Chinook Wind Mitigation Plan Set Attached to This Document (Attachment 1) and Included by Reference

IN LIEU FEE MITIGATION PLAN CHINOOK WIND MITIGATION PROJECT

Department of Natural Resources and Parks Water and Land Resources Division Capital Projects Section 201 South Jackson Street, Suite 5600 Seattle, Washington 98104-3855

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IN LIEU FEE MITIGATION PLAN CHINOOK WIND MITIGATION PROJECT

Prepared for:

US Army Corps of Engineers as Chair of the Interagency Review Team

for a project to be implemented by:

The King County Mitigation Reserves Program

Prepared by:

Mason Bowles, P.W.S., Senior Ecologist Anne-Gigi Chan, ILF Program Support Scott Muchard P.E., Senior Engineer Laird O’Rollins, Project Manager, Senior Ecologist Megan Webb, ILF Program Manager King County Department of Natural Resources and Parks

February 18, 2021

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In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - ii -

Executive Summary

The Chinook Wind Mitigation Project (CW Mitigation Project) is located on the right bank of the Duwamish River upstream of Tukwila International Boulevard in the City of Tukwila, within the King County In-Lieu Fee Program’s Central Puget Sound Service Area. The CW Mitigation Project will establish wetland and aquatic habitat to provide rearing and refuge habitat for juvenile salmonids, particularly Chinook salmon and steelhead; and restore floodplain functions along the Duwamish River

The project will establish 5.88 acres of riparian, high marsh, low marsh, mudflat and aquatic habitat. 3.98 acres will be creditable, including 0.05 acre of riparian habitat, 1.12 acres of high marsh, 1.14 acres of low marsh, 0.57 acre of mudflat, and 1.10 acres of aquatic habitat. A buffer of at least 50 feet will be established between the site boundaries and credited wetland and aquatic habitat. Persistent tidally-inundated fish habitat, aquatic edge, and low and high marsh will be established without incorporating steep slopes (nothing greater than 6:1 slopes).

The CW Mitigation Project is designed to provide increased ecological function within the landscape setting. The CW Mitigation Project is intended to re-establish wetland ecosystem processes, intertidal wetlands and aquatic habitat to provide forage and refuge habitat for Chinook salmon smolts.

This in-lieu fee mitigation site will offset unavoidable impacts in the Central Puget Sound and Green River-Duwamish service areas. The CW Mitigation Project will be monitored for successful achievement of performance standards for 10 years after construction. After successful achievement of the performance standards, the CW Mitigation Project will earn up to 9.60 in-lieu fee credits using an area-based method, not the Credit/Debit Method. All credits will be released over time as performance standards are met.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - iii -

Table of Contents

Executive Summary ...... iii Introduction ...... 7 A. Overview ...... 7 B. Impacts Being Mitigated ...... 7 C. Credit Generation ...... 8 D. Transfer of Obligations ...... 8 Goals and Objectives ...... 8 Mitigation Project Overview ...... 9 A. Location ...... 9 B. Chinook Wind Habitat Types ...... 11 C. Duwamish River Basin ...... 13 Site Selection ...... 14 A. Site Selection Process ...... 15 B. Mitigation Site Options ...... 15 C. Watershed Plans ...... 17 D. Watershed Threats Addressed by the CW Mitigation Project ...... 21 E. Likelihood of Success ...... 22 F. Nearby Mitigation and Restoration Projects ...... 24 G. Site Perimeter Protection ...... 24 Baseline Conditions ...... 24 A. Historic Land Use ...... 25 B. Duwamish River ...... 26 C. Wetlands ...... 27 D. Uplands ...... 27 E. Fish ...... 28 F. Wildlife ...... 28 G. Water Quality ...... 28 H. Soils...... 28 Mitigation Work Plan ...... 29 A. Contaminated Soils Clean-Up...... 29 B. Wetland Establishment ...... 30 C. Backwater Channel ...... 38 D. Large Wood ...... 38 E. Anticipated Effect of Sediments ...... 40 F. Perimeter Pedestrian Trail and Easement ...... 40 G. Signage/Access ...... 40 Determination of Mitigation Credit ...... 41 H. Credit Methodology ...... 42 A. Ratios ...... 42 B. Impacts ...... 42

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - iv - C. Resource Tradeoffs ...... 44 D. Non Credit-Debit Impacts ...... 44 Performance Standards ...... 47 Monitoring Methods ...... 53 A. Reporting...... 56 Maintenance plan ...... 57 Credit Release Schedule ...... 59 Adaptive Management Plan ...... 60 Site Protection ...... 62 Long Term Management Plan ...... 62 Financial Assurances ...... 64 Force Majeure ...... 64 Implementation ...... 65 A. Responsible Parties ...... 65 B. Reporting...... 65 C. Access ...... 66 References ...... 67

List of Figures

Figure 1 Vicinity Map ...... 71

Figure 2 Regulatory Buffers and Mitigation Credit Area ...... 72

Figure 3 Chinook Wind Area Public Land ...... 73

Figure 4 Known Duwamish River Mitigation and Restoration Projects ...... 74

Figure 5 Baseline Conditions After Demolition ...... 75

Figure 6 Duwamish Estuary Channel and Landcover Comparison (Source: King County Water and Land Resources Division 2005)...... 76

Figure 7 Duwamish River Valley Landcover circa 1865 (Source: Collins and Sheikh 2005)77

Figure 8 Large Wood and Habitat Features ...... 78

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - v - List of Tables

Table 1: Bank Boundary, Non-credit Generating and Perimeter Buffer Acreages ...... 11

Table 2: Proposed Habitat Types and Acreages ...... 11

Table 3 Challenges & Opportunities for habitat restoration in the Duwamish transition zone...... 18

Table 4 Riparian (Dry) Plant Species ...... 35

Table 5 Riparian (Moist) Plant Species ...... 36

Table 6 High Marsh Plant Species ...... 36

Table 7 High Marsh Seed Mix ...... 37

Table 8 Low Marsh Plant Species ...... 37

Table 9 Low Marsh Seed Mix ...... 37

Table 10 Low Marsh Wetland Sod ...... 38

Table 11 Chinook Wind Credit Generation ...... 42

Table 12 Example Compensation Calculations ...... 43

Table 13 Credit Release Schedule ...... 59

Table 14 Example Adaptive Management Strategies ...... 61

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - vi - Introduction

A. Overview The purpose of this Mitigation Plan is to describe the details of the Chinook Wind Mitigation Project (CW Mitigation Project), which will establish intertidal wetland and aquatic habitat to provide rearing and refuge habitat for juvenile salmonids, particularly Chinook salmon and steelhead; and restore floodplain functions along the Duwamish River.

The CW Mitigation Project will be implemented under King County’s In-Lieu Fee (ILF) Program, the Mitigation Reserves Program (ILF Program or KC MRP) by King County to provide compensatory mitigation for unavoidable impacts associated with permitted projects elsewhere in the Green River/Duwamish and Central Puget Sound service areas.

King County strives to implement projects that are appropriately designed for the landscape setting for maximum ecological success. Complex habitat is intentionally designed to restore processes and add habitat suitable for salmonids. The CW Mitigation Project will establish 5.88 acres of riparian, intertidal high and low marsh, mudflat, and aquatic habitats to provide forage and refuge habitat benefiting juvenile Chinook salmon, steelhead trout and other salmonid species that migrate through the Duwamish River. 3.98 of these acres will be credit generating.

This Mitigation Plan, in its entirety, will be appended to the King County Mitigation Reserves Program – In Lieu Fee Program Instrument.

B. Impacts Being Mitigated The CW Mitigation Project will offset impacts associated with the following impact projects:

• Integrity Homes: Terrace at Male Woods, NWS-2013-1199 • Sound Transit: South Sounder Easement #3, NWS-2013-0921 • Des Moines Creek Business Park Phase I, NWS-2014-154 • Sound Transit: South Sounder Easement # 4, NWS-2013-922 • Gregory Real Estate Three, LLC: Pacific Heights, WA DOE Admin Order 11654 • Lennar Northwest, Inc.: Addison Park, NWS-2016-309 • North Auburn Logistics Holdings: N. Auburn Logistics Commercial, NWS-2014-0928 • Des Moines Creek Business Park Phase III, NWS-2014-154 • King County: Kent Auburn Conveyance System, NWS-2015-256 • British Petroleum: BP Seattle Bulkhead Replacement, NWS-2011-761 • Eagle Creek Land: The Ridge, Kent KIVA RECR-2162729 • Kent 234 PPF, NWS-2016-574 • Boeing: South Oxbow Bridge, Tukwila SEPA Exemption A17-0019 • Auburn School District: Evergreen Heights Elementary, Auburn GRA14-0034 • Seattle Public Utilities: Puget Way SW Culvert, NWS-2013-604-WRD • O’Keefe Development: DC 192 Warehouse, Kent KIVA RECR-2170804 • Harbour Homes, LLC: Breimer Bluff, Kent KIVA RECC-2175086 • BPA: Tacoma-Covington Access Maintenance, NWS-2017-1116 • King County: Kent Auburn Conveyance System Additional, NWS-2015-256 • Fort Dent Real Estate: King Lasik, NWS-2017-421 • Harbour Homes, LLC: Breimer Bluff Ph. II, NWS-2017-275 In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 7 - • Luzee Properties LLC: Luzee Short Plat, WA DOE Admin Order 16184 • Sound Transit: Federal Way Link Extension, NWS-2013-687 • Auburn School District: Elementary School No. 16, NWS-2019-08 • King County: Georgetown Wet Weather Treatment Station, Seattle 3022084 • Muckleshoot Indian Tribe: Tribal Fishing Facility, NWS-2018-336 • Prologis: Prologis Park Auburn 12, NWS-2019-70 • KBHPNW, LLC, Sunrise View South, NWS-2019-161, Kent RECR-21900559 • KBHPNW, LLC, Fox Subdivision, NWS-2020-676, Kent RECR-2180266

Additional impact projects may be assigned to the CW Mitigation Project with Interagency Review Team (IRT) approval. Impact projects with elements that were not originally calculated using the Washington State Department of Ecology’s Calculating Credits and Debits for Compensatory Mitigation in Wetlands of Western Washington are further described in Section VII. E.

C. Credit Generation The CW Mitigation Project includes 3.98 acres of creditable area, including 0.05 acre of riparian habitat, 1.12 acres of high marsh, 1.14 acres of low marsh, 0.57 acre of mudflat, and 1.10 acres of aquatic habitat. Habitat types are defined in Section III.B. The CW Mitigation Project is not eligible to use the Washington State Department of Ecology’s Calculating Credits and Debits for Compensatory Mitigation in Wetlands of Western Washington (the Credit/Debit Method) because the wetlands at this site are categorized as estuarine. Credits will be calculated at the CW Mitigation Project using an area-based method with ratios associated with the habitat type and the type and category of wetland impacted.

Credit generation at the CW Mitigation Project is intended to offset impacts associated with the projects listed in Section I. B., however, surplus credits generated by the site may be used to offset other impacts in the service areas. Attribution of surplus mitigation credit to impact projects will be coordinated with the IRT.

D. Transfer of Obligations Responsibility for completing the mitigation has been transferred to King County via agreements with impact projects listed in Section I. B. through King County’s federally and state authorized ILF Program.

King County issued a Statement of Sale for each ILF purchase. Statements of Sale are on file with the KC MRP, as well as regulatory agencies. Goals and Objectives

The CW Mitigation Project is designed to meet the following goals and objectives.

Goal 1. Establish and protect wetland and aquatic functions at the Chinook Wind Mitigation Project.

Objective 1.1. Permanently protect riparian, wetland, and aquatic ecosystem functions through recordation of permanent legal protections.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 8 - Objective 1.2. Build project elements according to IRT-approved plans.

Goal 2. Establish riparian, intertidal high marsh, intertidal low marsh, mudflat, and aquatic habitats within the Lower Duwamish River.

Objective 2.1. Create intertidal wetland, mudflat, and aquatic area at the CW Mitigation Project. Objective 2.2. Establish native vegetation in wetland areas. Objective 2.3. Establish native vegetation in riparian areas. Objective 2.4. Maintain a mitigation site that is dominated by native vegetation through management of non-native and noxious weeds.

Goal 3. Increase aquatic habitat functions and availability for fish and wildlife by creating and maintaining persistently inundated off-channel features.

Objective 3.1. Create a fish passable backwater channel with an outlet elevation that is passable by fish during most tides.

Objective 3.2. Survey the backwater channel for juvenile salmonids between March 1 and May 31.

Objective 3.3. Place and retain large wood that can provide cover for fish and wildlife and habitat for invertebrate production.

Objective 3.4. Minimize impact of public access components on mitigation components by maintaining separation and controlling non-native vegetation.

Mitigation Project Overview

King County proposes to establish riparian, temperate Pacific tidal salt and brackish high and low marsh, mudflat and aquatic habitat on the Duwamish River. The total property is 5.88 acres, with wetland mitigation project features totaling over 4.21 acres (Table 1: Bank Boundary, Non- credit Generating and Perimeter Buffer Acreages

, Table 2, Figure 2). Mitigation actions are detailed on the Chinook Wind Mitigation Plan Set attached to this document (Attachment 1) and included by reference.

A. Location The CW Project is located within the Duwamish River sub-basin (WRIA 9) within of the City of Tukwila; latitude 47.50154° North, longitude -122.29358° West The property address is 11244 Tukwila International Boulevard, Tukwila 98168 (Figure 1). The site is located in a reach of the Duwamish – the transition zone – where salt and freshwater mix. This reach is listed as the highest priority for restoration in the WRIA 9 Salmon Habitat Plan (WRIA 9 Steering Committee 2005) (“the Habitat Plan”).

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 9 - The CW Mitigation Project is located on the right (east) bank of the Duwamish River at river mile (RM) 6.7 within the North Wind Reach of the Duwamish River which extends from RM 5.5 to RM 7. The CW Mitigation Project is located upstream of the Lower Duwamish Waterway Superfund site, which extends from the mouth to RM 5.5. The CW Mitigation Project is located within the ‘transition zone’ of the Duwamish River which extends from RM 1 to RM 10. The transition zone is tidally influenced and has seasonally variable salinities. It is considered the most important reach of the Duwamish River for juvenile fish making the physiological transition from freshwater to salt water as they migrate to Puget Sound from their natal streams.

The CW Mitigation Project consists of approximately 678 lineal feet of shoreline and a 2:1 bank that slopes down to the Duwamish River which supports a narrow band of riparian vegetation (Figure 2). The Duwamish River is approximately 170 feet wide adjacent to the property. The Duwamish Gardens Park is located approximately 235 feet upstream of the project site.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 10 - Table 1: Bank Boundary, Non-credit Generating and Perimeter Buffer Acreages

Table 2: Proposed Habitat Types and Acreages

Action Other Non-creditable Creditable Perimeter Non-creditable Totals Habitat Type Buffers area Creation/Re-establishment Aquatic (Estuarine Subtidal Unconsolidated Bottom 1.10 0 0 1.1 and Estuarine Intertidal Unconsolidated Shore) Creation/Re-establishment Mudflat 0.57 0 0 0.57 (Estuarine Intertidal Unconsolidated Shore) Creation/Re-establishment Low Marsh 1.14 0.02 0 1.16 (Estuarine Intertidal Emergent Wetland) Creation/Re-establishment High Marsh 1.12 0.26 0 1.38 (Estuarine Intertidal Emergent Wetland) Enhancement Riparian 0.05 1.11 0 1.16 (Upland) Trail Easement within the Protection 0 0.51 0 0.51 Perimeter Total 3.98 1.9 0 5.88 Totals By Habitat Category Total Aquatic Resource 3.93 0.28 0 4.21 Creation/Re-establishment Total Upland Enhancement 0.05 1.62 0 1.67 Total 5.88

B. Chinook Wind Habitat Types

The CW Mitigation Project includes habitat types, sizes, and configurations that were selected to specifically provide the most needed resources in the Duwamish River. The CW Mitigation Project’s location offers a unique opportunity to create and re-establish high quality intertidal estuarine wetlands and help address limiting factors for juvenile Chinook salmon. Intertidal mudflats and marsh are important habitat for juvenile Chinook rearing and juvenile Chinook need shallow low velocity habitats available at low tides and access to shallow off- channel areas. Ideal habitats appear to be large areas with gentle intertidal mudflat slopes that are protected from currents and provide refuge during low tides. The CW Mitigation Project was designed to provide these ideal habitats that are severely limited.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 11 - Due to its location in the transition zone between freshwater and saltwater, the salinity levels are expected to be variable at the CW Mitigation Project site. According to data collected at the United States Geological Survey (USGS) gage located on the right bank at the East Marginal Way Bridge, just upstream for the site, salinity could range from 0 to 26 ppt (USGS, 2020). Such variability is a result of both tidal and seasonal influences (McKeon et al, 2020). Salinity varies throughout the day and is highest during high tides. Salt-wedge excursion (salinity ≥ 25 ppt) is noted during low flows in the summer at high tides (Taylor et al., 2012; USGS, 2020). Native species with low to high salinity tolerance, such as tufted hairgrass (Deschampsia cespitosa), Lyngbye’s sedge (Carex lyngbyei), and Douglas aster (Symphyotrichum subspicatum), were planted at two nearby restoration sites, Duwamish Gardens and Northwind's Weir (NWW), just upstream and downstream, respectively, from the CW Mitigation Project Site. The year 5 monitoring report of NWW shows that not only did the planted species established well, a number of unplanted salt tolerant species, including western grasswort (Lilaeopsus occidentalis) and needle spikerush (Eleocharis acicularis), also established naturally at the site. For these reasons, salt tolerant species have been selected that will be able to tolerate both freshwater and saltwater influence. According to the Duwamish Blueprint, “the habitat feature most needed in the Duwamish above RM 5.5 from a salmonid perspective is shallow-water, off-channel habitats where juvenile salmonids can shelter, hold in low-salinity water, and feed (Ruggerone et al. 2006). Ideally, these habitats would feature a relatively shallow grade, a silt/clay to fine sand substrate, and be ringed with emergent vegetation and mixed riparian in the uplands” (Duwamish Blueprint, 2014).

Aquatic

Aquatic habitat at the CW Mitigation Project includes those areas that are less than elevation 3’ North American Vertical Datum of 1988 (NAVD88). These areas will be persistently inundated during the season in which juvenile Chinook salmon will be present in the area (February through May) and provide critically important habitat for Endangered Species Act listed (ESA- listed) juvenile Chinook. Areas below elevation 0’ NAVD88 will be inundated close to 100% of the time February through May. Under the Cowardin Classification, this habitat is classified as unconsolidated subtidal bottom and unconsolidated intertidal shore. When not inundated aquatic areas will function as mudflat. This habitat type, along with mudflat habitat are extremely limited in the Duwamish River system and have been identified as the most needed habitats in the Duwamish River.

Mudflat

Mudflat habitat at the CW Mitigation Project includes those areas that are between elevation 3’ NAVD88 and vegetated low marsh areas at approximately elevation 5’ NAVD88. Mudflat areas will be inundated 50% to 75% of the time during which juvenile Chinook salmon use the system. Under the Cowardin Classification, this habitat is classified as unconsolidated intertidal shore. These areas will not support vegetation, but are highly biologically productive, providing nutrients and habitat for macroinvertebrates, bivalves, etc., and are important in the food chain that supports salmon, including ESA-listed juvenile Chinook, and other aquatic species.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 12 - Low Marsh

Low marsh habitat at the CW Mitigation Project include those areas that are between elevation 5’ and elevation 7.5’ NAVD88. Under the Cowardin Classification, this wetland habitat is classified as estuarine intertidal emergent wetland. Low marsh areas will support saltwater tolerant plant species such as various bulrush species (Schoenoplectus species), Lyngbye's sedge (Carex lyngbyei) and common spikerush (Eleocharus palustris). These areas are highly productive of macroinvertebrates that serve as prey species for juvenile salmon and provide excellent habitat for those salmon when inundated.

High Marsh

High marsh habitat at the CW Mitigation Project include those areas that are between elevation 7.5’ and elevation 10’ NAVD88. Under the Cowardin Classification, this wetland habitat is classified as estuarine intertidal emergent wetland. High marsh areas are occasionally flooded and support plant species such as tufted hairgrass (Deschampsia cespitosa), Douglas aster (Symphyotrichum subspicatum) and Pacific silverweed (Argentina egedii). These areas are highly productive of macroinvertebrates and, when inundated, can provide excellent habitat for juvenile salmonids. High marsh areas also provide habitat for birds and other terrestrial wildlife. Portions of the high marsh area at the CW Mitigation Project will also be planted with black cottonwood (Populus balsamifera), hookers willow (Salix hookeriana) and other scrub/shrub species.

Riparian

Riparian habitat at the CW Mitigation Project include those areas that are above elevation 10’ NAVD88. This habitat is upland and will rarely be inundated. Riparian habitat provides an important buffer to the adjacent wetlands and provides shade and microclimate regulation, as well as terrestrial wildlife habitat. Taller trees may also aid in discouraging geese. Riparian areas will be vegetated with a mix of shrubs, trees, and herbs. For planting purposes, riparian habitat is split between moist riparian areas closer to the wetland and dry riparian areas further away.

C. Duwamish River Basin The Duwamish Estuary is vitally important to the region, both as an integral ecological link between the Green River and Puget Sound and as a center of trade and commerce that supports local jobs and strengthens Washington’s economy. But decades of heavy industrial use in the Duwamish corridor has taken its toll. The WRIA 9 Salmon Habitat Plan notes that, “the Duwamish has lost 97% of the habitat it provided 150 years ago. The Duwamish also suffers from decades of industrial pollution that have resulted in the lower 5.5 miles of the river becoming an Environmental Protection Agency Superfund cleanup site. Scientific assessment work for th(e) Plan suggests that this loss, degradation, and fragmentation of estuarine habitat in the Duwamish – particularly transition zone habitat — is a limiting habitat factor for the Chinook populations of the (Green-Duwamish) watershed” (WRIA 9 Steering Committee 2005).

The Duwamish River Basin begins at the confluence with the Black River at RM 11 and extends downstream to the river mouth. This area is characterized primarily by industrial development (43 percent) and residential development (39 percent) (Ostergaard et al. 2014). The cities of Seattle and Tukwila, operations of the Port of Seattle (the fifth largest port in the U.S.), and the

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 13 - region’s largest industrial complexes are in this basin. The loss of estuarine and riparian habitat has been extensive in the lower portion of the Duwamish River Basin. The shoreline has been dramatically altered: only 19,000 feet of vegetated riparian shoreline remains in the Duwamish Estuary (Collins and Sheikh 2005). The once extensive 3,850 acres of tidal mudflats, marshes, and swamps have been reduced to only 25 acres. (USACE 1997). The Habitat Plan provides the following description of the Duwamish River Basin: The Duwamish Estuary has been dredged and channelized, and 97% of the estuarine mudflats, marshes, and forested riparian swamps have been filled. The Duwamish Estuary was filled between 1900 and 1940 to create Harbor Island and the East and West Waterways, largely to support industrial and shipping activities. Most of the lower five miles of the Duwamish has little or no native riparian vegetation remaining. Development patterns and land uses have also significantly polluted water and sediments in the remaining channel via stormwater and wastewater effluents and historic industrial contaminants. Development and shoreline modifications in the Duwamish, combined with river diversions upstream, have resulted in a reduction of transition zone habitat, the location where juvenile salmonids make the transition from fresh water to salt water. The almost complete loss of marshes and swamps has significantly reduced the ability of this part of the watershed to support juvenile rearing. Lack of riparian vegetation, extensive infestations of non-native plants, armoring, and piers mean that the shoreline habitat remaining is of poor quality. Taken together, these changes dramatically reduced the quality and quantity of estuarine habitat, which is particularly important to juvenile Chinook salmon. (WRIA 9 Steering Committee 2005)

Site Selection

As described in the Program Instrument, the KC MRP selects mitigation sites to address watershed needs as determined through best available science. Mitigation goals in a watershed context in the Central Puget Sound watershed are described in the Compensation Planning Framework in Appendix I, Section 6.0 of the King County Mitigation Reserves Program – In Lieu Fee Program Instrument (Program Instrument) (King County 2012). These goals include: • Protect existing undeveloped shoreline areas in WRIAs 8 and 9 from development practices that would be detrimental to the nearshore ecosystem and restore ecosystem processes and functions to the benefit of nearshore ecosystem health. • Protect eelgrass and macroalgae beds from the adverse effects of shoreline modifications such as dredging, filling, overwater structures, armoring, and pollution. • Protect and enhance marine riparian vegetation. • Protect forage fish spawning areas and other upper intertidal habitats and species. • Concentrate restoration and enhancement efforts on areas with shoreline armoring and other development practices that reduce ecological processes and functions that support habitat quality. • Develop a restoration strategy for the WRIA 8 and 9 nearshore that takes an ecosystem perspective within the landscape and helps to build our knowledge of the nearshore environment.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 14 - • Identify critical areas for protection, restoration, and enhancement in WRIAs 8 and 9. Then protect, restore, and enhance them. Considering that the shorelines of Vashon and Maury Islands are the least developed, concentrate protection efforts on them first, but do not exclude the mainland. • Recreate intertidal acreage such as marshes, flats, and other habitats. • Restore and recover estuarine intertidal flat and marsh habitat. Initial considerations should focus on appropriate salinity regimes and elevations but should also consider other ecosystem processes in developing a functional design.

Additionally, the Central Puget Sound watershed is threatened by limiting factors that have dramatically altered aquatic resource conditions and the processes that form and maintain them as described in the Compensation Planning Framework in Appendix I, Section 6.0 of the Program Instrument (King County 2012).

A. Site Selection Process KC MRP initiated a service area wide site selection process to evaluate mitigation opportunities in the Central Puget Sound Service Area. The focus of the site selection process began as an effort to identify mitigation sites suitable to compensate for the British Petroleum’s BP Seattle Distribution Terminal North Bulkhead Replacement project. Due to the proposed project’s location on the Duwamish West Waterway, the site selection focused on projects that could provide benefit to the Duwamish River. Geographic area experts within King County were interviewed to identify potential mitigation projects. King County staff considered the following to be the key factors in determining potential mitigation receiving sites (listed in order of relative importance): 1. Replacement of functions lost 2. Ability of a mitigation project to address watershed needs 3. Feasibility of implementing a project and at a chosen site 4. Geographic proximity of mitigation site to impact sites

King County staff thoroughly reviewed property ownership and potential mitigation receiving sites in the Duwamish River corridor.

B. Mitigation Site Options Initially public lands in the Duwamish River corridor were reviewed, but other Duwamish River corridor properties and a Green River Service Area property were also evaluated. Much of the Duwamish River corridor is valuable industrial property that is difficult to acquire without significant funding.

The following sites were considered during the review process:

Fisher-Pendleton Mill The Fisher-Pendleton Mill site is located in the City of Seattle, on the western shoreline of Harbor Island. The site is at the mouth of West Waterway of the Duwamish River as it flows into Elliot Bay. The Duwamish estuary plays a key role in the life history of salmon and is where juvenile salmon feed and adapt to salt water as they migrate from the freshwater habitats upstream. The site is also located within the Harbor Island Area Superfund Site, managed by the U.S. Environmental Protection Agency.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 15 - The Fisher-Pendleton Mill site is part of a 9-parcel King County-owned/leased property managed by the Solid Waste Division. The site consists of a dilapidated creosote pier located on leased State aquatic land. The pier is associated with the Fisher Flouring Mill, which opened on Harbor Island in 1911, and is, therefore, likely over a century old. Potential mitigation actions at this site include creosote pier/piling removal as well as habitat restoration, re-establishment, and/or creation. Initial review of the site identified a high likelihood of disturbing contaminated sediments due to its location within the Harbor Island Area Superfund Site.

Although sediment sampling would be completed prior to piling removal and should sediment contamination be present, pilings could be cut off and capped instead, the KC MRP felt the risks at this site were high and continued to analyze other potential sites.

Cecil Moses Memorial Park King County’s Cecil Moses Memorial Park is located on the left bank of the Duwamish River at RM 6.25, in the City of Tukwila. It is in the critical transition zone for juvenile salmon moving downstream to Puget Sound with an extensive tidal mixing of fresh and salt waters which allows juvenile salmon to adapt from the fresh water of the Duwamish River to the salt water of Puget Sound. Habitat restoration has previously taken place at the northeastern portion of the site, but further mitigation opportunities are available at the park. These include the removal of the tire revetment along approximately 200 feet of the river bank, restoration of the bank where the tire revetment is currently located, and creation of approximately 0.5 acre of new salt marsh habitat which would build on the existing restoration project.

DeMeerleer Property The DeMeerleer property is a privately-owned property in unincorporated King County, along SE Green Valley Road, west of the Green River at approximately RM 34, located within the Green River floodplain and adjacent to the Porter Levee Natural Area, but separated by SE Green Valley Road. This property is located in the Green River Service Area and was considered during the review process for impacts located in the Green River Service Area portion of Water Resource Inventory Area (WRIA) 9. The 13.3-acre site consists of a relatively undisturbed Category I wetland and two smaller disconnected wetlands. The buffers of all three wetlands are disturbed by agricultural land use, commercial development, roadway, and invasive vegetation. Proposed mitigation actions included acquisition of the property, permanent preservation of the existing forested, scrub-shrub, and emergent palustrine wetlands, and removal of fill and re- establishment of approximately 1.2 acres of wetlands.

Chinook Wind The Chinook Wind property was a privately-owned property on the right bank of the Duwamish River, at RM 6.7, in the City of Tukwila. The 5.88-acre property is located upstream of the Lower Duwamish Waterway Superfund site and in the transition zone of the Duwamish River, where it is tidally-influenced and the mixing of fresh and salt waters is extremely important to migrating juvenile salmonids. The site consisted of multiple hotel buildings constructed in the 1960’s and an associated asphalt parking lot, all of which were in poor condition. Proposed mitigation actions included acquisition of the property, demolition of the structures, removal of fill, and re-establishment of approximately 4.21 acres of wetland.

The Chinook Wind Mitigation Project emerged as a preferable mitigation site for several reasons:

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 16 - • The CW Mitigation Project will provide off-channel, shallow water habitat for resting, feeding and cover for juvenile Chinook salmon transitioning from fresh to salt water. • Off-channel and shallow water habitats at the CW Mitigation site will provide opportunities for juvenile fish to move out of the main channel to slow water areas where they can feed and grow. • This site is unique from all existing restoration sites in the Duwamish because it would accommodate a deep channel adjacent to mud flats, so that small fish would not be washed down into the main channel with every low tide. Longer residence times in the transition zone allow smolts to become larger prior to entering the Puget Sound, which is believed to increase their survival rates. • Lack of off-channel habitat has been shown to be the biggest hindrance to salmon recovery in the entire Green/Duwamish Watershed. • The 5.88-acre site provides a rare opportunity for a large-scale project on the Duwamish River where restoration opportunities are limited, and land costs are high.

C. Watershed Plans The CW Mitigation Project design consists of creating a variety of habitat types including aquatic, mudflat, low marsh, high marsh, and riparian habitats following recommendations from watershed planning documents. Although mitigation and restoration may be seen as fundamentally different, the Mitigation Rule (Fed. Register Vol.73. No.70, April 10, 2008) specifies that the watershed approach should be used in planning compensatory mitigation and says, “it would always be preferable to have an appropriate watershed plan”, “developed for the specific goal of aquatic resource restoration, establishment, enhancement, and preservation”. Mitigation projects proponents are also encouraged to consult watershed planning documents in Washington State Department of Ecology’s Selecting Wetland Mitigation Sites Using a Watershed Approach (Hruby et al. 2009) which says, “Where relevant watershed plans are available, mitigation sites should be located in areas targeted by those plans for restoring ecological processes”.

For the above reasons, watershed plans related to salmon recovery and natural resource damages in the Duwamish River were consulted when planning the CW Mitigation Project.

1. Duwamish Blueprint The Duwamish Blueprint (Blueprint) was first developed in 2006 to implement Program D-3 outlined in WRIA 9 Salmon Habitat Plan: Making Our Watershed Fit for a King (WRIA 9 Steering Committee 2005). The purpose of the Blueprint is to provide guidance to governments, businesses, and citizen groups as they improve the ecosystem of the Duwamish Estuary transition zone. The Blueprint is to be a working document where periodic refinement is expected to take into consideration any subsequent scientific findings on the nature and extent of the transition zone. In 2014, the Duwamish Blueprint Working Group updated the 2006 draft with information about the Superfund Cleanup and related mitigation efforts, scientific data, and experience implementing habitat projects on the Duwamish (Ostergaard et al. 2014).

According to the Blueprint, creating transition zone habitat is one of the most important conditions for the recovery of Chinook salmon populations in the Green/Duwamish River. The habitats in most limited supply within the Duwamish are intertidal mudflats and marshes (NOAA June 2013). These habitats are ecologically important food sources, rearing and refuge areas, and

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 17 - spawning and nursery areas for Chinook, coho and chum salmon that use the Lower Duwamish River.

The Blueprint identifies the following challenges and opportunities for restoration in the Duwamish transition zone which can also be translated to mitigation projects:

Table 3 Challenges & Opportunities for habitat restoration in the Duwamish transition zone.

Challenges Implications for Restoration Opportunities for Habitat Improvement Structural/Physical Challenges Shoreline armoring, Difficulty and high cost of Identify places to reduce or overwater structures laying back shoreline that is remove armoring and overwater (piers, docks, boathouses, armored, and of restoring structures. pilings), buried utilities, vegetation or other kinds of marine debris habitat Sediment and upland Increased costs for restoration NRDA projects; leverage contamination, clean-up (studies, clean-up, long range mitigation funds to prepare sites impacts to potential monitoring); limitations on for restoration. restoration projects or restoration (ex. capped areas); existing habitat need to wait for cleanup before restoration can happen

Slope stability/over Erosion potential, difficult to Lay back banks – will also steepened banks re-vegetate, high temperatures mitigate sea level rise. Plant with willow and dogwood stakes.

Significant invasive Several years of control Long-term plan & strategy for vegetation (especially knotweed) prior to bank revegetation and any vegetation restoration. maintenance needed. King Difficulty removing invasives County noxious weed program – from riprapped areas. engage on regular basis. Difficulty obtaining Duwamish Alive and other permission from property stewardship opportunities need owners consistent source of funding.

Channel shape and Limits main channel Lay back banks so less steep. dredging/infrastructure restoration opportunities. Reduce dredging where affect bathymetry, Lack of innovative restoration possible. compatibility with river design techniques hydrodynamics, sediment movement/processes, vessel wake impacts

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 18 - Recontamination of Polluted water, high Source control, tree planting, sediments and water temperatures stress fish and green stormwater from upstream infrastructure should be encouraged in the entire Green/Duwamish watershed.

Creosote piles, derelict Ongoing source of pollution, Continue working with Puget structures and vessels, make restoration more Sound Partnership and fill difficult; disposal expensive Department of Natural Resources to prioritize removal of piles and derelict vessels.

Resource/Planning Challenges Existing land uses and Port and local government Setting targets for salmon zoning, conflicting interests in preserving recovery and measuring land uses industrial and water outcomes will help determine dependent uses amount of habitat needed. Evaluating the economic impacts of conversion to restored lands could help decision-makers.

2. WRIA 9 Chinook Salmon Conservation Plan In response to these federal listings, the WRIA 9 developed the WRIA 9 Salmon Habitat Plan to guide protection and restoration of Chinook salmon and bull trout in the Green/Duwamish and Central Puget Sound Watershed. The Habitat Plan recommends actions that should be taken to protect and restore salmon habitat, using an ecosystem approach, in the Green/Duwamish and Central Puget Sound Watershed. Throughout the Habitat Plan, mitigation is mentioned as a method to help protect salmon habitat. Policies were developed in the Habitat Plan to, “provide guidance for protecting, minimizing and preventing further degradation of salmonid habitat in WRIA 9.” (WRIA 9 Steering Committee 2005) Specifically, a policy related to using innovations to promote habitat protection/restoration, Policy IN4 says, “Support new and existing incentives to protect salmon habitat. Such incentives for local governments to choose from include but are not limited to: Mitigation banking and water rights acquisition to protect habitat”. (WRIA 9 Steering Committee 2005) A policy related to funding, Policy I16 says, “An appropriate level of mitigation funding should be re-directed (either on-site or off-site, whichever is applicable) toward Habitat Plan priority actions in the distinct habitats outlined in Policy MS1 in Chapter 5 (Duwamish Estuary transition zone habitat; Middle Green River, Lower Green River, Duwamish Estuary, and Marine

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 19 - Nearshore rearing habitat; and Middle Green River and upper Lower Green River spawning habitat).” (WRIA 9 Steering Committee 2005) The Habitat Plan provides funding strategies including: • Apply funds to the 10-year priority watershed projects identified in the Habitat Plan ; • Maximize existing salmon funding sources and draw on additional existing sources that could be, but have not been, used for salmon recovery priorities; • Use funds generated in the watershed; • Aggressively pursue appropriate use of mitigation funds; • Track success of overall funding, sources, and distribution against desired results; and • If funds fall short of goals, explore alternative sources or change the Habitat Plan implementation approach.

3. Final Lower Duwamish NRDA Restoration Plan and Programmatic Environmental Impact Statement Hazardous substance releases into the Lower Duwamish River (LDR) resulted in the contamination of the sediments and injuries to natural resources. The Elliott Bay Trustee Council (Trustees) developed the Lower Duwamish River Natural Resource Damage Assessment Restoration Plan and Programmatic Environmental Impact Statement to document the extent of damage and how to restore natural resources affected by hazardous substance releases into the Lower Duwamish River (NOAA 2013). Through this work, the Trustees concluded that clean-up of intertidal and subtidal contaminated sediments—combined with restoration of marshes, intertidal mudflats, shallow subtidal habitats, and riparian habitat—would directly benefit injured key resources in the LDR. The Lower Duwamish River Natural Resource Damage Assessment Restoration Plan and Programmatic Environmental Impact Statement provides design criteria to aid practitioners in implementing habitat that will benefit these resources. Included in these design criteria are definitions of each habitat type, recommended elevations and typical plant species. The below cross section shows the habitat as described in the Lower Duwamish River Natural Resource Damage Assessment Restoration Plan and Programmatic Environmental Impact Statement.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 20 -

Cross Section showing cross section of mudflat, marsh, and riparian habitat (NOAA 2013)

D. Watershed Threats Addressed by the CW Mitigation Project Threats to the Green/Duwamish Watershed were identified in the Program Instrument. The following threats will be decreased through the implementation of the CW Mitigation Project. The Habitat Limiting Factors and Reconnaissance Assessment Report: Green/Duwamish and Central Puget Sound Watersheds (Kerwin, et al. 2000) contains the following information about threats (excerpted from Table LU-1 in the referenced report):

Land Use and Human Activities Potential Result and Impact of Salmon Habitat • Channelization and confinement of stream channels for urban and rural land uses, potentially leading to:

o Reduced channel complexity; increased velocities; loss of pools for holding and rearing; loss of spawning gravel habitat; loss of side channels; loss of wood recruitment; loss of connectivity with flood plain and riparian zone • Loss of riparian vegetation due to urbanization, mining, forestry, agriculture, etc., potentially leading to:

o Reduced overhanging vegetation and shade cover; increased solar radiation; elevated water temperatures; loss of LWD recruitment; reduced terrestrial insect influx; reduced leaf litter influx; alteration of energy cycle In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 21 - • Loss of estuarine and nearshore habitats; port development, potentially leading to:

o Loss of important freshwater to saltwater transition habitats, including cover and food production for smolts; loss of staging and holding habitats for adult salmon; degraded water quality • Increased water infiltration and improved water quality related to removal of impervious surfaces (the buildings and parking lot). Approximately 4 acres of the site is impervious, 1.72 acres of which is parking lot.

Upon restoration, there would be significantly more gains in ecological functions. Per the Shoreline Master Program guidelines in WAC 173-26-221(5)(b): “The most commonly recognized functions of the shoreline vegetation include, but are not limited to:

• Providing shade necessary to maintain the cool temperatures required by salmonids, spawning forage fish, and other aquatic biota. • Providing organic inputs critical for aquatic life. • Providing food in the form of various insects and other benthic macroinvertebrates. • Stabilizing banks, minimizing erosion, and reducing the occurrence of landslides. The roots of trees and other riparian vegetation provide the bulk of this function. • Reducing fine sediment input into the aquatic environment through storm water retention and vegetative filtering. • Filtering and vegetative uptake of nutrients and pollutants from ground water and surface runoff. • Providing a source of large woody debris into the aquatic system. Large woody debris is the primary structural element that functions as a hydraulic roughness element to moderate flows. Large woody debris also serves a pool-forming function, providing critical salmonid rearing and refuge habitat. Abundant large woody debris increases aquatic diversity and stabilization. • Regulation of microclimate in the stream-riparian and intertidal corridors. • Providing critical wildlife habitat, including migration corridors and feeding, watering, rearing, and refugia areas.”

E. Likelihood of Success The CW Mitigation Project represents a rare opportunity to replace ecological functions on the Duwamish River lost due to extensive changes wrought on the river system over the past century. Among the many other changes, the floodplain and off-channel habitats were filled and developed first for farming and later for industrial and commercial uses. Consequently, there is extraordinary pressure on remaining habitats in the Duwamish. This project is designed to provide nearly 4 acres of new wetland and aquatic habitat that is optimized to serve as rearing habitat for Chinook salmon and other anadromous species that pass through the Duwamish River on their way to marine environments. The Duwamish Blueprint (Ostergaard et al. 2014) describes the type of habitat feature most needed in this reach of the Duwamish as,

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 22 - …Shallow-water, off-channel habitats where juvenile salmonids can shelter, hold in low-salinity water, and feed (Ruggerone et al. 2006). Ideally, these habitats would feature a relatively shallow grade, a silt/clay to fine sand substrate, and be ringed with emergent vegetation and mixed riparian in the uplands. (Ostergaard et al. 2014) This project is designed to provide exactly these elements and to maximize their quantity, quality and persistence over time. The design is a blind, backwater channel that will fill and drain (though not empty) with the tide cycles while remaining separated from the main channel by a “spit” feature, ensuring that water velocities within the backwater channel will remain slow. All slopes below the high-water line will be shallow (6:1 or shallower) and all areas capable of supporting vegetation will be densely planted. The soil profile within the CW Mitigation Project, and therefore the substrate of the finished project, is composed of sands and silts. In addition, the CW Mitigation Project is designed to remain inundated during the period when juvenile Chinook salmon will be present in this part of the system (February through May) so that juvenile fish aren’t flushed out of the site with each low tide. To help inform this design, the project design team visited numerous analog sites—both created and naturally-formed—to assess physical characteristics and to learn lessons from restoration practitioners. Sites visited included the Skagit River delta, the Qwuloolt, Quilceda Marsh and Union Slough projects on the Snohomish, the Place of Circling Waters on Hylebos Creek, the Gog-le-hi-te complex on the Puyallup River, and numerous projects on the Duwamish, including Slip 4 (Boeing) and the many projects developed by the Port of Seattle. The Duwamish Gardens project, constructed by the City of Tukwila in 2016 almost immediately upstream of the CW Mitigation Project, has been especially useful to watch and the staff involved have been very forthcoming with assistance and data. Visits to these sites and conversations with the restoration practitioners who designed and monitored them have informed not only the design of the CW Mitigation Project, but also maintenance practices that will aid in plant survival and overall project success. Many lessons from previous restoration projects on the Duwamish River have been compiled into the report entitled, “Habitat Restoration in an Urban Waterway: Lessons Learned from the Lower Duwamish River, November 19, 2015 Workshop Report” assembled by NOAA Fisheries staff (Kern et al. 2016). Excellent hydrologic flow and stage data is available for the site from the USGS/Tukwila gage (12113415) located just a few hundred feet upstream of the CW Mitigation Project. This gage provides accurate stage data for the site, which is critical in a tidal environment and enables the project designers to accurately assess the durations of inundation at various elevations within the site. This, along with the excellent reference site at Duwamish Gardens just upstream, provides the data needed to predict which plant species will thrive at given elevations and which vegetation communities will eventually form in given areas.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 23 - F. Nearby Mitigation and Restoration Projects The CW Mitigation Project is located approximately 235 feet downstream of the 2.16-acre Duwamish Gardens project that was constructed in 2015 and 2016. Duwamish Gardens provides off-channel and shallow water habitat for juvenile fish to eat, rest, and grow as they transition to salt water. Completion of the CW Mitigation Project will enhance the benefits of the Duwamish Gardens project, resulting in an uninterrupted length of river frontage in public ownership spanning approximately 1,400-feet, the entire length of the right bank of the river between East Marginal Way South to the east (upstream) and Tukwila International Blvd to the west (downstream). Downstream on the Duwamish River are the North Wind’s Weir project that turned the 2.5-acre site into off-channel habitat with mudflats and vegetated marsh and the 2.99- acre Cecil Moses Memorial Park that includes a slough and marsh created to increase habitat. Immediately across the Duwamish River from the CW Mitigation Project, the City of Tukwila recently constructed phase I of the Riverton Creek Flapgate Removal Project that will remove fish barriers and provide access to critical juvenile rearing habitat.

King County also completed the following habitat restoration projects on the Duwamish River: Hamm Creek Habitat Restoration Project, Herring’s House Park and Intertidal Habitat Restoration Project, and Turning Basin No. 3 Restoration Project. In total, King County has worked to restore 25 acres of habitat along the Duwamish River. Chinook Wind will increase the number of restored acres to over 30 acres. Various other mitigation and restoration projects have been implemented along the Lower Duwamish by public and private entities (Figure 3 and Figure 4).

G. Site Perimeter Protection WAC 173-700-304 requires buffers (perimeter protection) from certain adjacent land uses around a mitigation site to protect the functions at that site. The CW Mitigation Project is located in the City of Tukwila, in an urban area zoned Manufacturing Industrial Center/Heavy Industrial. With this zoning, the property would have been a valuable location for manufacturing or industrial development that could have locked the property into this type of development for decades. The CW Mitigation Project offers an extraordinary opportunity to provide a rare resource that is immensely important for ESA-listed juvenile Chinook. Because the CW Mitigation Project offers such a rare opportunity to provide a significant amount of habitat, upland and riparian areas surrounding the wetland and aquatic features will be reduced to allow for maximum wetland and aquatic area creation.

A perimeter protection area is included around the CW Mitigation Project to acknowledge the reduction in functions in areas adjacent to nearby urban development. Areas 0’-50’ from the property line or proposed trail easement, whichever is more interior, will earn zero credit (Figure 2). Baseline Conditions

The CW Mitigation Project is located in the transition zone of the Duwamish River in the City of Tukwila. It consists of two commercial parcels totaling 5.88 acres. The properties are zoned Manufacturing Industrial Center/Heavy Industrial (MIC/H) by the City of Tukwila. When the property was acquired by King County in 2015, the CW Mitigation Project included a 45,408 square foot two-story hotel built in 1963, a 10,290 square foot single story hotel lobby, a 3,900 square foot conference building, and various accessory sheds and small structures. Surrounding

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 24 - the structures was approximately 1.72 acres of asphalt parking area. All structures were demolished in 2018 and the asphalt parking area was removed, leaving only a small entrance pad (Figure 5).

Prior to acquisition of the property and demolition of the structures, the hotel facilities were leased to a variety of social service agencies as housing for people in transitional housing situations. The buildings and other infrastructure were deteriorating, and the condition of most buildings was poor. All three main buildings had asbestos that required abatement, as well as PCBs, mercury, and lead materials. Attachment 2, Chinook Wind Demolition Report documents the demolition process.

Photo 1 Chinook Wind Mitigation Project Site 2013 Aerial Photo

A. Historic Land Use CW Mitigation Project site was historically impacted by forest clearing and draining, filling, and dredging of wetlands. Unlike other parts of the Duwamish River, this segment of the River has not been re-aligned (Figure 6). Prior to European settlement of the Duwamish Estuary in the 1850’s, the Duwamish people inhabiting the area focused their economic, cultural, and spiritual lives around the annual runs of salmon and steelhead. Extensive logging of the estuary began in the 1880s and wetlands were drained and converted into farmland. WRIA 9 Strategic Assessment Report (King County Water and Land Resources Division 2005) shows that the project site was historically palustrine wetlands surrounded by forests (Figure 6). Collins and Sheikh’s (2005) reconstruction of historic riverine and estuarine habitats in the Duwamish also suggests that the site supported a freshwater and floodplain forest (Figure 7). Agricultural use at the project site persisted well into the 20th century, as demonstrated in the aerial views of the site in 1936 and 1959 (Photos 2a and b). A hotel was built on the site in 1963 and the structure was later used as In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 25 - transitional housing until it was demolished in 2016 after the property was acquired by King County in 2015.

Photos 2(a) Chinook Wind Mitigation Project Site 1936 (left) and (b) 1959 (right) Aerial Photos (Sources: King County iMap and Archives)

B. Duwamish River Inundated aquatic habitat in the Duwamish represent both an extremely limited and critically important habitat for ESA-listed juvenile Chinook as well as other juvenile salmonids and aquatic species. Urbanization, hydromodification, and diversion of flows from the Black and White rivers over the past 100 years have resulted in a loss of approximately 97% of Duwamish river estuarine delta wetlands, and a flow reduction of 70-75%. This has had a dramatic effect on the availability of shallow low-velocity aquatic habitats that juvenile Chinook salmon depend on for rearing, foraging, refuge from high velocities, and predator avoidance (Kerwin 2001; Everest & Chapman 1972; Beechie et al. 2005; Bjornn & Reiser 1991). The Duwamish Blueprint (2014) identified intertidal mudflats and marsh to be important habitat for juvenile Chinook rearing, though a critical link in providing quality Chinook habitat also includes making sure that they have these shallow low velocity habitats available at low tides when tidal inundation is not providing lower velocities and access to shallow off-channel areas.

Cordell et al. (2006) stated that in the Duwamish, ideal habitats not only appear to be large areas with gentle intertidal mudflat slopes that are protected from currents, but also provide refuge in a channel during low tides. Beamer et al. (2005) found that blind off-channel areas in the Skagit estuary that still had water at low tide had especially high densities of juvenile Chinook. They also found that slow water edges of distributary channels had high densities of juvenile Chinook salmon at low tide. As part of the update to the WRIA 9 Salmon Habitat Plan, Higgins (2017) summarized that findings from Ruggerone et al. (2006) combined with data from other reports (Ruggerone & Weitkamp 2004; Nelson et al. 2011; Oxborrow et al. 2016), and expected climate change impacts on habitat area within the Duwamish, indicate we need bigger restoration sites with more habitat heterogeneity (e.g. deeper water that would not drain out at low tide and available shallow water habitat throughout the full tidal range).

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 26 - Recent studies have shown that juvenile Chinook salmon that are attempting to rear in the Duwamish are surviving at very low rates, with estuary degradation being one of the factors that may be causing this (Campbell & Claiborne 2017). Campbell and Claiborne (2017) indicated that the Duwamish rearing Chinook fry contribution to the adult return in 2015 was extremely low (<1%), based on a subsample of adult otoliths analyzed as part of the larger Puget Sound Marine Survival project. Juveniles that were smaller than 60mm in size when they began to rear in salt water were almost nonexistent in the adult returning Chinook. Whereas the Skagit and Nooksack’s fry contributions were 36% and 24%, respectively. This indicates other watersheds with intact estuary habitat have estuary rearing Chinook fry that are surviving to adulthood at much higher numbers than Green River’s Chinook fry. WRIA 9 provided WDFW funding to collect adult otoliths from the 2016 and 2017 spawning seasons. Draft data for adults from these years found very similar results with less than 3% of the returning adults originating as estuarine rearing fry (Personal Communication Lance Campbell). Based on smolt trap data, an average of 60% of all juveniles migrate past the trap as fry. Some of these fry likely rear in the Lower Green and become the Lower Green parr life history type but based on other data (Ruggerone et al. 2006; Nelson et al. 2012) it is known that many of the fry move straight to the Duwamish. This loss of almost all the fry that reared in the Duwamish is severely limiting fry productivity, overall population productivity, and abundance, as well as reducing overall life history diversity.

Because of the confined nature of the upper Duwamish and transition zone, very little rearing habitat is present at low tide, creating a bottleneck for rearing habitat. We know that downstream movement of natural juvenile Chinook may be accelerated even further if they do not find adequate habitat, prey, or if habitats are occupied by other fish (Ruggerone & Weitkamp 2004), and based on Campbell and Claiborne (2017), we know that fish that do not rear to approximately 60mm in length or greater in fresh water are surviving at extremely low rates. Anderson and Topping (2017) found that spawning habitat in the Middle Green River is not currently limiting the productivity of the Chinook salmon population; rather, the lack of juvenile rearing habitat is the primary limiting factor. By providing critical low velocity aquatic habitat at the CW Mitigation Project, especially at low tide when it is the limiting factor for rearing habitat, we will have the greatest ability to support Chinook recovery and healthy populations for all other salmon species within the Green/Duwamish watershed.

C. Wetlands Collins and Sheikh (2005) reconstructed historic riverine and estuarine habitat in the Green and Duwamish and Elliot Bay from historical records. The Duwamish River was estimated to have had 835 acres of freshwater, intertidal and estuarine habitats. Maps from both the Collins and Sheikh’s report and WRIA 9 Strategic Assessment Report (King County Water and Land Resources Division 2005) show that the CW Mitigation Project site historically supported freshwater wetlands surrounded by floodplain forest (Figure 6 and Figure 7). Currently, The CW Mitigation Project does not contain any delineated wetlands or associated buffers.

D. Uplands Prior to demolition of the structures on site in 2016, most vegetation was ornamental, though areas along the riverfront shoreline areas contained—and still contain--stands of Himalayan blackberry as well as native and non-native trees and shrubs. Following demolition of the structures, most of the area is bare ground and pasture grasses. A stand of black locust trees (Robinia pseudoacacia) occupies the northeast corner of the site.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 27 - E. Fish Fifty-three species of resident and non-resident fish have been found on the Lower Duwamish Waterway (NOAA 2013). Salmonids that migrate through the lower Duwamish River include coho, chum, fall Puget Sound Chinook, sockeye, pink salmon, and summer and winter Puget Sound steelhead. Marine fishes in the area may include Pacific staghorn sculpin, starry flounder, English sole, shiner perch, and Pacific herring. This area provides important rearing habitat for herring, perch, sculpins and other fishes.

Chinook salmon migrate downstream as juvenile smolts in two pulses. Fry-migrants move immediately downstream after hatching and arrive in late January through March. Parr-migrants migrate into the Duwamish March through July (Kerwin & Nelson 2000). Chinook salmon in the Duwamish River consist primarily of summer/fall run fish and include a mixture of natural (wild) and hatchery spawning fish. Natural spawners are classified as ocean type fish because they typically spend little time in fresh water after emerging from eggs laid in the gravel. Juveniles have been found in the Duwamish through September, indicating that fry rear in the Duwamish estuary for up to nine months.

F. Wildlife There is an osprey perch pole located at the top of the streambank at the southeast corner of the project. Birds have been classified into four assemblages based on foraging (Simenstad 1983) and use similar habitat types as juvenile Chinook salmon and are linked with them through their food webs; therefore, the habitat value for birds is linked to habitat value for juvenile Chinook salmon (NOAA 2013). A variety of water birds typical of western Washington are found within the project area. Small mammals such as river otters, mink, raccoons, and grey squirrel inhabit the uplands surrounding the upper Duwamish Waterway.

G. Water Quality The Washington State of Department of Ecology (Ecology) assigns designated uses for each water body or water body segment. The designated use specifies the water quality standards which apply to the water body. For Aquatic Life Uses, the Duwamish River is categorized as habitat for “Salmonid Rearing and Migration Only”. For Recreational Uses, it is designated for “Secondary Contact Recreation”. Per the Washington Administrative Code (WAC) 173-201A- 020, “Primary Contact Recreation” means activities where an individual “would have direct contact with water to the point of complete submergence”. Therefore, “Secondary Contact Recreation” includes activities where immersion and ingestion are less likely. Certain segments of the Duwamish River are also on Ecology’s 303(d) list (Category 5) for not meeting standards on multiple parameters, including dissolved oxygen, pH, temperature, and bacteria.

H. Soils The Geological Map of Seattle (Troost et al. 2005) shows the area as Quaternary alluvium (Qal) sand, silt, gravel, and cobbles deposited by the Duwamish River and locally may contain very soft peat lenses.

Aspect Consulting performed a geotechnical investigation of the CW Mitigation Project on August 7, 2015. Between 4 and 7 feet of silty sand fill, likely either dredge spoils from the adjacent river channel or native soils redistributed across the site during historical farming activities on the site, were observed overlying alluvium consisting of interbedded sand and silt (Aspect Consulting

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 28 - 2015). This alluvium was characterized as very loose to medium dense and extended to about 15 feet below ground surface (bgs). Under this, soils (sand, silt and silty sand) were characterized as very loose/very soft (to 18’ bgs) and loose to medium dense (18’ to 21.5’ bgs).

1. Soil Contamination Soil contaminants have been identified by several testing efforts at the CW Mitigation Project. The first Level I and II Environmental Assessments were procured by the City of Tukwila in 2013, prior to purchase of the Chinook Wind property by King County. This assessment by Maul, Foster, Alongi and three others that followed (Hart Crowser, 2015, Aspect Consulting, 2017 and Hart Crowser, 2020) refined the extent of contaminated soils to two discrete areas of the site (Area 1 and Area 3; Figure 5). Both areas are in parts of the site that will be excavated to construct the project and are not expected to affect the final graded surfaces of the site.

In addition to the areas of contaminated soils identified by the environmental assessments, 30 creosote-coated wooden pilings were discovered buried where one of the former structures once stood (Area 2; Figure 5). The depths of these pilings are unknown.

2. Dredged Materials Management Office Coordination Throughout 2019, the project team met several times with the Dredged Materials Management Office (DMMO), which regulates the exposure of new and potentially contaminated sediments to the Duwamish River. These meetings resulted in the “Tier 1 Antidegradation Evaluation for the Chinook Wind In-Lieu Fee Mitigation Project, Duwamish River (NWS-2018-879)” (Antidegradation Memo). The Antidegradation Memo, included as Attachment 3, describes the locations of soils to be removed and how they are to be tested and disposed of. Contaminated soils were segmented into three areas. Area 1 and Area 3 are soils that tested for contamination. Area 2 is the soil around the creosote pilings that will be removed during regular construction. It also describes procedures for removing the creosote-coated pilings and for testing and possible replacement of the soils beneath those pilings when the final grade is established.

Mitigation Work Plan

A. Contaminated Soils Clean-Up In early 2020, the Department of Ecology (DOE) notified King County that the CW Mitigation Project is ineligible for DOE’s Voluntary Cleanup Program (VCP) because VCP does not cover “sediments” (defined as soils exposed directly to river processes). Cleanup projects eligible for VCP are supervised by DOE. Following completion of cleanup and DOE acceptance, VCP sites can be removed from DOE’s list of potentially contaminated sites. The other option to ensure a cleaned-up site is removed from DOE’s list of potentially contaminated sites is through an Agreed Order. Through this process, DOE would appoint a site manager and begin the formal process that would culminate in an Agreed Order that would govern cleanup activities. DOE staff informed King County that they have no staff to serve in such capacity and that the Agreed Order process would likely take many years to resolve. The remaining option for the CW Mitigation Project is to complete an “independent cleanup” without technical assistance from DOE or formal acceptance by DOE of the cleanup effort. The site will remain on DOE’s list of potentially contaminated sites, even after cleanup activities are completed.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 29 - 1. Independent Cleanup Independent cleanup occurs when contamination is cleaned up independently without a legal agreement with DOE. Because DOE does not consult on independent cleanups, some liability remains with the site owner. Liability can be minimized through thorough data collection. Data will be collected before, during and after construction to document cleanup activities and the status of the site when construction activities have been completed. Hart Crowser developed a Sampling and Analysis Plan (SAP) attached to this document (Attachment 4) and included by reference. The SAP was developed to:

• better delineate the extent of known contaminated areas, • ascertain whether contaminated groundwater from beneath the property to the north (on which there was a documented spill of hazardous materials many years prior) will find a shorter path to the river as a result of the project excavation, and • document the status of newly exposed soils after final grading is completed.

Implementation of the SAP began in summer 2020, when additional soil samples were collected and analyzed, and three groundwater monitoring wells were installed along the northern property boundary. No further contamination was identified during the soils sampling. Samples from the groundwater monitoring wells will be analyzed quarterly for one year to determine the status of groundwater entering the site from the north. The last of these samples will be collected by April 15, 2021. To date, no significant contaminants have been found in groundwater samples from these wells. These wells will be removed by the contractor if no evidence of contaminated groundwater is found.

In December 2020, the two areas of known soil contamination were excavated per the plan agreed upon in the Antidegradation Memo. 407 tons of soil were removed from the areas referred in the Antidegradation Memo as Area 1 and Area 3 and disposed of via Republic Services in an appropriate landfill. Consultants Anchor QEA performed more testing on the soils. Per protocol in the Antidegradation Memo, soils excavated from and within 50 feet of Area 1 and soils excavated from Area 3 were tested. No contaminants were identified. After excavations were completed, the newly exposed soils were tested, and all margins (edges of the excavation area) were found not to be contaminated.

Results of the SAP will be documented in a Post Project Soils Condition Report that will be submitted to the IRT with the As-Built Report.

B. Wetland Establishment

3. Grading The grading plan was derived by determining which elevations would receive the frequency of inundation via tides and river flow required to establish the desired wetland plant communities through the following processes:

1. Determine the desired wetland community types based on ecological criteria, historic conditions in this reach and design team experience;

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 30 - 2. Use tidal elevation and river stage data from USGS Gage 12113415, immediately upstream of the CW Mitigation Project, to determine frequencies and durations of inundation at different elevations within the soil profile. 3. Correlate these data with known tolerances of desired plant species in each plant community. 4. Validate these correlations with empirical observations of wetlands and plant species near the project site. 5. Determine the elevations and corresponding depths of excavation necessary to establish the appropriate levels of saturation for each wetland/riparian community type (Graph 1). 6. Refer to fish monitoring data to determine season of most frequent and critical use of the Duwamish River by juvenile Chinook salmon. 7. Refer to river stage/tidal data from USGS Gage 12113415, immediately upstream of the project site, to determine river stage range during months that the Duwamish is most frequently used by juvenile Chinook salmon (Graph 2). 8. Determine elevations and corresponding depths of excavation which will remain inundated by river/tidal flows during the Chinook salmon rearing season. 9. Refer to geotechnical data collected from subsurface soils at the site to determine slope stability at different elevations within the soil profile. 10. Complete grading plan which provides necessary elevations for persistent fish habitat during the Chinook salmon rearing season and hydrological conditions that will support low marsh, high marsh, moist riparian and dry riparian plant communities, while maintaining geotechnically stable slopes.

Aspect Consulting’s report recommends finished slopes below 5’ bgs be no steeper than 6H:1V and no steeper than 3H:1V above that elevation. The grading design of the CW Mitigation Project conforms to these recommendations.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 31 -

Graph 1 Estimated design elevations for wetland communities using empirical observations and tidal/river stage data (adapted from Shannon & Wilson, 2012)

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 32 -

River Stage at Chinook Wind Site, January through April, 2018 12

Elevation (Feet; NAVD 1988 Datum) 4

0 12/31/2017 0:00 1/20/2018 0:00 2/9/2018 0:00 3/1/2018 0:00 3/21/2018 0:00 4/10/2018 0:00 4/30/2018 0:00 Date/Time

Graph 2 River stage elevations during Chinook salmon rearing and early vegetation growing seasons

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 33 - 4. Native Planting Native plants will be installed to establish species diversity in each of four plant community types: low marsh, high marsh, moist riparian and dry riparian. Species were selected based on reference sites, research into historical plant communities, research into Native American plant use, species’ tolerance for salt water inundation, and design team experience. Wetland sod will be installed in some areas in addition to seeding of emergent species. Wetland sod will be sourced from a supplier that provides custom-grown, pre-vegetated mats. These pre-vegetated mats will consist of native emergent species. Wetland sod is planned to provide a robust erosion- resistant hedge in areas where local, lateral erosion is anticipated. They will be used in areas where there is a desire to ensure vegetation is established quickly and where additional stability is needed. As natural wetland processes form, the CW Mitigation Project is expected to change. Dynamic wetland and floodplain processes will define the characteristics of the site and specific acreages of individual community types will not be required if natural processes cause the communities to shift. Planting areas and quantities are shown in Table 4 through Table 10. Final plans may include adjusted quantities, size and/or spacing; species may be adjusted according to availability at the time of planting.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 34 - Table 4 Riparian (Dry) Plant Species

HABITAT SCIENTIFIC NAME COMMON NAME STOCK QTY TYPE RIPARIAN (DRY) Trees Acer macrophyllum Big leaf maple Bare Root 47 Alnus rubra Red alder Bare Root 32 Arbutus menziesii Madrone Bare Root 47 Pinus cortorta Shore pine Bare Root 95 Pseudotsuga menziesii Douglas-fir Bare Root 79 Tsuga heterophylla Western hemlock Bare Root 16 Shrubs Acer circinatum Vine maple Bare Root 112 Aruncus dioicus Goat’s beard Bare Root 112 Holodiscus discolor Oceanspray Bare Root 224 Mahonia aquifolium Tall Oregon grape Bare Root 449 Ribes sanguineum Red-flowering currant Bare Root 112 Rosa nutkana Nootka rose Bare Root 224 Rubus parviflorus Thimbleberry Bare Root 224 Sambucus racemosa Red elderberry Bare Root 112 Symphoricarpos albus Snowberry Bare Root 337 Vaccinium ovatum Evergreen huckleberry Bare Root 112 Groundcover Arctostaphylos uva-ursi Kinnikinnick Bare Root 1316 Athyrium felix-femina Lady fern Bare Root 112 Mahonia nervosa Dwarf Oregon grape Bare Root 329 Polystichum munitum Sword fern Bare Root 112 Rubus ursinus Trailing blackberry Bare Root 292 Herbs Aquilegia formasa Red columbine Bare Root 165 Symphyotrichum subspicatum Douglas aster Bare Root 165 Chamaenerion augustfolium Fireweed Bare Root 165 Elymus mollis American dune grass Bare Root 1316 Festuca idahoensis Idaho fescue Bare Root 165 Lupinus polyphyllus Long-leaved lupine Bare Root 165

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 35 - Table 5 Riparian (Moist) Plant Species

HABITAT SCIENTIFIC NAME COMMON NAME STOCK QTY TYPE RIPARIAN (MOIST) Trees Alnus rubra Red alder Bare Root 38 Picea sitchensis Sitka spruce Bare Root 56 Populus balsamifera Black cottonwood Live Stake 26 Pseudotsuga menziesii Douglas-fir Bare Root 190 Thuja plicata Western red-cedar1 Bare Root 68 Tsuga heterophylla Western hemlock Bare Root 38 Shrubs Amelanchier alnifolia Serviceberry Bare Root 684 Acer circinatum Vine maple Bare Root 342 Cornus sericea Red osier dogwood Bare Root 1368 Galutheria shallon Salal Bare Root 152 Lonicera involucrata Twinberry Bare Root 684 Malus fusca Pacific crabapple Bare Root 342 Physocarpus capitatus Pacific ninebark Bare Root 684 Rosa nutkana Nootka rose Bare Root 684 Rubus spectabilis Salmonberry Bare Root 315 Salix hookeriana Hookers willow Live Stake 1211 Salix scouleriana Scouler’s willow Live Stake 1077

Table 6 High Marsh Plant Species

HABITAT SCIENTIFIC NAME COMMON NAME STOCK QTY TYPE HIGH MARSH Trees Populus balsamifera Black cottonwood Live Stake 26 Shrubs Salix hookeriana Hookers willow Live Stake 1211 Salix scouleriana Scouler’s willow Live Stake 1077 Herbs Carex lynbyei Lyngbye’s sedge Bare Root 1280 Carex obnupta Slough sedge Bare Root 640 Eleocharis palustris Creeping spikerush Bare Root 480 Juncus articulatus Jointed rush Bare Root 480 Scirpus microcarpus Small-fruited bulrush Bare Root 320

1 Western red-cedar will be planted after Year 0 to allow shade to establish onsite first. In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 36 -

Table 7 High Marsh Seed Mix

HIGH MARSH SEED MIX SCIENTIFIC NAME COMMON NAME Herbs Angelica lucida Sea-watch Argentina pacifica Pacific silverweed Symphyotrichum subspicatum Douglas aster Carex lynbyei Lyngbye’s sedge Deschampsia caespitosa Tufted hairgrass Schoenoplectus acutus Common tule Schoenoplectus pungens Sweetgrass, chairmaker's rush Schoenoplectus tabernaemontani Softstem bulrush Sidalcea henersonii Henderson's checkermallow

Table 8 Low Marsh Plant Species

HABITAT SCIENTIFIC NAME COMMON NAME STOCK QTY TYPE LOW MARSH Herbs Carex lynbyei Lyngbye’s sedge Bare Root 959 Schoenoplectus acutus Common tule Bare Root 959 Schoenoplectus pungens Sweetgrass, chairmaker's Bare Root 959 rush Schoenoplectus Softstem bulrush Bare Root 959 tabernaemontani

Table 9 Low Marsh Seed Mix

Low Marsh Seed Mix Scientific Name Common Name Herbs Bolboschoenus maritimus Cosmopolitan bulrush Carex lyngbyei Lyngbyei’s sedge Eleocharus palustris Creeping spikerush Juncus balticus Baltic sedge Schoenoplectus americanus Three square rush Schoenoplectus tabernaemontani Softstem bulrush

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 37 - Table 10 Low Marsh Wetland Sod

Low Marsh Wetland Sod Scientific Name Common Name Herbs Bolboschoenus maritimus Cosmopolitan bulrush Schoenoplectus americanus Three square rush Schoenoplectus pungens Common bulrush, sweetgrass Schoenoplectus tabernaemontani Softstem bulrush

C. Backwater Channel A hook-shaped backwater channel will be excavated through the site. The design maximizes the channel’s length while maintaining physical separation from the mainstem channel. The channel will be excavated to a depth (at least El. -2’ NAVD88 at the deepest point where it joins the mainstem river channel) that is designed to maintain wetted channel at even the lowest tides/flows that would be encountered during the primary season in which Chinook salmon rear in the Duwamish. (Areas at El. -2’ NAVD88 would remain inundated at tides of greater than 0.54’ [tidal elevation].) This will allow juvenile salmonids to remain in the channel throughout tide cycles instead of being flushed into the main channel during low tides and river flows.

The channel banks will be graded to 6:1 or shallower slopes, which will be stable even when inundated. However, the channel and other morphological elements of the project will be subject to river and tidal processes and are expected to change due to those processes. It is likely that the bottom of the channel will slowly aggrade over time as fine sediments deposit in a low-energy environment. It is also likely that the channel banks will experience minor erosion due to both tidal retreat and to groundwater expressions. These changes are not expected to detrimentally affect the habitat quality of the channel unless they occur at excessive rates.

Portions of the backwater channel that are below El. 5’ NAVD88 are not expected to support vegetation due to the frequency and durations of inundation. These areas will not be planted and will function as mudflats as they accrete fine sediments and organic matter. Mudflats are important ecological settings as they provide valuable habitat for epibenthic organisms which in turn provide prey for salmonids and other wildlife.

D. Large Wood The CW Mitigation Project will utilize large wood for multiple objectives. Large wood provides important structure, and hydrologic and ecological functions that influence wetland establishment and fish utilization in intertidal wetlands. Large woody includes logs, sticks, branches, and other wood that falls into streams and rivers. When they decay, large wood may become nurse logs offering seedlings shade, nutrients, water, and protection from disease and pathogens, thus nurturing and making way for the new generation. The construction contractor will be given discretion on how much of the large wood used to construct the project will be sourced from existing trees on the CW Mitigation Project, and how much large wood will be purchased and imported to the site. Salvaged wood may be coniferous or deciduous. Deciduous salvage wood is expected to decompose more rapidly and may change size and shape or decompose completely throughout the establishment phase. Wood types are categorized by the

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 38 - objectives for which the large wood will be employed. These categories include wrack wood, perpendicular wrack wood, and roughness wood (Figure 8).

1. Wrack Wood The reach in which the CW Mitigation Project is located is affected by tides and water levels that fluctuate by around 10 feet per tidal cycle. These fluctuations vary daily and seasonally, depending on both tidal fluctuations and river discharge. River stage data is monitored by a USGS gage just upstream of the CW Mitigation Project. Large wood in tidal environments tends to be deposited around the high tide line where it will not be refloated until the next sufficiently high tide either remobilizes it or floats it up higher onto the shoreline. However, some very large pieces of wood may be retained at lower elevations due to the higher water levels necessary to float them. These large pieces may provide some habitat for juvenile salmonids (Simenstad et al, 2003).

Most large wood to be incorporated into the CW Mitigation Project will be anchored near the high-water line at around El. 10’ NAVD88 (Note that this elevation corresponds to about a 12.5’ tide). Due to the urban location of the project site, its proximity to commercial river uses, and the capacity of repeated tidal flows to mobilize and transport large wood, all large wood used to construct the site will need to be anchored in place with earth anchors driven into the substrate.

Large wood pieces to be placed near the high-water line will be referred to herein and in the project plan sets as wrack wood. Trees salvaged from the project site may be used for wrack wood incorporated into the CW Mitigation Project. Every effort will be made during salvage and construction to retain the rootballs and branches of these trees to maximize the complexity of the cover provided to fish, macroinvertebrates, and terrestrial wildlife.

2. Perpendicular Wrack Wood As described above, larger pieces of wood are occasionally deposited at lower elevations within the tidal prism and these pieces can provide habitat for juvenile salmonids. Specifically, the large wood laid along the slopes of the low- and high-marsh areas of the project site (between EL. 5’ and EL. 10’ NAVD88) are intended to provide cover for juvenile salmonids from avian predation, especially in the interim before marsh vegetation becomes established.

3. Roughness Wood The primary function of roughness wood is to influence the morphology of the site by promoting scour and stabilizing sediments. This type of large wood in a natural setting is primarily delivered to intertidal wetlands through riparian and coastal erosion mediated by floods, storms, and tides. Roughness wood will be installed at the CW Mitigation Project to replicate large wood structure, functions, and processes that would naturally occur over hundreds of years.

Roughness wood at the CW Mitigation Project is planned to influence the topography of the site by providing heavy, solid objects and firm substrates in an environment where the bottom consists mainly of fine sediments (Gonor et al. 1988). Research shows this type of wood serves a particularly import function by creating greater stability for the establishment of tidal marsh shrubs.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 39 - E. Anticipated Effect of Sediments Naturally formed backwater channels and wetlands are not static features in the landscape, but rather are slowly changed as the natural processes of erosion and sediment deposition continue to work on the landscape. Channel migration is not expected to occur in this reach, as it appears this particular reach has not migrated significantly since the earliest maps were created by European settlers. However, the entirety of the Duwamish River is a low-gradient depositional zone. The USGS estimates that 204,000 tons of sediment are delivered to the Lower Duwamish Waterway each year (Senter, C.A. et al 2018). The entirety of the CW Mitigation Project is composed of sediments deposited by the Duwamish River, including not only the surface but all sediments well beyond the depths of excavation required by this project.

A geomorphic review of the project design (Coastal Geologic Services 2019) estimates that some areas of the finished project may aggrade up to 2.2”/year at El. 0’ (NAVD88) and at lesser rates at higher elevations (0.1”/year at El. 10’). Some areas of the project will also likely experience erosion and redistribution of sediments. Some deposition of sediments is inevitable in an off- channel feature of a river with a high sediment load. The very qualities that make such a feature attractive to juvenile fish—low water velocities in areas separated from the mainstem channel— also promote sediment deposition. These rates of deposition will not occlude the channel opening, nor will they significantly change the durations of inundation of wetland areas within the monitoring period.

F. Perimeter Pedestrian Trail and Easement A 6-foot wide, packed gravel pedestrian trail is planned for construction by the City of Tukwila within a trail easement that extends 20 feet from the project site perimeter on the north and east sides of the CW Mitigation Project. On the west side of the CW Mitigation Project, the easement will be continuing at a width of 20 feet for approximately 78 feet and then it will be reduced to 10 feet and extend south for approximately 110 feet. The trail easement area on the western side of the CW Mitigation Project will accommodate the trail’s connection to the City of Tukwila Right-of-Way to the west, up to five feet of parking lot area that may need to extend into the site from the current access apron (in lieu of an onsite maintenance parking pad) and a bioretention area that will treat stormwater runoff from the parking area and residual runoff from the adjacent road before it enters the CW Mitigation Project. Portions of this trail easement that are not directly occupied by the trail or bioretention area will be planted with native vegetation. The bioretention area will be vegetated with native plants. Vehicular access for maintenance to the site will be permitted only through lockable gates or bollards.

Open spaces, such as the CW Mitigation Project, in urban areas can become susceptible to homeless encampments. Limited public access to the CW Mitigation Project is intended to accommodate the habitat benefits of the site while giving the site enough visibility to deter homeless encampments. This limited public access will also help King County meet code requirements of Publicly-Owned Shorelines in the City of Tukwila.

G. Signage/Access At the completion of project construction, King County will install signs that identify the site as a sensitive area. Additional signs and a trailhead kiosk may be installed within the trail easement, by the City of Tukwila, to identify the trail and provide educational content. The site will be fenced off from surrounding properties and vehicular access for maintenance to the site will be permitted only through lockable gates or bollards in the northwest corner of the CW Mitigation In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 40 - Project. The southern boundary of the site is occupied by the Duwamish River and will not be fenced.

Determination of Mitigation Credit

The CW Mitigation Project will provide rare and immensely important habitat in the Green Duwamish system: transition zone rearing and refuge habitat for endangered Chinook salmon, which in turn are a primary food source for endangered orca whales. The method used to determine mitigation credit for the CW Mitigation Project reflects the unique opportunity this site offers to support the continued existence of two of the Pacific Northwest’s most iconic species. The Green-Duwamish River was named one of America’s most endangered rivers by American Rivers in 2016 and 2019. The CW Mitigation Project will provide the largest estuarine wetland and aquatic area project in the Duwamish River. Its importance for species recovery and watershed function is doubly important due to the fact that there are no remaining naturally occurring estuarine wetlands of this size in the Duwamish River system, due to many decades of urbanization and intensive industrial uses in the Duwamish River valley. The CW Mitigation Project was designed to optimize the available habitat at the site by providing the exact type of habitat that is most needed as described in the Duwamish Blueprint, “shallow-water, off-channel habitats where juvenile salmonids can shelter, hold in low-salinity water, and feed (Ruggerone et al. 2006).” The Duwamish Blueprint goes on to describe that the ideal habitat features to promote recovery would include, “a relatively shallow grade, a silt/clay to fine sand substrate, and be ringed with emergent vegetation and mixed riparian in the uplands.” The mixture of habitat types and associated determination of mitigation credit at the CW Mitigation Project is also consistent with guidance in the Final Lower Duwamish River NRDA Restoration Plan Programmatic Environmental Impact Statement which recognizes that habitat types function in connection with each other and assigns higher functional values when habitat types are adjacent to each other (NOAA, 2013).

In addition to designing the CW Mitigation Project to provide the ideal habitat for the location, the site will be accessible to juvenile salmon virtually 100% of the time. Excavation elevations are at a level (El. -2 NAVD88) that will allow juvenile salmon to rest and feed within the CW Mitigation Project even at the lowest tides. This unique feature will provide shelter for juvenile salmon during extreme low tides when they would typically be forced to move to deeper water and flushed downriver. The CW Mitigation Project will provide the shelter needed by juvenile salmon to rest and grow, keeping them out of the contaminated areas of the Duwamish River for as long as possible. There is concern that juvenile salmon that get flushed out of rearing habitat may not be able to return to the area they were flushed out of, so the depth of excavation at the site is paramount to the value of this habitat.

Since the project site began as an upland site with a hotel, new intertidal wetlands, mudflats, and aquatic areas at the CW Mitigation Project will be categorized as created and/or reestablished. Created and/or reestablished wetlands onsite are expected to qualify as Category II wetlands under the Washington State Wetland Rating System.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 41 - A. Credit Methodology The King County Mitigation Reserves Program proposes to use ratios to quantify mitigation credits at the CW Mitigation Project. Ratios were selected as the preferred methodology due to the limitations of other established methodologies when working with both freshwater wetlands at impact sites and estuarine wetlands as compensation. Ratios give the flexibility to consider out-of-kind mitigation when appropriate to offset select impacts in the watershed.

B. Ratios Based on the configuration planned for the CW Mitigation Project (Figure 2), the CW Mitigation Project would earn credits based on acreages and ratios shown in Table 11 below. Washington State guidance says that ratios may be reduced when it is documented that proposed actions will provide compensation that is significantly greater than the wetlands being affected. The CW Mitigation Project includes many unique features and a landscape setting that is unlike any other mitigation project. The credit generating ratios in Table 11 are unique to the CW Mitigation Project and should not be used for other sites. These ratios reflect the significant gain in ecological function between the impacted Category III and IV freshwater wetlands and the planned Category II estuarine wetland as well as the unique location and extremely critical habitat that will be provided for species that are in dire need of habitat.

Table 11 Chinook Wind Credit Generation

Creditable Credit Generation Anticipated Acres at Ratio1 Habitat Type Number of Chinook Wind (habitat creation: Credits Site credit generation)

Aquatic 1.10 0.33:1 3.33

Mudflat 0.57 0.33:1 1.73

Low Marsh 1.14 0.50:1 2.28

High Marsh 1.12 0.50:1 2.24

Riparian 0.05 3:1 0.02

Total Acres 3.94 Total Credits 9.60

1Credit generation ratio applies to compensation for impacts to Category III and Category IV freshwater wetland impacts.

C. Impacts Both freshwater wetland impacts and impacts to saltwater systems will be compensated at the CW Mitigation Project, but the ratios and resulting amount of compensation provided for freshwater or saltwater impacts will differ. It is up to the regulatory agency or agencies to

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 42 - determine the compensation ratio (acreage of compensation to acreage of impact) that would be used to determine the number of credits that would be needed to offset the permitted impact. In all cases the IRT must approve “assignment” of a particular impact to the CW Mitigation Project.

Freshwater Impacts For impacts to freshwater Category III and Category IV wetlands, the required area of mitigation at the CW Mitigation Project will be calculated per ratios in Table 11, using acreage of permanent impact. Category II wetlands may be compensated at CW Mitigation Site on a case- by-case basis, however, site specific ratios may be applicable.

Impacts to Saltwater Systems In contrast, impacts to estuary and other saltwater systems will be compensated such that the acreage of mitigation on the ground at the CW Mitigation Project is equal to the compensation acreage required by the impact permit. For example, if an impact of 0.2 acre occurs in the intertidal zone of the Lower Duwamish and the permitting agencies require a 3:1 ratio for mitigation, then this impact would require 0.6 acre of area at the CW Mitigation Project. Habitat types providing compensation will be selected based on conditions of the impact project permit.

Table 12 shows examples of freshwater wetland and estuarine impacts and their compensation at Chinook Wind.

Table 12 Example Compensation Calculations

Regulator Acreage of CW Site Acreage Required Compensation at Specific Credits Impact of Ratio the CW Site Ratio Needed Impact (compensation: impact)

Example Cat. 0.15 1:1 N/A N/A 0.15 IV Freshwater Wetland Impact

Example 0.10 3:1 0.30 1:0.331 0.91 Intertidal Impact

1This is the inverse of the 0.33:1 ratio for Mudflat from Table 11. This calculation ensures the right amount of credits are deducted from the ledger.

Wetland buffer impact projects Various impact projects include wetland buffer impacts that were calculated and purchased using an area basis. Wetland buffer impacts may be offset at the CW Mitigation Project through enhanced buffers calculated on an area basis or through wetland credits. The non-credit generating perimeter protection will not be used to offset wetland buffer impacts. Assignment of buffer impact projects to the CW Mitigation Project will be coordinated with the IRT.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 43 - D. Resource Tradeoffs The CW Mitigation Project will provide both in-kind and out-of-kind mitigation. While out-of- kind mitigation is not traditionally the first choice for compensation, there are situations that support resource tradeoffs. According to Wetland Mitigation in Washington State- Part 1, Version 1, 2006, resource tradeoffs may be supported when the mitigation is providing ecological functions that are critical or limited in a watershed, particularly estuarine habitat. “With a greater awareness of the role that wetlands play in watersheds and larger landscapes, the agencies are now more likely to approve out-of-kind wetland mitigation projects when it provides an overall net gain in ecological functions that are critical or limited in a watershed.” This guidance further supports the resource tradeoffs expected at the CW Mitigation Project, “…estuarine habitat and shoreline functions are very limited in some river basins, particularly in the Puget Sound Area. Because restoration of these habitats is a priority to the agencies, it may be determined that the loss of reed canary grass pastureland in the lower watershed can be adequately offset through the removal of dikes to restore tidal flows and estuarine wetlands habitats.” The statements in this guidance document are consistent with the resource tradeoffs proposed at the CW Mitigation Project. Freshwater wetland impacts that will be offset at the CW Mitigation Project were predominantly Category III and Category IV wetlands dominated by reed canary grass that provided limited functions. The wetlands being created and/or reestablished at the CW Mitigation Project are expected to be high quality estuarine wetlands providing habitat that is extremely limited in the system, and critical to survival of out-migrating salmonids.

E. Non Credit-Debit Impacts Currently identified impact projects offset at the CW Mitigation Project are listed in Section I. B. and details are available in in-lieu fee use plans on file with the KC MRP. Several impact projects are non-standard or require area-based credit accounting. These non-credit-debit impact projects are addressed in detail below.

1. Sound Transit: South Sounder Easement # 4 Impact Description Sound Transit’s Seattle-to-Tacoma Sounder Commuter Rail Easement 4 Improvement Project involved track improvements within the City of Auburn from approximately 49th Street NW to approximately 5th Street N. This project resulted in impacts addressed with the Credit/Debit Method as well as non-credit-debit impact of 51 linear feet (186 square feet) of aquatic area in the North and South Hill Creek Tributaries.

The North and South Hill Creek Tributaries are man-made drainage ditches that function primarily as stormwater conveyance features, collecting runoff from adjacent roadways, industrial and commercial development, and the railroad, and discharging into Hill Creek. The South Tributary is documented as supporting coho salmon in the lower reach, while the North Tributary is not documented as supporting any anadromous salmonids from the confluence with Hill Creek upstream to the project area. It is possible that juvenile coho can access reaches of the ditch downstream of the project area during the winter months, when off-channel, low-energy areas, like this ditch, may provide overwintering habitat.

The project required the lengthening of two culverts, one in each tributary, and realignment of a third culvert in the South Tributary.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 44 - Mitigation Sound Transit purchased 372 square feet of aquatic mitigation from the KC MRP, using a 2:1 mitigation to loss ratio, which will compensate for the lost opportunity or potential to support riparian habitat. The KC MRP will provide 372 square feet of aquatic habitat at the CW Mitigation Project to offset the impact and deduct 0.03 credits from the CW Mitigation Project.

2. British Petroleum: BP Seattle Bulkhead Replacement Impact Description British Petroleum’s Seattle (Harbor Island) North Bulkhead Replacement Project involved the installation of a sheet pile wall anchored with ground tiebacks in the West Waterway of the Duwamish River. The project site is located within 0.2 miles of the West Waterway’s confluence with Elliot Bay. The West Waterway is classified as Type “S”, Shoreline of the State or Type “1” Water (Washington Administrative Code [WAC] 222-16-031). Based on Washington State’s Water Quality Standards (WAC 173-201A-600 and 602), the Duwamish River is categorized as “Salmonid Rearing and Migration Only” habitat. The West Waterway is also listed by the Washington State Department of Ecology as a Category 5 (polluted) water for sediments (Washington State Department of Ecology, 2012).

This project resulted in the conversion of intertidal shoreline aquatic habitat to upland, causing 4,206 square feet (0.10 acre) of permanent impact, based on the Ordinary High Water Mark (OHWM).

Mitigation British Petroleum (BP) applied on-site mitigation to offset part of the impact. For the remaining 4,131 square feet of permanent impact to the intertidal aquatic area, BP purchased 8,262 square feet of aquatic mitigation below the OHWM from the KC MRP, using a 2:1 mitigation to loss ratio. The KC MRP will provide 8,262 square feet of mudflat habitat at the CW Mitigation Project to offset the impact and deduct 0.575 credits from the CW Mitigation Project.

3. Boeing: South Oxbow Bridge Impact Description Boeing’s South Oxbow Bridge Repair Project consisted of permanent emergency repairs to the east abutment of the bridge located on the Lower Duwamish Waterway, in the City of Tukwila. Intertidal habitat along the Lower Duwamish Waterway shoreline adjacent to the existing bridge abutment is armored with rip rap overlain with river sediments. There is a deteriorated timber bridge abutment and bridge span, and there is no natural vegetation cover at the project area.

The project resulted in permanent displacement and fill of approximately 150 square feet of intertidal habitat as a result of the installation of a sheet pile wall waterward of the existing timber pile.

Mitigation Boeing purchased 150 square feet of intertidal mitigation from the KC MRP, using a 1:1 mitigation to loss ratio. The KC MRP will provide 150 square feet of mudflat habitat at the CW Mitigation Project to offset the impact and deduct 0.01 credits from the CW Mitigation Project.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 45 - 4. Seattle Public Utilities: Puget Way SW Culvert Impact Description Seattle Public Utilities’ (SPU) Puget Way Southwest Culvert Replacement Project involved the relocation of Puget Creek flow from the existing roadway culvert into a new culvert section in the right-of-way for Puget Way SW, located in the West Seattle neighborhood of the City of Seattle. Puget Creek is a tributary to the Duwamish Waterway and receives water from numerous stormwater drainage systems associated with the dense urban development in its watershed. Based on the study done by Cedarock Consultants in 2014, the mainstem of Puget Creek is classified as Type “F” Water, i.e. fish-bearing or potential fish-bearing (WAC 222-16-030), non- man-made barriers were observed in the reach of Puget Creek upstream from the project site, and habitat access upstream of the project site was considered properly functioning.

Among the permanent impacts to aquatic habitat are those resulting from SPU’s inability to replace the 54-foot long section of the existing culvert system with a new culvert section that would meet the State of Washington’s current fish passage requirements.

Mitigation SPU worked with regulators, affected tribes and the KC MRP to identify mitigation options appropriate to offset the impacts associated with the non-fish passable portion of the Puget Way SW Culvert Replacement project. SPU purchased mitigation credits equivalent to 38 logs to be placed and/or clustered in shallow areas. These large woody materials are intended to enhance juvenile rearing habitat and the ecological functions they provide in the estuarine environment would go well beyond benefits to native migratory fish. The KC MRP will provide 38 logs at the CW Mitigation Project that will be comprised of a combination of wrack wood and perpendicular wrack wood.

5. King County: Georgetown Wet Weather Treatment Station Impact Description King County Wastewater Treatment Division's (WTD) Georgetown West Weather Treatment Station Project (GWWTS) involved the construction of a new water treatment station, conveyance system, and new outfall into the Lower Duwamish Waterway in the City of Seattle. Subsequent to receiving permits and beginning construction of the outfall, several aspects of the project changed as a result of unforeseen considerations. These changes included reconfiguring the landscape restoration plan due to unanticipated utility conflicts and increased temporal impacts from leaving a sheet pile cofferdam structure within the intertidal zone for a longer duration than anticipated. These changes will result in removal of approximately 300 square feet of intertidal habitat function due to swale installation, and temporal impacts to approximately 735 square feet of intertidal habitat from cofferdam and work extension. The 300 square feet of intertidal habitat function is largely offset through project design changes that increased other areas of intertidal habitat functionality, substituted other riparian/terrestrial habitat functions, and retained the full range of general habitat quality improvements.

Mitigation King County WTD purchased a total of 224 square feet of intertidal mitigation from the KC MRP, using a 0.5:1 mitigation to loss ratio for the intertidal habitat function impacts, and a 0.1:1 mitigation to loss ratio for the temporal impacts. The KC MRP will provide 224 square feet of aquatic habitat at the CW Mitigation Project to offset the impact and deduct 0.016 credits from the CW Mitigation Project.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 46 - 6. Muckleshoot Indian Tribe: 1st Ave Tribal Fishing Facility Impact Description The Muckleshoot Indian Tribe (MIT) 1st Avenue Tribal Fishing Facility Improvement project involved the modification and expansion of existing moorage areas at the existing fishing facility to eliminate overlap with moorage and fish offloading areas and make offloading fish from vessels safer and more efficient. The project is located at river mile 2.5 of the Lower Duwamish River in the City of Seattle, on tribally owned property along the eastern shoreline of the Lower Duwamish River.

The unavoidable impacts to aquatic habitat requiring compensatory mitigation result from the combined net increase of 3,901 square feet of overwater cover and 10 square feet of benthic fill, for a total of 3,911 square feet.

Mitigation MIT purchased a total of 3,911 square feet of intertidal mitigation from the KC MRP, using a 1:1 mitigation to loss ratio. The KC MRP will provide 3,911 square feet of aquatic habitat at the CW Mitigation Project to offset the impact and deduct 0.272 credits from the CW Mitigation Project.

Performance Standards

These standards document project performance and provide a practical way to manage the project site over the establishment phase.

Goal 1. Establish and protect wetland and aquatic functions at the Chinook Wind Mitigation Project.

Objective 1.1. Permanently protect riparian, wetland, and aquatic ecosystem functions through recordation of permanent legal protections.

Performance Standards for Administrative Documentation Functions

1.1.1. Complete development of an approved Mitigation plan has been approved by the IRT and mitigation plan. appended to the Instrument. 1.1.2. Protect ecosystem functions on the site Provide IRT with a copy of the recorded legal by placing IRT-approved legal restrictions on restrictions. parcels 092304-9153 and 092304-9292. 1.1.3. Obtain all required environmental Copies of authorizations. documentation, permits and other authorizations needed to establish and maintain the mitigation site.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 47 - Objective 1.2. Build project elements according to IRT-approved plans

Performance Standards for Construction Documentation

1.2.1. Grading, earthwork complete and habitat As-built drawing submitted to IRT for approval. features are installed. 1.2.2. Planting of site completed. As-built planting plan submitted to IRT for approval.

Goal 2. Establish riparian, intertidal high marsh, intertidal low marsh, mudflat, and aquatic habitats within the Lower Duwamish River.

Objective 2.1. Create intertidal wetland, mudflat, and aquatic area at the CW Mitigation Project. Performance Standards for Documentation Wetlands, Mudflat and Aquatic Areas

2.1.1. A minimum of 3.9 acres of Monitoring report will document hydrology by demonstrating the mitigation areas will have tidal that tides inundate the mitigation site as follows: or wetland hydrology present at Percent of Time of Year 3. Habitat Elevation Time Year2 Inundated

Aquatic/Mudflat < El. 5' >53% Feb-May Low Marsh El. 5' to < El. 7.5' 53% to 23% April-Oct High Marsh El. 7.5' to < El. 10'3 23% to 1% April-Oct

2.1.2. In Years 5 and 10, there will In Years 5 and 10, monitoring reports will document the be a minimum of 3.9 acres of combined wetlands and aquatic/mudflat features within the CW wetland, mudflat and aquatic area Mitigation Project boundary. present in the CW Mitigation Project, not including non-credit Wetland Areas: Delineate wetland boundaries according to the generating site perimeter protection Corps 1987 manual and the applicable regional supplement or easements. (ERDC/EL TR-10-3 May 2010 or as revised).

Aquatic/Mudflat: In order to count the “aquatic/mudflat features” towards the 3.9 acres, the ordinary high water mark (OHWM) must be delineated and mapped according to methodology approved by Washington State Department of Ecology and U.S. Army Corps of Engineers. Depositional areas as a result of flooding may also be included as aquatic/mudflat features.

2 Aquatic and mudflat data will be collected when juvenile Chinook salmon are likely to use the site (Feb – May). Low marsh and high marsh data will be collected during the growing season (April – Oct). 3 Capillary fringe and groundwater gradients will extend wetland hydrology to elevations above those directly inundated by tides. In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 48 -

Objective 2.2. Establish native vegetation in wetland areas. Performance Standards for Vegetation in Documentation Created Wetland Areas

2.2.1. At Year 1, the average density of planted Monitoring reports documenting planted native native shrubs and trees in woody planting areas of shrub and tree density in Year 1. the high marsh habitat will exceed 1,740 per acre (4/100 ft2 or 5 feet o.c.).

2.2.2. Crown cover of native shrubs and trees in Monitoring reports documenting measurements of woody planting areas of the high marsh habitat native crown cover. Crown cover will be will be a minimum of 15% at Year 3, 30% at Year measured in Years 3, 5, 7, and 10. 5, 50% at Year 7, and 70% at Year 10. Volunteers of desirable native tree and shrub species taller than one foot can count towards achieving the crown cover percentages.

2.2.3. Crown cover of native emergent within the Monitoring reports documenting measurements of low marsh and high marsh areas between Els. 5’ native crown cover. Crown cover will be and 10’ NAVD88 will be a minimum of 15% at measured in Years 3, 5, 7, and 10. Year 3, 30% at Year 5, 50% at Year 7, and 70% at Year 10.

Objective 2.3. Establish native vegetation in riparian areas. Performance Standards for Vegetation in Documentation Riparian Areas

2.3.1. At Year 1, the average density of planted Monitoring reports documenting planted native native shrubs and trees in riparian areas (between shrub and tree density in Year 1. Els. 10’ and 13’) will exceed 1,740 per acre (4/100 ft2 or 5 feet o.c.).

2.3.2. Crown cover of native shrubs and trees in Monitoring reports documenting measurements of riparian areas (between Els. 10’ and 13’) will be a native crown cover. Crown cover will be minimum of 15% at Year 3, 30% at Year 5, 50% measured in Years 3, 5, 7, and 10. at Year 7, and 70% at Year 10. Volunteers of desirable native tree and shrub species taller than one foot can count towards achieving the crown cover percentages.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 49 - Objective 2.4. Maintain a mitigation site that is dominated by native vegetation through management of non-native and noxious weeds.

Performance Standards for Non-native and Documentation Noxious Weeds on the Mitigation Site

2.4.1. In Years 1, 3, 5, 7, and 10, King County- Monitoring report documenting the control of any listed Class A weeds designated for control by the Class A weeds and non-native knotweed at Years County Weed Board will be absent from the CW 1, 3, 5, 7, and 10. Mitigation Project as well as non-native knotweed [including but not limited to: Japanese knotweed (Polygonum cuspidatum), giant knotweed (Polygonum sachalinense), Himalayan knotweed (Polygonum polystachyum), Bohemian knotweed (Polygonum x bohemicum) and related hybrids]. If present, these weeds will be controlled.

2.4.2. The combined ground cover (total cover of Monitoring reports documenting non-native the target vegetation on an area of ground; invasive species cover and control efforts in the Bonham (2013)) of the following invasive plants created and re-established wetland. Document will be a maximum of 10% at Years 3, 5, 7, and percent cover of listed invasive plants at Years 3, 10 in the created and re-established wetland 5, 7, and 10. Document the percent cover of habitats: invasive species in each habitat type. Qualitative monitoring will be documented in Year 1. • non-native blackberries (Rubus armeniacus and R. laciniatus), • Scotch broom (Cytisus scoparius) • thistles (Cirsium arvense, C. vulgare, Carduus nutans, and Onopordum acanthium), • purple loosestrife (Lythrum salicaria), • yellow-flag iris (Iris pseudacorus), • English and Atlantic ivy (Hedera helix and H. hibernica), • English holly (Ilex aquifolium) • butterfly bush (Buddleia davidii), • field bindweed (Convolvulus arvensis) • large bindweed (Convolvulus sylvatica), • black/climbing/ivy bindweed (Fallopia convolvulus) • morning glory/hedge bindweed (Convolvulus sepium), • non-native cordgrass (Spartina alterniflora. S. anglica, S. densiflora, S. patens, and Spartina x townsendii), • common reed (Phragmites australis), • Any other Class B or Class C weeds designated for control by King County

2.4.3. The combined ground cover of reed Monitoring reports documenting non-native canarygrass (phalaris arundinacea) will be a invasive species cover and control efforts. maximum of 20% at Years 3, 5, 7, and 10.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 50 - Document percent cover of listed invasive plants at Years 3, 5, 7, and 10.

Goal 3. Increase aquatic habitat functions and availability for fish and wildlife by creating and maintaining persistently inundated off-channel features.

Objective 3.1. Create a fish passable backwater channel with an outlet elevation that is passable by fish during most tides.

Performance Standards for Backwater Documentation Channel

3.1.1. At Year 0, backwater channel will be As-built drawing submitted to IRT for approval. constructed to allow fish use and passage in the as-built condition.

3.1.2. At Years 1, 3, 5, 7 and 10, the channel Monitoring report documenting elevation of outlet outlet minimum elevation does not exceed El. 4’ during low tide in July or August at Years 1, 3, 5, NAVD 88 as measured during once during low 7, and 10. tide in July or August.

Objective 3.2. Survey the backwater channel for juvenile salmonids between March 1 and May 31.

Performance Standard for Backwater Documentation Channels

3.2.1. In Years 1, 3, 5, 7, and 10, backwater Monitoring reports documenting results of survey channel will be surveyed for presence/absence of for juvenile salmonids in the backwater channel. juvenile salmonids. Survey will occur between March 1 and May 31 at Years 1, 3, 5, 7, and 10.

Objective 3.3. Place and retain large wood that can provide cover for fish and wildlife and habitat for invertebrate production.

Performance Standards for Large Wood Documentation

3.3.1. Retention of large wood, documented in the In Years 1, 3, 5, 7, and 10, count the number of As-Built drawing, will be at least 90% in Year 1, large wood pieces remaining at the CW 80% in Year 3, 70% in Year 5, 60% in Year 7, Mitigation Project. Pieces undisturbed by the river and 50% in Year 10. but obscured by vegetation or racked wood are assumed to be present. Placed and recruited wood (at least as large as placed wood) will count toward the Year 10, 50% retention Performance Standard.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 51 - Objective 3.4. Minimize impact of public access components on mitigation components by maintaining separation and controlling non-native vegetation.

Performance Standards for Public Access Documentation Components

3.4.1. In Years 1, 3, 5, 7, and 10 fences and signs In Years 1, 3, 5, 7, and 10, inventory and will be inspected and maintained as necessary. photograph the condition of public access components.

3.4.2. In Years 1, 3, 5, 7, and 10, King County- Monitoring report documenting the control of any listed Class A weeds designated for control by the Class A weeds and non-native knotweed at Years County Weed Board will be absent from the trail 1, 3, 5, 7, and 10. easement as well as non-native knotweed [including but not limited to: Japanese knotweed (Polygonum cuspidatum), giant knotweed (Polygonum sachalinense), Himalayan knotweed (Polygonum polystachyum), Bohemian knotweed (Polygonum x bohemicum) and related hybrids]. If present, these weeds will be controlled.

3.4.3. The combined ground cover (total cover of Monitoring reports documenting non-native the target vegetation on an area of ground; invasive species cover and control efforts in the Bonham (2013)) of the following invasive plants trail easement. Document percent cover of listed will be a maximum of 30% at Years 3, 5, 7, and invasive plants at Years 3, 5, 7, and 10. Document 10 in the trail easement: the percent cover of invasive species in the trail easement. Qualitative monitoring will be • non-native blackberries (Rubus armeniacus documented in Year 1. and R. laciniatus), • Scotch broom (Cytisus scoparius) • thistles (Cirsium arvense, C. vulgare, Carduus nutans, and Onopordum acanthium), • purple loosestrife (Lythrum salicaria), • yellow-flag iris (Iris pseudacorus), • English and Atlantic ivy (Hedera helix and H. hibernica), • English holly (Ilex aquifolium) • butterfly bush (Buddleia davidii), • field bindweed (Convolvulus arvensis) • large bindweed (Convolvulus sylvatica), • black/climbing/ivy bindweed (Fallopia convolvulus) • morning glory/hedge bindweed (Convolvulus sepium), • non-native cordgrass (Spartina alterniflora. S. anglica, S. densiflora, S. patens, and Spartina x townsendii), • common reed (Phragmites australis), • reed canarygrass (phalaris arundinacea) • Any other Class B or Class C weeds designated for control by King County

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 52 - Monitoring Methods

Mitigation monitoring will be documented in a monitoring report in Years 1, 3, 5, 7, and 10 after construction or until the IRT approves the final report. Reports will be submitted to the IRT by April following the monitoring activities unless the IRT approves an extension. The monitoring methods may be revised with IRT approval to improve consistency and accuracy.

Protocol for mapping wetlands and river features:

In Years 5 and 10, document the combined wetlands and aquatic habitat features on the entire site.

Conduct a wetland delineation in Years 5 and 10, in accordance with the 1987 Corps manual and the Regional Supplement for the Western Mountains, Valleys, and Coast Region (ERDC/EL TR- 10-3 or as revised). Year 5 documentation will be in a memo format. Year 10 documentation will be a report that includes a full wetland rating. The wetland delineation must also include the following:

• A brief description and references for methodology used (both for wetland delineation and for delineating OHWM and “aquatic features” (aquatic and mudflat habitats); • The names of staff conducting the delineation; • Dates of field work; • Explanation of any “Difficult Wetland Situations” methods were used (see Chapter 5 of the WMVCR Supplement); and • A map of the aquatic features outside of delineated wetland. Aquatic features are areas that are too frequently inundated by tides to support sufficient vegetation to be categorized as a wetland or created wetlands that were naturally altered by riverine processes and may include channels, permanently or seasonally-disconnected side flows, isolated or altered backwaters and pools, and depositional areas such as sand/ gravel bars and shelves, and other accumulations as a result of flooding. • Use of a precision GPS to map features in the field. Recent orthophotography or LiDAR elevations (taken within one year of the monitoring year) can be used to determine wetland boundaries with field verification.

Protocol for demonstrating tidal or wetland hydrology:

In Year 3, hydrologic data collected from the nearby river stage gauge (USGS Gauge 12113415) and at least one shallow groundwater well located at El. 10’ NAVD88 within the project site will be used to document the extent of wetland hydrology per criteria in the 1987 Corps manual and the Regional Supplement for the Western Mountains, Valleys, and Coast Region (ERDC/EL TR- 10-3). Recent orthophotography or LiDAR elevations (taken within one year of the monitoring year) can be useful to show wetland saturation and hydrology but require field verification.

1. Collect data February-May for mudflat and aquatic areas. 2. Collect data April-October for low marsh and high marsh areas.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 53 - Protocol for determining density of shrubs and trees:

1. Randomly locate plots to sample 1%-5% of each of the two habitat types with woody vegetation: 1) riparian areas (above El. 10’ NAVD88), and 2) high marsh areas planted with scrub-shrub species (areas with woody-stemmed vegetation below El. 10’ NAVD88). The performance standards address each habitat type separately, and each habitat type will be sampled independently to the extent possible. 2. Establish rectangular belt transects 20 x 2 m (65.6 x 6.6 ft) along a tape measure to fit the sample entirely inside the habitat type. 3. Use two 2-m (6.6 ft) PVC pipes marked at the midpoints to delineate each quadrat, using the measuring tape as a reference point. Advance one pole at a time (e.g., in a ‘leap-frog’ pattern) to survey the next quadrat without double-counting. 4. Count the combined number of live planted woody shrub and tree stems in each belt transect sample. The base of the plant must fall within the belt transect to be counted. 5. Results will be presented as density of living, installed plants per acre (and average feet on center spacing) and compared to the performance standard. 6. Monitor the two habitat types in Year 1.

Protocols for estimating percent crown cover of vegetation:

1. Measure cover of native species and non-native weeds at the end of the growing season before leaf drop (e.g., August to mid-September). Native species will be measured in each of the three habitat types 1) riparian; 2) high marsh wetland; and 3) low marsh wetland. Non-native weeds will be measured on the entire mitigation site, including the trail easement. 2. Calculate cover of native vegetation (woody and non-woody) and non-native weeds as the reciprocal of Crown-Free Projection or CFP (Bonham 2013). a. CFP = (S/T)*100, where S is the number of native vegetation-intercepted sightings and T is the total number of observations made with the use of a two- way leveled periscope (a GRS densitometer) pointed toward the sky or the ground. 3. Collect plant occurrence data at vertical intercepts located at each ½ meter (1.6 ft) or 1 meter-mark (3.3 ft) along each transect, for a total of 100 sample points per planting zone. At each interval, a “hit” on a species is recorded if a vertical line at that point would intercept the stem or foliage of that species. Only one “hit” is recorded for a species at a point even if the same species would be intercepted more than once at that point. 4. Tally the total number of “hits” for each species along each transect. The result is a list of species and their frequencies of occurrence (Mueller-Dombois and Ellenberg 1974; Tiner 1999). Report cover as percentages: 5. Total cover = Percent of sample points with hits (out of 100%). 6. Species-specific cover = Percent of sample points hitting the species of interest. 7. For total and species-specific cover, calculate the average across replicated transects for each habitat type. 8. Measure weed cover at the same sample points as vegetation cover and record species to generate total and species-specific weed cover estimates. 9. Monitor weed cover in Years 1, 3, 5, 7, and 10. Year 1 monitoring is qualitative

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 54 - 10. Monitor native species cover in riparian, high marsh wetland, and low marsh wetland in Years 3, 5, 7, and 10. 11. During monitoring site visits, note any presence of zero-tolerance invasives outside of monitoring transects.

Protocol for assessing aquatic habitat functions and availability for fish and wildlife:

1. Establish a permanent hub of known elevation west of the channel outlet and above El. 10’ 2. Assess backwater channel connectivity to the mainstem river channel one time at low tide in July or August by measuring the minimum elevation of the thalweg at the interface between the backwater channel and mainstem river channel using the established elevation hub, a level and stadia rod. 3. Document use of the backwater channel by juvenile salmonids one time between March 1 and May 31 of each monitoring year. Fish sampling will be conducted using a PSP (Puget Sound Protocol) beach seine. The “Puget Sound Protocol” (PSP) net was adopted for use in marine nearshore areas and based on studies by Simenstadt (1991). The net set will attempt to cover both vegetated and mudflat areas of the site. Seining will be conducted with one individual on the bank holding one end of the net, while a boat deploys the net out away from the bank in a downstream direction. Once deployed, the boat operator will use the boat to push the net upstream and in a large semi-circle around the individual on the bank. Once the semi-circle has been completed, both ends of the net will be drawn together on the bank and the net hauled in. In the event that the seine became snagged or otherwise compromised, the set will be abandoned, and data discarded. Another set would then be attempted near, but not overlapping (to the extent possible) with the previous attempt. Monitoring in subsequent years will attempt to replicate the earlier net set locations and methods. In the event that large numbers of fish are captured, a portion of fish will be subsampled for length measurements and the rest simply counted and released without being anesthetized. During each seine set, a GPS will be used from the bow of the boat to log the exact outline of each seine set, enabling the calculation of the area sampled for each set. The number of each species captured within the set will be divided by the area to produce a density measurement for the seine set (fish/100m2). Sampling will be conducted during high tides when intertidal areas are underwater. 4. Monitor in Years 1, 3, 5, 7, and 10

Protocol for estimating retention rate for placed large wood:

Count large wood pieces remaining within the mitigation project area, including wood deposited by the river (recruited wood). Only count recruited pieces that meet the criteria for large wood (>6’ long and >6” in diameter).

1. Analyze large wood survey data by comparing observed large wood abundance (placed and recruited) to placed wood abundance recorded in the approved as-built report. 2. Monitor in Years 1, 3, 5, 7, and 10.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 55 - Protocols for inspecting public access components:

1. In Years 1, 3, 5, 7, and 10 walk the perimeter of the credit-generating mitigation area and note condition of signs and fences and evidence of degradation by the public, including but not limited to encampments, trash or other debris, unauthorized trails, or other evidence of human-caused degradation of ecological functions 2. Photograph the condition of fences, signage, and signs of trash, vandalism. 3. Document maintenance implemented to correct issues identified by monitoring activities.

A. Reporting

1. As-Built Plans As-built reports will be submitted to the IRT upon the completion of construction to verify topography, hydrology, habitat features, planting, and contaminated soil cleanup. At a minimum, the following components should be included in the as-built reports:

• Name and contact information for the parties responsible for the mitigation site construction; • Ecology, Corps, and Local permit numbers; • Dates when activities began and ended such as grading, installation of the large wood, removal of invasive plants, installing plants, installing habitat features, etc.; • Description of any problems encountered, and solutions implemented (with reasons for changes) during construction of the mitigation site; • Maps showing topography, mitigation action areas (riparian, low marsh, high marsh, mudflat, aquatic), plant communities (as listed in the planting tables) installed, locations of installed large wood and habitat features; photopoint locations; etc.; • Maps documenting as-built changes from the approved design; • Post Project Soils Condition Report

2. Monitoring Report Monitoring reports will include the following elements:

• An overview of the current ecological condition of the mitigation site; • Data summary description and tables (include raw plot data in an appendix); • Assessment of applicable performance standards and whether they were achieved - include tables which list the applicable performance standards for the monitoring year, and whether or not each performance standard was met, along with any corrective actions proposed; • Description and schedule of maintenance actions undertaken since the previous monitoring report and maintenance actions recommended to keep the site on course to satisfy PSs; • Discussion about the likely causes and impacts of any setback or failure that occurred and recommendations for future actions and strategies that might resolve those problems; • Observations of fish and wildlife use of the site; • Photographs of the site;

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 56 - • Dates monitoring was conducted and names of people who conducted the monitoring; • Monitoring map(s) based on the as-built maps showing the different vegetation communities and the mitigation action areas (aquatic, low marsh, high marsh, riparian); locations of large wood; locations of monitoring plots/transects; photo points; etc.

The monitoring report must document any IRT-approved changes to the monitoring methods. Maintenance plan

Maintenance plays an important role in successfully establishing vegetation at a project site and addressing unacceptable impacts and damage. The goal of the maintenance plan is to ensure the mitigation project performance standards are met.

Site maintenance will be managed by King County staff during the 10-year monitoring period. Maintenance crews will also report back to King County staff with any damage (goose/animal browse, vandalism, unknown cause of mortality) or other issues observed on site. Areas within the trail easement will be maintained by the City of Tukwila. Long term management of the site is expected to be transferred to the City of Tukwila following IRT approval.

Goose Management

Geese have been known to cause extensive and expensive damage to plantings along the Duwamish River, especially to new shoots and starts of emergent plants. Physical structures to exclude geese from vulnerable plants will be installed during project construction and maintained as needed until plants are sufficiently mature. Other means of discouraging geese from the site will also be considered as needed.

Plant Maintenance

King County staff will manage and determine the maintenance needs of the site annually. If plants fail to thrive because of low soil moisture, King County may reduce competition for water by treating competitive grasses around the plants or by adding wood mulch or similar. Irrigation may also be used.

Plant Replacement Plan

Ungulate browsers, voles, beavers, birds and human vandalism may damage plantings. If this damage is extensive enough, so the project is unable to meet the performance standards for cover, amendment planting may be necessary. If plant mortality or slow growth prevents the project from meeting performance standards, supplemental plantings may be added to increase cover. If plants die because the hydrology is different than expected, substitute native plant species with a more suitable life-history will be installed.

Structure Maintenance/Repair

In each monitoring year, any anchoring for large wood will be inspected and replaced as determined by the project engineer or equivalent.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 57 - Weed Treatment

Invasive weeds will be removed by hand or treated with suitable herbicides by licensed staff and in accordance with King County best management practices and the manufacturer’s label. Aggressive grasses around individual plants may be controlled if the competition inhibits native plant growth.

Fence and Signs

In each monitoring year, the fence and signs between the mitigation area and the trail easement will be inspected. Missing or vandalized signs will be replaced. Broken fence elements will be repaired or replaced. Signs of public access between the trail and the mitigation area will be assessed to determine if actions can be taken to discourage off trail navigation, such as installing additional vegetation.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 58 - Credit Release Schedule

Table 13 Credit Release Schedule

Chinook Wind Mitigation Project Credit Release Schedule Total Credits 9.60 Pre Construction Credits 1 Year 0 Credits 2 Year 1 Credits Year 3 Credits Year 5 Credits Year 7 Credits Year 10 Credits3 Total Credits Administrative Protections 1.1.1. Approved Mitigation Plan 0.44 0.44 1.1.2. Legal Protections Property 0.44 0.44 1.1.3. Permits 0.44 0.44 Construction 1.2.1 Grading/Earthwork, Habitat Features Installed 0.48 0.48 1.2.2. Planting Complete 0.48 0.48 3.1.1. Backwater Channels Allow Fish Passage 0.48 0.48 Wetlands & Tidal Features 2.1.1. Hydrology 0.30 0.30 2.1.2. Minimum Wetland Acreage 0.36 0.36 0.72 3.1.2. Backwater Channel Inundation 0.16 0.16 0.16 0.16 0.16 0.80 3.2.1 Backwater Channel Juvenile Salmonid Survey 0.08 0.08 0.08 0.08 0.08 0.40 Vegetation 2.2.1. Woody Planting Density (Wetland Creation) 0.12 0.12 2.3.1. Planting Density (Riparian Area) 0.12 0.12 2.2.2. Crown Cover (Woody Wetland Creation) 0.13 0.13 0.13 0.13 0.52 2.2.3. Crown Cover (Emergent Wetland Creation) 0.13 0.13 0.13 0.13 2.3.2. Crown Cover (Riparian Area) 0.13 0.13 0.13 0.13 0.52 2.4.1. Cover of Invasive Species (zero tolerance) 0.13 0.13 0.13 0.13 0.13 0.65 2.4.2. Cover of Invasive Species (10% tolerance) 0.13 0.13 0.13 0.13 0.13 0.65 2.4.3. Cover of Reed Canarygrass 0.13 0.13 0.13 0.13 0.52 Large Wood 3.3.1. Large Wood Retention 0.13 0.13 0.13 0.13 0.13 0.65 Public Access Components 3.4.1. Public Access Components Inspected and Maintained 0.07 0.07 0.07 0.07 0.07 0.35 Total Credits Available in the Period 1.32 1.44 0.94 1.52 1.58 1.22 1.58 9.60 Percentage of Credits Available 14% 15% 10% 16% 16% 13% 16% Cumulative Percentage of Credits Available 14% 29% 39% 54% 71% 84% 100%

1 WAC 173-700-331 states that up to 14% of the potential credits for the bank may be released at preconstruction 2 WAC 173-700-332 states that up to 30% of the potential credits for the bank may be released when the bank is constructed and the IRT approves the as-built 3 WAC 173-700-334 outlines the criteria for final credit release Year 0 is the calendar year during which construction is completed and the as-built drawings are submitted by the Sponsor and approved by the IRT. Year 1 is the first year of site monitoring following approval of the as-built drawings.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 59 - Adaptive Management Plan

An adaptive management plan is one way King County and the IRT to facilitate the successful achievement of mitigation obligations at the CW Mitigation Project while at the same time being consistent with natural processes. As described in the Adaptive Management and Contingencies Planning in Appendix O of the Program Instrument (King County 2012), “Adaptive management plans included with mitigation plans will necessarily lack specific measures to address underperformance, since the type of underperformance will not be known at the time the Mitigation Plan is developed. Specific corrective measures will be developed if and when underperformance details become clear. Any and all adaptive management measures will be appended to the Mitigation Plan and the IRT will review and comment on any additions or amendments to Mitigation Plans.” Regular monitoring will be used to determine whether performance standards are being met and may reveal the causes of underperformance and inform possible solutions.

Although many problems may be unforeseeable, a few plausible problem scenarios can be developed for the purpose of scenario or situation-planning. Conditions of concerns can then be described and time-bounded, and a progression of potential actions can be proposed to address each problem scenario. Strategies described below represent examples of progressive steps toward addressing unacceptable project outcomes. Many of the actions listed below would require permits, IRT approval, and King County authorization.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 60 - Table 14 Example Adaptive Management Strategies

Scenario Description Progression of Adaptive Management Strategies Wetland shortfall Post-construction delineations 1. Consult with IRT and appropriate agencies show wetland establishment area 2. Change the plant community is less than expected 3. Adjust credits 4. Modify soil hydrology by either raising water levels or lowering ground surface through minor grading 5. Establish additional compensatory wetland areas

Plants fail to thrive Plant cover performance 1. Install plants at higher density standards are not met for reasons 2. Use different plant species other than goose activity 3. Consult with IRT and appropriate agencies

Geese impacts Plant cover performance 1. Consult with IRT and appropriate agencies standards are not met because of 2. Install additional goose exclusion goose browse measures or repair existing structures 3. Investigate new or alternative means of excluding geese from the site.

Weeds not controlled Noxious weeds performance 1. Initiate additional invasive removal (e.g. standards not met hand; mechanical, or chemical as part of an integrated pest management approach 2. Extend establishment phase

Too much LW lost Placed wood retention 1. Consult with IRT and appropriate agencies performance standards unmet 2. Increase stability of remaining LW 3. Install additional wood within the project area 4. Install additional wood outside the project area

Vandalism/un- Encampments, dumping, or 1. Report to City of Tukwila Police authorized use trail-building damages the site 2. Install signage to discourage such activities 3. Restrict access (various options) 4. Consult with IRT and appropriate agencies, including Sheriff

Vandalism/damage in Encampments, dumping, or 1. Report to City of Tukwila Public Works trail easement vandalism to fencing or signs in and City of Tukwila Police trail easement 2. Work with City of Tukwila Public Works to minimize opportunities for vandalism (e.g. close at night, host work parties, etc.) 3. Restrict access (various options) 4. Consult with IRT and appropriate agencies, including Sheriff

King County retains the flexibility to implement adaptive management actions in consultation with the IRT that are consistent with the larger mitigation objectives. Minor adaptive management actions (re-planting, weed control, vandalism) do not require consultation with the IRT and will be implemented and reported on in required monitoring reports. Emergency actions

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 61 - to avoid or reduce off-site flooding or damages also do not require consultation with the IRT, but the IRT should be informed and/or consulted after emergency action has been taken.

If monitoring results indicate that performance standards are not attainable due to goose activities or other natural processes, such as deposition, erosion or channel migration, King County will consult with the IRT on appropriate responses and/or revisions to performance measures. The intent of both parties will be to meet the mitigation obligations without compromising natural processes or implementing actions adverse to the WRIA 9 Salmon Recovery Plan. Site Protection

All of the parcels within the CW Mitigation Project are owned by King County. These parcels will be permanently protected by restrictive covenants or a conservation easement placed on title consistent with the requirements of the In-Lieu Fee Program as described in the Program Instrument. A trail easement is planned to be granted to the City of Tukwila after a restrictive covenant is recorded on the parcels. The trail easement granted to the City of Tukwila will include discrete rights as described in VI. F. The trail easement will be subordinate to the restrictive covenant so provisions of the restrictive covenant will also apply to the trail easement area. Following the establishment phase, King County intends to transfer fee ownership of the CW Mitigation Project to the City of Tukwila. Any transfer of fee ownership will be coordinated with the IRT.

Long Term Management Plan

Long term maintenance of the CW Mitigation Project refers to monitoring and maintenance beyond the ten-year establishment phase. King County intends for the site to need little or no long-term maintenance, but some maintenance activities may be needed. After the ten-year establishment phase for the CW Mitigation Project, King County intends to transfer fee ownership to the City of Tukwila. Long term responsibility for the site and controlling listed noxious weeds as required by law is also expected to be transferred to the City of Tukwila, after IRT and City of Tukwila approval.

Long-Term Management and Maintenance Plan (LTMMP)

King County, as ILF Sponsor, is responsible for ensuring that an LTMMP is developed and implemented to protect and maintain in perpetuity the wetland functions and values of the CW Mitigation Project. This plan must be approved by the Corps, following consultation with the IRT, prior to the termination of the establishment period of the CW Mitigation Project. Once the establishment period of the CW Mitigation Project has terminated pursuant to the ILF Instrument, the Sponsor will assume responsibility for implementing that LTMMP, unless the Sponsor assigns this responsibility pursuant to the provisions of ILF Instrument; it is possible that the Sponsor could assign LTMM responsibility to the City of Tukwila. The Sponsor will seek IRT review and approval for any assignment to another King County workgroup or external entity.

To gain IRT approval, the LTMMP will consist of enumerated objectives. King County or its approved steward assignee will document that it is achieving each guideline and objective in the In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 62 - LTMMP by submitting status reports to the IRT on a schedule approved by the IRT. The purpose of the CW Mitigation Project is to establish wetland and riparian habitat and provide backwater/off-channel rearing and refuge habitat for juvenile salmonids that achieves the intended level of wetland ecosystem functionality. As such, natural changes (i.e., sediment deposition, channel migration, flood deposits) to the vegetative community, other than changes caused by noxious weeds, that occur after all CW Mitigation Project performance standards have been met are not expected to require remediation.

The LTMMP will include those elements necessary to provide long-term protection for the wetland ecosystem and habitat resources of the CW Mitigation Project. The specific elements of the Plan must be tailored to meet the specific protection needs of the CW Mitigation Project. At minimum, the IRT will likely find the following core elements to be necessary for inclusion in the LTMMP. The particular characteristics of the CW Mitigation Project at the end of the establishment period may necessitate including other elements not specified below, that are needed to protect the ecosystem resources present at the site.

(1) The CW Mitigation Project will be inspected for signs of trespass and vandalism during monitoring visits. Maintenance will include reasonable actions to deter trespass and repair vandalized features. Signage will be posted on site listing legal uses of the site. Inspections will include reporting the condition of the trail easement area. This area may need maintenance to limit noxious weed intrusion. Fences and signs will be monitored and repaired as needed.

(2) Monitor the condition of structural elements and facilities of the CW Mitigation Site such as signage. The LTMMP will include provisions to maintain and repair these improvements as necessary to achieve the objectives and functional performance goals of the CW Mitigation Project and comply with the provisions of the restrictive covenant or conservation easement. Improvements that are no longer needed to facilitate or protect the ecological function of the CW Mitigation Project may be removed or abandoned if consistent with the terms and conditions of the restrictive covenant or conservation easement.

(3) Inspect the site to locate and control noxious weeds on the applicable list of noxious weeds maintained by King County and/or as directed by the IRT. The IRT anticipates that this long- term control will involve identifying and eradicating a relatively small number of recurrences. In the event the Corps, in consultation with the IRT, determine that the watershed within which the site is located becomes infested with these species in the future, so that their effective control on the CW Mitigation Site is either no longer practicable or unreasonably expensive, the IRT will consider appropriate changes to the LTMMP.

If the Sponsor elects to request the approval of the IRT to assign long-term management and maintenance to a Long-Term Steward, such as the City of Tukwila, pursuant to the King County ILF Instrument, the long-term management and maintenance assignment agreement will reflect that the assignee has assumed the obligation, owed to the IRT, of accomplishing the LTMMP.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 63 - Financial Assurances

As stated in Appendix R of the Program Instrument, the federal rule requires in-lieu fee program sponsors to provide financial assurances “sufficient to ensure a high level of confidence that the compensatory mitigation project will be successfully completed, in accordance with its performance standards.” [33 CFR 332.4(c)(13)] King County has several safeguards “built in” to the program to ensure adequate funds including:

• Credits prices based on actual project costs • A percentage of each fee is directed to a contingency fund • A land fee is included in addition to the credit fee • An interest-accruing, stand-alone mitigation fund which is protected by code from being used for other purposes • Allocation of interest to the contingency account

Should the sources of money be insufficient to secure the required number of credits, the MRP is committed to seeking funds through the King County appropriations process in order to meet permit requirements that have been assumed by the program (King County, 2012).

Force Majeure

If an event occurs, beyond the reasonable control of King County, which results in significant adverse impacts to the project, the Force Majeure terms of the ILF Mitigation Reserves Program Instrument will apply.

A. Force Majeure: The Sponsor may request, pursuant to Article VI.C. of the Basic Agreement of the Program Instrument, and the Corps may approve changes to the construction, operation, project objectives, performance standards, timelines or crediting formula of the Mitigation Reserves Program, pursuant to the standards and procedures specified in applicable Appendices if all of the following occur: an act or event causes substantial damage such that it is determined to be a force majeure; such act or event has a significant adverse impact on the quality of the aquatic functions, native vegetation, or soils of the mitigation site; and such act or event was beyond the reasonable control of the Sponsor, its agents, contractors, or consultants to prevent or mitigate.

1. The evaluation of the damage caused by a force majeure and the resulting changes to mitigation requirements will necessarily involve communication among the Parties and the IRT. If the Sponsor asserts a mitigation site has sustained significant adverse impacts due to an event or act which may be determined to be a force majeure, the Sponsor shall give written notice to the Corps and the IRT as soon as is reasonably practicable. After receiving written notice, the Corps, in consultation with the Sponsor and the IRT, shall evaluate whether the event qualifies as force majeure. The Corps, in consultation with the Sponsor and the IRT, will then evaluate whether significant adverse impacts have occurred to the site. If a force majeure event is determined to have

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 64 - occurred and significant adverse impacts are found to have occurred to the site, the Corps, in consultation with the IRT and the Sponsor, will evaluate whether and to what extent changes to the mitigation site will be in the best interest of the site and the aquatic environment, and may approve such changes as detailed in paragraph A above. The Corps retains sole discretion over the final determination of whether an act or event constitutes force majeure, whether significant adverse impacts to a mitigation site have occurred, and to what extent changes to a mitigation site will be permitted.

2. Force majeure events include natural or human-caused catastrophic events or deliberate and unlawful acts by third parties. a. Examples of a natural catastrophic event include, but are not limited to: a flood equal to or greater in magnitude than the 100-year flood event; an earthquake of a force projected from an earthquake with a return period of 475 years; drought that is significantly longer than the periodic multi-year drought cycles that are typical of weather patterns in the Pacific Northwest; as well as events of the following type when they reach a substantially damaging nature: disease, wildfire, depredation, regional pest infestation, or significant fluviogeomorphic change. b. Examples of a human-caused catastrophic event include, but are not limited to substantial damage resulting from the following: war, insurrection, riot or other civil disorders, spill of a hazardous or toxic substance, or fire. c. Examples of a deliberate and unlawful act include, but are not limited to substantial damage resulting from the following: the dumping of a hazardous or toxic substance, as well as significant acts of vandalism or arson. Implementation

Responsibility for completing the mitigation has been transferred to King County as part of agreements with multiple impact project proponents through King County’s state and federally authorized ILF Mitigation Program. King County will implement this mitigation by utilizing a combination of King County resources, contractors and sub-contractors. While the timing of some actions may be dictated by agreements between KC and these contractors, overall responsibility for meeting these mitigation obligations will remain with King County.

A. Responsible Parties Senior Managing Ecologist and ILF Program Manager King County Department of Natural Resources and Parks M.S. KSC-NR-0600 201 South Jackson Street Seattle, WA 98104-3855

B. Reporting Once the mitigation is installed, King County will provide an “as-built” drawing to the IRT. Following construction, the project will be monitored annually for 10 years to track the success of the project and identify maintenance needs. Monitoring reports evaluating the success of the project in meeting the stated goals, objectives and performance standards will be prepared and

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 65 - submitted in Years 1, 3, 5, 7, and 10 in accordance with the approved monitoring and maintenance plan.

C. Access Access to the site will be provided to members of the IRT to verify site conditions and ensure the mitigation is implemented according to the approved plan. The site is publicly owned and access is allowed for passive recreation, such as fishing or bird watching for members of the public; however, signs will be posted proclaiming the site as a mitigation site and environmentally sensitive area, including language to prevent access using any mode of travel other than walking. An easement granted to the City of Tukwila will allow public access to the perimeter trail. The perimeter trail will be physically separated from the CW Mitigation Site by a split rail fence. While the Sponsor cannot outright exclude members of the public from accessing the portion of the site where King County is implementing the CW Mitigation Project, such public access will not be encouraged in any way. To help discourage public use of the environmentally sensitive areas of the CW Mitigation Project, species with thorns (e.g. Nootka rose) will be planted in these areas to discourage human traffic off of the trail. Areas between the trail easement or the site and Elevation 10’ will be graded to a 4:1 slope and densely planted. These design features will be implemented to discourage camping and other undesirable uses of these areas. Areas below Elevation 10’ will be frequently inundated by tides and therefore muddy and inhospitable to camping and most other potential human uses. Public use of the site (or lack thereof) will be periodically assessed by the Sponsor and discussed with the IRT. Any corrective measures necessary related to public access will be addressed through adaptive management in coordination with the IRT.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 66 - References

Anderson, J. H. and P.C. Topping. 2017. Draft Juvenile Life History Strategies and freshwater productivity of Green River Chinook Salmon. Prepared for the WRIA 9 Implementation Technical Committee, Seattle WA.

Aspect Consulting. 2015. Geotechnical Subsurface Conditions Summary and Stable Slope Assessment, Chinook Wind Property, 11244 and 11250 Tukwila International Boulevard, Tukwila, Washington. Technical memorandum for King County Water and Land Resources Division, Seattle, WA.

Beamer, E., A. McBride, C. Greene, R. Henderson, G. Hood, K. Wolf, K. Larsen, C. Rice, and K. Fresh. 2005. Delta and nearshore restoration for the recovery of wild Skagit River Chinook salmon: linking estuary restoration to wild Chinook salmon populations. Supplement to Skagit Chinook Recovery Plan, Skagit River System Cooperative, LaConner, Washington.

Beechie, T. J., M. Liermann, E. M. Beamer, and R. Henderson. 2005. A classification of habitat types in a large river and their use by juvenile salmonids. Transactions of the American Fisheries Society, 134(3): 717-729.

Bjornn, T. and D.W. Reiser. 1991. Habitat requirements of salmonids in streams. American Fisheries Society Special Publication, 19(837): 83-138.

Campbell, L. and A. Claiborne. 2017. Otolith Study by WDFW from 2016 CWM grant.

Coastal Geologic Services, Inc. 2019. Chinook Wind Geomorphological Assessment. Prepared for King County Water and Land Resources Division. Seattle, Washington.

Collins, B. and A. Sheikh. 2005. Historical Habitats in the Green and Duwamish River Valleys and the Elliott Bay Nearshore, King County, Washington. King County Department of Natural Resources and Parks, Seattle, WA.

Cordell, J., J. Toft, M. Cooksey, and A. Gray. 2006. Fish assemblages and patterns of Chinook salmon abundance, diet, and growth at restored sites in the Duwamish River. 2005 Juvenile Chinook Duwamish River Studies, 2, p.1.

Everest, F. H. and D.W. Chapman. 1972. Habitat selection and spatial interaction by juvenile chinook salmon and steelhead trout in two Idaho streams. Journal of the Fisheries Board of Canada, 29(1): 91-100.

Gonor, J. J., J.R. Sedell, J. R., and P.A. Benner. 1988. What we know about large trees in estuaries, in the sea, and on coastal beaches. From the forest to the sea, a story of fallen trees, Maser, C., Tarrant, RF, Trappe, JM, and Franklin, JF, tech eds. USDA For. Serv. Gen. Tech. Rep. GTR-PNW-229, Pacific Northwest Res. Sta., Portland, OR, 83-112.

Green/Duwamish and Central Puget Sound Watershed Water Resource Inventory Area 9 (WRIA 9) Steering Committee. August 2005. Salmon Habitat Plan – Making Our Watershed Fit for a King. Prepared for the WRIA 9 Forum.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 67 - Higgins, K. 2017. A synthesis of changes in our knowledge of Chinook salmon productivity and habitat uses in WRIA 9 (2004 – 2016). An update to the 2005 WRIA 9 Strategic Assessment as approved by the Watershed Ecosystem Forum November 2017.

Hruby, T., K. Harper, and S. Stanley. 2009. Selecting Wetland Mitigation Sites Using a Watershed Approach. Washington State Department of Ecology Publication #09-06-032.

Kern, J., L. Jennings, L. Senkyr, R. Hoff. August, 2016. Habitat Restoration in an Urban Waterway: Lessons Learned from the Lower Duwamish River; November 19, 2015 Workshop Report. NOAA Fisheries. Seattle, WA

Kerwin, J., and T.S. Nelson. 2000. Habitat limiting factors and reconnaissance assessment report, Green/Duwamish and Central Puget Sound watersheds (WRIA 9 and Vashon Island). Washington Conservation Commission and the King County Department of Natural Resources. Seattle, WA.

King County Water and Land Resources Division, Department of Natural Resources and Parks, WRIA 9 Watershed Coordination Services, and WRIA 9 Technical Committee. 2005 WRIA 9 Strategic Assessment Report – Scientific Foundation for Salmonid Habitat Conservation. Prepared for Water Resources inventory Area (WRIA) 9 Steering Committee, Seattle, WA.

McKeon, M.A., A.R.Horner-Devine, and S.N. Giddings. 2020. Seasonal Changes in Structure and Dynamics in an Urbanized Salt Wedge Estuary. Estuaries and Coasts. https://doi.org/10.1007/s12237-020-00788-z

National Oceanic and Atmospheric Administration. 2013. Final Lower Duwamish River NRDA Restoration Plan and Programmatic Environmental Impact Statement. Seattle, WA. Nelson, T.S., H.B. Berge, G. Ruggerone, H. Kim, R. Schaefer, M. Boles, and J. Cordell. 2011.Draft. Juvenile Chinook migration, growth, and habitat use in the Lower Green River, Duwamish River, and nearshore of Elliott Bay, 2001-2003. King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

Ostergaard, E., D. Clark, K. Minsch, S. Whiting, J. Stern, R. Hoff, B. Anderson, L. Johnston, L. Arber, and G. Blomberg. 2014. Duwamish Blueprint: Salmon Habitat in the Duwamish Transition Zone. Prepared by the Duwamish Blueprint Working Group for the WRIA 9 Watershed Ecosystem Forum. Seattle, WA.

Oxborrow, B., J.R. Cordell, and J. Toft. 2016. Draft: Evaluation of Selected U.S. Army Corps of Engineers Habiat Restoration Projects, 2016. School of Aquatic and Fishery Sciences, University of Washington. Seattle, WA.

Ruggerone, G.T., and D. Weitkamp. 2004. WRIA 9 Chinook salmon research framework: identifying key research questions about Chinook salmon life histories and habitat use in the Middle and Lower Green River, Duwamish waterway, and marine nearshore areas. Prepared for WRIA 9.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 68 - Ruggerone, G., T. Nelson, J. Hall, E. Jeanes, J. Cordell, J. Toft, M. Cooksey, and A. Gray. 2006. 2005 Juvenile Chinook Duwamish River Studies. Habitat Utilization, Migration Timing, Growth, and Diet of Juvenile Chinook Salmon in the Duwamish River. Seattle, WA

Senter, C.A., Conn, K.E., Black, R.W., Peterson, N., Vanderpool-Kimura, A., and Foreman, J.R., 2018, Suspended-sediment transport from the Green-Duwamish River to the Lower Duwamish Waterway, Seattle, Washington, 2013–17: U.S. Geological Survey Open-File Report 2018–1029, 23 p., https://doi.org/10.3133/ofr20181029.

Simenstad, C. A., A. Wick, S. Van de Wetering, and D. L. Bottom. 2003. Dynamics and ecological functions of wood in estuarine and coastal marine ecosystems. Pages 265-277 in S. V. Gregory, K. Boyer, and A. Gurnell (eds.), The Ecology and Management of Wood in World Rivers. American Fisheries Society Symposium 37, Bethesda, Maryland.

Taylor, W., B. Kwasnowski, and I. Sahlberg. 2012. Duwamish Gardens, City of Tukwila, WA, Ordinary High Water Mark (OHWM) Determination. Cardno Tec.

Toft, J. and J. Cordell. 2016. Densities of Juvenile Salmon at Restored Sites in the Duwamish River Estuary Transition Zone, 2016. Prepared for WRIA 9. School of Aquatic and Fishery Sciences, University of Washington. Seattle, Washington.

Troost, D.G., D.B. Booth, A.P. Wisher, and S.A. Shimel. 2005. The Geologic Map of Seattle: A Progress Report, U.S. Geological Survey, Open File Report 2005-1252, Scale 1:24,000, December 2005.

United States Geological Survey. 2020.National Water Information System: Duwamish River at E Marginal Way Bridge at Duwamish, WA. Data Available online at: https://waterdata.usgs.gov/monitoring- location/12113415/#parameterCode=00480&startDT=2018-12-01&endDT=2019-09-19 Database accessed December 24, 2020.

Washington State Department of Ecology. 2012. Current EPA Approved Water Quality Assessment. Available online at: http://www.ecy.wa.gov/programs/wq/303d/currentassessmt.html. Database accessed January 14, 2013.

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 69 -

Figures

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 70 -

Figure 1 Vicinity Map

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 71 -

Figure 2 Regulatory Buffers and Mitigation Credit Area

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 72 -

Figure 3 Chinook Wind Area Public Land

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 73 -

Figure 4 Known Duwamish River Mitigation and Restoration Projects

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 74 -

Figure 5 Baseline Conditions After Demolition

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 75 -

Figure 6 Duwamish Estuary Channel and Landcover Comparison (Source: King County Water and Land Resources Division 2005)

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 76 -

Figure 7 Duwamish River Valley Landcover circa 1865 (Source: Collins and Sheikh 2005)

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Figure 8 Large Wood and Habitat Features

In Lieu Fee Mitigation Plan Chinook Wind Mitigation Project February 2021 - 78 -