2025.02_BA_USCG_BaseSeattle.pdf

BIOLOGICAL ASSESSMENT

for the Base Seattle Slip 36 Area, East Waterway Operable Unit

Harbor Island Superfund Site Seattle, Washington

Prepared for:

U.S. Coast Guard

Civil Engineering Unit Oakland Oakland, California

Prepared by:

Arcadis U.S., Inc.

February 2025

Biological Assessment Base Seattle Slip 36 Area ii

Contents

Abbreviations and Acronyms .................................................................................................................... v

1 Introduction

1.1 Purpose and Scope of the Biological Assessment

2 Species Considered in this Biological Assessment

2.1 Species Potentially Affected

2.2 Species Unlikely to be Affected

2.2.1 Aquatic/Marine Species

2.2.2 Terrestrial Species

2.2.3 Plants

2.3 Designated Critical Habitat

2.4 Consultation to Date

3 Description of Proposed Action

3.1 Applicant

3.2 Project Background

3.3 Existing Facilities

3.4 Purpose and Need

3.5 Action Area

3.6 Description of Proposed Action

3.7 Pier Demolition including Pile Removal

3.8 Pier Replacement

3.8.1 Pier 36B Replacement

3.8.2 Pier 36A Replacement

3.9 Existing Pier Improvements

3.10 Dredging and Placement of Fill

3.11 Dredged Material Management, Transport, and Disposal

3.12 Staging

3.13 Construction Timing

3.14 Construction Best Management Practices

3.15 Conservation Measures

4 Status of Species and Designated Critical Habitat within the Action Area or Vicinity

4.1 Fish

4.1.1 Bull Trout (Salvelinus confluentus)

4.1.2 Bocaccio Rockfish (Sebastes paucispinis) Puget Sound/Georgia Basin Distinct Population Segment

4.1.3 Yelloweye Rockfish (Sebastes ruberrimus) Puget Sound/Georgia Basin Distinct Population Segment iii

4.2 Salmonids

4.2.1 Puget Sound Steelhead (Oncorhynchus mykiss) Distinct Population Segment

4.2.2 Puget Sound Chinook Salmon (Oncorhynchus tshawytscha) Evolutionary Significant Unit18

4.3 Essential Fish Habitat

4.3.1 Pacific Coast Salmon

4.3.2 Pacific Groundfish Essential Fish Habitat

4.3.3 Coastal Pelagic Essential Fish Habitat

4.4 Marine Mammal Protection Act Protected Species

5 Environmental Baseline and Cumulative Effects

5.1 Description of the Environmental Baseline

5.1.1 Aquatic Habitat

5.1.2 Water Quality

5.1.3 Sediment Quality

5.1.4 Land Use

5.2 Past, Current, and Future Projects within the Vicinity of the Action Area

5.3 Cumulative Effects

5.4 Interdependent or Interrelated Effects

6 Effects of the Proposed Action

6.1 Effects and Measures to Reduce Effects on Listed Fish and Salmonids

6.2 Effects and Measures to Reduce Effects on Marine Mammals

6.3 Effects and Measures to Reduce Effects on Designated Critical Habitat

6.4 Effects and Measures to Reduce Effects on Essential Fish Habitat

6.5 Effects on Environmental Baseline

7 Conclusions and Determination

7.1 Determination for Listed Fish and Designated Critical Habitat

7.2 Conclusions and Determination on Essential Fish Habitat

8 References iv

Tables

Table 1 Summary of In-Water Activities

Table 2 Managed Fish Species under Magnuson-Stevens Fishery Conservation Management Act

Table 3 Summary of Noise Impacts on Fish

Table 4 Summary of Potential Noise Impacts on Marine Mammals

Table 5 Effects Determination for Listed Species

Table 6 Effects Determination on Essential Fish Habitat

Figures

Figure 1 Site Location Map

Figure 2 Base Seattle Site Plan

Figure 3 Slip 36 Site Plan and Bathymetry

Figure 4 Action Area

Figure 5 Proposed Removal Action Components

Appendices

Appendix A U.S. Fish and Wildlife Service and National Marine Fisheries Service Species and Habitat

Lists

Appendix B Washington Department of Fish and Wildlife State Listed Species and State Candidate

Species

Appendix C Washington Natural Heritage Program Vascular Plant Species of Conservation Concern v

Abbreviations and Acronyms

°C degrees Celsius

°F degrees Fahrenheit

Appledore Appledore Marine Engineering, LLC

Arcadis Arcadis U.S., Inc.

BA biological assessment

BMP best management practice

CFR Code of Federal Regulations

CPS Coastal Pelagic Species

CPSFMP Coastal Pelagic Species Fisheries Management Plan

CY cubic yards dB decibels

DPS Distinct Population Segment

Ecology Washington Department of Ecology

EEZ Exclusive Economic Zone

EFH Essential Fish Habitat

EIS Environmental Impact Statement

ESA Endangered Species Act

ESU Evolutionary Significant Unit

Fed. Reg. Federal Regulation

HUC hydrologic unit code

IPaC USFWS Information for Planning and Consultation

MLLW mean lower low water

MMC Marine Mammal Commission

NMFS National Marine Fisheries Service

NOAA National Oceanic and Atmospheric Administration

NTCRA Non-Time Critical Removal Action

PAH polycyclic aromatic hydrocarbon

PCB polychlorinated biphenyls

PCGFMP Pacific Coast Groundfish Fisheries Management Plan

PCSFMP Pacific Coast Salmon Fishery Management Plan

PFMC Pacific Fishery Management Council

PHS Priority Habitat and Species

PSC Polar Security Cutter vi

RAL remedial action level

RMC residuals management cover

SEL sound exposure levels

SSDC Shared Strategy Development Committee

SWIFD Statewide Washington Integrated Fish Distribution

T&E threatened and endangered

USACE United States Army Corps of Engineers

USCG United States Coast Guard

USEPA United States Environmental Protection Agency

USFWS United States Fish and Wildlife Service

WDFW Washington Department of Fish and Wildlife

WDNR Washington Department of Natural Resources

Windward Windward Environmental LLC

WM DRF Waste Management Duwamish Reload Facility

1 Introduction

1.1 Purpose and Scope of the Biological Assessment

This biological assessment (BA) presents the potential effects of the United States Coast Guard (USCG)

Civil Engineering Unit Oakland project site for the Base Seattle Slip 36 area within the East Waterway

Operable Unit of the Harbor Island Superfund Site, located in Seattle, Washington (Figure 1) on state and federally listed threatened or endangered species (T&E), candidate species, and their habitat or designated critical habitat. This BA was prepared in accordance with legal requirements set forth in regulations promulgated under Section 7 of the Endangered Species Act (ESA) (50 Code of Federal

Regulations [CFR] 402; 16 United States Code 1536 (c)).

Arcadis U.S., Inc. (Arcadis) has prepared this BA on behalf of the USCG for consultation with the National

Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS) under Section 7 of the

ESA. This BA also provides analysis for Essential Fish Habitat (EFH) considerations for species managed under the Magnuson-Stevens Fishery Conservation Management Act as amended by the Sustainable

Fisheries Act of 1996 (Public Law 104-267), as well as species protected under the Marine Mammal

Protection Act.

2 Species Considered in this Biological Assessment

The species list for the proposed action was obtained from the USFWS Information for Planning and

Consultation (IPaC) website (USFWS 2022a), the NMFS Managed Species Directory – West Coast List

(NMFS 2022c), Washington Department of Natural Resources (WDNR) Animal Species of Concern List

(WDNR 2022), and the Washington Natural Heritage Program Vascular Plant Species of Conservation

Concern List (Fertig 2021). The Priority Habitat and Species (PHS) identified in the Washington

Department of Fish and Wildlife (WDFW) web mapping tool (WDFW 2021) and in the Statewide

Washington Integrated Fish Distribution (SWIFD) webmap (WDFW 2018) were also used to determine whether there were documented occurrences of listed species within the vicinity of the proposed action.

The NMFS EFH mapping tool, NMFS critical habitat mapping tool, and IPaC results were used to determine whether critical habitat or EFH were mapped within the Action Area (NMFS 2021, 2022a,b;

USFWS 2022a). The habitat requirements for the listed species were compared to habitats present in the

Action Area to determine the likelihood of each species occurring and the potential for them to be affected by the proposed action. T&E species lists for the Action Area as identified by the USFWS and NMFS are included in Appendix A.

2.1 Species Potentially Affected

Suitable habitat for the following listed or candidate species is present in the Action Area; therefore, these species may potentially be affected by the proposed action:

• Steelhead (Oncorhynchus mykiss) – Puget Sound Distinct Population Segment (DPS) – Federally

Threatened

• Chinook salmon (Onchorhynchus tshawytscha) – Puget Sound DPS (pop. 15) – Federally Threatened

• Bull trout (Salvelinus confluentus) – Coastal – Puget Sound – Federally Threatened

• Bocaccio rockfish (Sebastes paucispinis) – Puget Sound DPS – Federally Endangered, State

Threatened

• Yelloweye rockfish (Sebastes ruberrimus) – Puget Sound – Federally Threatened, State Threatened

• Killer whale (Orcinus orca) – Southern Resident DPS – Federally Endangered, State Endangered.

2.2 Species Unlikely to be Affected

The species identified below are identified by IPaC or NMFS lists as having potential to occur within the

Action Area or vicinity; however, after further evaluation, it was determined that these species are unlikely to be affected by the proposed action because suitable habitat does not occur within the Action Area, or because the proposed action is outside of the known range for the species. The species are not discussed further in this BA because the proposed action was determined to have no effect on these species.

2.2.1 Aquatic/Marine Species

• Eulachon smelt (Thaleichthys pacificus) – Southern DPS – Federally Threatened, State

Endangered:

This species is anadromous but spends the vast majority of its life in the ocean. The Southern DPS is a protected entity and spawns in rivers from Northern California to British Columbia (National Oceanic and Atmospheric Administration [NOAA] 2022c). According to WDNR (2014), Washington rivers used for spawning by the Eulachon smelt include “Bear, Columbia (Lower and major tributaries), Cowlitz, Elochoman, Elwah, Grays, Kalama, Lewis, Naselle, Nemah, Quinault, Queets, Toutle and

Wynoochee”. None of these rivers overlap the Action Area and there are no mapped records for this species in the Action Area or vicinity on the Washington PHS mapper or the SWIFD webmap (WDFW

2021, 2018). No critical habitat for this species is present within the Action Area or vicinity, and the closest mapped critical habitat is more than 80 miles to the northwest within Elwha River (NOAA

2022c) This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Green sturgeon (Acipenser medirostris) – Southern DPS – Federally Threatened:

Green sturgeon are anadromous fish that spawn in freshwater rivers. The southern DPS green sturgeon spawn in the Upper Sacramento, Feather, and Yuba rivers in California from April to July

(NOAA 2022d). After spawning, they are known to summer and autumn off the coast of Oregon and

Washington but are rare within inland waters and Puget Sound (NOAA 2022d). There are no mapped records for this species in the Action Area or vicinity on the Washington PHS mapper or the SWIFD webmap (WDFW 2021, 2018). No critical habitat for this species is present within the Action Area or vicinity, and the closest mapped critical habitat is more than 60 miles to the northwest in the Salish

Sea (NOAA 2022d). This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Humpback whale (Megaptera novaeangliae) – Mexico DPS – Federally Threatened, State

Endangered; Central America DPS – Federally Endangered, State Endangered:

The Central American DPS, Mexico DPS, and Hawaii DPS of humpback whales spend summers in

Washington waters, particularly in open waters and coastal areas. The greatest number of individuals are seen between July and September. Once common in the Salish Sea and Puget Sound, this species was historically over-hunted, but local sightings have been increasing since the 1980s

(Calambokidis and Steiger 1990, Puget Sound Express 2016); currently, the species is scarce in the inland waters (WDFW 2022d).

There are no mapped records for this species in the Action Area or Elliott Bay on the Washington

PHS mapper (WDFW 2021). No critical habitat for this species is present within the Action Area or

Elliott Bay, and the closest mapped critical habitat is more than 100 miles to the northwest in the western reaches of the Strait of Juan de Fuca (NMFS 2022b). In May 2019 a juvenile humpback was fatally struck by a ferry in Elliott Bay (Kiro 7 News 2019). In November 2023, a young humpback whale was observed within Elliot Bay for approximately 3 to 4 days (Valdez 2023). While humpback whales could be in the greater Puget Sound area, it is unlikely for them to be within the Action Area because it is very narrow and located in a busy, developed area with ship and barge traffic. This species is much more likely to be found in the open, deeper waters within Puget Sound, and even more likely within the Salish Sea to the north, which provides more direct access to open ocean. This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Loggerhead sea turtle (Caretta caretta) – Federally and State Endangered, Green sea turtle

(Chelonia mydas) – Federally and State Threatened, Leatherback sea turtle (Dermochelys coriacea)

– Federally and State Endangered:

Sea turtles are rare in Washington and generally only observed along the western coast. None of these three species are expected to occur within the inland waters of Puget Sound or Elliott Bay, and there is no appropriate nesting habitat in the Action Area or vicinity (WDFW 2015). All three species nest at lower latitudes on tropical and subtropical beaches (WDFW 2022c,e,f). No critical habitat for any of the three turtle species is present within the Action Area or vicinity. The closest mapped critical habitat is for leatherback sea turtle and stretches along the entire western coast of Washington and does not include Puget Sound (NMFS 2022b). These species are unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Northwestern pond turtle (Actinemys marmorata) – State Endangered:

Northwestern pond turtles inhabit freshwater ponds and lakes with surrounding open, upland habitats in the Puget Sound lowland region. They require logs and/or other surfaces for basking, and nest in grasslands and woodlands around the ponds (WDFW 2022h).

There are no freshwater ponds, lakes, grasslands, or woodlands in the Action Area or vicinity to support this species. Northwestern pond turtles are mapped north of the Action Area around Lake

Union but are not likely to occur in the Action Area and, thus, will not be affected by the proposed action.

2.2.2 Terrestrial Species

• Marbled murrelet (Brachyramphus marmoratus) – Federally Threatened, State Endangered:

Marbled murrelets feed on fish in marine waters but nest up to 50 miles inland (WDNR 2018). This species is found along the Pacific coast, including Puget Sound, and feeds on Pacific herring, anchovy, sand lance, and capelin. They nest in large mature conifers with platforms and large mossy branches (WDNR 2018).

There are no mapped records for this species in the Action Area or Elliott Bay on the Washington

PHS mapper (WDFW 2021). No critical habitat for this species is present within the Action Area or

Elliott Bay. No suitable forested habitat is present in the Action Area for nesting. The vicinity does contain marine waters known to support Pacific herring that marbled murrelet could feed on.

However, the Action Area and vicinity are busy, industrial, narrow, and confined by docks and large ship movement. The Action Area does not contain prime habitat for this species, and marbled murrelet are expected to use the more suitable marine habitat in northern Elliott Bay by Discovery

Park or along the western coast of Puget Sound. This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Streaked horned lark (Eremophila alpestris strigata) – Federally Threatened, State Endangered:

Streaked horn lark habitat consists of bare ground, including open country with short or no vegetation.

This species breeds in short grasslands, desert, short sage scrub, and tundra (Cornell Lab of

Ornithology 2019a). They nest in depressions or scrapes in the ground.

No suitable bare ground habitat is present in the Action Area. The Action Area consists of industrial docks, concrete, asphalt, and estuary waters. The ground is not suitable for nesting, and no grassland or prairies for foraging are present. This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Yellow-billed cuckoo (Coccuzus americanus) – Federally Threatened, State Endangered:

Yellow-billed cuckoos exist almost exclusively in large, continuous swaths of dense vegetation (50 acres or larger), particularly willow thickets and riparian woodlands along streams and rivers (Cornell

Lab of Ornithology 2019b; Daw 2014). The Action Area is entirely industrial and developed and does not contain any suitable vegetation or freshwater sources for yellow-billed cuckoo. This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Monarch butterfly (Danaus plexippus) – Federal Candidate:

Monarchs that breed west of the Rocky Mountains overwinter in California require secure sources of milkweed. In Washington, milkweed is typically found near wetlands, riparian areas, and in weedy habitats. This species also requires nighttime roosting trees. Monarchs begin their migration south in the late summer (WDFW 2022g). The Action Area does not contain milkweed or suitable roosting trees. This species is unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

2.2.3 Plants

The Action Area is an industrial dock surrounded by concrete, asphalt, and buildings. No vegetated areas or suitable habitat for plant establishment are present. The following plant species are unlikely to occur in the Action Area and, thus, will not be affected by the proposed action.

• Triangular-lobed moonwort (Botrychium ascendens) – State Threatened

• Stalked moonwort (Botrychium pedunculosum) – State Threatened

• Golden paintbrush (Castilleja levisecta) – Federally and State Threatened

• Weak thistle (Cirsium remotifolium var. remotifolium) – State Endangered

• Pacific peavine (Lathyrus vestitus var. ochropetalus) – State Endangered

• White meconella (Meconella oregana) – State Endangered.

2.3 Designated Critical Habitat

According to NMFS and USFWS, the Action Area and vicinity are located within designated critical habitat for the following species:

• Bull trout

• Bocaccio rockfish

• Yelloweye rockfish

• Southern resident killer whale

• Chinook salmon Puget Sound Evolutionary Significant Unit (ESU)

• Steelhead (Puget Sound DPS).

2.4 Consultation to Date

To date, there has been no documented contact with USFWS or NMFS staff regarding the proposed action.

The initial species list for the proposed action as discussed in Section 2.1 was obtained from the USFWS

IPaC website (Appendix A), NMFS’s West Coast Species list, the Washington State T&E Species list

(Appendix B), and the Washington Natural Heritage Program Vascular Plant List (Appendix C).

3 Description of Proposed Action

3.1 Applicant

This BA was prepared by the USCG to satisfy the requirements of Section 7 of the ESA (16 United States

Code 1536 (c)) for the planned Non-Time Critical Removal Action (NTCRA) for Slip 36 of the East

Waterway Operable Unit of the Harbor Island Superfund Site. The proposed action described in this BA will be performed pursuant to the Comprehensive Environmental Response, Compensation, and Liability

Act (i.e., Superfund) and is consistent with the East Waterway Operable Unit Interim Record of Decision

(United State Environmental Protection Agency (USEPA) 2024a). Details of the NTCRA are described in the Action Memorandum (USEPA 2024b).

3.2 Project Background

Base Seattle is the largest USCG facility in the Pacific Northwest and provides a full range of support functions for USCG vessels and missions in the Pacific Northwest and polar areas of operation and serves as the homeport for several USCG cutters (Figure 2). Current facilities and infrastructure at Base

Seattle are in poor condition, which hinders the USCG from executing missions efficiently. The replacement of current ice breakers with new Polar Security Cutters (PSCs) and possible future homeporting of other major cutters necessitates facility enhancements to support these advanced operating assets.

The USCG is preparing a programmatic Environmental Impact Statement (EIS) to address the base modernization activities to be conducted within the uplands, including (but not limited to) construction of new infrastructure and modifications to update existing upland facilities and upland infrastructure. Note that the EIS only addresses modernization activities for the proposed uplands base and does not include the in-water activities to be conducted under the proposed action described in this BA.

Base Seattle currently includes shore side buildings and Slip 36, which is located perpendicular to the

East Waterway in an east/west orientation. Slip 36 was constructed in 1927 and originally dredged to -35 feet mean lower low water (MLLW). The berth has been dredged several times to accommodate

USCG operations, including most recently from 2004 to 2005 to lower the sediment elevation in Slip 36 to -40 feet MLLW (from a previous elevation of -38 feet MLLW).

3.3 Existing Facilities

Slip 36 includes Pier 36A (west) and Pier 36B (east) on the south, Pier 37 on the north, and the slip apron at the head or east side. These structures are described below and shown on Figure 3, based on information from a waterfront facility inspection conducted in 2020 (Appledore Marine Engineering, LLC

[Appledore] 2020).

• The seawall bulkhead consists of approximately 1,500 feet of coated steel sheet pile with concrete cap. The installation date is not known and may vary for different portions of the structure. The bulkhead serves as a retaining wall and shoreline protection for the upland parking and roadway. The slope adjacent to the bulkhead under Pier 36A, Pier 36B, and the slip apron is armored with riprap for erosion protection.

• Pier 36A was rebuilt in 2005 with concrete piles, and the pier face was moved to the south approximately 50 feet to increase the width of Slip 36. Approximately 1,100 timber piles from the previous structure were removed or broken off at the mud line. To facilitate a sheer cut for dredging, an underwater steel sheet-pile retaining wall (104 feet long) was installed. The sheet pile was driven to approximately 84 feet in depth below sediment surface, and the exposed face varies from 10 to 20 feet based on the angle of the southern slope. To increase the shear strength of the sediment, due to risk of instability in a seismic event, the USCG installed 3-foot-diameter gravel columns on a 9-foot grid, extending 27 feet from the wall face along the extent of Pier 36A and to an elevation of -100 feet

MLLW (approximately 60 feet deep). A total of approximately 153 gravel columns were installed.

• Pier 36B was constructed in 1942 and consists of a timber structure with an asphalt overlay supported by creosote-treated timber piles. Building 3 is partially constructed on Pier 36B. Numerous repairs have been completed on Pier 36B to restore pilings and other structural components, most recently in

2018. Surface loads are currently limited on Pier 36B due to significant structural damage and loss of bearing capacity in timber piles from marine boring organisms. Riprap armoring is present on the upper portions of the slope extending to the bulkhead.

• The slip apron was constructed in 1992 as a replacement for a timber structure and consists of concrete elements, including pre-cast deck panels, cast-in-place pile caps, and prestressed concrete piles. During construction, timber piles from the previous structure were cut or removed and remain under the reconstructed slip apron. Riprap armoring is present on the upper portions of the slopes extending to the bulkhead.

• Pier 37 (Berths C and D) was reconstructed within the same extent as the prior pier in 1996 using precast concrete piles driven to a depth of approximately 150 feet and batter piles intended to mitigate liquefaction risk. During reconstruction, the creosote-treated timber piles of the previous structure were broken off at the mud line to retain the sheer strength of the sediment that the piles provided, and the broken-off timber piles remain under the reconstructed Pier 37. Pier 37 is connected to

Terminal 46 to the north and does not include a bulkhead.

• The boathouse and floating docks located in the eastern end of Slip 36 consist of concrete float modules held in place by concrete guide piles and were constructed in 1989 and 2006 (Appledore

2020). The docks and boathouse provide berthing space for small boats, including rapid response vessels that support critical USCG missions locally in Puget Sound.

3.4 Purpose and Need

The proposed action includes activities to deepen and widen Slip 36 to address both the required removal actions identified in the Action Memorandum (USEPA 2024b) and to implement associated repairs or upgrades to in-water infrastructure needed based on the berth expansion and removal actions and/or to provide site resiliency. The primary purpose of the proposed action is to address sediment within Slip 36 that has constituent concentrations greater than the East Waterway Operable Unit Interim Record of

Decision remedial action levels (RALs [USEPA 2024a]) and to control potential sources of recontamination within Slip 36.

Slip 36 at Base Seattle is proposed as the home port for new PSCs. The USCG determined that the existing depths within Slip 36 are inadequate and that Pier 36 is structurally inadequate to accommodate

PSCs or other vessels of its class. Facility enhancements are necessary to support PSCs and possible future homeporting of other major cutters. Removing sediment will address contamination and increase the depth of Slip 36 which will improve USCG operations and allow berthing of the new PSCs. The minimum operational depth necessary in Slip 36 to meet USCG requirements is -42 feet MLLW. PSCs are considered mission critical to the USCG; therefore, the ability to homeport these vessels is an essential component of the proposed action.

3.5 Action Area

Under 50 CFR § 402.02, the Action Area is defined as including all areas that may be affected directly or indirectly by the proposed action, rather than only the immediate vicinity of the the proposed action.

Therefore, the Action Area for the Base Seattle proposed action includes the entirety of the future Slip 36 extent as well as the area between Slip 36 and the federal navigational channel and extending north into the southeastern portion of Elliott Bay and south into the East Waterway. These areas are included in the

Action Area to account for potential temporary increase in turbidity and potential noise effects resulting from pile driving. The Action Area is shown on Figure 4.

3.6 Description of Proposed Action

The proposed action entails deepening and widening Slip 36 for operational improvements to accommodate larger vessels as described in the Action Memorandum (USEPA 2024b). Activities include:

• Dredging – Contaminated sediment will be removed in open water areas to meet the RALs to a minimum depth of -43 feet MLLW to meet USCG operational requirements and allow for placement of a dredge residuals management cover (RMC) layer. Sediment will be removed to the maximum extent possible without compromising or destabilizing existing structures or slopes. Approximately

65,000 cubic yards (CY) of sediment will be removed through dredging.

• RMC Layer – A 9-inch layer of clean sand will be placed as an RMC layer over all dredged areas in

Slip 36. The RMC layer will be designed to achieve a cleaner surface layer after dredging where dredge residuals may be present.

• In-Situ Treatment Due to Structural Stability – In areas where dredging to RALs is not possible to protect the stability of existing structures, in-situ treatment consisting of clean sand amended with activated carbon (2 percent), or equivalent as determined by USEPA, will be placed. The in-situ treatment layer is anticipated to be 18 inches, or as determined in the design and subsequently approved by USEPA. The total volume of fill material to be placed for the RMC layer and in-situ treatment in open water areas is 13,000 CY.

• In-Situ Treatment Under Piers – In under pier areas with exposed sediment that contains contaminants of concern at concentrations above the RALs, in-situ treatment applied. The in-situ treatment amendment will consist of activated carbon-impregnated materials placed in a 3-inch

(minimum) layer, or equivalent as approved by USEPA. In-situ treatment amendment will not be placed in areas that do not have exposed sediment due to armoring. The area of exposed, under pier sediment that requires in-situ treatment will be determined in design. The maximum placement volume is estimated to be 1,650 CY.

In addition to the NTCRA components that are described in the Action Memorandum, USCG will implement infrastructure work in Slip 36 related to waterfront structures, including the following components:

• Removal and Replacement of Pier 36B – The USCG has determined that Pier 36B is no longer structurally sound, does not meet current or future facility requirements, and needs to be demolished and replaced with a new structure. Building 3 (which is partially on the existing Pier 36B) will be demolished and the existing decking and creosote-treated wooden piles will be removed. A sheet pile toe wall will be installed to retain upland soil and facilitate sediment removal to widen Slip 36. A new

Pier 36B structure will be constructed using concrete piles and pier decking.

• Removal and Replacement of Pier 36A – The existing Pier 36A structure is not designed to withstand additional loads associated with the required deepening of Slip 36 and USCG requirements for future resiliency. The existing Pier 36A, including concrete decking and piles, will be removed and replaced with a new structure in the same footprint. The existing sheet pile stone wall will remain in place.

• Removal and Replacement of Floating Docks – The existing small boat docks located at the east end of Slip 36 will be removed and replaced to facilitate dredging and other structural work. The existing gangways and piles will be removed. During construction, a temporary dock will be installed to maintain USCG operational capabilities. The temporary dock will be removed and replaced with new floating docks in the same area as the existing structures.

• Armor Placement – The existing slope at the east end of Slip 36 adjacent to the Slip 36 Apron will be armored to protect against erosion.

Work will be phased over multiple in-water and upland construction seasons. Phase one will include demolition of Pier 36B and the floating docks, installation of temporary docks, installation of the Pier 36B toe and bulkhead walls, and sediment dredging. Phase two will include installation of the new Pier 36B structure. Phase three will include demolition and reconstruction of Pier 36A. The proposed action is described in further detail by activity in the subsequent sections.

3.7 Pier Demolition including Pile Removal

Demolition of Pier 36 will consist of the following activities:

• Demolition of Building 3: The existing Building 3 currently located on Pier 36B will be demolished and removed in its entirety. Building 3 is an approximately 91,000-square-foot warehouse retrofitted with interior office and berthing space and is primarily constructed of concrete and steel. A hazardous materials survey will be conducted prior to demolition, and wastes will be segregated for handling and disposal, as required. Demolition waste and debris will be managed within the upland areas of Base

Seattle prior to being loaded into containers or railcars for transport (by rail or road) to an off-site disposal facility. Best management practices (BMPs) will be used during demolition to protect against discharge of waste or debris into Waters of the United States.

• Pier 36B Demolition: Demolition of Pier 36B will occur using both land-based and water-based equipment including excavators, land-based and barge-mounted cranes, and hand tools. However, work activities associated with the foundation for Building 3 and miscellaneous concrete pile caps as well as various repairs may require the use of a jackhammer. Approximately 63,000 square feet of decking and 630 linear feet of concrete bulkhead will be removed.

• Pier 36B Pile Removal: Approximately 1,700 existing creosote-treated timber piles, 36 concrete piles,12 steel piles, and 150 timber piles will be removed using a impact hammer with a crane hoist or other methods (e.g., sling), depending on the condition of the pile. Timber piles will be removed in their entirety, if possible, using direct pull from a crane or impact hammer. Piles that cannot be removed will be cut off at the mudline and left in place or removed with a clamshell on a barge-mounted crane. Removed piles will be stockpiled in an area with drainage control and will be disposed at an appropriate landfill authorized to accept creosote-treated wood.

• Pier 36A Demolition: Demolition of Pier 36A will occur using primarily water-based equipment, with some support from land-based equipment as feasible based on access. The equipment would include excavators, barge-mounted cranes, and hand tools. The majority of Pier 36A components are comprised of concrete and will require the use of jackhammers to demolish. Approximately 16,500 square feet of decking and 334 linear feet of concrete bulkhead will be removed.

• Pier 36A Pile Removal: Approximately 170 existing concrete piles will be removed using a impact pile driver with a crane hoist or other methods (e.g., sling). It is likely that many or all of the piles may be too long to remove. Piles that cannot be removed will be cut off at the mudline and abandoned in place. Removed piles will be stockpiled in an area with drainage control and disposed or recycled at an appropriate factility.

• Floating Dock Demolition: Demolition of the existing floating docks at the east end of Slip 36 will using primarily water-based equipment, with some support from land-based equipment as feasible based on access.

3.8 Pier Replacement

Following demolition of the existing Pier 36, Pier 36A will be placed within the same footprint. Pier 36B will be replaced with a new structure aligned with Pier 36A, as shown on Figure 5.

3.8.1 Pier 36B Replacement

Pier 36B replacement will consist of the following activities:

• Pile Installation: Sheet and steel piles will be installed to support the new Pier 36B. Piles will be installed using a impact hammer. A summary of the piles required for each component is provided below.

o Toe Wall: Up to 149 steel piles (48 inch diameter) will be installed to create the toe wall at the new Pier 36B and facilitate dredging to widen Slip 36. Approximately 1,600 blows will be required to install each pile. The toe wall will be installed during the first phase of work after demolition of

Pier 36B and prior to sediment removal adjacent to Pier 36B.

o Bulkhead Wall: A new bulkhead combination wall consisting of 162 sheet piles (27.5 inches wide), 93 steel pipe piles (36 inch diameter) will be installed. The steel pipe piles include four open end piles and two closed end piles that are longer (112 feet). The remaining 87 steel pipe piles will be between 50 and 60 feet long. Approximately 80 blows will be required to install each sheet pile. The steel pipe piles will require 700 (50 to 60 feet long piles), 1,000 (112 feet long, open end piles), or 1,700 blows (112 feet long, closed end piles). The bulkhead wall will be installed during the first phase of work.

o Pier 36B Piles: Up to 128 steel piles (36 inch diameter, closed end) will be installed to support the new Pier 36B structure. The piles will be between 109 and 125 feet long. Approximately 1,700 blows will be required to install each pile. The pier piles will be installed during the second phase of work.

• Pier Deck Installation: Approximately 30,200 square feet of pre-cast concrete decking will be installed as part of the new Pier 36B. The deck will be installed during the second phase of work.

3.8.2 Pier 36A Replacement

Pier 36A replacement will consist of the following activities:

• Pile Installation: Steel and sheet piles will be installed to support the new Pier 36B and as part of the bulkhead wall. Piles will be installed using a impact hammer. Steel pile installation will occur over the course of approximately 100 days. The work will be conducted during the third phase, is currently in design, and the number of blows per pile has not been determined. A summary of the piles required for each component is provided below.

o Bulkhead Wall: A new bulkhead combination wall consisting of 88 sheet piles and 44 steel pile piles (36 inch diameter, closed end) will be installed. The steel piles will be approximately 60 feet long.

o Pier 36A Piles: Up to 113 steel piles (36 inch diameter, closed end) will be installed to support the new Pier 36A structure. The piles will be between 111 and 164 feet long.

• Pier Deck Installation: Approximately 19,000 square feet of pre-cast concrete decking will be installed as part of Pier 36A. The deck will be installed will be conducted during the third phase of work.

Pier replacement activities are expected to occur over no more than five in-water work windows. The anticipated daily blows from the impact hammer are not expected to exceed 2385 blows per day.

3.9 Existing Pier Improvements

It is anticipated that in-water and upland structural improvements will be necessary to replace Pier 36A.

The type and scope of retrofits will be further refined during design but may include tie backs installed at

Pier 36A and/or upland ground anchors to provide structural stability along the pier. If ground anchors are used, drilling below the water line could occur from either a drill rig mounted on a barge or from uplands. If steel tie rods are used, installation would occur by trenching into the existing slope and then backfilling the trench with clean imported fill material. Steel tie rods would not require drilling but would require moving the existing riprap to approximately the mean higher high water level and then replacing the rip rap along the slope. In addition to tiebacks, it is anticipated that ground improvement of upland soils at Pier 36A will be required. Ground improvement activities would be conducted from the upland rather than in-water.

3.10 Dredging and Placement of Fill

Sediment will be dredged from approximately nine acres of open water areas to a minimum depth of -43 feet MLLW (plus 1 foot of overdredging). The estimated dredge volume is presented in Section 3.6.

Dredging is expected to be conducted using mechanical methods, such as a barge-mounted crane with an environmental bucket. The dredged materials will be placed into a barge and transported to the Waste

Management Duwamish Reload Facility (WM DRF) located approximately 5 miles south of the Action

Area. Sediment would be gravity dewatered on the barge and then transferred to a handling area at the transload facility and amended with dewatering reagents as necessary (e.g., portland cement or fly ash) to reduce the water content and meet disposal requirements. The amended sediment will be loaded into railcars for transportation to the disposal facility. Dredging activities may be conducted in single (12-hour) or double (24-hour) shifts. Dredging production rates of approximately 500 to 1,000 CY per single shift are expected, depending on the equipment, slopes, and dredge cut.

An RMC layer consisting of imported granular material (sand) will be placed in areas where sediment concentrations meet the RALs. The RMC layer will be placed over approximately 5 acres. In areas where sediment concentrations do not meet the RALs due to structural constraints that limit dredging or where limited contaminants of concern are present, open water in-situ treatment will be applied and consist of imported granular material mixed with activated carbon (2 percent) and placed over sediment. The open water in-situ treamtent area is approximately 2 acres. Fill material will be delivered to the project site on barges and are typically placed using a barge crane and bucket in open water areas. Fill quantities are discussed in Section 3.6.

In areas with exposed sediment underneath existing piers, under pier in-situ treatment will be applied. The material consists of aggregate with an activated carbon coating and would likely be placed over the sediment using specialty equipment due to the limited access. The material would be placed in a minimum 3-inch layer (to be confirmed during design).

Limited sediment removal underneath Pier 36A would be conducted between demolition and reconstruction of the pier using the same methodology described above for open water dredging.

Sediment will be removed and backfill and/or in-situ treatment materials will be placed followed by riprap armoring. Spaces between riprap armoring will be filled with smaller diameter stone (fish mix).

3.11 Dredged Material Management, Transport, and Disposal

Dredged sediment will be placed directly on barges and transported to the WM DRF. Disposal of dredged sediment will be consistent with the requirements of the interagency Dredged Materials Management

Program (United States Army Corps of Engineers [USACE] 2021). No open water disposal will occur.

Dredged material will be placed on a haul barge and transported to WM DRF for mangement and subsequent land transport to the landfill. Barges will be brought to the site via Duwamish Waterway and the West Waterway federal navigation channel (Figure 4). Dredging within Slip 36 is expected to occur over the course of approximately 150 days within three agency-approved in-water work windows.

3.12 Staging

Waste and construction materials may be staged in the upland portions of Base Seattle and other off-site locations. Demolition waste and debris may be stockpiled in areas with controls to prevent runnoff and waste from entering the waterway. Construction materials, including heavy equipment, fill materials, and other supplies, may also be stockpiled in areas with controls as required by the spill prevention plan.

BMPs and controls will be used to protect against discharge of sediment and water to the waterway.

3.13 Construction Timing

In-water work is expected to begin in 2025. All in-water construction work will occur during appropriate work windows to avoid and minimize impacts on migratory fish. In-water construction work is expected to occur over the course of four to five in-water work windows. Upland activities that do not involve in-water work (e.g., mobilization/demobilization, demolition of upland infrastructure, material handling, and transportation) may be conducted outside of the in-water work windows. Table 1 summarizes the estimated duration for the in-water work activities and the in-water work windows.

Table 1 Summary of In-Water Activities

In-Water Activity In-Water

Work Window Estimated Activity Duration

Pier 36A Demolition and Pile Removal

July 16 –

February 15

3 – 6 months

Pier 36B Demolition and Pile Removal

(includes Building 3 demolition) 6 – 9 months

Pier 36A Pile Installation 4 – 6 months

Pier 36B Pile Installation 4 – 6 months

Existing Pier Improvements

Total duration to be determined based on design.

May occur in multiple work windows depending on location and type of improvement.

Open Water Dredging 3 – 7 months

Under Pier Dredging 1 – 2 months

Fill Placement 1 – 2 months

3.14 Construction Best Management Practices

The following construction BMPs will be implemented during the removal action activities to reduce the potential for take of listed fish and marine mammal species, their habitat, designated critical habitat, and

EFH.

The following BMPs will be incorporated into the project description to reduce the potential for impacts on listed species:

• All in-water work will be limited to the periods determined by the participating agencies to reduce impacts on listed fish, salmonids, and marine mammals.

• All equipment will be inspected daily to ensure it is in working condition free of leaks of oils or fuels.

• Waste produced during demolition will be characterized in upland areas to reduce potential for discharge into Waters of the United States.

• During demolition, tarps or similar material (i.e., eagle netting) will be installed to prevent demolition waste and debris from entering Waters of the United States.

• No waste materials, including concrete, fuels, oils, or solvents will be allowed to enter the waterway.

• Barge operator(s) will follow all appropriate measures to prevent spills (i.e., cover load) and will have a spill kit onboard during all barge transport.

• A spill prevention plan will be prepared and measures implemented throughout the in-water work.

• Resuspension and sheen controls and monitoring will be implemented throughout the in-water work.

3.15 Conservation Measures

The following conservation measures have been identified and will be implemented to reduce the potential for take of listed species.

Conservation Measure 1. In-Water Work Windows:

No in-water work such as dredging, pile driving, demolition, and placement of clean fill will occur within the agency-approved in-water work window for juvenile salmonids and bull trout of July 16 to

February 15 to reduce and minimize potential effects on listed fish within the Action Area, including species rearing in the Duwamish estuary (USACE 2017).

Conservation Measure 2. Noise Reduction:

Pile-driving, including removal of existing piles, will occur within the agency-approved in-water work window between July 16 and February 15 to minimize impacts on listed species. If marine mammals are observed within 200 feet of the activity, pile driving will cease until the animal has left the area.

Noise reduction measures such as using a vibratory hammer when feasible, installing a bubble curtain, reducing impact hammer blows per day, installing wood block cushions on the impact hammer, or other appropriate noise reduction methods will be implemented to reduce noise levels.

Conservation Measure 3. Spill Prevention and Response:

Spill prevention and response procedures identified in the Base Seattle Integrated Emergency

Response Plan will be implemented during all in-water work. A spill kit will be kept onboard all equipment in the event of an unintended leak or spill. All dredging equipment, including barges, will be maintained in good repair and be free of leaks of hydraulic or lubricating fluids. All equipment used below the high tide line will use biodegradable hydraulic fluids. Fueling of marine‐based equipment will be performed using proper fuel transfer procedures. Fueling of land‐based equipment will occur by mobile trucks in a staging area or over pavement, and the location will be inspected after fueling to document that no spills have occurred. Any spills will be cleaned up immediately following the Base

Seattle Integrated Emergency Response Plan procedures.

Conservation Measure 4. Hazardous Materials and Waste:

All maintenance materials, waste, or hazardous wastes, including creosote piles, dredged materials, demolition waste, and construction wastes or debris will be removed as a result of the proposed action and transported to an authorized beneficial reuse or disposal facility, as appropriate, in compliance with applicable local, state, and federal laws and regulations.

Conservation Measure 5. Dredging:

Dredging and placement of fill material will be conducted using an environmental bucket (clam shell) to the extent feasible (i.e., except when debris is present). With the exception of incidental spillage associated with mechanical dredging, no overflow or decant water will be discharged from the barge.

The mouth of the bucket will remain open on descent to reduce turbidity to the extent feasible.

Dredging work will occur within previously disturbed areas of Slip 36.

Conservation Measure 6. Water Quality Controls and Monitoring:

Water quality controls such as operational best practices will be implemented during placement of fill material, as needed to minimize resuspension and water quality impacts during in-water demolition, debris removal, pier improvements, and other in-water construction activities. Materials and debris will be prevented from entering the waterway during demolition. Tarps, debris booms, or similar containment methods will be installed beneath structures being demolished to prevent debris from entering the water to the extent feasible. Water quality monitoring will be conducted to verify that water quality controls are effectively mitigating resuspension during construction and demolition.

Conservation Measure 7. Turbidity Controls:

Turbidity effects will be limited to the immediate area of construction during dredging and placement of fill material. Dredging will use an environmental bucket that will remain open on descent.

Placement of fill material will occur using methods and placement rates that reduce turbidity to the extent feasible. If silt curtains are used, they will be inspected daily throughout construction to ensure that T&E species and forage fish are not trapped.

4 Status of Species and Designated Critical Habitat within the Action Area or Vicinity

The following state and federally listed species have the potential to occur in the Action Area (Figure 4).

The species included in this section were identified using the USFWS, NMFS, and WDFW species lists included in Appendices A and B.

4.1 Fish

4.1.1 Bull Trout (Salvelinus confluentus)

Bull trout were listed as a federally threatened species in 1999 (USFWS 2006). Bull trout have several life history strategies, including resident/migratory, fluvial, and…