee in which the typical stream buffer functions is highly limited. The post-construction buffer in the levee work area will provide the same level of function at protecting and maintaining the critical habitat as the pre-construction buffer. As discussed above, the potential for temporary impacts to water quality from erosion of disturbed soils will be greatly minimized by using temporary erosion control measures and promptly establishing permanent vegetation cover after construction. Over time, the establishment of the approximately 35,590 square-foot buffer enhancement area will contribute to improved wildlife habitat. 96 of 336 12 Vegetation communities and habitat structures The areas of proposed construction are within the top of a constructed levee with a surface of grass and gravel, which precludes or greatly limits the buffer from fully performing the typical buffer functions listed above. No trees, shrubs, or other riparian vegetation will be removed. After construction, the surface of the levee work area will be returned to its pre-construction condition of a grass surface cover by seeding all disturbed areas with native grasses. The post- construction stream buffer/riparian management area ecological functions in these areas will be equivalent to the pre-construction functions. Therefore, the proposed project will cause no long-term direct or indirect effects on the vegetation communities and habitat structures in the Green River riparian habitat area. However, short-term temporary indirect impacts from construction disturbance, limited to minor degradation of water quality in the Green River from potential erosion of exposed soils, is possible. As discussed above, the potential for temporary impacts to water quality from erosion of disturbed soils will be greatly minimized by using temporary erosion control measures and promptly establishing permanent vegetation cover after construction. Over time, the establishment of the approximately 35,590 square-foot buffer enhancement area, which will be planted with native trees and shrubs, will contribute to increased ecological function of this area, which is currently dominated by reed canary grass. Water quality Short-term temporary impacts from construction disturbance, limited to minor degradation of water quality in the Green River from potential erosion of exposed soils, is possible. However, as discussed above, this risk will be greatly minimized by completing the project in the dry season and using temporary erosion control measures in compliance with City of Auburn development regulations. Water quantity, including flood and low flow depths, volumes and velocities The proposal involves placing fill where there is an adequate freeboard to contain 12,000 cfs, but at an elevation above the 1% annual chance exceedance (100-year) floodplain elevation. The purpose of the fill is to ensure a uniform level of flood containment through the levee system. The added levee height of up to 2.75 feet would only impact river flow patterns under flood events with flows greater than 12,000 cfs by containing flows riverward of the levee. In this location, containing the river within the levee system under such extreme , low-recurrence flood events will contain flows from entering in a highly developed floodplain comprised of single and multifamily residences and city streets. While floodplains can serve critical ecological functions for riverine species, in this case it is unsuitable as floodplain refugia or aquatic habitat in its current developed condition. The channel’s natural planform pattern and migration processes The project will add fill to three low sections of an existing levee above the 100-year floodplain elevation so that it provides a uniform level of flood containment. The levee is already armored 97 of 336 13 with large rock and resistant to channel migration. The proposed work will not alter the channel’s natural planform pattern and migration process from the existing condition. Spawning substrate All ground-disturbing actions will occur landward and above the ordinary high water mark (OHWM) of the Green River. Spawning substrate will not be affected through the addition of fill material to top of the Dykstra Levee. Sedimentation into the Green River will be controlled minimized by use of temporary erosion control measures and promptly establishing permanent vegetation cover after construction. Floodplain Refugia The added levee height would only impact river flow patterns under flood events where flows exceed 12,000 cfs by containing flows riverward of the levee. All construction on the levee is above the 100-year floodplain. In this situation, containing the river within the levee system under such extreme flood would prevent floodwaters from entering a highly developed floodplain comprised of residential development, which is unsuitable as floodplain refugia for salmonids and other riverine species. No suitable floodplain refugia for ESA-listed salmonids or Priority Species will be adversely impacted or cut off by the proposed project. The approximately 35,590 square-foot riparian enhancement area along the toe Area A may contribute to increased effectiveness of this area to serve as floodplain refugia for salmonids by increasing surface roughness and structural complexity, and by providing a future source of large woody debris. Measures to Avoid or Minimize Potential Adverse Effects As described above, the only identified impact beyond existing conditions is the potential for water quality degradation from erosion during construction, which could adversely impact aquatic habitat and species. Due to the temporary nature and ability to limit the risk of this potential impact, we expect implementation of our proposal will not cause a net loss of shoreline ecological functions. The following measures will be employed to avoid and minimize adverse effects. • Construction will occur in the dry season. • Temporary erosion and sedimentation control measures will be installed prior to any ground disturbance. • The amount of ground disturbance at any one time will be minimized. • The installation, monitoring and maintenance of temporary erosion and sedimentation control measures will be supervised by a Washington State Certified Erosion and Sedimentation Control Lead. • If any failure of a temporary erosion and sedimentation control measure occurs, construction will halt until the problem is corrected. 98 of 336 14 • All City of Auburn grading and stormwater standards for construction will be followed. • Permanent vegetative cover (native grass mix) will be installed immediately after construction to stabilize soils. The site will be inspected frequently after construction to verify that the vegetative cover is taking hold. • In conjunction with the construction on the levee, an approximately 35,590 square-foot area along the waterward side of the levee that is currently dominated by invasive reed canary grass will be revegetated with native trees and shrubs to improve the currently degraded riparian habitat conditions. The incorporation of the revegetation component is expected to improve stream buffer/riparian management area functions by addressing several habitat limiting factors identified in the SWIF, including creating shade that may help moderate water temperatures, increasing future large word recruitment, and increasing insect and detrital inputs into the aquatic food web. Effect Determination As provided above, the only potential direct, indirect, interdependent, interrelated, or cumulative effect from the proposal is the potential for minor temporary water quality impacts as a result of erosion that could occur when soils near the Green River are exposed during construction, and enhancement of riparian area function by revegetating with native trees and shrubs. Temporary erosion and sedimentation controls and careful sit e management overseen by a Washington State Certified Erosion and Sedimentation Control Lead will greatly minimize the risk of erosion and water quality impacts to the greatest extent possible. However, should these measures not be 100 % effective, the impacts on ESA-listed species are expected to be discountable or insignificant, depending on whether the species are present when the temporary water quality impact occurs. If any best management practices to protect water quality fails or is infective at controlling erosion, construction would stop, exposed erodible soils would be contained or covered, and the best management practice would be corrected or replaced with an alternative before resuming construction. Any water quality impact would be minimal and very brief, and unlikely to cause adverse impact the ESA-listed salmonid or elements considered above. Therefore, the appropriate effect determination for the proposal is May Affect, Not Likely to Adversely Affect (NLAA). Monitoring Facility performance Post-construction monitoring will ensure that the fill added to the levee is stable and no erosion of materials is occurring. The key factor will be to ensure that permanent vegetative cover is established over all disturbed areas. After construction and seeding the work area with a native 99 of 336 15 grass seed mix, the site will be inspected biweekly by a representative of the King County River and Floodplain Management Section (RFMS) to verify grass seed germination and growth. At each inspection, the inspector will determine whether additional seeding or irrigation is needed. Once complete vegetative coverage is achieved, it is expected that the owners of the private residences will resume maintenance of the grass. The structural integrity of the fill will be qualitatively assessed every other year during summer low flow inspections by an Engineer from the King County RFMS. If any damage is observed, the Engineer will determine whether additional evaluation by an RFMS Geologist or other technical experts is needed to determine if levee improvement is performing as designed. Pursuant to RMFS protocols, the facility will also be evaluated after Phase 3 floods and in response to complaints of issues reported by members of the public. If damage or other issues of concern are identified, RFMS staff will determine a course of action. If any repairs or modifications to the levee are determined to be necessary, all applicable permitting agencies will be consulted to determine permitting needs and any necessary permits will be obtained prior to performing repairs or modifications. Riparian enhancement The riparian revegetation area will be monitored for five years in accordance with the King County River and Floodplain Management Section Program and Project Effectiveness Monitoring Framework (2015). Data on cover and survival of installed plants and invasive weeds will be collected one, three, and five years after plant installation. This data will be used to guide maintenance needs at the site, which will include watering, weeding, and plant replacement, as necessary. After the 5-year monitoring period, maintenance of the revegetation area will continue in accordance with the King County River and Floodplain Management Section’s site maintenance program. 100 of 336 16 References City of Auburn, Washington. 2020. Auburn City Code. https://auburn.municipal.codes/ City of Auburn, Washington. 2019. Auburn Shoreline Master Program. FEMA. 2010. Regional Guidance for Floodplain Habitat Assessment and Mitigation. FEMA Region 10, , Bothell, WA. FEMA. 2013 .Puget Sound BiOp Floodplain Habitat Assessment Worksheet FEMA Region 10, , Bothell, WA. King County. 2015. King County River and Floodplain Management Section Monitoring Framework. Seattle. WA. King County Flood Control District. 2016. Green River, King County Washington, System -Wide Improvement Framework (SWIF) Interim Report. Seattle, WA. https://www.kingcounty.gov/depts/dnrp/wlr/sections-programs/river-floodplain- section/capital-projects/green-river-system-wiHtde-improvement-framework.aspx King County. 2020. Hydraulic and Hydrologic Analysis Report, Green River Dykstra Levee Improvement Project. Seattle, WA.a WDFW. 2020. Priority Habitat and Species Database, http://wdfw.wa.gov/conservation/phs/. 101 of 336 17 Appendix A: Galli-Dykstra wetland and ordinary high water mark reconnaissance 102 of 336 18 Water and Land Resources Division Department of Natural Resources and Parks King Street Center 201 South Jackson Street, Suite 600 Seattle, WA 98104-3855 206-477-4800 Fax 206-296-0192 TTY Relay: 711 May 1, 2020 TO: Seth Amrhein and Jay Young, PE – River and Floodplain Management Section FM: Thomas Bannister, PWS RE: Galli – Dykstra Levee wetland and ordinary high water mark reconnaissance The purpose of this memorandum is to document observations and findings regarding the presence of wetlands and the locations of ordinary high water mark (OHWM) in the vicinity of King County’s proposed Galli–Dykstra Levee Repair Project. As part of the project, the King County River and Floodplain Management Section (RFMS) is proposing to add additional freeboard to the Galli–Dykstra Levee located on the left bank of the Green River in Auburn, Washington. Scheduled for the summer of 2020, RFMS will add additional material to the top of the earthen levee within the three work areas mapped below. On April 21, 2020, an RFMS Professional Wetland Scientist (PWS) completed a site reconnaissance within the three work areas. According to the USGS gage (12113000) near Auburn (https://waterdata.usgs.gov/nwis/uv?site_no=12113000), discharge was recorded at approximately 1,050 cubic feet per second at the time of the April 21 site reconnaissance. Prior to the field reconnaissance, the PWS completed a background review of publicly available information regarding the potential presence of wetlands in the vicinity of the work areas. King County iMap (https://www.kingcounty.gov/services/gis/Maps/imap.aspx) does not map wetlands in the vicinity of the project. The U.S. Fish and Wildlife Service’s Nation Wetland Inventory (NWI) mapper (https://www.fws.gov/wetlands/data/mapper.html) identifies the Green River as riverine aquatic habitat. NWI maps a vegetated mid-channel bar approximately 1,200 feet upstream of Work Area A and approximately 1,300 downstream of Work Area B. This mid- channel bar is clearly visible in recent aerial imagery and wetland conditions likely exist on the bar. However, this bar was not observed during the April 21 site reconnaissance because of its distance from the work areas. NWI also maps a palustrine wetland on the right bank of the Green River opposite of Work Area B. The PWS did not investigate the presence of wetlands on the right bank because the occurrence of wetlands on the opposite bank of the river would have no regulatory bearing on the project. 103 of 336 19 Following the guidance by the Washington State Department of Ecology’s (Ecology) Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State, the PWS completed a hydrologic analysis of the Green River for purpose of delineating the OHWM adjacent to the three work areas. According to Ecology, the frequency of “ordinary” high flow events for streams are expected to occur between the 1-year and 2-year peak flows, with the 1-year recurrence interval representing the lower end of ordinary high and the 2-year recurrence interval representing the upper end, and the ordinary high water event falling somewhere in between. However, flow in the Lower Green River is managed by the Howard Hansen Dam located at RM 64.5. Flow management from the dam often results in sustained high flows in the Lower Green that can last for weeks as compared to an unmanaged, natural system where high flows generally subside after several hours or days. The altered hydrologic regime is important to consider because high flow recurrence intervals of the Green River do not reflect natural channel forming processes that dictate the location of OHWM. To illustrate this point, the 1-year recurrence interval in the Lower Green River is generally associated with a discharge value of 6,000 cubic feet per second (cfs) while the 2-year recurrence interval is generally associated with a discharge value of 9,000 cfs. Channel forming processes that result in observable indicators of OHWM in the Lower Green River are known to generally occur at flows around 2,000 cfs which is considerably lower than the 1-year recurrence interval on this managed river. According to the USGS gage (12113000) near Auburn (https://waterdata.usgs.gov/nwis/uv?site_no=12113000), discharge in the river at the time of the April 21 field reconnaissance was approximately 1,050 cubic feet per second (cfs). During the reconnaissance, the PWS observed facultative vegetation, predominantly grasses, on a high flood terrace immediately waterward of the levee adjacent to Work Area A. The water surface elevation of the river was approximately 4-5 feet lower than the elevation of the terrace. The terrace consists of sand deposits from the river and indictors of recent inundation were observed by the PWS. These indicators are most likely a result of the significant (approximately 12,000 104 of 336 20 cfs) flow event in February 2020. Shallow soils probes on the terrace yielded dry, very sandy soils with no hydric soil indicators. As a result of the elevation of the terrace above the river and the permeability of the sandy substrate, the duration and frequency of inundation of this area is likely not sufficient to support wetland conditions. Adjacent to the three work areas, the PWS observed a distinct scour along the bank indicative of the OHWM. See figure below. Upland vegetation dominates the area above the elevation of the scour. For the most part, the banks adjacent to the work areas and below the scour are predominantly unvegetated and frequently disturbed by river flow. Hydrophytic vegetation including willows and rushes, were occasionally observed fringing the water line along the steeply sloping bank of the levee prism. The occurrence of these clusters of hydrophytic vegetation waterward of the scoured bank is isolated and sporadic. These small, isolated areas of hydrophytic vegetation likely meet riverine wetland criteria. However, these narrow, vegetated bands of hydrophytic vegetation are located waterward of OHWM. Buffers associated with these small wetlands would overlap with the regulated area associated with the river, landward of OHWM. As such, the presence of these small wetland areas has no regulatory implications on the project. Following the April 21 reconnaissance, the USGS gage reported an increase in flow to approximately 1,950 cfs on April 24, 2020. This flow discharge is considered to be representative of an ordinary high water event. The PWS returned to the site on this day to observe and document flow conditions at the three work areas. During the April 24 site visit, the edge of water was located along the distinct scoured bank and at the transition between upland and hydrophytic vegetation within the three work areas. Relying on detailed topographic LiDAR data, the PWS digitized the location of the OHWM adjacent to the three work areas in ArcGIS. The Green River is a Shoreline of the State and because the three work areas are located within 200 feet of the OHWM (within the Shoreline 105 of 336 21 Management Zone), the project is subject to the requirements of the City of Auburn Shoreline Master Program and Auburn City Code Chapter 16.08. The OHWM and the extents of the Shoreline Management Zone relative to the three work areas are illustrated below. 106 of 336 22 107 of 336 23 Enclosure(s) (number) 108 of 336 Revised Geotechnical Engineering Report Dykstra Levee at RM 29.5 to RM 30.9 King County, Washington November 5, 2020 Prepared By: Department of Local Services Road Services Division Materials Laboratory 155 Monroe Avenue NE, Bldg. D Renton, WA 98056-4199 Geotechnical Investigation 109 of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of 336 TABLE OF CONTENTS REVISED GEOTECHNICAL ENGINEERING REPORT Dykstra Levee at RM 29.5 to RM 30.9 Project NO. 1135536 SECTION 1.0 – INTRODUCTION……………………………………………………………….1 SECTION 1.1 – General…...…………………….…….………………………………….…...1 SECTION 1.2 – Site Description.……………….….…………………………….……………1 SECTION 2.0 – SUBSURFACE CONDITIONS……………………………………….………2 SECTION 2.1 – Geologic Mapping Review………….…….…………………. ….…………2 SECTION 2.2 – Geotechnical Drilling……………….……….……………….……………....2 SECTION 2.3 – Groundwater……...……………….………...…………………....………….3 SECTION 3.0 – SLOPE STABILITY ANALYSES.…………………………………………….3 SECTION 3.1 – Existing Slope Condition.……………………………………………………3 SECTION 3.2 – Soil Parameters………………………………………………………………3 SECTION 3.3 – Stability Analysis Conditions...………………………………………………4 SECTION 4.0 – CONCLUSIONS AND RECOMMENDATIONS…………………………….5 SECTION 4.1 – Fill Construction Recommendations…….….…………...…………………5 SECTION 4.2 – Constructed Levee Fill Sections…...……….………………………………6 SECTION 5.0 – CONTINUING GEOTECHNICAL SERVICES….………………………….7 SECTION 6.0 – REFERENCES……………………………….….…………….………………8 111 of 336 TABLE OF CONTENTS (Continued) REVISED GEOTECHNICAL ENGINEERING REPORT Dykstra Levee at RM 29.5 to RM 30.9 Project NO. 1135536 LIST OF FIGURES FIGURE 1: PROJECT LOCATION MAP FIGURE 2A-2C: BORING LOCATIONS LIST OF TABLES TABLE 1: SOIL PARAMETERS TABLE 2: SLOPE STABILITY SUMMARY TABLE 3: LEVEE FILL GRADATION SPECIFICATIONS APPENDICES APPENDIX A: BORING LOGS AND LABORATORY TEST RESULTS APPENDIX B: SLOPE STABILITY ANALYSES CRITICAL FAILURE SURFACE DIAGRAMS 112 of 336 Mailstop: RSD-TR-0100 | 155 Monroe Avenue NE, Bldg. D, Renton, WA 98056-4199 206-477-8100 | maint.roads@kingcounty.gov | www.kingcounty.gov/roads REVISED GEOTECHNICAL ENGINEERING REPORT DYKSTRA LEVEE AT RM 29.5 TO RM 30.9 1.0 INTRODUCTION 1.1 General As requested, the King County Materials Laboratory (KCML) has completed our geotechnical investigation for the Dykstra Levee Repair project. The project will raise the levee elevation along the west bank of the Green River in order to meet the levee accreditation requirements of the Federal Emergency Management Agency (FEMA). The purpose of our study is to evaluate subsurface and groundwater conditions in order to provide geotechnical recommendations for design and construction that can be utilized to raise the elevation of the levee between RM 29.5 and RM 30.9. The general project location is shown on the Vicinity Map, Figure 1, at the conclusion of this text. 1.2 Site Description The Dykstra Levee at the subject site borders the Green River and provides flood protection for the people and property in the surrounding City of Auburn. The levee runs adjacent to the Dykstra City Park, the Madison at River’s Edge Apartments, and several privately-owned residential homes. Reconstruction and repair of the levee is designed to increase the levee elevation to a level at or greater than the elevation of a 100-year storm plus an additional three feet (FIS+3). The amount of fill needed to raise the levee profile to meet the FIS+3 is typically less than 1 foot. However, there is a deeper section of fill required from approximately RM 29.77 to RM 29.85 (King County Plan Sta. 16+50 to Sta. 21+00) that will need up to 3 feet of fill. The crest of the levee is designed to be a minimum of 12 feet in width. The reconstruction design will generally maintain the existing levee orientation. Along the landside of the levee, the elevation of the levee crest is generally equal to the surrounding terrain. On the riverside, the levee slope inclination generally ranges from 2.25H(horizontal):1.0V(vertical) to 3.5H:1.0V with intermittent sections of increased steepness. The width of the levee crest varies from approximately 14 to 29 feet and is mostly vegetated with short grass. The riverside bank of the levee consists of grass, shrubs, and small trees. Inspection of the bank shows no significant signs of erosion or material loss. Records show there have been three repairs to the riverbank within the subject site completed in 1994, 2008, and 2015. 113 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 2 of 8 2.0 SUBSURFACE CONDITIONS 2.1 Geologic Map Review We reviewed the online Washington State Department of natural Resources Geological Information Portal for expected soil profiles in the project vicinity. The geologic map viewed was in a scale of 1:24,000. A brief description of the mapped surficial geologic unit within the subject site is as follows: Quaternary Alluvium (Qaw): Quaternary unconsolidated or semi-consolidated alluvial clay, silt, sand gravel, and or cobble deposits; locally includes peat, muck, and diatomite; locally includes beach, dune, lacustrine, estuarine, marsh, landslide, lahar, glacial, or colluvial deposits; locally includes volcaniclastic or tephra deposits; locally includes modified land and artificial fill. 2.2 Geotechnical Drilling Site-specific soil and groundwater conditions were explored on January 21, 2020 and February 13, 2020 by drilling 11 borings, 9 to a depth of 21.5 feet bgs, 1 to 41.5 feet bgs, and 1 to 51.5 feet bgs. Drilling was completed using a track mounted Deidrich D-90 drill rig equipped with nominal 4.25” I.D. continuous flight hollow-stem auger. Standard Penetration Tests (SPT) were taken at 2.5-foot vertical intervals to 15 feet bgs and 5.0- foot intervals past 15 feet as the borings were advanced below ground level. The SPT provides a measure of compaction or relative density of granular soils, and consistency or stiffness of cohesive fine-grained soils. In addition, disturbed but representative soil samples were collected at each testing interval and returned to our laboratory for analysis. Eighteen soil samples were tested and used to further classify soils at various depths. The remaining collected soil samples will be stored in sealed plastic bags for additional testing if requested. Approximate boring locations are shown in Figure 2A-2C. Detailed copies of the boring logs, along with laboratory test results, are enclosed for your review in Appendix A. Stratigraphy units encountered during drilling can generally be divided into the following three categories: Topsoil: The top three to six inches of the levee generally consists of a loose silty sand with gravel and cobbles with numerous organics. Fill: Fill underlying the topsoil ranged from approximately 7 to 13 feet bgs and generally consists of loose to medium dense brown silty sand with gravel to a poorly graded sand with silt and gravel. Alluvial Deposits: Alluvial deposits consisting of medium dense to dense gray gravel with silt and sand, to a poorly graded sand with gravel, underlie the fill to the termination depth of the borings. 114 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 3 of 8 2.3 Groundwater Groundwater was observed in each boring. Groundwater elevations varied from 4 feet bgs to 12 feet bgs and corresponded approximately to the adjacent river elevation at the time of drilling. Groundwater elevations may vary based on the time of year, precipitation levels, and other factors. 3.0 SLOPE STABILITY ANALYSES 3.1 Existing Slope Conditions The thickest section of new fill will be needed near STA 18+50 to raise the levee profile to the 100-year flood elevation plus 3 feet (FIS+3). Therefore, we utilized the slope profile at STA. 18+50 as the critical cross section to model. Soil and groundwater conditions identified in soil borings B-3 and B-4 were transposed onto the Station 18+50 cross section to develop a simplified model for subsequent slope stability analyses. Preliminary slope stability analyses of the critical embankment section were performed utilizing the slope stability analysis software program, Galena, developed by Clover Associates Pty, Limited. For these preliminary stability analyses, we followed the general guidelines as set forth in the US Army Corp of Engineers (COE) Engineering Manuals EM 1110-2-1913 (Design and Construction of Levees) and EM 1110-2-1902 (Slope Stability). For the slope stability computations, the Simplified Bishop Slip Circle analysis option was utilized. This program employs limit equilibrium force resolutions to arrive at a Factor of Safety (FS) for a given embankment cross-section. A FS of 1.0 indicates an imminent embankment failure condition. For our analyses, we modeled both the critical cross section and a modification of the critical cross section. Modeling of the critical cross section captured the impact of raising the levee (FIS+3) on the existing crest profile. Our modified section steepened and extended the slope below the added fill to the existing river channel at a slope inclination of 2.5H:1V. For all raised slope sections, we assumed the width of the crest levee will be a minimum of 12 feet and that the outer slopes of the raised FIS+3 section would be placed at a slope no steeper than 2H:1V. For existing levees, required stability analysis include long-term and rapid drawdown. Earthquake loading was not considered since there is low probability of an earthquake coinciding with periods of high water. End of construction analysis are also not required on existing levee systems. 3.2 Soil Parameters Shear strength parameters for the slope stability model are based on empirical relationships developed between the Standard Penetration Test (SPT) and the friction angle of granular soils 115 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 4 of 8 and fine-grained soils, as applicable. Material properties utilized in the slope stability analyses are provided below in Table 1. Soil Type Unit Weight Friction Angle Cohesion Loose to Medium Dense SM/SP-SM 120 pcf 32 0 Loose to Medium Dense SM/SP-SM (bwt)* 125pcf 32 0 Medium Dense to Dense GP-GM/SW-SM 130 pcf 34 0 Levee Fill 125 pcf 35 0 Table 1: Soil Parameters (bwt)* - Below Water Table 3.3 Stability Analysis Conditions A brief description of the stability conditions analyzed are provided below: Long-Term Long-term stability is generally required analysis for the steady seepage condition. For long-term steady seepage, the concern would be with the landside stability of the levee slope due to saturation of the outer slope soil. At the subject site, based on the surveyed profiles, steady seepage of the landside slope would not be a stability issue since the surveyed profiles show the landslide slopes to be non-existent or generally less than 1 foot. Therefore, we ended up checking the long-term stability of the riverside slope utilizing a low flow condition. On the riverside, high water levels provide a stabilizing force to the riverside slopes. Therefore, a low flow condition is more conservative than a high-water condition for this analysis. A surcharge load of 250 psf was utilized for vehicular loading in the analyses. For our analyses, we used the recommended COE Manual EM 1110-2-1913, Design and Construction of Levees target FS of 1.4 for long-term stability. Rapid Drawdown During prolonged flooding, high water levels will saturate the majority of the embankment slope. Rapid drawdown represents the condition where the water level of the river drops faster than the embankment soil can drain. When this occurs, pore water pressures may develop within the slow draining soil, significantly increasing the potential for slope instability. For drawdown condition modeling, we assumed that for every foot of river drawdown, the water level in the soil will drop at a rate of about 0.5 feet. For our modeling, we assumed a high-water condition elevation of 60.92 and a post storm river elevation of 55.0. This creates a head differential of about 3 feet between the contact soil and the river. For rapid drawdown, COE Manual EM 1110-2-1913 recommends a FS of 1.0 to 1.2. For our analyses, we utilized a target FS of 1.1. 116 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 5 of 8 Slope Stability Summary Multiple analyses with range constraints were selected for evaluating the slope stability of each slope condition. Diagrams showing the critical failure surfaces and associated safety factors (Figures A-1 through A-6) are provided in Appendix A for review. The results of our stability analyses are summarized below in Table 2. Figure Condition Slope FS Target FS A-1 Exising Slope, Long Term 1.94 1.4 A-2 Exising Slope, Rapid Drawdown 1.38 1.1 A-3 Existing Slope, Raised Upper Slope FIS+3, Long Term 1.50 1.4 A-4 Existing Slope, Raised Upper Slope FIS+3, Rapid Drawdown 1.23 1.1 A-5 Modified Slope 2.5H:1V, Raised Upper Slope FIS+3, Long Term 1.48 1.4 A-6 Modified Slope 2.5:H:1V, Raised Upper Slope FIS+3, Rapid Drawdown 1.10 1.1 Table 2: Slope Stability Summary 4.0 CONCLUSIONS AND RECOMMENDATIONS Based on our modeling, the existing levee profile will be able to be raised while meeting the conditions for long term and rapid drawdown stability. From our analysis, rapid drawdown is the critical failure mechanism for slope instability along this section of levee. We recommend the slopes of the raised sections be inclined at no steeper than 2H:1V. A small block wall up to 2 feet in exposed height may be constructed on the landside levee slope if needed to keep the fill within the levee right of way. 4.1 Fill Construction Recommendations We recommend the new backfill material for the levee should consist of generally well graded silty sand with gravel that closely resemble the soil characteristics of the existing levee fill. Our recommended specification for the silty sand and gravel fill is as follows: Sieve Size Percent Passing 3"100 2"90-100 1"70-90 1/2"55-85 #4 35-75 #200 20-30 Table 3: Levee Fill Gradation Specification 117 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 6 of 8 If requested, our office can help locate suitable fill material that will meet the project specification and design intent at the time of construction. At locations of the levee where vehicle access may be required, a base material that is less likely to rut may be desired for the upper 6 inches of fill. In these locations, we recommend using Crushed Surfacing Top Course (CSTC meeting WSDOT Specification Section 9-03.9(3),). 4.2 Constructed Levee Fill Sections 1. Surface vegetation, topsoil, and any other deleterious material should be removed using a straight-edge bucket to minimize disturbance of the underlying soil. The depth of the required excavation is anticipated to generally be 6 inches. 2. The base of the excavation should then be leveled, and the subgrade compacted in accordance with Section 2-03.3(14) C, Method C of the WSDOT Standard Specifications. We recommend a KCML representative be onsite to inspect the exposed subgrade for suitability. 3. Following preparation of the base, for sections that will have vehicular traffic, a construction geotextile for separation and stabilization is recommended to be placed at the bottom of the excavation. We recommend utilizing the woven geotextile, Mirafi 580i. The geotextile should be placed under tension, flat and taut, and extend the entire width and length of the bottom of the excavation. A minimum overlap of two (2) feet is recommended, if needed. No construction traffic of any kind should be allowed directly onto the geotextile. 4. The excavation should then be backfilled to the desired elevation utilizing the approved levee fill. The backfill material should generally be placed in 6-inch lifts and compacted mechanically or by hand in order to reestablish the original shape of the levee. 5. Where vehicle access is necessary, CSTC should be utilized in the upper six inches of the fill to reduce potential rutting. Placement and compaction of the CSTC should be in accordance with Section 2-03.3(14)C, Method C of the WSDOT Standard Specifications. 6. Once the levee fill has reached the desired elevation, sod or seeded topsoil may be placed if desired. 7. Compaction testing and quality control testing of materials shall be conducted to confirm the quality of materials and verify adequate required compaction. KCML is available to perform these tasks. 118 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 7 of 8 5.0 CONTINUING GEOTECHNICAL SERVICES As requested, we have provided site-specific subsurface conditions and preliminary design recommendations that can be used for design of the levee repair. As the design develops, we are available to provide additional geotechnical analysis, design parameters, and construction recommendations as needed. We appreciate the opportunity to have been of service on this project and trust this report addresses your current needs. Should you have question, require clarification, or desire additional information, please contact Casey Wagner (206-255-1881) or Doug Walters (206-477-2112) at your convenience. Respectfully Submitted, King County Materials Laboratory Doug Walters, P.E. King County Materials Engineer 119 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 8 of 8 6.0 REFERENCES American Association of State Highway & Transportation Officials (AASHTO), 2017, LRFD Bridge Design Specifications, 8th Edition, November 2017 Clover Associates, Galena Slope Stability Analysis System, Software Program, Version 7.20.1.01, 27 May 2019 King County Geotechnical Engineering Report, Dykstra Levee at RM 29.5 to RM 30.9. 17 March 2020 U.S. Army Corps of Engineers (USACE), April 2000, Design and Construction of Levees, Engineer Manual EM 1110-2-1913. U.S. Army Corps of Engineers (USACE), October 2003, Slope Stability, Engineer Manual EM 1110-2-1902. United States Department of Transportation Federal Highway Administration, December 2006, Soils and Foundations, FHWA NHI-06-089 United States Geological Survey Earthquake Hazards Program Website Link, Website: http://earthquake.usgs.gov/research Washington State Department of Transportation (WSDOT), December 2013, Geotechnical Design Manual M 46-03, Section 9.2.3.1 WSDOT Geotechnical Design Manual M 46-03 (Section 9.2.3.1) and FHWA NHI-06-088 (Sections 6.2 and 6.4.5) WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, 2020 120 of 336 121 of 336 122 of 336 123 of 336 124 of 336 125 of 336 126 of 336 127 of 336 128 of 336 129 of 336 130 of 336 131 of 336 132 of 336 133 of 336 134 of 336 135 of 336 136 of 336 137 of 336 138 of 336 139 of 336 140 of 336 141 of 336 142 of 336 143 of 336 144 of 336 145 of 336 146 of 336 147 of 336 148 of 336 149 of 336 150 of 336 151 of 336 152 of 336 Stormwater Site Plan Report Green River Dykstra Levee Improvement Project Permit No. GRA20‐0015 Submitted to: City of Auburn Department of Planning and Development 25 West Main Street Auburn, WA 98001 Prepared by: Alex Jones, P.E. King County Water and Land Resources Division, Stormwater Services Section 201 S. Jackson St., Ste. 600, Seattle, WA 98104 alexander.jones@kingcounty.gov; 206‐477‐4719 Reviewed by: Jay Young, P.E. King County Water and Land Resources Division, River and Flood Plain Management Section 201 S. Jackson St., Ste. 600, Seattle, WA 98104 jay.young@kingcounty.gov; 206‐477‐4858 _ Jay Young, P.E. Project Manager August 21, 2020November 23, 2020 153 of 336 2 Table of Contents Chapter 1 – Project Overview ....................................................................................................................... 3 Chapter 2 – Existing Conditions Summary .................................................................................................... 4 Chapter 3 – Off‐Site Analysis (Minimum Requirement #10) ........................................................................ 5 Qualitative Analysis .................................................................................................................................. 5 Area A: ..................................................................................................................................... 5 Area B: ..................................................................................................................................... 5 Area C: ..................................................................................................................................... 6 Chapter 4 – Permanent Stormwater Control Plan ........................................................................................ 7 Chapter 5 – Discussion of Minimum Requirements ..................................................................................... 8 Figures Figure 1 – General Vicinity Map Figure 2 – Area A: Levee Fill Area with Downstream Drainage System Figure 3 – Area B: Levee Fill Area with Downstream Drainage System Figure 4 – Area C: Levee Fill Area with Downstream Drainage System Figure 5 – Flow Chart for Determining Requirements for Redevelopment (Figure I‐2.4.2 Ecology SWMM for Western Washington Vol. I) Figure 6 – Flow Chart for Determining LID MR #5 Requirements in the City of Auburn (Figure 2.5.1 COA Supplemental Manual to the Ecology SWMM for Western Washington) Attachments Attachment A – Drawings Attachment B – Photographs Attachment C – Construction Stormwater Pollution Prevention Plan (SWPPP) Attachment D – Special Reports (Geotechnical and Critical Areas) 154 of 336 3 Chapter 1 – Project Overview This project proposes to raise portions of the existing levee along the left bank of the Green River between 26th St NE and 8th St NE in Auburn, WA (Figure 1). The improvements are designed to meet long‐term flood protection goals, including providing up to three feet of freeboard to the adjacent areas that are located within the mapped special flood hazard area. This Stormwater Site Plan (SSP) Report is issued to comply with submittal requirements for a Civil Site Improvement Permit (Permit No. GRA20‐0015) from the City of Auburn. Other permitting for this proposal includes compliance with City of Auburn’s Shoreline Master Program; a Floodplain Development Permit; an environmental impact review through the State Environmental Policy Act (SEPA); and a Hydraulic Project Approval (HPA) from Washington Department of Fish and Wildlife. Three segments (Areas A, B, and C) along the Dykstra Levee have been surveyed and found to be below the height needed to provide flood containment of 12,000 cubic feet per second (cfs) plus three feet of freeboard. The three sections of the Dykstra Levee that do not meet this required elevation are approximately 960 (Area A), 600 (Area B), and 400 (Area C) feet long. Segments of this levee are proposed to be raised from approximately one to three feet from their current elevation, with the greatest rise in Area A, to meet this protection level. Areas B and C require approximately one foot, on certain portions of these levee segments (see Dykstra Levee construction plans for details in Attachment A). The construction would generally involve removing some of the levee top surface down to a stable layer, followed by adding suitable fill material to bring the levee height up to the appropriate elevation with designed compaction. The side slopes would be shaped to match the existing slopes of the face and back of the levee. Some minor adjustments of the face of the existing levee may be needed to blend the imported/compacted material into the existing prism. This SSP Report covers three distinct and separate areas identified by the following parcel numbers;  Area A (Parcel Identification Nos. 0721059038, 8944150000, and 8944130000);  Area B (Parcel Identification Nos. 7349400540, 7349400550, 7349400560, 7349400570, 7349400580, 7349400590, 7349400600, and7349400610); and  Area C (Parcel Identification Nos. 7349400350, 7349400360, 7349400370, 7349400380, 7349400390, 7349400400, and 734940TR‐A). 155 of 336 4 Chapter 2 – Existing Conditions Summary Area A consists of approximately 960 feet on the left bank (shoreline) of the Green River (river) along Dykstra Park, Villa Del Rio Condominiums, and Madison at River’s Edge Apartments (Figures 1 and 2) located on 22nd Street NE. The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation (Photos 1‐8 in Attachment B). The levee along this section is proposed to be raised up to approximately three feet in some locations. Stormwater either infiltrates into the levee prism, sheet flows toward the river to the north, or sheet flows to the south toward the apartments and condominiums bordering the proposed work area. Area B consists of 600 feet on the left bank (shoreline) of the river along Riverview Drive NE (Figures 1 and 3). The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation (Photos 9‐12 in Attachment B). The levee along this section is proposed to be raised up to approximately one foot in some locations. Stormwater either infiltrates into the levee prism, sheet flows toward the river to the south or east, or sheet flows to the north toward the single‐family residential parcels bordering the proposed work area. Area C consists of 400 feet on the left bank (shoreline) of the river along Riverview Drive NE (Figures 1 and 4). The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation (Photos 13‐16 in Attachment B). The levee along this section is proposed to be raised up to approximately one foot in some locations. Stormwater either infiltrates into the levee prism, sheet flows toward the river to the east, or sheet flows to the west toward the single‐family residential parcels bordering the proposed work area. The work areas contain no existing stormwater flow control or water quality facilities. No stormwater systems directly serve the work area, though there are private subgrade roof drain pipes and City of Auburn trunk lines that cross one or more work areas as described below in Chapters 2 and 5. There are no water supply lines, septic systems, or sanitary sewer lines within the proposed work area. There are no known registered groundwater wells located within 100 feet of the work areas. Nearby known utilities are depicted in the drawings (Attachment A). Critical areas in the vicinity of the work are summarized in the Critical Areas Report and Habitat Impact Assessment for this proposed project included in Attachment D. Hydraulic and hydrologic analyses were conducted to verify proposed improvements as part of the Dykstra Levee Repair Project will not result in any increase in flood levels during the occurrence of the 100‐year flood conditions (base flood discharge). Fill placed as a result of the project will be confined to areas above the base flood elevation. The Geotechnical Engineering Report is also included in Attachment D and summarizes the results of exploratory soil borings within the proposed work areas. The Geotechnical Engineering Report concludes the levee can be raised meeting stability concerns with the recommendation that raised sections be inclined at no steeper than 2H:1V. 156 of 336 5 Chapter 3 – Off‐Site Analysis (Minimum Requirement #10) Qualitative Analysis Area A: There are no upstream drainage systems contributing run‐on to the proposed project Area A. As described above, rain that falls on the levee prism would do one, or a combination, of three things: stormwater infiltrates into the levee prism, sheet flows toward the river to the north, or sheet flows to the south toward the condominiums or apartments bordering the proposed work area. Drainage collecting south of the levee is likely to be captured by the private systems shown on Figure 2 and discussed in detail in MR #5 in Chapter 5 below. As summarized above in MR #5 in Chapter 5 of this report, the condominiums and apartments bordering the south side of the project area contain a variety of drainage systems on the north side of those buildings. We have separated these areas into A1 through A3 as shown on Figure 2. Figure 2 depicts only those building drainage features observed nearest and most relevant to the project area. Based on the existing drainage infrastructure already in place that borders the southern side of project Area A, there has likely been a history of previously existing ponding in some areas. This project is not expected to exacerbate those issues. Rather, King County proposes to slightly slope the levee 1 to 2% to the north, and propose minor drainage improvements during construction that directly affect the levee structure as listed in MR #5 in Chapter 5 of this report. Detailed drainage plans of the adjacent private condominium and apartment complex were not available at this time; however, both private stormwater systems likely connect to City of Auburn’s Municipal Separate Storm Sewer System (MS4) in 22nd Street NE. This public system then discharges to a 36‐inch line, which outfalls to the Green River near the western portion of project Area A (Figure 2) near the boundary of Dykstra Park. The remaining 0.25 miles of flow path is within the river itself (to account for the 0.25‐miles downstream evaluation). Attempts to procure drainage complaint records and drainage maps were made from the City of Auburn at the time of initial site visits in order to evaluate any existing surface water issues near the project area, but have not been successful to date. During site visits on April 22 and April 29, 2020, a King County Engineer (Alex Jones) did not observe surface evidence of current drainage problems such as ponding, channelized flow paths from concentrated water, or erosion near the proposed project area at that time. Though Mr. Jones was able to speak to one local resident who volunteered information related to prior drainage issues off the levee to the south, other individual residents were not approached or interviewed regarding potential historical drainage issues in the area due to the current stay‐at‐home order by the Governor at the time of the site visit and COVID‐19 impacts. Area B: There are no upstream drainage systems contributing run‐on to the proposed project Area B. Rain that falls on the levee prism in this area would do one, or a combination, of three things: stormwater infiltrates into the levee prism, sheet flows toward the river to the south or east, or sheet flows toward 157 of 336 6 the single‐family residential parcels bordering the proposed work Area B to the north. Drainage collecting north of the levee would be captured by private residential systems. As stated above, some of the residences on the north side of project Area B contain downspouts that discharge to surface, while others appear to discharge into the ground. These properties are generally at or above the curbline for Riverview Drive NE. Three catch basins are located to adjacent to these properties in City of Auburn Right‐of‐Way (ROW). These catch basins were not observed to contain stub‐ins from adjacent properties, so downspouts that enter the ground must discharge at other surface locations on those properties, or into infiltration systems/drywells. Drainage from the surface of residential parcels bordering project Area B to the north enters the ROW system in Riverview Drive NE. The ROW MS4 flows to the north for approximately 0.1 miles from the project area. Stormwater then flows through a 24‐inch pipe (in an easement) to the east to the river bank where it outfalls to surface water (receiving water) (Figure 3). The remaining 0.15 miles of flow path is within the river itself (to account for the 0.25‐miles downstream evaluation of potential impacts). There are no known flooding, erosion, or water quality problems along any of the identified downstream flow paths. King County proposes to slightly slope the levee between 1 and 2% toward the river; this should reduce the surface water input to City of Auburn’s MS4 from private property. During site visits on April 22 and April 29, 2020, a King County Engineer (Alex Jones) did not observe evidence of drainage problems such as ponding, channelized flow paths from concentrated water, or erosion near proposed project Area B. King County did not receive a response regarding a request for drainage complaints/issues in this area from the City of Auburn. Due to the stay‐at‐home order by the Governor at the time of the site visit and COVID‐19 impacts, individual residents were not approached or interviewed regarding potential historical drainage issues in the area. Area C: There are no upstream drainage systems contributing run‐on to proposed project Area C. As described above, rain that falls on the levee prism would do one, or a combination, of three things: stormwater infiltrates into the levee prism, sheet flows toward the river to the east, or sheet flows toward the single‐family residential parcels bordering proposed work Area C to the west. Drainage collecting west of the levee would be captured by private residential systems. The residences bordering the west side of the project area appear to contain mostly downspouts that discharge to surface (from those that could be viewed). All of these properties along Pike Street NE are generally at or above the curbline. Parcel 7349400400 at the intersection of 14th Street NE and Riverview Drive NE may be lower than the curbline; drainage would be expected to infiltrate here. One grated catch basin is located to adjacent to the properties along Pike Street NE in City of Auburn ROW. There was not a stub‐in from adjacent properties into this structure. Downspouts would be expected to discharge at surface locations on those properties, and infiltrate or drain to the curbline. This area discharges to a 36‐inch outfall directly to the river near the southern extent of the project area 158 of 336 7 (Figure 4). The remaining 0.25 miles of flow path is within the river itself (to account for the 0.25‐miles downstream evaluation). The 42‐inch outfall to the river near the northern portion of project Area C does not take surface flow from the area of the project. It is a trunk line conveying surface water from a separate upstream discharge area. Nearest to parcel 7349400400 is a grated catch basin in City of Auburn ROW that discharges to the north, to an 18‐inch outfall to the Green River. This outfall is located approximately 140 feet from the project area. The remaining 0.25 miles of flow path is within the river itself (to account for the 0.25‐ miles downstream evaluation). King County proposes to slightly slope the levee between 1 and 2% toward the river; this should reduce the surface water input to City of Auburn’s MS4 from private property. During site visits on April 22 and April 29, 2020, a King County Engineer (Alex Jones) did not observe evidence of drainage problems such as ponding, channelized flow paths from concentrated water, or erosion near proposed project Area C. King County did not receive a response regarding a request for drainage complaints/issues in this area from the City of Auburn. Due to the stay‐at‐home order by the Governor at the time of the site visit and COVID‐19 impacts, individual residents were not approached or interviewed regarding potential historical drainage issues in the area. Chapter 4 – Permanent Stormwater Control Plan King County proposes to slightly slope the new levee top by 1 to 2% toward the river. Stormwater that doesn’t infiltrate into the levee surface will sheet flow that direction. The parcels adjacent to the work areas will not experience a significant increase in runoff from the proposed project, and the proposed project will not cause significant adverse impact to downstream receiving waters and properties. This project consists of raising a several sections of an existing flood protection levee a maximum of approximately three feet above existing grade in some locations, resulting in no change of land use, site activity, or surface types. There will be no new pollution‐generating impervious surface as a result of the project. No new water quality treatment facility is proposed to be constructed. This site is not classified as a ‘high‐use site’ according to the definition in Appendix G in Volume I of Ecology’s Stormwater Management Manual for Western Washington (SWMMWW). According to Volume I of Ecology’s SMMWW, a threshold discharge area (TDA) is defined as ‘an on‐site area draining to a single natural discharge location or multiple discharge locations that combine within one‐quarter mile downstream (as determined by the shortest flow path)’. Work Areas B and C are within 0.25 miles of each other along the river and, therefore, any run‐off would combine in the same TDA. However, Area A is in a separate TDA by defnition. Except for a slight proposed slope to the river from the improved levee areas, pre‐developed and post‐ developed site conditions will be generally the same. Since the project will not change the dimensions of the land cover (grass or gravel road), the pre‐construction and post‐construction inputs to the model would be the same; and therefore, will not show an increase in flows from any of the TDAs. 159 of 336 8 As such, the project does not propose to construct any permanent on‐site stormwater management systems (i.e., conveyance system, water quality facility, or flow control facility) that would require design, modeling, or on‐going maintenance. Chapter 5 – Discussion of Minimum Requirements Per the 2017 City of Auburn Supplemental Manual to the SWMMWW, the project is required to meet Minimum Requirements (MRs) #1 through #5, and #10 based on the total hard surface area being replaced (the proposed project consisting of distinct Areas A, B, and C as described above is being applied for as one project, though work may be phased). Figure I‐2.4.2 Flow Chart for Determining Requirements for Redevelopment (Volume I of Ecology’s SMMWW) is included as Figure 5. This flow chart identifies the MRs applicable to the project (#1 through #5). Section 2.4.2 in the City of Auburn Supplemental Manual requires that all redevelopment projects that meet the thresholds for MRs #1 through #5 must also meet MR #10. MR #1 Stormwater Site Plan Report – This document satisfies the requirement for a complete Stormwater Site Plan report. MR #2 Construction Stormwater Pollution Prevention Plan (SWPPP) – The SWPPP is attached to this report as Attachment C. In addition, temporary erosion and sediment control details (TESC) are included in the plan set in Attachment A. These documents satisfy this minimum requirement. MR #3 Source Control of Pollution – Source Control Best Management Practices (BMPs) during construction will be addressed in the SWPPP and in the TESC plan (see MR #2). The project is an improvement to an existing flood control levee top (raising the elevation with no significant change in surface type or use) and will not result in any significant pollution‐generating activities following construction. The only activity on the levee after construction would be mowing/vegetation control and periodic repairs, if necessary. This requirement has been considered and no further action is necessary. MR #4 Preservation of Natural Drainage Systems and Outfalls – The levee in proposed project Areas A, B, and C has been in place for decades, and is not a natural drainage system, but rather a historical established existing condition. The levee was originally installed for flood control and will maintain that use. The project will not create new discharge nor increase the discharge from the project area, and will maintain the historical drainage condition. As such, the proposed project will not change the existing drainage system nor locations of outfalls. The project will slope the top of the levee towards the river to recreate the suspected natural flow direction prior to construction of the levee. 160 of 336 9 MR #5 On‐Site Stormwater Management – Area A: King County proposes to slightly slope the new levee top by 1 to 2% toward the river. Stormwater that doesn’t infiltrate into the levee surface will sheet flow that direction (to the north). The parcels adjacent to the south will not experience a significant increase in runoff from the proposed project, and the proposed project will not cause significant adverse impact to downstream receiving waters and properties. The condominiums and apartments bordering the south side of the project area contain a variety of drainage systems on the north side of those buildings. We have separated these areas into A1 through A3 as shown on Figure 2. Figure 2 depicts only those building drainage features observed nearest to the project area: Area A1: The majority of the downspouts serving the north side of these two buildings (Villa Del Rio Condominiums) discharge below the ground. Typical 4‐inch plastic roof drainage lines were identified crossing the levee below ground and discharging to the slope on the northern side of the levee in most cases. Not all the pipe outfalls were located at the time of the site visit. A local resident indicated to us that this area was prone to ponding during storms when the downspouts had drained to surface, and the pipes were installed to carry the roof water away from the buildings. This modification by the private property owners apparently solved the issue. It is unknown when these modifications were performed. Area A2: All of the downspouts serving the northern side of these two buildings (Madison at River’s Edge Apartments) discharge to surface. There is a sump and pump located between the two buildings. Yard drains on either side of the sump discharge to that point (one from the east and one from the west) (Figure 2; photographs in Attachment B). The central sump was full of sediment and the sump pump is not currently operational. The sump pump is served by a power post nearby. Two 6‐inch plastic drainage lines connect the yard drains with the sump. The sump pump is connected to a 2‐inch plastic discharge line trending north below ground through the levee prism. The outfall of the 2‐inch pump was not located at the time of the site visit, but it is presumed to discharge to the north slope of the levee. Area A3: The north of side of this apartment building is served by a mixture of downspouts that drain to surface and downspouts that drain into the ground. The slope is generally to the south towards the parking lot, with curb cuts/outlets near this area. Parking lot surface water closest to Area A3 drains to a catch basin in the paved driveway/parking area (Figure 2). Drainage plans were not immediately available to confirm its discharge point; however, the apartment stormwater system likely connects to City of Auburn’s Municipal Separate Storm Sewer System (MS4) in 22nd Street NE. This street storm sewer system then discharges to a 36‐inch line which outfalls to the river near the western portion of the project area (Figure 2) near the boundary of Dykstra Park. 161 of 336 10 Drainage complaint records and drainage maps were requested from the City of Auburn in order to evaluate any existing drainage issues near the project area at the time of the site visits, but have not been received. In addition to promoting sheet flow toward the river, the following conceptual on‐site stormwater management activities proposed for the project area are: 1) For Area A1, manifold downspout piping together to two locations that discharge through the levee, rather than many individual outfalls from downspouts. Add yard drains to enable system cleaning and inspection by the homeowner’s association. This improvement would preserve the solution already developed for ponding in this area, but reduce the number of outfalls through the levee prism. Unused drain pipes shall be removed or otherwise appropriately abandoned/filled. 2) For Area A2, clean and restore the sump and pump system previously used for pumping surface water from this area. Clean the two yard drains and conveyance piping. The system has clearly not been maintained recently by the apartment complex, and its position indicates that it was installed by a private property owner at some point to address surface water ponding along the north side of the apartments in this area. The 2‐inch discharge line through the levee would be located and cleaned. 3) No additional on‐site stormwater management is required for Area A3. The slope appears sufficient for the apartment complex system in the nearby parking lot to accept any stormwater ponded behind the levee at that location. Area B: King County proposes to slightly slope the new levee by 1 to 2% toward the river. Stormwater that doesn’t infiltrate into the levee surface will sheet flow that direction. The parcels adjacent to the north will not experience a significant increase in runoff from the proposed project, and the proposed project will not cause significant adverse impact to downstream receiving waters and properties. Typical of areas behind levees, some localized areas might experience ponding during storm events, however, these areas will likely be those already prone to that condition. As summarized in Chapter 3, some of the residences on the north side of the project area contain downspouts that discharge to surface, while others appear to discharge into the ground. These properties are generally at or above the curbline for Riverview Drive NE. Drainage from the surface of residential parcels bordering the project area to the north that is no handled by infiltration on private property would enter the ROW MS4 in Riverview Drive NE. The ROW system flows to the north for approximately 0.1 miles from the project area. Stormwater then flows through a 24‐inch pipe (in an easement) to the east to the river bank where it outfalls to the river (Figure 3). Drainage complaint records were requested from the City of Auburn at the time of the site visits in order to evaluate any existing drainage issues in the vicinity of the project area, but have not been received. No other stormwater management is recommended for proposed work area, except for promoting sheet flow toward the river. 162 of 336 11 Area C: King County proposes to slightly slope the new levee by 1 to 2% toward the river. Stormwater that doesn’t infiltrate into the levee surface will sheet flow that direction. The parcels adjacent to the west will not experience a significant increase in runoff from the proposed project, and the proposed project will not cause significant adverse impact to downstream receiving waters and properties. Typical of areas behind levees, some localized areas might experience ponding during storm events, however, these areas will likely be those already prone to that condition. As summarized in Chapter 3, the residences on the west side of the project area appear to contain downspouts that discharge to surface (from areas that could be viewed). All but one of these properties are generally at or above the curbline for Pike Street NE. Parcel 7349400400 appears to be slightly below curbline for Riverview Drive NE. Drainage from the surface of residential parcels bordering the project area to the west that does not infiltrate on private properties would enter the ROW MS4 (in Pike Street NE or Riverview Drive NE. The ROW system adjacent to these parcels discharges to one of two outfalls to the river through drainage easements; an 18‐inch pipe approximately 140 feet north of the project area; and a 36‐inch pipe near the southern boundary of the project area (Figure 4). A 42‐inch trunk line at the northern boundary of the project area conveys surface water from upstream areas, but does not appear to serve the project area. Drainage complaint records were requested from the City of Auburn at the time of the site visit in order to evaluate any existing drainage issues in the vicinity of the project area, but have not been received. No other stormwater management is recommended for proposed work area, except for promoting sheet flow toward the river. LID MR #5 Requirements: The flow chart for determining LID MR #5 requirements in the City of Auburn (Figure 2.5.1 in the Supplemental Manual to the SWMMWW – Volume I Minimum Technical Requirements and Site Planning, Version 3, Jan. 2020) was used to comply with this MR (Figure 6 attached to this document). Using the List option (List #1), the discussion demonstrating compliance is summarized below. Each BMP must be infeasible, in order on that list, before evaluating the next BMP:  Lawn/Landscaped Areas – There are no lawn or landscaped areas on the surface of the raised levee. The levee needs to be driven on by equipment and maintained as a flood control structure that serves a public safety purpose. In addition, the levee top must periodically be mowed for inspection and maintenance. Areas near the water level/toe may be left to grow native vegetation. The areas of retained native vegetation are exempt from BMP T5.13. Therefore, this BMP is not considered feasible.  Roof Surfaces – There are no roof surfaces proposed to be installed as part of the proposed levee improvement; therefore BMP T5.10A (or BMP T5.30), BMP T7.30 (or BMP T5.14A), BMP T5.10B, and BMP T5.10C are not considered feasible. 163 of 336 12  Other Hard Surfaces – The levee top will consist of a hardened gravel surface similar to the existing condition: o BMP T5.30 Full Dispersion: The top of the levee (i.e., the work area or site) does not currently contain 65% forested or native condition (Figure 2; Photos 1‐4). Therefore, this BMP is not considered feasible. o BMP T5.15 Permeable Pavement: The levee exists for public health and safety, and is not intended for regular pedestrian, bicycle, or automobile traffic. In addition, the levee is a shoreline structure that should be not be used to infiltrate water by design. Due to the nature of this feature, this BMP is not considered feasible. o BMP T7.30 Bioretention or BMP T14A Raingardens: The levee work area consists of a prism that doesn’t contain space to accommodate bioretention (or raingardens). In addition, the levee top must be constructed and compacted appropriately to function as a flood mitigation measure. The nature of the site is not compatible or consistent with designed infiltration into the ground. The levee must be able to handle heavy equipment and trucks to satisfy the purpose as a public health and safety shoreline feature. Therefore, this BMP is not considered feasible. o BMP T5.11 Concentrated Flow Dispersion or BMP T5.12 Sheet Flow Dispersion:  For BMP T5.11, a vegetated flow path of at least 50 feet between the edge of the levee and the river is not consistent with the purposes and design of the feature. The levee is a shoreline structure, and design guidelines for this LID BMP cannot be met. In addition, concentrated points of discharge along the levee top may encourage erosion. Therefore, BMP T5.11 is not considered feasible.  For BMP T5.12, the nature of the design and construction of the protective levee does not allow for the vegetated buffer width (10 feet) and transition zone in the design guidelines. In addition, slopes on the shoreline typically exceed 20% in portions of the work area. See Dykstra Levee construction plans included as Attachment B. Therefore, BMP T5.12 is not considered feasible. For this project, LID BMPs have been determined to be infeasible and MR #5 has been met. MR #10 Off‐Site Analysis and Mitigation – See Chapter 3 above. 164 of 336 13 FIGURES 165 of 336 14 Figure 1: General Vicinity Map 166 of 336 15 Figure 2: Work Area A with Storm Drainage Characteristics (Downstream Flow Path). 167 of 336 16 Figure 3: Work Area B with Storm Drainage Characteristics (Downstream Flow Path). 168 of 336 17 Figure 4: Work Area C with Storm Drainage Characteristics (Downstream Flow Path). 169 of 336 18 Figure 5: Figure I‐2.4.2 Flow Chart for Determining Requirements for Redevelopment 170 of 336 19 Figure 6: Figure I‐2.4.2 Flow Chart for Determining Requirements for Redevelopment 171 of 336 20 ATTACHMENT A – Drawings (attached to permit application under separate cover) 172 of 336 21 ATTACHMENT B – Photographs 173 of 336 22 Photo 1: Looking east at top of levee in work Area A1. Photo 2: Another view looking east at top of levee in work Area A1. 174 of 336 23 Photo 3: Looking west at top of levee toward work Area A1. Photo 4: Adjacent condominium complex in work Area A1. Example of downspout into ground. 175 of 336 24 Photo 5: Sump and pump in Area A2. See Figure 2. Photo 6: Looking east at levee fill Area A2. 176 of 336 25 Photo 7: Another view looking east at the levee in Area A3. Photo 8: Looking west from work Area A3. 177 of 336 26 Photo 9: Looking toward the downstream end of project Area B. Photo 10: Looking east from the middle of project Area B. 178 of 336 27 Photo 11: Looking west from the middle of project Area B. Photo 12: Looking toward the upstream end of project Area B. 179 of 336 28 Photo 13: Looking south at the top of levee in work Area C. Residential properties on west side. Photo 14: Looking north at Area C and residential properties on west side. 180 of 336 29 Photo 15: Another view looking south at work Area C toward the southern end of the project. Photo 16: Looking north from the southern end of work Area C. 181 of 336 30 ATTACHMENT C – SWPPP 182 of 336 Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP) for Dykstra Levee Improvement Project Prepared for: Department of Ecology Northwest Office Permittee / Owner Developer Operator / Contractor King County Not Applicable TBD East of Dykstra Park and along and east of Riverview Dr. NE between 22nd Street NE and 12 Street NE Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number Jay Young King County 206-477-4858 SWPPP Prepared By Name Organization Contact Phone Number Jay Young King County 206-477-4858 SWPPP Preparation Date May 29, 2020 Project Construction Dates Activity / Phase Start Date End Date Authorization to Begin Work TBD Begin Field Work TBD End of Construction TBD ATTACHMENT C - SWPPP 183 of 336 Table of Contents 1. Project Information 1.1 Existing Conditions 1.2 Proposed Construction Activities 2. Construction Stormwater Best Management Practices (BMPs) 2.1 The 12 Elements 3. Pollution Prevention Team 4. Monitoring and Sampling Requirements 4.1 Site Inspection 4.2 Stormwater Quality Sampling 5. Discharges to 303(d) or Total Max. Daily Load (TMDL) Waterbodies 5.1 303(d) Listed Waterbodies 5.2 TMDL Waterbodies 6. Reporting and Record Keeping 6.1 Record Keeping 6.2 Reporting List of Appendices A. Site Map B. BMP Detail C. Site Inspection Form ATTACHMENT C - SWPPP 184 of 336 List of Acronyms and Abbreviations Acronym / Abbreviation Explanation 303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies BFO Bellingham Field Office of the Department of Ecology BMP(s) Best Management Practice(s) CESCL Certified Erosion and Sediment Control Lead CO2 Carbon Dioxide CRO Central Regional Office of the Department of Ecology CSWGP Construction Stormwater General Permit CWA Clean Water Act DMR Discharge Monitoring Report DO Dissolved Oxygen Ecology Washington State Department of Ecology EPA United States Environmental Protection Agency ERO Eastern Regional Office of the Department of Ecology ERTS Environmental Report Tracking System ESC Erosion and Sediment Control GULD General Use Level Designation NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Units NWRO Northwest Regional Office of the Department of Ecology pH Power of Hydrogen RCW Revised Code of Washington SPCC Spill Prevention, Control, and Countermeasure su Standard Units SWMMEW Stormwater Management Manual for Eastern Washington SWMMWW Stormwater Management Manual for Western Washington SWPPP Stormwater Pollution Prevention Plan TESC Temporary Erosion and Sediment Control SWRO Southwest Regional Office of the Department of Ecology TMDL Total Maximum Daily Load VFO Vancouver Field Office of the Department of Ecology WAC Washington Administrative Code WSDOT Washington Department of Transportation WWHM Western Washington Hydrology Model ATTACHMENT C - SWPPP 185 of 336 Project Information (1.0) Project/Site Name: Dykstra Levee Improvement Project Street/Location: The project site is located on the left band of the Green River between River Mile (RM) 29.7 and 30.8. The levee segment is located just south of Dykstra park and extends south parrelling Riverview Dr. NE to 12th Street NE. City: Auburn State: WA Zip code: 98002 Subdivision: NA Receiving waterbody: Green River Natural Resources Area, Ground, Wetland Existing Conditions (1.1) Total acreage (including support activities such as off-site equipment staging yards, material storage areas, borrow areas). Total acreage: 0.9 acres Disturbed acreage: 0.9 acres Existing structures: none Landscape topography: Flat to gently sloping levee crest, steep levee sideslope towards riverbanks Drainage patterns: Infiltration and Overland drainage. Existing Vegetation: Grass, brush and trees Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes): Green River and wetlands within the Green River Natural Resouces Area List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: Green River impaired for temperature Table 1 includes a list of suspected and/or known contaminants associated with the construction activity. Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration None ATTACHMENT C - SWPPP 186 of 336 Proposed Construction Activities (1.2) Description of site development (example: subdivision): Levee Flood protection Description of construction activities (example: site preparation, demolition, excavation): This project proposes to raise portions of the existing levee along the left bank of the Green River between 26th St NE and 8th St NE in Auburn, WA. The improvements are designed to meet long-term flood protection goals, including providing up to three feet of freeboard to the adjacent areas that are located within the mapped special flood hazard area. The construction would generally involve removing some of the levee top surface down to a stable layer, followed by adding suitable fill material to bring the levee height up to the appropriate elevation with designed compaction. The side slopes would be shaped to match the existing slopes of the face and back of the levee Description of site drainage including flow from and onto adjacent properties. Must be consistent with Site Map in Appendix A: Existing Conditions (Area “A”): Area a consists of approximately 960 feet on the left bank (shoreline) of the Green River (river) along Dykstra Park, Villa Del Rio Condominiums, and Madison at River’s Edge Apartments located on 22nd Street NE. The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation. The levee along this section is proposed to be raised up to approximately three feet in some locations. Stormwater either infiltrates into the levee prism, sheet flows toward the river to the north, or sheet flows toward the apartments and condominiums bordering the proposed work area to the south. Existing Conditions (Area “B”): Area B consists of 600 feet on the left bank (shoreline) of the Green River (river) along Riverview Drive NE. The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation. The levee along this section is proposed to be raised up to approximately one foot in some locations. Stormwater either infiltrates into the levee prism, sheet flows toward the river to the south or east, or sheet flows toward the single-family residential parcels bordering the proposed work area to the north. Existing Conditions (Area “C”): Area C consists of 400 feet on the left bank (shoreline) of the Green River (river) along Riverview Drive NE. The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation. The levee along this section is proposed to be raised up to approximately one feet in some locations. Stormwater either infiltrates into the levee prism, sheet flows toward the river to the east, or sheet flows toward the single-family residential parcels bordering the proposed work area to the west. ATTACHMENT C - SWPPP 187 of 336 Description of final stabilization (example: extent of revegetation, paving, landscaping): The site will be seeded with a grass and covered with straw mulch or wood chip mulch. ATTACHMENT C - SWPPP 188 of 336 Construction Stormwater Best Management Practices (BMPs) (2.0) The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e. hand-written notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. 2.1 The 13 BMP Elements To avoid potential erosion and sediment control issues that may cause a violation(s), the Certified Erosion and Sediment Control Lead (CESCL) will promptly initiate the implementation of one or more of alternative BMPs after the first sign that existing BMPs are ineffective or failing. 2.1.1 Element #1 – Mark Clearing Limits To protect existing vegetation and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Trees that are to be preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both in the field and on the plans. In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing limits that will be applied for this project include:  Preserving natural vegetation  Fencing trees to be preserved, per approved plans.  High visibility fencing and silt fencing demarcating area of construction, per approved plans. 2.1.2 Element #2 – Establish Construction Access Routes Construction access routes within the site are identified in the plans to minimize site disturbance. Travel routes between the staging area to the construction area and the staging area itself will be stabilized to minimize the tracking of sediment onto the road, and street sweeping and street cleaning will be employed as necessary to keep paved roadway surfaces clean. Stabilized construction entrances will be constructed per the approved plans. The specific BMPs related to establishing construction access that will be used on this project include:  Site ingress and egress restriction and demarcation  Identification of on-site access routes  Street sweeping as necessary  Stabilized construction entrances as necessary ATTACHMENT C - SWPPP 189 of 336 2.1.3 Element #3 – Control Flow Rates The proposed project will not increase flow volumes, velocity or peak flow rates of stormwater runoff from the project site. No BMPs (e.g., stormwater retention or detention facilities, permanent infiltration ponds, or other low impact development) are considered for implementation as drainage patterns and runoff rates are not expected to significantly change during the course of the project. 2.1.4 2.1.4 Element #4 – Install Sediment Controls Sediment movement will be minimized by controlling runoff at the source wherever possible. Runoff will pass through an appropriate sediment removal BMP before being discharged toward the receiving waterbody. The specific BMPs to be used for both minimizing runoff and controlling sediment movement where it occurs on this project include:  Infiltration  Temporary and permanent seeding and mulching  Plastic sheeting as necessary  Silt fencing In addition, sediment will be removed from paved areas in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires away from the site and to minimize wash off of sediments from adjacent streets in runoff. 2.1.5 Element #5 – Stabilize Soils Exposed and disturbed soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. The specific BMPs for soil stabilization that shall be used on this project include:  Seeding  Mulching with 3 inches of straw mulch  Dust control as necessary  Revegetation with native vegetation The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain exposed and un-worked for more than 7 days during the dry season (May 1 to September 30) and 2 days during the wet season (October 1 to April 30) (see Table below). Regardless of the time of year, all soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. All soil disturbing construction activities are scheduled for the dry ATTACHMENT C - SWPPP 190 of 336 season and are not anticipated to extend into the wet season. Anticipated start date of construction is Fall 2019/Spring 2020 and end date is Summer, 2020. Soil Stabilization Requirements for West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Work will occur in the wet season. In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting or mulch. All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. Permanent mulching, hydromulching/seeding and/or native vegetation will be installed as construction is completed. 2.1.6 Element #6 – Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion. Any erosion that does occur on cut slopes for the trench will be contained within the trench. Otherwise, the following specific BMPs will be used to protect slopes for this project:  Plastic Covering exposed soils.  Mulching/seeding disturbed soils per plans.  Native revegetation of entire site after construction.  Phase grading to minimize exposed cut & fill slopes. ATTACHMENT C - SWPPP 191 of 336 2.1.7 Element #7 – Protect Drain Inlets All operable inlets shall be protected and maintained with a sediment filtering device. The following specific BMPs will be used to inlets for this project:  Catch basin inserts  Whenever possible divert stormwater runoff away from inlets to swales, ditches, etc.. 2.1.8 Element #8 – Stabilize Channels and Outlets Where site runoff is te be conveyed in channels, or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion. Stabilization including armoring material adequate to prevent erosion of outlets, and slopes shall be provided at the outlets of all conveyance stystems. Any runoff that cannot be contained will be treated with sediment control BMPs and dispersed into vegetated areas. 2.1.9 Element #9 – Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. There will not be any pH modifying sources on site. BMPs to be implemented to control specific sources of pollutants are discussed below, to be used as needed. Vehicles, construction equipment, and/or petroleum product storage/dispensing:  All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected daily at a minimum to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills.  Locations for any on-site fueling and petroleum product storage containers shall not be located within 100-ft of the wetted edge of the North Fork Snoqualmie River. Locations shall be identified on the TESC plans prior to construction.  On-site fueling tanks and petroleum product storage containers shall include secondary containment, including hand-held refueling containers.  Spill prevention measures, such as drip pans, will be used when conducting maintenance and repair of vehicles or equipment. ATTACHMENT C - SWPPP 192 of 336  In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if raining, over the vehicle.  Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Chemical storage:  Any chemicals stored in the construction areas will conform to the appropriate source control BMPs listed in Volume IV of the Ecology stormwater manual. In Western Washington, all chemicals shall have cover, containment, and protection provided on site, per BMP C153 for Material Delivery, Storage and Containment in SWMMWW 2005  Application of agricultural chemicals, including fertilizers and pesticides, shall be conducted in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers’ recommendations for application procedures and rates shall be followed. Sanitary wastewater:  Portable sanitation facilities will be firmly secured, regularly maintained, and emptied when necessary. Solid Waste:  Solid waste will be stored in secure, clearly marked containers. pH-modifying sources:  No pH-modifying sources will be present on site. The primary construction materials are locally quarried riprap, logs, and in situ alluvial soils. Other:  Other BMPs will be administered as necessary to address any additional pollutant sources on site. 2.1.10 Element #10 – Control Dewatering There will be no dewatering activities associated with this project. ATTACHMENT C - SWPPP 193 of 336 2.1.11 Element #11 – Maintain BMPs All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW). Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to once every calendar month. All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either BMPs or vegetation shall be permanently stabilized. Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater from sediment and compaction. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed and the facility shall be returned to conditions specified in the construction documents. ATTACHMENT C - SWPPP 194 of 336 2.1.12 Element #12 – Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles:  Design the project to fit the existing topography, soils, and drainage patterns.  Emphasize erosion control rather than sediment control.  Minimize the extent and duration of the area exposed.  Keep runoff velocities low.  Retain sediment on site.  Thoroughly monitor site and maintain all TESC measures.  Schedule major earthwork during the dry season.  Prevent soil disturbing activities during months with the highest anticipated precipitation and flood flows. As this project site is located west of the Cascade Mountain Crest, the project will be managed according to the following key project components: Phasing of Construction  The construction project is being phased to the extent practicable in order to prevent soil erosion, and, to the maximum extent possible, the transport of sediment from the site during construction.  Protection of exposed areas and maintenance of BMPs shall be an integral part of the clearing activities during each phase of construction. Inspection and Monitoring  All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections shall be conducted by a person who is knowledgeable in the principles and practices of erosion and sediment control. This person has the necessary skills to: Assess the site conditions and construction activities that could impact the quality of stormwater, and ATTACHMENT C - SWPPP 195 of 336 Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges.  A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times.  Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible. Maintaining an Updated Construction SWPPP  This SWPPP shall be retained on-site at all times  The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state.  The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. Construction Phasing and BMP Implementation The BMP implementation schedule will be driven by the construction schedule.. The erosion and sediment control schedule will generally follow the following progression:  Construction notice to proceed  Mobilize equipment on site  Deliver, store and install erosion and sediment control measures  Monitor, repair and replace erosion and sediment control measures  Install permanent site stabilizing vegetation and other BMP’s.  Remove temporary erosion and sediment control measures as required ATTACHMENT C - SWPPP 196 of 336 The project site is located west of the Cascade Mountain Crest. As such, the dry season is considered to be from May 1 to September 30 and the wet season is considered to be from October 1 to April 30. ATTACHMENT C - SWPPP 197 of 336 2.1.13 Element #13 – Protect Low Impact Development (LID) BMPs No LID BMPs are proposed as part of this project. 3.0 Pollution Prevention Team Table 6 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) Jay Young 206-477-4858 Resident Engineer Emergency Ecology Contact TBD Emergency Permittee/ Owner Contact Jay Young 206-477-4858 (O) 425-444-6653 (C) Non-Emergency Owner Contact Jay Young 206-477-4858 (O) Monitoring Personnel TBD [Insert Number] Ecology Regional Office NW Region 425-649-7000 ATTACHMENT C - SWPPP 198 of 336 4.0 Site Inspections and Monitoring Monitoring includes visual inspection, monitoring for water quality parameters of concern, and documentation of the inspection and monitoring findings in a site log book. A site log book will be maintained for all on-site construction activities and will include:  A record of the implementation of the SWPPP and other permit requirements;  Site inspections; and,  Stormwater quality monitoring. For convenience, the inspection form and water quality monitoring forms included in this SWPPP include the required information for the site log book. This SWPPP may function as the site log book if desired, or the forms may be separated and included in a separate site log book. However, if separated, the site log book but must be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. 4.1 Site Inspection All BMPs will be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead (CESCL). The name and contact information for the CESCL is provided in Section 3 of this SWPPP. Site inspection will occur in all areas disturbed by construction activities and at all stormwater discharge points. Stormwater will be examined for the presence of suspended sediment, turbidity, discoloration, and oily sheen. The site inspector will evaluate and document the effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the BMPs to improve the quality of stormwater discharges. All maintenance and repairs will be documented in the site log book or forms provided in this document. All new BMPs or design changes will be documented in the SWPPP as soon as possible. 4.1.1 Site Inspection Frequency Site inspections will be conducted at least once a week and within 24 hours following any discharge from the site. For sites with temporary stabilization measures, the site inspection frequency can be reduced to once every month if the site operator has successfully applied for inactive status for the site using the Permit Fee Activity Status Change Form. 4.1.2 Site Inspection Documentation The site inspector will record each site inspection using a site log inspection form (see Appendix C). The site inspection log forms may be separated from this SWPPP document, but will be ATTACHMENT C - SWPPP 199 of 336 maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. 4.2 Stormwater Quality Monitoring Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Table 8 – Turbidity Sampling Method Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) X Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size) The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency less than 33 centimeters. If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site log book. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) within 24 hours. https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue  Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima): (509) 575-2490  Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400  Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000  Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period ATTACHMENT C - SWPPP 200 of 336 3. Document BMP implementation and maintenance in the site log book. 4. Continue to sample discharges daily until one of the following is true:  Turbidity is 25 NTU (or lower).  Transparency is 33 cm (or greater).  Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater The discharge stops or is eliminated. ATTACHMENT C - SWPPP 201 of 336 5.0 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies 5.1 303(d) Listed Waterbodies The 303(d) status is listed on the Water Quality Atlas: https://ecology.wa.gov/Water- Shorelines/Water-quality/Water-improvement/Assessment-of-state-waters-303d Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes No List the impairment(s): Green River for temperature and dissolved oxygen The receiving waterbody, Green River, is impaired for: temperature. All stormwater and dewatering discharges from the site are subject to an effluent limit of 8.5 su for pH and/or 25 NTU for turbidity. If yes, discharges must comply with applicable effluent limitations in S8.C and S8.D of the CSWGP. Describe the method(s) for 303(d) compliance: List and describe BMPs: Implement BMPs to control sediment and flow rate into the Green River, in particular Elements 1 thru 5 of this document. 5.2 TMDL Waterbodies Green River for temperature BMPs: Planting of fast growing trees to provide shading of the river banks and channel. ATTACHMENT C - SWPPP 202 of 336 6.0 Reporting and Recordkeeping 6.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include:  A record of the implementation of the SWPPP and other permit requirements  Site inspections  Sample logs 6.1.2 Records Retention and Access to Records Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site:  CSWGP  Permit Coverage Letter  SWPPP  Site Log Book Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. 6.1.3 Updating the SWPPP The SWPPP will be modified if:  Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site.  There is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be prepared. ATTACHMENT C - SWPPP 203 of 336 6.2 Reporting 6.2.1 Discharge Monitoring Reports Cumulative soil disturbance is less than one (1) acre; therefore, Discharge Monitoring Reports (DMRs) will not be submitted to Ecology. ATTACHMENT C - SWPPP 204 of 336 Appendix/Glossary A. Site Map See Drawing Plans B. BMP Detail See details on the the Drawing Plans C. Site Inspection Form ATTACHMENT C - SWPPP 205 of 336 Appendix A – Site Map See contract plans ATTACHMENT C - SWPPP 206 of 336 Appendix B – BMP Detail See details on the Drawing sheets ATTACHMENT C - SWPPP 207 of 336 Appendix C – Site Inspection Forms The results of each inspection shall be summarized in an inspection report or checklist that is entered into or attached to the site log book. It is suggested that the inspection report or checklist be included in this appendix to keep monitoring and inspection information in one document, but this is optional. However, it is mandatory that this SWPPP and the site inspection forms be kept onsite at all times during construction, and that inspections be performed and documented as outlined below. At a minimum, each inspection report or checklist shall include: 1. Inspection date/times 2. Weather information: general conditions during inspection, approximate amount of precipitation since the last inspection, and approximate amount of precipitation within the last 24 hours. 3. A summary or list of all BMPs that have been implemented, including observations of all erosion/sediment control structures or practices. 4. The following shall be noted: a. locations of BMPs inspected, b. locations of BMPs that need maintenance, c. the reason maintenance is needed, d. locations of BMPs that failed to operate as designed or intended, and e. locations where additional or different BMPs are needed, and the reason(s) why 5. A description of stormwater discharged from the site. The presence of suspended sediment, turbid water, discoloration, and/or oil sheen shall be noted, as applicable. 6. A description of any water quality monitoring performed during inspection, and the results of that monitoring. 7. General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. 8. A statement that, in the judgment of the person conducting the site inspection, the site is either in compliance or out of compliance with the terms and conditions of the SWPPP and the NPDES permit. If the site inspection indicates that the site is out of compliance, the inspection report shall include a summary of the remedial actions required to bring the site back into compliance, as well as a schedule of implementation. 9. Name, title, and signature of person conducting the site inspection; and the following statement: “I certify under penalty of law that this report is true, accurate, and complete, to the best of my knowledge and belief”. ATTACHMENT C - SWPPP 208 of 336 When the site inspection indicates that the site is not in compliance, the Permittee shall take immediate action(s) to: stop, contain, and clean up the unauthorized discharges, or otherwise stop the noncompliance; correct the problem(s); implement appropriate Best Management Practices (BMPs), and/or conduct maintenance of existing BMPs; and achieve compliance with all applicable standards and permit conditions. In addition, if the noncompliance causes a threat to human health or the environment, the Permittee shall comply with the Noncompliance Notification requirements in Special Condition S5.F. A 5-page site inspection form template can be found here and opened in MS Word: https://ecology.wa.gov/Asset-Collections/Doc-Assets/Water-quality/Water-Quality- Permits/Stormwater-General-Permits/Construction-Stormwater-General-Permit/InspectionForm ATTACHMENT C - SWPPP 209 of 336 31 ATTACHMENT D – Special Reports (Geotechnical and Critical Areas) 210 of 336 Revised Geotechnical Engineering Report Dykstra Levee at RM 29.5 to RM 30.9 King County, Washington November 5, 2020 Prepared By: Department of Local Services Road Services Division Materials Laboratory 155 Monroe Avenue NE, Bldg. D Renton, WA 98056-4199 Geotechnical Investigation ATTACHMENT D - Geotechnical and Critical Areas 211 of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eotechnical and Critical Areas 212 of 336 TABLE OF CONTENTS REVISED GEOTECHNICAL ENGINEERING REPORT Dykstra Levee at RM 29.5 to RM 30.9 Project NO. 1135536 SECTION 1.0 – INTRODUCTION……………………………………………………………….1 SECTION 1.1 – General…...…………………….…….………………………………….…...1 SECTION 1.2 – Site Description.……………….….…………………………….……………1 SECTION 2.0 – SUBSURFACE CONDITIONS……………………………………….………2 SECTION 2.1 – Geologic Mapping Review………….…….…………………. ….…………2 SECTION 2.2 – Geotechnical Drilling……………….……….……………….……………....2 SECTION 2.3 – Groundwater……...……………….………...…………………....………….3 SECTION 3.0 – SLOPE STABILITY ANALYSES.…………………………………………….3 SECTION 3.1 – Existing Slope Condition.……………………………………………………3 SECTION 3.2 – Soil Parameters………………………………………………………………3 SECTION 3.3 – Stability Analysis Conditions...………………………………………………4 SECTION 4.0 – CONCLUSIONS AND RECOMMENDATIONS…………………………….5 SECTION 4.1 – Fill Construction Recommendations…….….…………...…………………5 SECTION 4.2 – Constructed Levee Fill Sections…...……….………………………………6 SECTION 5.0 – CONTINUING GEOTECHNICAL SERVICES….………………………….7 SECTION 6.0 – REFERENCES……………………………….….…………….………………8 ATTACHMENT D - Geotechnical and Critical Areas 213 of 336 TABLE OF CONTENTS (Continued) REVISED GEOTECHNICAL ENGINEERING REPORT Dykstra Levee at RM 29.5 to RM 30.9 Project NO. 1135536 LIST OF FIGURES FIGURE 1: PROJECT LOCATION MAP FIGURE 2A-2C: BORING LOCATIONS LIST OF TABLES TABLE 1: SOIL PARAMETERS TABLE 2: SLOPE STABILITY SUMMARY TABLE 3: LEVEE FILL GRADATION SPECIFICATIONS APPENDICES APPENDIX A: BORING LOGS AND LABORATORY TEST RESULTS APPENDIX B: SLOPE STABILITY ANALYSES CRITICAL FAILURE SURFACE DIAGRAMS ATTACHMENT D - Geotechnical and Critical Areas 214 of 336 Mailstop: RSD-TR-0100 | 155 Monroe Avenue NE, Bldg. D, Renton, WA 98056-4199 206-477-8100 | maint.roads@kingcounty.gov | www.kingcounty.gov/roads REVISED GEOTECHNICAL ENGINEERING REPORT DYKSTRA LEVEE AT RM 29.5 TO RM 30.9 1.0 INTRODUCTION 1.1 General As requested, the King County Materials Laboratory (KCML) has completed our geotechnical investigation for the Dykstra Levee Repair project. The project will raise the levee elevation along the west bank of the Green River in order to meet the levee accreditation requirements of the Federal Emergency Management Agency (FEMA). The purpose of our study is to evaluate subsurface and groundwater conditions in order to provide geotechnical recommendations for design and construction that can be utilized to raise the elevation of the levee between RM 29.5 and RM 30.9. The general project location is shown on the Vicinity Map, Figure 1, at the conclusion of this text. 1.2 Site Description The Dykstra Levee at the subject site borders the Green River and provides flood protection for the people and property in the surrounding City of Auburn. The levee runs adjacent to the Dykstra City Park, the Madison at River’s Edge Apartments, and several privately-owned residential homes. Reconstruction and repair of the levee is designed to increase the levee elevation to a level at or greater than the elevation of a 100-year storm plus an additional three feet (FIS+3). The amount of fill needed to raise the levee profile to meet the FIS+3 is typically less than 1 foot. However, there is a deeper section of fill required from approximately RM 29.77 to RM 29.85 (King County Plan Sta. 16+50 to Sta. 21+00) that will need up to 3 feet of fill. The crest of the levee is designed to be a minimum of 12 feet in width. The reconstruction design will generally maintain the existing levee orientation. Along the landside of the levee, the elevation of the levee crest is generally equal to the surrounding terrain. On the riverside, the levee slope inclination generally ranges from 2.25H(horizontal):1.0V(vertical) to 3.5H:1.0V with intermittent sections of increased steepness. The width of the levee crest varies from approximately 14 to 29 feet and is mostly vegetated with short grass. The riverside bank of the levee consists of grass, shrubs, and small trees. Inspection of the bank shows no significant signs of erosion or material loss. Records show there have been three repairs to the riverbank within the subject site completed in 1994, 2008, and 2015. ATTACHMENT D - Geotechnical and Critical Areas 215 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 2 of 8 2.0 SUBSURFACE CONDITIONS 2.1 Geologic Map Review We reviewed the online Washington State Department of natural Resources Geological Information Portal for expected soil profiles in the project vicinity. The geologic map viewed was in a scale of 1:24,000. A brief description of the mapped surficial geologic unit within the subject site is as follows: Quaternary Alluvium (Qaw): Quaternary unconsolidated or semi-consolidated alluvial clay, silt, sand gravel, and or cobble deposits; locally includes peat, muck, and diatomite; locally includes beach, dune, lacustrine, estuarine, marsh, landslide, lahar, glacial, or colluvial deposits; locally includes volcaniclastic or tephra deposits; locally includes modified land and artificial fill. 2.2 Geotechnical Drilling Site-specific soil and groundwater conditions were explored on January 21, 2020 and February 13, 2020 by drilling 11 borings, 9 to a depth of 21.5 feet bgs, 1 to 41.5 feet bgs, and 1 to 51.5 feet bgs. Drilling was completed using a track mounted Deidrich D-90 drill rig equipped with nominal 4.25” I.D. continuous flight hollow-stem auger. Standard Penetration Tests (SPT) were taken at 2.5-foot vertical intervals to 15 feet bgs and 5.0- foot intervals past 15 feet as the borings were advanced below ground level. The SPT provides a measure of compaction or relative density of granular soils, and consistency or stiffness of cohesive fine-grained soils. In addition, disturbed but representative soil samples were collected at each testing interval and returned to our laboratory for analysis. Eighteen soil samples were tested and used to further classify soils at various depths. The remaining collected soil samples will be stored in sealed plastic bags for additional testing if requested. Approximate boring locations are shown in Figure 2A-2C. Detailed copies of the boring logs, along with laboratory test results, are enclosed for your review in Appendix A. Stratigraphy units encountered during drilling can generally be divided into the following three categories: Topsoil: The top three to six inches of the levee generally consists of a loose silty sand with gravel and cobbles with numerous organics. Fill: Fill underlying the topsoil ranged from approximately 7 to 13 feet bgs and generally consists of loose to medium dense brown silty sand with gravel to a poorly graded sand with silt and gravel. Alluvial Deposits: Alluvial deposits consisting of medium dense to dense gray gravel with silt and sand, to a poorly graded sand with gravel, underlie the fill to the termination depth of the borings. ATTACHMENT D - Geotechnical and Critical Areas 216 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 3 of 8 2.3 Groundwater Groundwater was observed in each boring. Groundwater elevations varied from 4 feet bgs to 12 feet bgs and corresponded approximately to the adjacent river elevation at the time of drilling. Groundwater elevations may vary based on the time of year, precipitation levels, and other factors. 3.0 SLOPE STABILITY ANALYSES 3.1 Existing Slope Conditions The thickest section of new fill will be needed near STA 18+50 to raise the levee profile to the 100-year flood elevation plus 3 feet (FIS+3). Therefore, we utilized the slope profile at STA. 18+50 as the critical cross section to model. Soil and groundwater conditions identified in soil borings B-3 and B-4 were transposed onto the Station 18+50 cross section to develop a simplified model for subsequent slope stability analyses. Preliminary slope stability analyses of the critical embankment section were performed utilizing the slope stability analysis software program, Galena, developed by Clover Associates Pty, Limited. For these preliminary stability analyses, we followed the general guidelines as set forth in the US Army Corp of Engineers (COE) Engineering Manuals EM 1110-2-1913 (Design and Construction of Levees) and EM 1110-2-1902 (Slope Stability). For the slope stability computations, the Simplified Bishop Slip Circle analysis option was utilized. This program employs limit equilibrium force resolutions to arrive at a Factor of Safety (FS) for a given embankment cross-section. A FS of 1.0 indicates an imminent embankment failure condition. For our analyses, we modeled both the critical cross section and a modification of the critical cross section. Modeling of the critical cross section captured the impact of raising the levee (FIS+3) on the existing crest profile. Our modified section steepened and extended the slope below the added fill to the existing river channel at a slope inclination of 2.5H:1V. For all raised slope sections, we assumed the width of the crest levee will be a minimum of 12 feet and that the outer slopes of the raised FIS+3 section would be placed at a slope no steeper than 2H:1V. For existing levees, required stability analysis include long-term and rapid drawdown. Earthquake loading was not considered since there is low probability of an earthquake coinciding with periods of high water. End of construction analysis are also not required on existing levee systems. 3.2 Soil Parameters Shear strength parameters for the slope stability model are based on empirical relationships developed between the Standard Penetration Test (SPT) and the friction angle of granular soils ATTACHMENT D - Geotechnical and Critical Areas 217 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 4 of 8 and fine-grained soils, as applicable. Material properties utilized in the slope stability analyses are provided below in Table 1. Soil Type Unit Weight Friction Angle Cohesion Loose to Medium Dense SM/SP-SM 120 pcf 32 0 Loose to Medium Dense SM/SP-SM (bwt)* 125pcf 32 0 Medium Dense to Dense GP-GM/SW-SM 130 pcf 34 0 Levee Fill 125 pcf 35 0 Table 1: Soil Parameters (bwt)* - Below Water Table 3.3 Stability Analysis Conditions A brief description of the stability conditions analyzed are provided below: Long-Term Long-term stability is generally required analysis for the steady seepage condition. For long-term steady seepage, the concern would be with the landside stability of the levee slope due to saturation of the outer slope soil. At the subject site, based on the surveyed profiles, steady seepage of the landside slope would not be a stability issue since the surveyed profiles show the landslide slopes to be non-existent or generally less than 1 foot. Therefore, we ended up checking the long-term stability of the riverside slope utilizing a low flow condition. On the riverside, high water levels provide a stabilizing force to the riverside slopes. Therefore, a low flow condition is more conservative than a high-water condition for this analysis. A surcharge load of 250 psf was utilized for vehicular loading in the analyses. For our analyses, we used the recommended COE Manual EM 1110-2-1913, Design and Construction of Levees target FS of 1.4 for long-term stability. Rapid Drawdown During prolonged flooding, high water levels will saturate the majority of the embankment slope. Rapid drawdown represents the condition where the water level of the river drops faster than the embankment soil can drain. When this occurs, pore water pressures may develop within the slow draining soil, significantly increasing the potential for slope instability. For drawdown condition modeling, we assumed that for every foot of river drawdown, the water level in the soil will drop at a rate of about 0.5 feet. For our modeling, we assumed a high-water condition elevation of 60.92 and a post storm river elevation of 55.0. This creates a head differential of about 3 feet between the contact soil and the river. For rapid drawdown, COE Manual EM 1110-2-1913 recommends a FS of 1.0 to 1.2. For our analyses, we utilized a target FS of 1.1. ATTACHMENT D - Geotechnical and Critical Areas 218 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 5 of 8 Slope Stability Summary Multiple analyses with range constraints were selected for evaluating the slope stability of each slope condition. Diagrams showing the critical failure surfaces and associated safety factors (Figures A-1 through A-6) are provided in Appendix A for review. The results of our stability analyses are summarized below in Table 2. Figure Condition Slope FS Target FS A-1 Exising Slope, Long Term 1.94 1.4 A-2 Exising Slope, Rapid Drawdown 1.38 1.1 A-3 Existing Slope, Raised Upper Slope FIS+3, Long Term 1.50 1.4 A-4 Existing Slope, Raised Upper Slope FIS+3, Rapid Drawdown 1.23 1.1 A-5 Modified Slope 2.5H:1V, Raised Upper Slope FIS+3, Long Term 1.48 1.4 A-6 Modified Slope 2.5:H:1V, Raised Upper Slope FIS+3, Rapid Drawdown 1.10 1.1 Table 2: Slope Stability Summary 4.0 CONCLUSIONS AND RECOMMENDATIONS Based on our modeling, the existing levee profile will be able to be raised while meeting the conditions for long term and rapid drawdown stability. From our analysis, rapid drawdown is the critical failure mechanism for slope instability along this section of levee. We recommend the slopes of the raised sections be inclined at no steeper than 2H:1V. A small block wall up to 2 feet in exposed height may be constructed on the landside levee slope if needed to keep the fill within the levee right of way. 4.1 Fill Construction Recommendations We recommend the new backfill material for the levee should consist of generally well graded silty sand with gravel that closely resemble the soil characteristics of the existing levee fill. Our recommended specification for the silty sand and gravel fill is as follows: Sieve Size Percent Passing 3"100 2"90-100 1"70-90 1/2"55-85 #4 35-75 #200 20-30 Table 3: Levee Fill Gradation Specification ATTACHMENT D - Geotechnical and Critical Areas 219 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 6 of 8 If requested, our office can help locate suitable fill material that will meet the project specification and design intent at the time of construction. At locations of the levee where vehicle access may be required, a base material that is less likely to rut may be desired for the upper 6 inches of fill. In these locations, we recommend using Crushed Surfacing Top Course (CSTC meeting WSDOT Specification Section 9-03.9(3),). 4.2 Constructed Levee Fill Sections 1. Surface vegetation, topsoil, and any other deleterious material should be removed using a straight-edge bucket to minimize disturbance of the underlying soil. The depth of the required excavation is anticipated to generally be 6 inches. 2. The base of the excavation should then be leveled, and the subgrade compacted in accordance with Section 2-03.3(14) C, Method C of the WSDOT Standard Specifications. We recommend a KCML representative be onsite to inspect the exposed subgrade for suitability. 3. Following preparation of the base, for sections that will have vehicular traffic, a construction geotextile for separation and stabilization is recommended to be placed at the bottom of the excavation. We recommend utilizing the woven geotextile, Mirafi 580i. The geotextile should be placed under tension, flat and taut, and extend the entire width and length of the bottom of the excavation. A minimum overlap of two (2) feet is recommended, if needed. No construction traffic of any kind should be allowed directly onto the geotextile. 4. The excavation should then be backfilled to the desired elevation utilizing the approved levee fill. The backfill material should generally be placed in 6-inch lifts and compacted mechanically or by hand in order to reestablish the original shape of the levee. 5. Where vehicle access is necessary, CSTC should be utilized in the upper six inches of the fill to reduce potential rutting. Placement and compaction of the CSTC should be in accordance with Section 2-03.3(14)C, Method C of the WSDOT Standard Specifications. 6. Once the levee fill has reached the desired elevation, sod or seeded topsoil may be placed if desired. 7. Compaction testing and quality control testing of materials shall be conducted to confirm the quality of materials and verify adequate required compaction. KCML is available to perform these tasks. ATTACHMENT D - Geotechnical and Critical Areas 220 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 7 of 8 5.0 CONTINUING GEOTECHNICAL SERVICES As requested, we have provided site-specific subsurface conditions and preliminary design recommendations that can be used for design of the levee repair. As the design develops, we are available to provide additional geotechnical analysis, design parameters, and construction recommendations as needed. We appreciate the opportunity to have been of service on this project and trust this report addresses your current needs. Should you have question, require clarification, or desire additional information, please contact Casey Wagner (206-255-1881) or Doug Walters (206-477-2112) at your convenience. Respectfully Submitted, King County Materials Laboratory Doug Walters, P.E. King County Materials Engineer 11/5/2020 ATTACHMENT D - Geotechnical and Critical Areas 221 of 336 Dykstra Levee at RM 29.5 to 30.9 November 5, 2020 Geotechnical Investigation Page 8 of 8 6.0 REFERENCES American Association of State Highway & Transportation Officials (AASHTO), 2017, LRFD Bridge Design Specifications, 8th Edition, November 2017 Clover Associates, Galena Slope Stability Analysis System, Software Program, Version 7.20.1.01, 27 May 2019 King County Geotechnical Engineering Report, Dykstra Levee at RM 29.5 to RM 30.9. 17 March 2020 U.S. Army Corps of Engineers (USACE), April 2000, Design and Construction of Levees, Engineer Manual EM 1110-2-1913. U.S. Army Corps of Engineers (USACE), October 2003, Slope Stability, Engineer Manual EM 1110-2-1902. United States Department of Transportation Federal Highway Administration, December 2006, Soils and Foundations, FHWA NHI-06-089 United States Geological Survey Earthquake Hazards Program Website Link, Website: http://earthquake.usgs.gov/research Washington State Department of Transportation (WSDOT), December 2013, Geotechnical Design Manual M 46-03, Section 9.2.3.1 WSDOT Geotechnical Design Manual M 46-03 (Section 9.2.3.1) and FHWA NHI-06-088 (Sections 6.2 and 6.4.5) WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, 2020 ATTACHMENT D - Geotechnical and Critical Areas 222 of 336 ATTACHMENT D - Geotechnical and Critical Areas 223 of 336 ATTACHMENT D - Geotechnical and Critical Areas 224 of 336 ATTACHMENT D - Geotechnical and Critical Areas 225 of 336 ATTACHMENT D - Geotechnical and Critical Areas 226 of 336 ATTACHMENT D - Geotechnical and Critical Areas 227 of 336 ATTACHMENT D - Geotechnical and Critical Areas 228 of 336 ATTACHMENT D - Geotechnical and Critical Areas 229 of 336 ATTACHMENT D - Geotechnical and Critical Areas 230 of 336 ATTACHMENT D - Geotechnical and Critical Areas 231 of 336 ATTACHMENT D - Geotechnical and Critical Areas 232 of 336 ATTACHMENT D - Geotechnical and Critical Areas 233 of 336 ATTACHMENT D - Geotechnical and Critical Areas 234 of 336 ATTACHMENT D - Geotechnical and Critical Areas 235 of 336 ATTACHMENT D - Geotechnical and Critical Areas 236 of 336 ATTACHMENT D - Geotechnical and Critical Areas 237 of 336 ATTACHMENT D - Geotechnical and Critical Areas 238 of 336 ATTACHMENT D - Geotechnical and Critical Areas 239 of 336 ATTACHMENT D - Geotechnical and Critical Areas 240 of 336 ATTACHMENT D - Geotechnical and Critical Areas 241 of 336 ATTACHMENT D - Geotechnical and Critical Areas 242 of 336 ATTACHMENT D - Geotechnical and Critical Areas 243 of 336 ATTACHMENT D - Geotechnical and Critical Areas 244 of 336 ATTACHMENT D - Geotechnical and Critical Areas 245 of 336 ATTACHMENT D - Geotechnical and Critical Areas 246 of 336 ATTACHMENT D - Geotechnical and Critical Areas 247 of 336 ATTACHMENT D - Geotechnical and Critical Areas 248 of 336 ATTACHMENT D - Geotechnical and Critical Areas 249 of 336 ATTACHMENT D - Geotechnical and Critical Areas 250 of 336 ATTACHMENT D - Geotechnical and Critical Areas 251 of 336 ATTACHMENT D - Geotechnical and Critical Areas 252 of 336 ATTACHMENT D - Geotechnical and Critical Areas 253 of 336 ATTACHMENT D - Geotechnical and Critical Areas 254 of 336 Hydraulic and Hydrologic Analysis Report Green River Dykstra Levee Improvement Project Permit No. GRA20‐0015 Submitted to: City of Auburn Department of Planning and Development 25 West Main Street Auburn, WA 98001 Prepared by: Jay Young, P.E. King County Water and Land Resources Division, River and Flood Plain Management Section 201 S. Jackson St., Ste. 600, Seattle, WA 98104 jay.young@kingcounty.gov; 206‐477‐4858 _ Jay Young, P.E. Project Manager September 22, 2020 255 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 1 Table of Contents Chapter 1 – Project Overview ....................................................................................................................... 2 Chapter 2 – Existing Conditions Summary .................................................................................................... 3 Chapter 3 – Hydraulic and Hydrologic Analysis ............................................................................................ 4 Figures & Tables Figure 1 – General Vicinity Map Figure 2 – Area A: Levee Fill Area Figure 3 – Area B: Levee Fill Area Figure 4 – Area C: Levee Fill Area Figure 5 – Project and FEMA Cross‐section locations, as shown on FEMA’s Preliminary Digital Flood Insurance Rate Maps. Figure 6 – FEMA Flood Insurance Rate Map of project vicinity. Note levee is drawn landward of Special Flood Hazard Area/Floodway. Table 1 – FEMA Floodway Data for the Green River reflecting cross‐section water surface elevations for the 100‐year return interval flows (NAVD88). Figure 7: Sheet 15 reflecting FEMA cross‐section ED elevation & location Figure 8: Sheet 18 reflecting FEMA cross‐section EE elevation & location Figure 9: Sheet 19 reflecting FEMA cross‐section EH elevation & location Attachments Attachment A – Project Drawing Plan Set Attachment B – Photographs 256 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 2 Chapter 1 – Project Overview The Galli’s and Dykstra levees are in the City of Auburn along the left bank of the Green River and provide flood risk reduction benefits to residential and commercial areas of Auburn and unincorporated King County. The need for the project is based on concerns about potential low areas along the levees. At the request of the City of Auburn, in 2019 King County, as service provider to the King County Flood Control District, initiated a feasibility study to evaluate the existing levee heights and stability to ensure the levees function as designed and provide a uniform level of flood risk reduction to the area. Feasibility studies identified three areas along the Dykstra levee where corrective action is needed to address low spots. No low areas were identified along the Galli’s levee segment. The area farthest north (Area A) extends from the pedestrian bridge at Dykstra Park, (just south of Brannon Park) to adjacent multi‐family buildings to the south. The other two locations (Area B and Area C) are farther to the south and adjacent to approximately 15 single‐family homes. Proposed levee improvements include raising the height of the existing Dykstra levee at these discrete locations as shown in Figure 1. The improvements are designed to provide flood risk reduction benefits to residential and commercial areas of Auburn and unincorporated King County. Project goals include providing an uniform level of flood risk reduction to contain flood flows of 12,000 cfs (1% annual chance exceedance or 100‐yr flood event) plus 3 feet of freeboard. This Hydraulic and Hydrologic Analysis (H&H) Report is issued to comply with submittal requirements for a Civil Site Improvement Permit (Permit No. GRA20‐0015) from the City of Auburn. Other permitting for this proposal includes compliance with City of Auburn’s Shoreline Master Program; a Floodplain Development Permit; an environmental impact review through the State Environmental Policy Act (SEPA); and a Hydraulic Project Approval (HPA) from Washington Department of Fish and Wildlife. This H & H Report covers three distinct and separate areas identified by the following parcel numbers;  Area A (Parcel Identification Nos. 0721059038, 8944150000, and 8944130000);  Area B (Parcel Identification Nos. 7349400540, 7349400550, 7349400560, 7349400570, 7349400580, 7349400590, 7349400600, and7349400610); and  Area C (Parcel Identification Nos. 7349400350, 7349400360, 7349400370, 7349400380, 7349400390, 7349400400, and 734940TR‐A). The construction would generally involve removing some of the levee top surface down to a stable layer, followed by adding suitable fill material to bring the levee height up to the appropriate elevation with designed compaction. The side slopes would be shaped to match the existing slopes of the face and back of the levee. Some minor adjustments of the face of the existing levee may be needed to blend the imported/compacted material into the existing prism. 257 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 3 Chapter 2 – Existing Conditions Summary Three segments (Areas A, B, and C) along the Dykstra Levee have been surveyed and found to be below the height needed to provide flood containment of 12,000 cubic feet per second (cfs) plus three feet of freeboard. The three sections of the Dykstra Levee that do not meet this required elevation are approximately 960 (Area A), 600 (Area B), and 400 (Area C) feet long. Segments of this levee are proposed to be raised from approximately one to three feet from their current elevation, with the greatest rise in Area A, to meet this protection level. Areas B and C require approximately one foot, on certain portions of these levee segments (see Dykstra Levee construction plans for existing topography and details for proposed improvements in Attachment A). Area A consists of approximately 960 feet on the left bank (shoreline) of the Green River (river) along Dykstra Park, Villa Del Rio Condominiums, and Madison at River’s Edge Apartments (Figures 1 and 2) located on 22nd Street NE. The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation (Photos 1‐6 in Attachment B). The levee along this section is proposed to be raised up to approximately three feet in some locations. Area B consists of 600 feet on the left bank (shoreline) of the river along Riverview Drive NE (Figures 1 and 3). The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation (Photos 7‐10 in Attachment B). The levee along this section is proposed to be raised up to approximately one foot in some locations. Area C consists of 400 feet on the left bank (shoreline) of the river along Riverview Drive NE (Figures 1 and 4). The levee top is comprised of hardened gravel surfacing with low grass and other sparse vegetation (Photos 11‐14 in Attachment B). The levee along this section is proposed to be raised up to approximately one foot in some locations. 258 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 4 Chapter 3 – Hydraulic and Hydrologic Analysis A level Three Floodplain Development Permit was determined to be necessary for the Dykstra Levee Repair project based on information provided during the pre‐application meeting and conference summary (PRE20‐0003). Protected areas, as defined in ACC 15.68.060.BB, within the project area include the Special Flood Hazard Area (SFHA)/100‐Year Regulatory Floodplain, the Floodway, the Riparian Habitat Zone (RHZ), and the Channel Migration Area (CMA). The Floodplain Development Permit Application requests information about the Base Flood Elevation. Additionally, Per ACC 15.68.130.E and 15.68.160.C, hydrologic and hydraulic analyses prepared by a licensed professional engineer is required for the portions of levee located within the floodway. Hydraulic and hydrologic analyses were conducted to verify proposed improvements as part of the Dykstra Levee Repair Project will not result in any increase in flood levels during the occurrence of the 100‐year flood conditions (base flood discharge). Fill placed as a result of the project will be confined to areas above the base flood elevation. Areas A, B and C are depicted on the FEMA’s Preliminary Digital Flood Insurance Rate Maps (Figure 5). A very small portion of the Dykstra Levee in Area A falls within the regulatory boundary of the SFHA and Floodway, as depicted on the FEMA Flood Insurance Rate Map (FIRM; Map # 53033C1254). However, the FIRM panel depicts the levee as being outside of the SFHA and Floodway (see Figure 6). The elevation of the water surface profile of the regulatory base flood elevations (BFE), from the HEC‐ RAS 2010 FEMA Flood Insurance Study (FIS) for King County (Digital submittal March 2010 FEMA APPROVED) and Volume 2 of the 2010 FEMA Flood Insurance Study was plotted against a longitudinal survey profile of the top of the Dykstra Levee to identify potential low areas. The 2010 FIS was also used for the developing the preliminary 2017 FEMA maps which went into effect in August. The elevations of the BFE for areas A, B, and C were obtained from FEMA’s Preliminary Digital Flood Insurance Rate Maps are provided in Table 1. FEMA cross‐sections within the project area 1% annual chance flood water surface elevation are reflected in the project plans set (see Figure 7, 8, & 9) verifying the FIS 2010 profile (RAS 2010 FEMA Flood Insurance Study (FIS)) is correctly reflected. The complete levee profile elevation and site topography is provided in the project plan set and demonstrates that the surveyed elevation of the top of the levee, including Areas A, B and C are above the regulatory BFE and Floodway elevations (see Figure 7, 8, & 9). 259 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 5 Chapter 4 – Conclusions and Recommendations Based on the hydraulic analysis conducted and comparison with site topography all proposed fill for the project is confined to areas above the base flood elevation. Moreover, fifty foot interval cross‐sections reflected in the project plan set (see sheets 23‐47) confirm all proposed fill is above the base flood elevation and therefore would not increase flood levels during the occurrence of the base (100‐year) flood discharge. 260 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 6 FIGURES 261 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 7 Figure 1: General Vicinity Map 262 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 8 Figure 2: Work Area A with Storm Drainage Characteristics (Downstream Flow Path). 263 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 9 Figure 3: Work Area B with Storm Drainage Characteristics (Downstream Flow Path). 264 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 10 Figure 4: Work Area C with Storm Drainage Characteristics (Downstream Flow Path). 265 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 11 Figure 5: Project and FEMA Cross‐section locations, as shown on FEMA’s Preliminary Digital Flood Insurance Rate Maps. 266 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 12 Figure 6: FEMA Flood Insurance Rate Map of project vicinity. Note levee is drawn landward of Special Flood Hazard Area/Floodway. 267 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 13 Table 1 Cross‐sections and water surface elevations (WSELs) for the 100‐ year return interval flows (NAVD88). 268 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 14 Figure 7 Sheet 15 reflecting FEMA cross‐sections ED elevations and location 269 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 15 Figure 8: Sheet 18 reflecting FEMA cross‐section EE elevation & location 270 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 16 Figure 9: Sheet 19 reflecting FEMA cross‐section EH elevation & location 271 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 17 ATTACHMENT A – Project Drawing Plan Set (attached to permit application under separate cover) 272 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 18 ATTACHMENT B – Photographs 273 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 19 Photo 1: Looking east at top of levee in work Area A1. Photo 2: Another view looking east at top of levee in work Area A1. 274 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 20 Photo 3: Looking west at top of levee toward work Area A1. Photo 4: Looking east at levee fill Area A2. 275 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 21 Photo 5: Another view looking east at the levee in Area A3. Photo 6: Looking west from work Area A3. 276 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 22 Photo 7: Looking toward the downstream end of project Area B. Photo 8: Looking east from the middle of project Area B. 277 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 23 Photo 9: Looking west from the middle of project Area B. Photo 10: Looking toward the upstream end of project Area B. 278 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 24 Photo 11: Looking south at the top of levee in work Area C. Residential properties on west side. Photo 12: Looking north at Area C and residential properties on west side. 279 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 25 Photo 13: Another view looking south at work Area C toward the southern end of the project. Photo 14: Looking north from the southern end of work Area C 280 of 336 Dykstra Levee Repair Project; Hydraulic and Hydrologic Analysis, Final – King County 26 281 of 336 Form Updated: March 2019 Page 1 of 8 SEPA ENVIRONMENTAL CHECKLIST Date Received: Physical Address: Auburn City Hall Annex, 2nd Floor 1 E Main St Mailing Address: 25 W Main St Auburn, WA 98001 Webpage & Application Submittal: www.auburnwa.gov applications@auburnwa.gov Phone and Email: 253-931-3090 permitcenter@auburnwa.gov Project Name: King County Dykstra Levee Improvement Parcel Number(s): Area “A”:0721059038; 8944150000; 8944130000 Area “B”: 7349400540; 7349400550; 7349400560; 7349400570; 7349400580; 7349400590; 7349400600 Area “C”: 7349400350; 734900360; 7349400370; 7349400380; 7349400390; 7349400400 A. Background [help] 1. Name of proposed project, if applicable: King County Dykstra Levee Improvement 2. Name of Applicant: King County River and Floodplain Management Section Name of Agent (if applicable): Seth Amrhein 3. Address and phone number of Applicant: KSC-NR-0600, 201 S. Jackson St. Suite 600, Seattle, WA 98104 Address and phone number of Agent (if applicable): KSC-NR-0600, 201 S. Jackson St. Suite 600, Seattle, WA 98104 4. Date Checklist prepared: January 6th, 2021 Date(s) Checklist Revised: 5. Agency requesting checklist: City of Auburn, WA 6. Proposed timing or schedule (including phasing, if applicable). Construction on Areas “A,” “B,” and “C” will be completed in the spring or summer of 2021. The revegetation habitat enhancement along Area A will be completed in fall of 2021 or winter of 2022. 7. Do you have any plans for future additions, expansion, or further activity related to or connected with this proposal? If yes, explain. No. 8. List any environmental information you know about that has been prepared, or will be prepared, directly related to this proposal. King County, 2020. Geotechnical Engineering Report Dykstra Levee at RM 29.5 to RM 30.9, King County, Washington. Prepared by King County Department of Local Services, Road Services Division Materials Laboratory. Renton, Washington. King County, 2021. Critical Area Report and Habitat Impact Assessment. Prepared by King County River and Floodplain Management Section. Seattle, Washington. King County, 2020. Stormwater Site Plan Report: Green River Dykstra Improvement Project. Seattle, Washington. Prepared by King County Water and Land Resources Division. Seattle, Washington King County, 2020. Hydraulic and Hydrologic Analysis Report: Green River Dykstra Levee Improvement Project Permit No. GRA20-0015. Prepared by King County River and Floodplain Management Section. Seattle, Washington. King County, 2019. Green River System Wide Improvement Framework Report. Prepared by King County Water and Land Resources Division. Seattle, Washington 282 of 336 Form Updated: March 2019 Page 2 of 8 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. 10. List any government approvals or permits that will be needed for your proposal, if known. Grading permit, Shoreline Substantial Development Permit, Construction Permit, and Floodplain Development Permit from the City of Auburn. Hydraulic Project Approval from the Washington State Department of Fish and Wildlife. 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. Three segments along the Dykstra Levee in the City of Auburn have been found to be below the height needed to provide flood containment of 12,000 cubic feet per second (CFS) plus an additional 3 feet of freeboard. The three sections of the Dykstra Levee that do not meet the requisite elevation are approximately 400, 600, and 960 feet long. Section A will be raised up to 3 feet. Sections B and C will be raised less than 1 foot. The work will involve stripping away the existing levee top surface of grass down to a stable substrate, which will be followed by adding suitable fill material to bring the levee height up to the appropriate elevation. The side slopes of the added fill will be contoured to match the existing slopes of the face and back of the levee. Some minor adjustments of the face of the existing levee may be needed to match the slope added material. In three locations, block retaining walls up to 30 feet long may be needed to support added fill on the landward side of the levee to avoid impacts to yards and existing homes. In conjunction with work on the Dykstra Levee, an approximately 35,590-square foot area along the waterward side of the levee that is currently dominated by invasive reed canary grass will be revegetated with native trees and shrubs to improve the currently degraded riparian habitat conditions. 283 of 336 Form Updated: March 2019 Page 3 of 8 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 project will occur on three segments of the Dykstra Levee in the City of Auburn, Washington. The work on Area “A” will occur on King County Parcel Numbers: 0721059038; 8944150000; 8944130000 The work on Area “B” will occur on King County Parcel Numbers: 7349400540; 7349400550; 7349400560; 7349400570; 7349400580; 7349400590; 7349400600 The Work on Area “C” will occur on King County Parcel Numbers: 7349400350; 734900360; 7349400370; 7349400380; 7349400390; 7349400400 284 of 336 Form Updated: March 2019 Page 4 of 8 B. Environmental Elements [help] 1. Earth [help] a. General description of the site: x flat,  rolling,  hilly,  steep slopes,  mountainous,  other b. What is the steepest slope on the site (approximate percent slope)? On the riverside, the levee slope inclination generally ranges from 44 % to 29 %. 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. The Washington State Department of Natural Resources Geologic Information Portal indicated Quaternary Alluvium comprised of unconsolidated or semi-consolidated alluvial clay, silt, sand gravel, and/or cobble deposits comprise the expected soil profile in the project vicinity. Geotechnical drilling on the levee conducted by the King County Road Services Division Materials Laboratory encountered 3-6 inches of topsoil. Fill underlying the topsoil ranged from approximately 7-13 feet below ground surface and consists of loose to medium dense brown silty sand with grave to a poorly graded sand with silt and gravel. Alluvial deposits consisting of medium dense to dense gray gravel with silt and sand, to poorly graded sand with gravel, underlie the fill to the termination depth of the borings. The soils in the project area do not have agricultural or commercial significance. No soils will be extracted from the project sight. d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. Yes. A geotechnical report, prepared by the King County Road Services Division Materials Laboratory, evaluated subsurface and groundwater conditions in order to provide geotechnical recommendations of design and construction for the three identified low areas. The report indicated there have been no significant signs of erosion or material loss on the riverbank in the location of the proposed work. However, there have been several PL 84-99 repair projects along the Galli’s-Dykstra levee including in 1976, 1994, 2008, 2009 and in 2015. Some erosion at the levee toe from the 2020 flood events was identified during a site visit in June/July 2020. The current levee and proposed work are located in a mapped channel migration zone. However, the levee itself functions as an impediment to channel migration. The levee is currently armored with large rock, making it resistant to channel migration. The proposed work will not alter the channel’s natural planform pattern and migration process from the existing condition. The 2019 Green River System Wide Improvement Framework Report evaluated channel incision between 1986 and 2011 in this reach and noted two locations with incision greater than 3 feet at RM 28.99 and 30.59, both of which are located near the apexes of bends. 5 survey cross-sections were completed in this reach to evaluate changes in the channel since the 2006 survey for the flood insurance study and found very minimal or no change. 285 of 336 Form Updated: March 2019 Page 5 of 8 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. The purpose of the fill is to increase the elevation of three sections of the Dykstra Levee along the Green River so that it provides 3 feet of freeboard above flows of 12,000 CFS along the length of the levee. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. Temporary erosion could occur as a result of land disturbance from grading, hauling of material and general project construction. There is potential for short term turbidity impacts on the Green River adjacent to and downstream of the project area during the construction, particularly if work is done in rainy weather. Erosion and sedimentation controls will be installed, as described below, to minimize the risk of impacts to water quality. g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? No impervious surfaces will be created by this project. h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: A Temporary Erosion and Sediment Control Plan will be developed prior to construction, and measures will be implemented both prior to and during ground disturbing activities, as needed. The following best management practices will be on-site or readily accessible during all construction activities: quarry spalls for temporary construction entrances, straw wattles, plastic sheeting, and silt fencing. Following construction, all disturbed areas will be vegetated to provide permanent stabilization. 2. Air [help] 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. The project has the potential to generate construction related dust. Dust control will be performed on an as-needed basis by stabilizing construction access surfaces and watering. Construction vehicles and equipment (excavators, dump trucks, pick-up trucks, etc.) will be used during construction. This equipment will emit gasses including carbon dioxide (CO2), methane and nitrous oxide, as well as others in much smaller amounts. b. Are there any off-site sources of emissions or odor that may affect your proposal? If so, generally describe. No c. Proposed measures to reduce or control emissions or other impacts to air, if any: Engines will not idle unnecessarily and will be kept in proper working order with all filters and other emission control devices functional. To help reduce transportation costs, it is expected that the contractor will source construction materials from locations closer to the project site, thus helping reduce delivery vehicle mileage and corresponding emissions. 286 of 336 Form Updated: March 2019 Page 6 of 8 3. Water [help] a. Surface Water. [help] 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. The project is on a levee immediately adjacent to the Green River, which turns into to Duwamish Waterway before it drains into Puget Sound. The Green River is within Water Resource Inventory Area 9. 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. No work will occur in or over water. Construction will occur on a levee within 200 feet of the ordinary high-water mark of the Green River. Revegetation with native trees and shrubs will occur within a bench between the levee and the ordinary high water mark 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. None. 4. Will the proposal require surface water withdrawals or diversions? Give general description, purpose, and approximate quantities if known. No. 5. Does the proposal lie within a 100-year floodplain? If so, note location on the site plan. All planned construction on the levee is at an elevation above the 100-year floodplain. Supporting documentation for this conclusion is provided in the Hydraulic and Hydrologic Analysis Report: Green River Dykstra Levee Improvement Project (King County, 2020). The proposed revegetation to improve riparian habitat is within the 100-year 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. No. b. Ground Water. [help] 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. No. 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. n/a 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. No new runoff will be generated by this project. Except for a slight proposed 1-2 % slope to the river from the improved levee areas, pre-and-post-project site conditions will be generally the same. Stormwater that doesn’t infiltrate into the levee surface will sheet flow toward the Green River. The project does not propose to construct any permanent on- site stormwater management systems (i.e., conveyance system, water quality facility, or flow control facility). A detailed analysis of runoff/stormwater management and the 287 of 336 Form Updated: March 2019 Page 7 of 8 project’s compliance with the 2017 City of Auburn Supplemental Manual to the Stormwater Management Manual for Western Washington is provided in the Stormwater Site Plan Report: Green River Dykstra Levee Improvement Project(King County, 2020). 2. Could waste materials enter ground or surface waters? If so, generally describe. No. Waste materials will be prevented from entering the ground or surface waters by maintaining a clean site, properly disposing of debris and use of best management practices to contain material within the project site. 3. Does the proposal alter or otherwise affect drainage patterns in the vicinity of the site? If so, describe. Minor changes will be made to the roof runoff conveyance from the residential buildings landward of the levee and the crest of the levee will be slightly sloped (1-2 %) toward the Green River in the improved areas. Pre-and-post-project site runoff conditions will be generally the same. A detailed analysis of pre-and post-project site conditions is provided in the Stormwater Site Plan Report: Green River Dykstra Levee Improvement Project(King County, 2020). 288 of 336 Form Updated: March 2019 Page 8 of 8 4. Plants [help] a. Check the types of vegetation found on the site: X deciduous tree:  alder,  maple,  aspen,  other  evergreen tree:  fir,  cedar,  pine,  other X shrubs X grass  pasture  crop or grain  orchards, vineyards or other permanent crops X wet soil plants:  cattail,  buttercup,  bullrush,  skunk cabbage,  other  water plants:  water lily,  eelgrass,  milfoil,  other  other types of vegetation b. What kind and amount of vegetation will be removed or altered? Grass and potentially some ornamental shrubs. d. List threatened and endangered species known to be on or near the site. The Green River is habitat for Puget Sound Chinook salmon and steelhead trout. Both are listed as threatened under the federal endangered species act. e. Proposed landscaping, use of native plants, or other measures to preserve or enhance vegetation on the site, if any: All existing native vegetation will be protected. The areas of work on the Dykstra Levee are currently predominantly grass-covered and will be seeded with native grasses after construction. In conjunction with the work on the levee, an approximately 35,590- square foot area along the waterward side of the levee that is currently dominated by invasive reed canary grass will be revegetated with native trees and shrubs to improve the currently degraded riparian habitat conditions. f. List all noxious weeds and invasive species known to be on or near the site. Blackberry and reed canary grass. 5. Animals [help] a. Check any birds and other animals which have been observed on or near the site or are known to be on or near the site. X Birds: X hawk, X heron, X eagle, X songbirds,  geese, X ducks, X crows,  other X Mammals:  deer,  bear,  elk,  beaver, X other (small mammals) X Fish:  bass, X salmon, X trout,  herring,  shellfish,  other b. List any threatened and endangered species known to be on or near the site. c. Is the site part of a migration route? If so, explain. The site is along the Green River, which is a migration route for chum, coho, pink, sockeye, and chinook salmon, steelhead trout. The river also contains resident cutthroat trout, mountain whitefish, rainbow trout, as well as a variety of non- salmonid fish species. d. Proposed measures to preserve or enhance wildlife, if any: The proposal will preserve wildlife habitat by keeping within the constructed footprint of the existing levee. No native trees or shrubs will be removed. All construction on the levee will occur on the levee crest above the 100-year floodplain. Erosion control measures will be used during construction and construction will occur in the dry season to minimize the risk of erosion, which could impact water quality and harm aquatic wildlife in the Green River. An approximately 35,590-square foot area along the waterward side of the levee that is currently dominated by invasive reed canary grass will be revegetated with native trees and shrubs to enhance the currently degraded riparian habitat conditions. This area is identified as critical for shade on the Muckleshoot Indian Tribe’s sun analysis maps due 289 of 336 Form Updated: March 2019 Page 9 of 8 to its southern exposure. Over time the planted trees will provide shade to the river to contribute toward moderation of water temperature, as recommended in the Washington Department of Ecology’s Green River Temperature Total Maximum Daily Load (TMDL) Water Quality Improvement Report (2011). As the trees mature and eventually fall into the river, they will provide a source of large wood, which is critical for the formation of habitat features favored by salmonids that inhabit the Green River. e. List any invasive animal species known to be on or near the site. None 6. Energy and Natural Resources [help] 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. n/a b. Would your project affect the potential use of solar energy by adjacent properties? If so, generally describe. n/a 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: n/a 290 of 336 Form Updated: March 2019 Page 10 of 8 7. Environmental Health [help] 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. Malfunction of construction equipment could leak diesel, gas, oil, or hydraulic fluid onto the site. 1. Describe any known or possible contamination at the site from present or past uses. None are known. 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. None are known. 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. Fuel, oil, and hydraulic fluid may be on the project site during construction. 4. Describe special emergency services that might be required. None. 5. Proposed measures to reduce or control environmental health hazards, if any: All machinery will be inspected for leaks prior to entering the site. An emergency spill kit will be kept on the site at all times to respond to the potential loss of diesel gas, oil, or hydraulic fluid from construction machinery. All construction equipment will be refueled at a designated fueling area on the site that is as far as possible from the Green River. All equipment will be inspected daily to determine if there are leaking seals or gaskets that require replacement. Best Management Practices (BMPs) such as fuel containment and a spill response plan will be used during construction to reduce and control environmental health hazards. b. Noise. 1. What types of noise exist in the area which may affect your project (for example: traffic, equipment, operation, other)? Minimal noise exists at the site vicinity. There is light vehicle traffic on adjacent and nearby residential streets. 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. The project will generate some noise due to the use of heavy equipment, such as excavators, backhoes, and dump trucks. Construction of the project will likely take five to ten days and construction activities will be limited to hours between 7:00am and 7:00pm, Monday through Friday, or more stringent limitations required by the City of Auburn. 3. Proposed measures to reduce or control noise impacts, if any: Construction activities will be limited to weekday hours between 7:00am and 7:00pm, Monday through Friday, or more stringent limitations required by the City of Auburn. 291 of 336 Form Updated: March 2019 Page 11 of 8 8. Land and Shoreline Use [help] 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. The properties adjacent to the work area contain a City of Auburn park and single and multi-family residences. 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? The project site was historically used for agriculture but has been converted to single and multi-family residential usage in the 1960s and 70s. 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: No. 292 of 336 Form Updated: March 2019 Page 12 of 8 c. Describe any structures on the site. The properties on which the work will occur contain single and multi-family dwellings. d. Will any structures be demolished? If so, what? No. e. What is the current zoning classification of the site? Residential 7 DU/Acre (R7) and Residential 20 DU/Acre (R20). f. What is the current Comprehensive Plan designation of the site? Single family and multi-family g. If applicable, what is the current Shoreline Master Program designation of the site? Shoreline Residential h. Has any part of the site been classified as a critical area? If so, specify. The Green River adjacent to the work area is a Type S stream and “critical habitat” wildlife area. i. Approximately how many people would reside or work in the completed project? The project will not alter residential capacity on the project work area. j. Approximately how many people would the completed project displace? None. k. Proposed measures to avoid or reduce displacement impacts, if any: None. No impacts. L. Proposed measures to ensure the proposal is compatible with existing and projected land uses and plans, if any: None. n/a l. Proposed measures to reduce or control impacts to agricultural and forest lands of long- term commercial significance, if any: None. No impacts. 9. Housing [help] a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low- income housing. None. b. Approximately how many units, if any, would be eliminated? Indicate whether high, middle, or low- income housing. None. c. Proposed measures to reduce or control housing impacts, if any: None. 10. Aesthetics [help] a. What is the tallest height of any proposed structure(s), not including antennas; what is the principal exterior building material(s) proposed? n/a 293 of 336 Form Updated: March 2019 Page 13 of 8 b. What views in the immediate vicinity would be altered or obstructed? None. c. Proposed measures to reduce or control aesthetic impacts, if any: Preexisting land cover of grass will be reestablished after construction. 11. Light and Glare [help] a. What type of light or glare will the proposal produce? What time of day would it mainly occur? None. 294 of 336 Form Updated: March 2019 Page 14 of 8 b. Could light or glare from the finished project be a safety hazard or interfere with views? n/a c. What existing off-site sources of light or glare may affect your proposal? None. d. Proposed measures to reduce or control light and glare impacts, if any: None. 12. Recreation [help] a. What designated and informal recreational opportunities are in the immediate vicinity? City of Auburn Park with lawn and playground. b. Would the proposed project displace any existing recreational uses? If so, describe. No. c. Proposed measures to reduce or control impacts on recreation, including recreation opportunities to be provided by the project or applicant, if any: None. 13. Historic and Cultural Preservation [help] 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. No. 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. No. All work is on a constructed levee. 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 (DAHP), archaeological surveys, historic maps, GIS data, etc. All work is on a constructed levee. King County Historic Preservation Program staff reviewed available information for known archaeological sites in the project area and determined that there are none. 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. None. 14. Transportation [help] 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. Pike St NE, 22nd Way NE, Riverview Dr NE 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? Bus stops are ½ to 1 mile from work area. 295 of 336 Form Updated: March 2019 Page 15 of 8 c. How many additional parking spaces would the completed project or non-project proposal have? How many would the project or proposal eliminate? None. 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). No. e. Will the project or proposal use (or occur in the immediate vicinity of) water, rail, or air transportation? If so, generally describe. No. 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? None. 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. No. h. Proposed measures to reduce or control transportation impacts, if any: None. 15. Public Services [help] 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. No. b. Proposed measures to reduce or control direct impacts on public services, if any. None. 16. Utilities [help] a. Check utilities currently available at the site: X electricity, X natural gas, X water, X refuse service, X telephone, X sanitary sewer,  septic system,  other c. 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. None. C. Signature [help] Signature: Name of Signee: Seth Amrhein Position and Agency/Organization: Environmental Scientist, King County WLRD, River and Floodplain Management Section. Date Submitted: 296 of 336 NOTICE OF APPLICATION (NOA) and DETERMINATION OF NON-SIGNIFICANCE (DNS) KING COUNTY DYKSTRA LEVEE IMPROVEMENT PROJECT SEP20-0008 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 to allow for additional fill to be placed on three segments of an existing levee in order to provide additional flood protection to nearby property. The area has a shoreline designation of “Shoreline Residential”. Location: The project is located along the left bank of the Green River, between 26th St NE and 8th St NE. Notice of Application: July 16, 2020 Application Complete: May 14, 2020 Permit Application: May 14, 2020 File Nos. SEP20-0008 SHL20-0004 Applicant: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Property Owner: Various property owners, led by: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Studies/Plans Submitted With Application:  Critical Areas Report & Habitat Impact Assessment, prepared by King County Department of Natural Resources & Parks, dated May 10, 2020  Geotechnical Investigation, prepared by King County Department of Local Services, March 17, 2020  Preliminary Stormwater Report, prepared by King County Water and Land Resources Division, undated  SEPA Environmental Checklist, prepared by King County Water and Land Resources Division, dated Other Permits, Plans, and Approvals Needed:  Grading Permit, Shoreline Substantial Development Permit Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and Public Works Design and Construction Standards. 297 of 336 NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0008 (Continued) Page 2 of 4 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 July 31, 2020 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 August 14, 2020. For questions regarding this project, please contact Dustin Lawrence, AICP, Senior Planner, at planning@auburnwa.gov or 253-931-3092. Public Hearing: TBD 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. July 16, 2020 298 of 336 NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0008 (Continued) Page 3 of 4 Project Site Areas of proposed work Areas of proposed work Areas of proposed work 299 of 336 WITHDRAW AL OF DETERMINATION OF NON SIGNIFICANCE (DNS) KING COUNTY DYKSTRA LEVEE IMPROVEMENT PROJECT SEP20-0008 The City of Auburn is withdrawing the Determination of Non-Significance (DNS) issued on July 16, 2020 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 to allow for additional fill to be placed on three segments of an existing levee in order to provide additional flood protection to nearby property. The area has a shoreline designation of “Shoreline Residential”. Location: The project is located along the left bank of the Green River, between 26th St NE and 8th St NE. Notice of Application: July 16, 2020 Application Complete: May 14, 2020 Permit Application: May 14, 2020 File Nos. SEP20-0008 SHL20-0004 Applicant: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Property Owner: Various property owners, led by: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Studies/Plans Submitted With Application:  Critical Areas Report & Habitat Impact Assessment, prepared by King County Department of Natural Resources & Parks, dated May 10, 2020  Geotechnical Investigation, prepared by King County Department of Local Services, March 17, 2020  Preliminary Stormwater Report, prepared by King County Water and Land Resources Division, undated  SEPA Environmental Checklist, prepared by King County Water and Land Resources Division, dated Other Permits, Plans, and Approvals Needed:  Grading Permit, Shoreline Substantial Development Permit Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and Public Works Design and Construction Standards. Lead Agency: City of Auburn 300 of 336 WITHDRAW AL OF DETERMINATION OF NON-SIGNIFICANCE SEP20-0008 (Continued) Page 2 of 3 In accordance with WAC 197-11-340(3)(a)(ii), the lead agency for this proposal has determined that additional time is necessary to determine if the proposal will have probable significant adverse impacts on the environment. This decision was made in response to information received during the public comment period for the proposal. A new determination will be issued once the City and the applicant have had an opportunity to review the comments and, if necessary, modify the proposal accordingly. Public Comment Period: When an updated Determination is issued, a new comment period will be established and noticed. For questions regarding this project, please contact Dustin Lawrence, AICP, Senior Planner, at planning@auburnwa.gov or 253-931-3092. Public Hearing: TBD 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. August 14, 2020 301 of 336 WITHDRAW AL OF DETERMINATION OF NON-SIGNIFICANCE SEP20-0008 (Continued) Page 3 of 3 Project Site Areas of proposed work Areas of proposed work Areas of proposed work 302 of 336 REVISED NOTICE OF APPLICATION (NOA) & DETERMINATION OF NON- SIGNIFICANCE (DNS) KING COUNTY DYKSTRA LEVEE IMPROVEMENT PROJECT SEP20-0008 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 to allow for additional fill to be placed on three segments of an existing levee in order to provide additional flood protection to nearby property. The area has a shoreline designation of “Shoreline Residential”. Note: This Determination was previously issued and subsequently withdrawn by the applicant, on July 15, 2020 and August 14, 2020, respectively. Additional information has been provided with the Environmental Checklist and supporting materials and as such, a revised determination is being issued. The additional information includes a planting plan for native vegetation along a portion of “Area A” in order to address concerns from the Muckleshoot Indian Tribe. Additional responses to the Muckleshoot Indian Tribes concerns have been outlined in the updated materials provided with the revised Environmental Checklist. Location: The project is located along the left bank of the Green River, between 26th St NE and 8th St NE. Notice of Application: February 26, 2021 Application Complete: May 14, 2020 Permit Application: May 14, 2020 File Nos. SEP20-0008 SHL20-0004 Applicant: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Property Owner: Various property owners, led by: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Studies/Plans Submitted With Application: • Critical Areas Report & Habitat Impact Assessment, prepared by King County Department of Natural Resources & Parks, dated May 10, 2020, updated January 6, 2021 • Geotechnical Investigation, prepared by King County Department of Local Services, March 17, 2020, updated November 5, 2020 • Preliminary Stormwater Report, prepared by King County Water and Land Resources Division, undated November 23, 2020 303 of 336 NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0008 (Continued) Page 2 of 4 • SEPA Environmental Checklist, prepared by King County Water and Land Resources Division, dated May 19, 2020, updated January 26, 2021 Other Permits, Plans, and Approvals Needed: • Grading Permit, Shoreline Substantial Development Permit Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and 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 March 13, 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 27, 2021. For questions regarding this project, please contact Dustin Lawrence, AICP, CFM, Senior Planner, at planning@auburnwa.gov or 253-931-3092. Public Hearing: TBD 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 26, 2021 304 of 336 NOTICE OF APPLICATION and DETERMINATION OF NON-SIGNIFICANCE SEP20-0008 (Continued) Page 3 of 4 Project Site Areas of proposed work Areas of proposed work Areas of proposed work 305 of 336 NOTICE OF PUBLIC HEARING Dykstra Levee Improvement Project SHL20-0004 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 to allow for additional fill to be placed on three segments of an existing levee in order to provide additional flood protection to nearby property. The area has a shoreline designation of “Shoreline Residential”. Location: The project is located along the left bank of the Green River, between 26th St NE and 8th St NE. Notice of Application: April 2, 2021 Permit Application: May 14, 2020 Complete Application: May 14, 2020 File No. SEP20-0008 SHL20-0004 Applicant: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Owner: Various property owners, led by: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Studies/Plans Submitted with Application: • Critical Areas Report & Habitat Impact Assessment, prepared by King County Department of Natural Resources & Parks, dated May 10, 2020, updated January 6, 2021 • Geotechnical Investigation, prepared by King County Department of Local Services, March 17, 2020, updated November 5, 2020 • Preliminary Stormwater Report, prepared by King County Water and Land Resources Division, undated November 23, 2020 • SEPA Environmental Checklist, prepared by King County Water and Land Resources Division, dated May 19, 2020, updated January 26, 2021 Other Permits, Plans, and Approvals Needed: • Grading Permit, Shoreline Substantial Development Permit Statement of Consistency and List of Applicable Development Regulations: This proposal is subject to and shall be consistent with the Auburn City Code, Comprehensive Plan, and Design and Construction Standards. Public Comment Period: All persons may comment on this application. Comments must be in writing and received by the end of the comment period at 5:00 p.m. on May 19, 2021 to the 306 of 336 NOTICE OF PUBLIC HEARING SHL20-0004 (Continued) Page 2 of 2 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, CFM, Senior Planner, at planning@auburnwa.gov or (253) 931-3092. Public Hearing: The meeting of the City of Auburn Hearing Examiner scheduled for May 19, 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/98766513075 Meeting ID: 987 6651 3075 One tap mobile +12532158782,,98766513075# US (Tacoma) +16699009128,,98766513075# US (San Jose) VICINITY MAP: Areas of proposed work Areas of proposed work Areas of proposed work 307 of 336 MUCKLESHOOT INDIAN TRIBE Fisheries Division 39015 - 172nd Avenue SE  Auburn, Washington 98092-9763 Phone: (253) 939-3311  Fax: (253) 931-0752 July 31, 2020 Mr. Jeff Tate Director/SEPA Responsible Official Auburn Department of Community Development 25 West Main Street Auburn, WA 98001 RE: King County Dykstra Levee Improvement Project, Notice of Application and Determination of Non-Significance (DNS), SEP20-0008 and SHL20-0004 Dear Mr. Tate: Our Habitat Program staff have reviewed the Notice of Application for a Shoreline Substantial Development Permit and DNS under SEPA for King County’s proposed levee modifications at three sites on the Dykstra Levee along the Green River. This works covers 1,960 feet or 24% of the total levee length (1.5 miles) of the Dykstra Levee. We offer the following comments in the interest of protecting and restoring the Tribe’s treaty-protected fisheries resources. The project is proposing to raise the levee in these three locations by 1-3 feet to provide flood containment of 12,000 cubic feet per second (cfs) plus an additional 3 feet of freeboard . As noted in the Critical Area Report and Habitat Impact Assessment (CAR), the project is required by Auburn’s code to conduct a habitat impact analysis that evaluates the impact of the project on water quality and aquatic and riparian habitat (ACC 15.68.135.J). The project is also required to conduct an analysis the impact of the project on the habitat of species protected under the Endangered Species Act (ESA), including direct, indirect, interdependent, interrelated, or cumulative effects per ACC 15.68.135.J.4. We have reviewed the CAR and the SEPA checklist and find errors and omissions in both documents. The basis for this determination is provided in the attached document specific comments. Muckleshoot tribal commercial, subsistence, and ceremonial fisheries are dependent upon heathy salmon and steelhead populations in the Green/Duwamish watershed and other watersheds that comprise their Usual and Accustomed fishing areas. Salmon and steelhead populations in the Green/Duwamish watershed are declining despite salmon habitat restoration projects to date. Significant improvements are needed on levees/revetments along the Green River, including the Dykstra levee. This Dykstra levee modification project (and previous levee repair projects at the Dykstra levee) highlights the need for Green River levee modernization that uses levee relocation and designs to achieve adequate riparian shade, to protect known treaty fishing sites (which are in the project reach and beyond), and to 308 of 336 Muckleshoot Indian Tribe Fisheries Division Habitat Program July 31, 2020 Dykstra Levee Modifications SEPA and Shoreline Comments Page 2 of 6 allow places for natural scour and erosional processes to occur. The CAR for this project references the King County Council approved 2019 Green River System Wide Improvement Framework (SWIF) Report, but fails to consider all of the recommendations and analyses in it. For example, the 2019 SWIF Report includes vegetation guidelines for existing PL 84-99 levee systems, as well as, guidance for design of future of PL 84-99 shoreline capital projects and repairs. As part of the SWIF Report, this reach of the Green River was identified to provide “Key opportunities for restoration and enhancement include riparian vegetation improvements (removing invasives and planting native trees and shrubs), sloping banks back to create more riparian area and shallow water habitat, placing additional wood or log jams for cover and pool formation, and floodplain and side-channel restoration, including off-channel or backwater habitats.” Further, Map 11 in the 2019 SWIF Report shows that a 50 foot buffer could be planted at these levee repairs site without any further modifications to the existing levee footprint. The project lacks any of the restoration and enhancement elements described above necessary to improve shading, riparian functions, water quality, and aquatic habitats to support Green River salmon and steelhead and ultimately Muckleshoot fisheries. The project needs to be redesigned to address these deficiencies, including, but not limited to, a levee setback alternative and enhancement of the Green River and its riparian corridor for salmon and steelhead. Thank you for your attention to these concerns. We request a written response to these comments and a modified project design for our review. Please contact me at karen.walter@muckleshoot.nsn.us if you have any questions. Sincerely, Karen Walter (digital signature) Karen Walter Watersheds and Land Use Team Leader Cc: Dustin Lawrence, City of Auburn Community Development Josh Baldi, King County DNRP Joe Burcar, WDOE NW Region Larry Fisher, WDFW Region 4 309 of 336 Muckleshoot Indian Tribe Fisheries Division Habitat Program July 31, 2020 Dykstra Levee Modifications SEPA and Shoreline Comments Page 3 of 6 SEPA Environmental Checklist Comments Section 1.d. Unstable soils and erosion in the project vicinity With regard to unstable soils, the SEPA checklist states “The geotechnical report prepared by the King County…indicated there have been no significant signs of erosion or material loss on the riverbank.” The responses suggesting that there are no significant signs of erosion or material loss seems overly narrow or incorrect. The Green River has eroded its banks in the vicinity of the project area and it will continue to do so given its physical capacity. The responses in the SEPA checklist also conflict with findings from in the 2019 SWIF Report. The report denotes five sites within 0.5 river-miles of the proposed project where repairs were required and completed to accommodate the river’s natural and extant power to erode its banks in the project area. Additional repair work was done by the US Army Corps of Engineers in 2016 under the PL 84-99 program which demonstrates unstable soils and erosion issues. Section 3.a. 5. Floodplain The SEPA checklist notes that “All planned work is at an elevation above the 100-year floodplain.” This should be clearly documented. According to the available information on King County’s IMAP, the regulated floodplain and FEMA Preliminary Floodway is mapped at or near the levee crest, such as Site “A” where work is proposed at parcel 8944130000. The applicant needs to provide additional information to demonstrate that all of the parcels are outside of the 100-year floodplain. Issues not considered in the checklist Channel Migration Zone issues The SEPA checklist fails to consider channel migration zones which should be assessed for environmental impact purposes. Channel migration zones, which are shown on King County’s IMAP, extend across the levee crest were work is proposed, such as at Site “A” at parcel 8944130000. Channel migration zones are part of the King County Critical Areas Ordinance, and they are regulated by City of Auburn under Chapter 15.68 (Flood Hazard Areas). This project’s environmental review under SEPA should consider the proposed project in context of mapped channel migration hazards. Green River channel narrowing and incision issues The SEPA review for this project should evaluate alternatives beyond adding fill to raise the existing Dykstra levee at the proposed locations, such as a levee setback that will improve degraded salmon habitat at the site, and rectify channel narrowing caused by levees, as well as, thalweg incision, possibly associated with levees. 310 of 336 Muckleshoot Indian Tribe Fisheries Division Habitat Program July 31, 2020 Dykstra Levee Modifications SEPA and Shoreline Comments Page 4 of 6 As identified in the 2019 SWIF report, the Green River is narrowed by levees within the river reach for the project. Specifically, “within the confined section of the reach, the bank full width varies from 140 to 170 feet; through the unconfined sections the bank full with is generally much greater, ranging from 200 feet to over 400 feet where vegetated mid-channel bars have formed.” From a review of available aerial photograph on King County’s IMAP, channel narrowing is evident between 1936 and 2019, at Site “A” where work is proposed at parcel 8944130000, and where a portion of levee resides in the former river channel. Green River thalwag incision is documented in the FEMA Study cross sections from 1986 and 2006 available for the project area. This information was reviewed in the 2019 SWIF which states “most of the reach has been subject to thalweg incision,” apparently between 1- and 2-feet in the project area. Green River channel narrowing and channel incision have degraded salmon habitat and may contribute to damage of levees in the project area. Channel migration processes are important to create and sustain fish habitat. These issues further illustrate the need for this project to consider alternatives to the singular proposal of repairs in place, such as a levee setback. Critical Area Report and Habitat Impact Assessment comments The analysis provided in the CAR is inadequate in its evaluation of the project’s impact on water quality and aquatic and riparian habitat and effect on ESA listed salmon and Essential Fish Habitat salmon species. The CAR lacks any analysis or discussion about the current degraded riparian and aquatic habitat conditions along the Dykstra levee project areas and the existing impaired water quality. The existing Dykstra levee is deficient for riparian shade, future wood recruitment, and the adjacent sections of the Green River have inadequate aquatic habitat for salmon. These conditions were fully analyzed in King County’s approved 2019 Green River System Wide Improvement Framework Report and its Appendix A: 2014 Final Aquatic, Floodplain, and Riparian Habitat Technical Memo. This SWIF Report is cited in the CAR; however, none of its findings and recommendations regarding riparian and aquatic habitat are used in this project’s impact analysis. The Dykstra sites fall within Reach 3 of the SWIF report. The existing conditions in Reach 3 are described as having the majority of area with fair (56%) or good (24%) shade conditions, but also nearly 20% of the reach has poor shade conditions, both along the PL84-99 levee system #5 and other areas. Figure 4-24 in the 2014 Tech Memo shows the lack of existing shade producing vegetation in the project areas and Figure 5-8 (page 5-10) shows the Current Effective Shade Conditions for the project area as fair to poor for the project sites. This matters because this section of the Green River is between two adjacent reaches listed as temperature impaired in Washington’s 303(d) list (segments 48624 and 48625). The Washington Department of Ecology’s Green River Temperature Total Maximum Daily Load (TMDL) Water Quality Improvement Report (2011) found that the Dykstra levee area (between 8 th Street NE and 277th Street 311 of 336 Muckleshoot Indian Tribe Fisheries Division Habitat Program July 31, 2020 Dykstra Levee Modifications SEPA and Shoreline Comments Page 5 of 6 Bridge) exceeded the 16 degrees C State water quality standard by almost 5 degrees C based on data collected for the study in 2006. To address the water quality exceedances, the TMDL report recommended planting a continuous 150 foot wide riparian buffer of trees 104 feet or taller from river mile 60 downstream. The 2014 Habitat Tech Memo states “Notable locations identified as critically important for shade in Reach 3 include the majority of the left bank from RM 26 to 29, RM29.2 to 29.8, RM 30 to 30.5, and the majority of the left bank from RM 30.7 to 33. All three of the Dykstra levee project sites are found within these locations of Reach 3. Improving shade conditions is the sole approach recommended to improve water temperatures in the Green River. This is important because typical lower river summer temperatures are in the range of those causing severe infections of warm water-related bacterial and parasitic diseases in salmon and trout leading to pre-spawning mortality (EPA 2001). Based on unpublished data collected by MIT Fisheries staff, 10 percent of female Chinook carcasses sampled in the Green River had died before releasing their eggs, while 67 percent of those sampled in lower Soos Creek also died before spawning in 2014. Given the declining Chinook and steelhead populations in the Green River, it is essential to change current riparian conditions along the Green River, including the project sites. In fact, the 2019 SWIF report states that “Vegetation management to improve habitat and water quality in the Lower Green Rivers is very important to the recovery of Chinook salmon that tend to spend all of their time in freshwater in the mainstem Green River.” Aquatic habitat is also degraded in this portion of the Green River. As noted in the 2014 Habitat Tech Memo, this section of the Green River (RM 26 to 34) lacks pools and wood jams (see Figure 4-7 from the 2014 Memo). Only 5% of this reach had habitat that classified as pools whereas farther upstream in the middle Green River; pools comprise 27% percent of the river habitat. Further, deep pools (>= 8 feet) were noted to be “extremely rare in the project reach and limited in size.” The Dykstra levee is within the Green River spawning distribution for ESA listed Chinook salmon and the lack of pools is a concern for both adult and juvenile Chinook and other salmon species. Trees planted in the currently denuded riparian areas along the Dykstra levee can be a source of future wood recruitment that in turn creates pools, cover, velocity refuge, and other habitats used by adult and juvenile salmon and steelhead in the Green River. As proposed, the Dykstra levee modifications will perpetuate unfavorable conditions for salmon in this reach of the Green River. The levee fill with be mostly comprised of rock, which presents challenges for riparian trees to grow to functional sizes. The block retaining walls on the landward side of the levees will also preclude tree growth, and will help maintain a steep face on the waterward side that will offer few areas of slow-water margin habitat for fish to seek velocity refuge. The levee project should be redesigned to include soil lifts or benches with adequate material to plant and grow trees and survive floods. This may require easements or property acquisitions to do so. 312 of 336 Muckleshoot Indian Tribe Fisheries Division Habitat Program July 31, 2020 Dykstra Levee Modifications SEPA and Shoreline Comments Page 6 of 6 References: Environmental Protection Agency 2001: Water Quality Temperature Issue Paper 4 https://www.epa.gov/sites/production/files/2018-01/documents/r10-water-quality-temperature-issue-paper4-2001.pdf King County 2019 Green River System Wide Improvement Framework Report https://kingcounty.legistar.com/LegislationDetail.aspx?ID=3871123&GUID=F72499B6-CB4B-469C-BA18-98FFF80CDA40 Washington Department of Ecology 2011. Green River Temperature Total Maximum Daily Load Water Quality Improvement Report. https://kingcounty.legistar.com/LegislationDetail.aspx?ID=3871123&GUID=F72499B6-CB4B-469C-BA18-98FFF80CDA40 313 of 336 314 of 336 315 of 336 316 of 336 317 of 336 318 of 336 319 of 336 1 Dustin Lawrence From:JM Diebag <diebag.jm@gmail.com> Sent:Monday, July 20, 2020 7:02 PM To:Planning-1 Subject:King County Dykstra Levee Improvement Project Sep 20-0008 CAUTION: The following message originated from outside the City of Auburn. Be careful opening links and attachments Mr. Lawerence, This morning I was contacted via phone by Jay Young, the King County Senior Engineer on the King County Dykstra Levee Improvement Project Sep 20-0008. I had seen the yellow sign of Notice of Application and Determination posted at the fisherman's access point on Riverview Drive and left him a message on 07/17/20 regarding Area C of the project. Also, I left you a message last Friday, 07/17/20, and was contacted by one of your colleagues this morning instructing me to communicate with you via email. So, I want to confirm with the City of Auburn what Mr. Young shared with me regarding where "...the additional fill..." will be placed to the existing levee. Please see copied email below: Dear Mr. Young, Thank you for the return phone call today, 07/20/20, regarding the King County Dykstra Levee Improvement Project Sep 20-0008 in Auburn, WA. I want to reconfirm some information that I heard over our telephone conversation: 1. 1202 Pike Street NE is located in the Lone's 3rd Addition to Auburn and is not a part of the Dykstra Levee Improvement Project Sep 20-0008. 2. The Dykstra Levee Improvement Project 20-0008, AREA C begins at the property of 1126 Pike Street NE. I look forward to receiving your confirmation of this information. Sincerely, Melinda Diebag I look forward to hearing from you regarding this information so that I am assured that my property is not a part of this improvement project. Sincerely, Melinda Diebag 320 of 336 Water and Land Resources Division Department of Natural Resources and Parks King Street Center 201 South Jackson Street, Suite 5600 Seattle, WA 98104-3855 206-477-4800 Fax 206-296-0192 TTY Relay: 711 January 8, 2021 Martin Fox, PhD Muckleshoot Indian Tribe 39015 172nd Avenue Southeast Auburn, WA 98092 RE: Muckleshoot Indian Tribe Fisheries Division King County Dykstra Levee Repair Project, Notice of Application and Determination of Non-Significance (DNS), SEP20-0008 and SHL20-0004 comment letter, submitted to the City of Auburn, dated July 31, 2020 Dear Dr. Fox: Thank you for your response letter to the City of Auburn on our Notice of Application for our Shoreline Substantial Development Permit and Determination of Non-Significance (DNS) under SEPA (State Environmental Protection Act). We have reviewed the detailed and thoughtful comments on the King County Dykstra Levee Repair Project that Karen Walter submitted to the City of Auburn on behalf of the Muckleshoot Indian Tribe. In response, we have carefully considered these comments and revised our submittal materials (plans and supporting documentation) for our Shoreline Substantial Development Permit and SEPA review with the City of Auburn. We are also pursuing new easements to include additional riparian plantings in response to your comments and to increase consistency with the Lower Green System Wide Improvement Framework (SWIF) within the scope of this Interim Risk Reduction Measure (IRRM) project. The revised plans include the riparian plantings. At the request of the City of Auburn, King County initiated a feasibility study in 2019 to evaluate the existing levee heights and stability to ensure the levee functions as designed and provides a uniform level of flood risk reduction to the homes in the neighborhood and commercial areas in Auburn. The study identified three areas (A, B and C) along the existing levee that compromise the level of flood risk reduction, due to inadequate freeboard. Implementation of this IRRM will address near term vulnerabilities. Ms. Walter identified several omissions of technical information in King County’s SEPA checklist prepared for the proposal. We have updated the SEPA checklist to include additional background on ongoing bank erosion and previous bank repair work in the project area. Our geotechnical report was focused on evaluating levee stability and to provide geotechnical 321 of 336 Martin Fox, PhD January 8, 2021 Page 2 recommendations for design of the proposed correction action at the identified low spots. The observation about bank erosion made in the report is specific to the project area and not a generalization of conditions throughout the Green River. The report was updated to note previous bank repair work in the vicinity of the current proposal. We also added details in the SEPA checklist to support our statement that all work is at an elevation above the 100-year floodplain. The elevations used to delineate the 100-year floodplain were obtained from the Flood Insurance Study for King County and plotted against surveyed elevations of the waterward and landward levee crests, and levee centerline of the Dykstra levee. Profiles of these surveyed elevations and the 100-year flood elevation provided in our updated plan set demonstrate that all the proposed work is in areas above the floodplain elevation. Finally, we added discussion of the mapped channel migration zone in the SEPA checklist. As was discussed in the Critical Areas Report and Habitat Impact Assessment submitted to the City, channel migration processes will not be altered by the proposal to add fill to the three identified low sections of the Dykstra levee to provide a uniform level of flood containment. The levee face is currently armored with large rock to resist channel migration. The work to increase the height of the levee in three low sections will not affect channel migration processes. The remainder of Ms. Walter’s comments outline various aspects of habitat degradation in the Green River, including channel narrowing and incision, water quality and riparian shade and wood recruitment deficiencies, water temperature conditions, and a of lack pools and wood jams that create favorable habitat for salmon. The Dykstra Levee and other flood facilities along the Green River have contributed to these conditions, which have adversely impacted salmon populations. While our view is that the current proposal to minimally modify the Dykstra levee crest elevation will not in itself exacerbate the currently existing degraded habitat conditions in the Green River, we acknowledge and respect the notion of Ms. Walter that such levee improvement work “…will perpetuate unfavorable conditions for salmon in this reach of the Green River.” Ms. Walter urges consideration of alternatives other than adding fill, specifically a levee setback, which could allow rectification of some of the geomorphic factors causing habitat degradation that may be attributable to levees. You reiterated this view that a levee setback is the approach favored by the Muckleshoot Indian Tribe at our site meeting on November 22, 2020. Planning for longer term more comprehensive levee improvements that address flood risk and broader objectives, including consideration of levee setbacks is being pursued by the King County Flood Control District through a SEPA Programmatic Environmental Impact Statement (EIS). We understand there will be multiple engagement opportunities as part of the Lower Green River corridor planning effort, and we look forward to considering longer term multi- benefit solutions throughout the Lower Green River as part of this process. A setback option would likely take years of planning and studies, acquisition of dozens of private parcels, which may not have owners willing to sell, and allocated funds, which we do not currently have. We have been able to directly address Ms. Walter’s comments that our original proposal did not include measures to rectify the current deficiencies in riparian shade and future wood recruitment along the Dykstra levee. As was noted, improving riparian shade conditions is recommended in 322 of 336 Martin Fox, PhD January 8, 2021 Page 3 the Washington Department of Ecology’s Green River Temperature Total Maximum Daily Load (TMDL) Water Quality Improvement Report (2011) to improve water temperatures in the Green River. Identifying opportunities for restoration and enhancement including riparian vegetation improvements was also identified as part of the SWIF (2019). We have negotiated with riparian property owners along “Area A” where a large bench has formed along the toe of the levee. We are in the process of procuring easements to allow planting of native trees and shrubs in this approximately three-fourths-acre area. This area is identified as critical for shade on the MIT’s sun analysis maps due to its southern exposure. We have prepared a preliminary planting plan that proposes addition of 59 trees and 1,464 shrubs. Proposed trees species are predominately fast-growing species, such as black cottonwood and red alder, which will rapidly contribute to riparian shade and large wood recruitment over a longer timeframe. As discussed at our site meeting, we have considered adding unanchored large wood as habitat features in the planting area. After consulting with City of Auburn staff, we have been advised that the City of Auburn Floodplain Development Management Code (Chapter 15.68) does not have a viable permitting path for placement of materials or structures, even for habitat enhancement purposes, in the floodway. The City, itself, is evidently struggling with this issue with one of their own projects. The FEMA August 2020 rescindment of FEMA Region X Policy on Fish Enhancement Structures in the Floodway is an additional challenge. For these reasons, we have concluded that it is not feasible for us to include a large wood placement component with our current project. Thank you again for meeting with us at the site and for reviewing our response to Ms. Walter’s comment letter. We hope you are pleased that we have been able to add on the revegetation component to our project. We believe that, over time, this action will significantly improve habitat in the project area. We will continue to look for opportunities for restoration and enhancement including riparian vegetation improvements and placement of large wood along the Green River as identified in the SWIF. We also hope you understand that, while a setback levee to replace the Dykstra levee is not currently feasible, it is our understanding that such multiple benefit floodplain management solutions will be evaluated by the King County Flood Control District in the Lower Green River corridor planning effort, which will guide decisions on future capital improvement projects. Please consider our explanation in this letter, our revised plans, which include the above- mentioned revegetation plan, our revised SEPA checklist, and revised Critical Area Report and Habitat Impact Assessment. We hope our response satisfactorily addresses the Muckleshoot Indian Tribe’s comments on the repair project. We intend to resubmit our permit package by the end of January to meet our targeted implementation of the revised Dykstra Levee Repair project in spring 2021. 323 of 336 Martin Fox, PhD January 8, 2021 Page 4 Please do not hesitate to contact me at jay.young@kingcounty.gov or (206) 477-4858 if you have any questions. Best Regards, Jay Young, Senior Engineer King County Water and Land Resource Division cc: Dustin Lawrence, Senior Planner, City of Auburn Department of Community Development Shannon Howard, Development Review Engineer, City of Auburn Department of Community Development Lorin Reinelt, Managing Engineer, King County Water and Land Resource Division Seth Amrhein, Senior Ecologist, King County Water and Land Resource Division 324 of 336 2/25/2021 2Q== (250×906) data:image/jpg;base64,/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAQCAwMDAgQDAwMEBAQEBQkGBQUFBQsICAYJDQsNDQ0LDAwOEBQRDg…1/1 325 of 336 3/31/2021 GSjOWBkwZFyhvmm6hYrmpevPyDrChCm+MEnyljmUMhhHSGVTGc55FbWxsHBwcnIZFpM+ysrGXKdPJ6JSy1JkyffP6f6wRwGjb6KSg… data:image/jpg;base64,iVBORw0KGgoAAAANSUhEUgAAASkAAAM7CAIAAACZevFsAAAAAXNSR0IArs4c6QAAAAlwSFlzAAALEwAACxMBAJqcGA…1/1 326 of 336 AFFIDAVIT OF POSTING OF LEGAL NOTICE BY APPLICANT Application Number: SEP20-0008 Applicant: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Owner: Various property owners, led by: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Location: The project is located along the left bank of the Green River, between 26th St NE and 8th St NE Closing Date for Public Comments: March 13, 2021 I certify that on _February 25th, 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. Seth Amrhein March 1st, 2012 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. 327 of 336 AFFIDAVIT OF POSTING OF LEGAL NOTICE BY APPLICANT Application Number: SHL20-0004 Applicant: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Owner: Various property owners, led by: King County, Department of Natural Resources KSC-NR-0600 Seattle, WA 98104 Location: The project is located along the left bank of the Green River, between 26th St NE and 8th St NE Closing Date for Public Comments: March 13, 2021 I certify that on __April 7, 2021_______ I did erect a land use posting board at the location above, which included a Notice of Public Hearing 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. Seth Amrhein 4/7/2021 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. 328 of 336 329 of 336 330 of 336 331 of 336 332 of 336 333 of 336 334 of 336 335 of 336 336 of 336