Lower Duwamish and East Waterway Cleanup Projects

Map of Duwamish Superfund site.
View the enlarged Duwamish Superfund Project map. (PDF)

The Lower Duwamish Waterway and the East Waterway are economically, ecologically, and culturally significant for the residents of Seattle. More than a century of urbanization and industrial activity polluted the sediments in both waterways, posing risks to people and the environment, and prompted the U.S. Environmental Protection Agency (EPA) to list both areas as Superfund sites.

Though the two waterways are physically connected, they are two separate, active cleanup projects led by the EPA. The characteristics of the two sites are somewhat different because the East Waterway is located further downstream from the Lower Duwamish Waterway Superfund Site but within the Lower Duwamish estuary. The East Waterway has deeper water and can be used by larger vessels than the Lower Duwamish Waterway. The City of Seattle is involved with two separate working groups that have collaborated to fund and clean up these contaminated waterways.

A passenger tour boat passes in front of a container ship at dock.
Shipping Activity at Terminal 30 in the East Waterway

The City of Seattle is deeply committed to making equity-based investments in the Duwamish River community. The City continues to engage with community members to understand their concerns and help improve the quality of life for those who live and work near and/or fish in the Duwamish Waterway.

The City’s participation in Lower Duwamish and East Waterway cleanup and habitat restoration projects, along with its stormwater permitting, combined sewer overflow control, and source control efforts, together represent a wholistic effort to restore the City of Seattle’s only river.

Two young children stand at the rail of the boat and look at the water.
Youth participants on the 2022 Lower Duwamish Boat Tour hosted by the Lower Duwamish Waterway Group.

On September 23, 2021, the City of Seattle, King County, and the Port of Seattle sent a letter to EPA about the Lower Duwamish Waterway and East Waterway cleanup plans and our continued dedication to reducing unacceptable risks to human health and the environment. View the EPA letter in full.

The traditional Native canoe 'Haynisisoos' pulls up at shore with paddles up.
Participants in a welcoming canoe near Terminal 107 park for a 2015 celebration of the Duwamish River’s First Peoples. Photo credit: Robert Zverina.

Lower Duwamish Waterway

More than 100 years of industrial and urban use has polluted the sediments (mud on the river bottom), water, and marine life in the Lower Duwamish Waterway. Contamination from polychlorinated biphenyls (PCBs) and other industrial chemicals including arsenic, polycyclic aromatic hydrocarbons (PAHs), and dioxins and furans poses risk to people and wildlife, with PCBs posing the greatest risk.

PCBs are toxic chemicals that were commonly used from 1929 to 1979 for numerous industrial activities and in some household products and building materials. They were widely used in hydraulic oils, electrical transformers, electrical equipment, caulk, and oil-based paint. PCBs can be harmful when released into the environment, in part because they persist and travel up through the food chain where people and wildlife can then be exposed to PCBs through eating contaminated fish and shellfish.

In 2001, EPA listed the last five miles of the Duwamish River as a Superfund Site. As such, EPA is the lead agency for the cleanup of the Lower Duwamish Waterway. The Lower Duwamish Waterway Group (LDWG) is a collaboration between the City of Seattle, King County, and the Boeing Company, who are working together with EPA to study contamination levels, design and implement detailed cleanup plans, and educate and involve the community in the EPA-led process. You can find more information at the LDWG website, including project documents, recent activities, and project schedules.

A dredge barge working in the Duwamish on a hazy day.
Dredging to remove contaminated sediment in the Lower Duwamish Waterway

The members of LDWG have been committed to the cleanup of the Lower Duwamish. One example of this commitment was their completion of five "early action" cleanups to reduce the risk of exposure to contaminated sediment and get a head start on the Lower Duwamish Superfund cleanup. These early-action areas were some of the most contaminated sediment areas of the LDW with the greatest opportunities for reducing polychlorinated biphenyl (PCB) contamination.

In total, these early efforts cleaned up about 29 acres of sediment and reduced average surface sediment levels of PCB contamination by over one-half, a significant step forward in the cleanup of the Lower Duwamish. The City of Seattle and the other members of LDWG have long been active in the strategic source control and pollution prevention effort in the watershed. Led by Ecology, this source control program has served as an effective example for other projects and communities.

A sunny day with kayaks beached on the banks of the Duwamish with commercial vessels in background.
Kayaks on the bank of the Lower Duwamish Waterway

Currently the members of LDWG are working on scientific studies and engineering design for river cleanup and controlling sources of pollution to the river. For engineering design and cleanup construction, the five-mile long Waterway is being managed in three reaches (upper, middle, and lower).

  • The upper reach attained 100% design in early 2024. The construction contractor is expected to begin cleanup work in fall 2024, with construction continuing for three construction seasons and concluding in early 2027. To protect salmon and other fish, each construction season is limited to approximately October-February.
  • The middle reach design started in 2022 and cleanup construction is planned to start in 2027
  • The lower reach design is planned to start in 2025 and cleanup construction is planned to start in 2030 or 2031

Learn more about sediment cleanup and how to participate in the cleanup process at the LDWG website.

East Waterway

The East Waterway, located at the mouth of the Duwamish River, contains historical pollution from industrial and urban use. Contamination of sediments at the bottom of the East Waterway by PCBs, arsenic, dioxin/furans, and PAHs pose risk to people and the environment, with PCBs posing the greatest risk.

The East Waterway is one part of the larger Harbor Island Superfund Site and is the last piece of that Superfund Site to undergo cleanup. EPA is overseeing the cleanup of the East Waterway to remove and remediate historical contaminants that threaten human and environmental health. The cleanup area stretches one mile and covers 157 acres. It is located immediately downstream and north of the Lower Duwamish Waterway Superfund Site, along the east side of Harbor Island.

Map with the Harbor island Superfund Site, the East Waterway, and the Lower Duwamish Waterway Superfund Site.
East Waterway Cleanup Location. Credit: Port of Seattle

The East Waterway Group (EWG) is a collaboration among the City of Seattle, King County, and the Port of Seattle. While EPA is the lead agency for the cleanup, the EWG members are working with EPA to study contamination levels, design detailed cleanup plans, and share information with and encourage input from the community. The City of Seattle and our fellow EWG members are committed to effective and timely cleanup of the East Waterway to improve public health and protect the environment.

In May 2024, EPA issued their cleanup plan (also known as a Record of Decision) detailing the EPA’s chosen remedy for the East Waterway. This Record of Decision finalizes the Proposed Plan which the EPA presented in April 2023. EPA held a formal period from April 28 – August 11, 2023 to solicit comments and input on the Proposed Plan, and the Record of Decision includes a Responsiveness Summary that summarizes and responds to those comments.. Both the Record of Decision and the earlier Proposed Plan are available on EPA’s website.

Westward view of Harbor Island with port operations, storage fuel tanks and various buildings and equipment at sunset.
Aerial photo of Harbor Island and the East Waterway taken in 2012.

Visit the East Waterway Group website for the response to the EPA’s Record of Decision from the EWG members, as well as for more information on the cleanup including project documents, recent activities, project schedules, and answers to frequently asked questions.

Learn more

Learn more about EPA and Washington Department of Ecology's (DOE) oversight of Lower Duwamish Waterway cleanup:

Learn more about United States Environmental Protection Agency’s (EPA) oversight of East Waterway cleanup: EPA and East Waterway.

Learn more about citywide work to control sources of pollution, how to report a pollution problem, or how you can prevent pollution.

Lower Duwamish Waterway pollution source control program

The City's program to keep pollution from entering the Lower Duwamish Waterway (LDW) is an important element of the watershed-wide source control strategy led by Ecology. Learn more about Ecology's Source Control Strategy.

The City’s program has three elements: source tracing, business inspections, and pipe cleaning.

Source tracing/characterization sampling

The City collects and tests sediment samples from area catch basins and pipes. When elevated contaminant levels (arsenic, copper, lead, mercury, and zinc, semi-volatile organic compounds, PCBs, and total petroleum hydrocarbons) are found, additional sampling and inspections are conducted upstream to locate the source.

Business inspections

The City inspects and works with businesses to ensure that they are using best management practices to keep stormwater pollution, including hazardous materials and industrial waste, out of storm drains that flow to the LDW. We inspect businesses based on identified or potential pollution risk.

Pipe cleaning

When the City finds elevated contaminant levels in storm drain sediment, it cleans the pipes to remove the sediment and stop pollution from reaching the waterway. Material removed from the pipe is collected, dewatered, and shipped offsite for disposal. The pipe is then checked periodically to see whether the contamination comes back. If it does, the whole process starts over again with more sampling and business inspections to find and control the source.

Source control implementation

The City has a Source Control Implementation Plan (SCIP) that describes our work to control pollution sources over the next five years. Washington State Department of Ecology approved the City of Seattle's 2021-2026 SCIP on December 17, 2020 to fulfill the requirements contained in Appendix 13 of the 2019 NPDES Municipal Stormwater Permit. More information can be found on Washington Department of Ecology’s website.

The Source Control Implementation Plan Documents are available for review:

Below are the 2015-2021 Source Control Implementation Plan Documents:


Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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