Lower Duwamish and East Waterway Projects

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View the Duwamish Superfund Project pdf for the enlarged map

The Lower Duwamish Waterway and the East Waterway are economically, ecologically, and culturally significant for the citizens of Seattle. More than a century of urbanization and industrial activity polluted the sediments in both waterways, posing risks to people and wildlife, and prompted 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 EPA. The City of Seattle is involved with two separate working groups that have partnered to fund and clean up these contaminated waterways.

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.

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.

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 for the cleanup of the Lower Duwamish Waterway. The Lower Duwamish Waterway Group (LDWG) is a partnership between The Boeing Company, the City of Seattle, King County, and the Port of Seattle. LDWG is 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 LDWG.org including project documents, recent activities, and project schedules.

LDWG is committed to the cleanup of the Lower Duwamish. LDWG partners completed 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 the sediment. 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 our LDWG partners 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.

Currently LDWG is working on scientific studies and engineering design for river cleanup and controlling sources of pollution to the river. Future cleanup construction will include dredging and capping of contaminated sediments.
Learn more about sediment cleanup at LDWG.org.

Learn more about pollution source control below.

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 wildlife 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.

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East Waterway Cleanup Location, Credit: Port of Seattle

The East Waterway Group (EWG) is a public partnership between the City of Seattle, King County, and the Port of Seattle. EWG is working together with EPA to study contamination levels, design detailed cleanup plans, and educate and involve the community. The EWG is committed to the EPA-led cleanup of the East Waterway. For more information on the cleanup including project documents, recent activities, project schedules, and answers to frequently asked questions, visit the East Waterway Group website.

EPA is expected to release a Proposed Plan for the East Waterway cleanup in 2022. EPA is organizing multiple informational meetings to encourage meaningful public engagement on the Proposed Plan. Following that release, there will be a formal comment period with multiple opportunities and formats for public comment. EPA will carefully consider, and respond to comments, and will then finalize its cleanup plan in their Record of Decision.

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: