Skip to main content

Sediment cleanup begins in upper reach of Lower Duwamish Waterway Superfund Site to remove legacy pollution

Summary

Dec. 10, 2024: Led by the U.S. Environmental Protection Agency and implemented by the City of Seattle, King County, and Boeing, sediment cleanup work has begun in the upper reach of the Lower Duwamish Waterway Superfund Site, where over a century of urbanization and industrial activity has polluted the riverbed with toxic contaminants.

News

Construction kicked off in late November to clean up the five-mile Lower Duwamish Waterway Superfund Site as workers began removing contaminated sediment in the uppermost segment of the project area. The City of Seattle, King County, and Boeing are working together to implement the multi-year project as members of the Lower Duwamish Waterway Group.

The U.S. Environmental Protection Agency is overseeing the cleanup design and construction for the waterway, and the Washington State Department of Ecology is the agency coordinating source control efforts on land. 

“EPA is very pleased that the remaining phase of the cleanup of the Lower Duwamish Waterway is finally moving forward,” said Casey Sixkiller, Regional Administrator of EPA’s Northwest and Alaska Region 10 office in Seattle. “While previous efforts have reduced sitewide PCB levels by half, this work signals the start of a new and critical chapter of cleanup and will further reduce risks to people and the fish and wildlife in the Duwamish River valley.”

The in-water project will continue to improve water quality and reduce the risks sediment contamination presents to people and fish after more than a century of heavy industrial and commercial use.

“The Muckleshoot Tribe has been fishing in the Duwamish River for thousands of years,” said Chairman Jaison Elkins of the Muckleshoot Indian Tribe. “For generations, salmon have sustained our way of life. The cleanup of the Duwamish River is an important step to removing sediment contamination and restoring the river for our culture and future generations.”

“We are glad to see these important steps towards clean-up of the Duwamish River, where the Suquamish Tribe has treaty fishing rights as guaranteed by the 1855 Treaty of Point Elliott,” said Chairman Leonard Forsman of the Suquamish Tribe. “We look forward to continued progress in reversing the damage done by years of pollution and destructive land use, and hope to see the full recovery of salmon and other marine species.”

The Lower Duwamish Waterway Superfund Site is divided into three segments (reaches) for sediment cleanup: lower, middle, and upper. Construction activities in the upper reach spans the southernmost two miles of the Superfund site between Duwamish Waterway Park and the South 102nd Street bridge. 

King County, which is managing this portion of the work, hired Pacific Pile and Marine from Seattle’s South Park neighborhood as the construction contractor. The cleanup activities include a combination of dredging, capping, and enhanced natural recovery. 

“The start of Duwamish River sediment cleanup marks a major step in our commitment to take on historic pollution impacting this essential waterway,” said King County Executive Dow Constantine. “Restoring the Duwamish will require all of us working together in good-faith partnerships among local, state, and federal governments, private partners, industry, and the people who live and work here. King County’s investment in this project and others on the waterway reflects our vision of a revitalized Duwamish River, supporting a healthy environment and community for generations to come.”

Sediment removal work area out on the water with a digger working within a floating turbidity barrier and a barge to carry away polluted sediment.
Digger removing polluted sediment from the lower Duwamish River

The cleanup in the upper reach will take place seasonally from October through February; in-water construction in the Duwamish is restricted to these months to protect certain fish species, such as young salmon that migrate through the river to Puget Sound. Upper reach cleanup is expected to conclude in February 2027.

“Since time immemorial, the Duwamish River has been foundational to the people and communities of this region and the natural ecosystem it supports,” Seattle Mayor Bruce Harrell said. “This cleanup of Seattle’s only river is a much-needed investment in our city and for communities who have been burdened by legacy pollution. We have an obligation and responsibility to care for our natural environment, and through deep partnerships between our residents and businesses, the leadership of the U.S. EPA and Washington State Department of Ecology, and dedication of the City of Seattle, King County, and Boeing, we are building Seattle’s healthy and sustainable future." 

After the Lower Duwamish Waterway upper reach cleanup is complete, construction will continue downstream toward Harbor Island for the middle and lower reaches. Cleanup construction of all three reaches will take about 10 years. The members of the Lower Duwamish Waterway Group, or LDWG, are funding this construction, while working separately with EPA on the process by which other parties found to have contributed to the historical contamination will help fund the remediation.

Cleaning up legacy pollution

Over a century of urbanization and industrial activity has polluted the sediment at the bottom of the Lower Duwamish Waterway with toxic contaminants. Contaminants found in the river sediment include polychlorinated biphenyls – known as PCBs – heavy metals like arsenic, lead, zinc, and other types of contaminants including dioxins, furans, and polycyclic aromatic hydrocarbons, known as PAHs.

Removing polluted sediment from a barge for processing and disposal
Dock worker handling the lines to tie up a barge filled with polluted sediment from the Duwamish Waterway

“For more than a decade, we’ve embraced our commitment to the health of the Lower Duwamish Waterway and surrounding communities in Seattle by investing in cleanup activities and habitat restoration,” said Jill Graftenreed, Boeing vice president, Global Enterprise Sustainability. “Boeing partners with businesses, tribes, the local community and government agencies to find and implement workable and sustainable solutions to restore and protect human and environmental health.” 

The Washington State Department of Health currently advises people not to eat fish and shellfish that live year-round in the waterway. Salmon caught in the Lower Duwamish Waterway are a safe choice to eat because they only spend a short time in the waterway as they migrate through to spawning areas upstream.

"As a proud member of the South Park community, Pacific Pile and Marine views the Lower Duwamish cleanup as a transformative project with lasting economic and environmental benefits,” said JC Clark, Chief Operating Officer of Pacific Pile and Marine. “By restoring this vital waterway, we are creating jobs, developing local skills, and fostering a sustainable environment for businesses and residents. Guided by our commitment to safety and quality, we are honored to be part of an effort that unites people to build a healthier and more resilient future."

Once complete, the cleanup of contaminated sediment from all three reaches and pollution source control is anticipated to reduce the waterway’s PCB sediment contamination by over 90 percent.

Investing in the health of the Duwamish River

The Lower Duwamish Waterway Group members are proud to continue improving the waterway’s ecosystem and protecting public health. Early action cleanups have already been conducted in five “hot spot” areas that held some of the most contaminated sediments. These early efforts cleaned up about 29 acres of sediment and reduced average surface sediment levels of PCB contamination by more than 50 percent. There are also other projects under way to address contamination in the Duwamish River, such as: 

  • The EPA- and Ecology-led cleanups of contaminated properties on land along the Lower Duwamish Waterway. There are currently over 20 of these cleanup sites underway.  
  • The Department of Ecology’s Source Control Strategy program, which aims to manage contamination sources and help to minimize the risk of the waterway sediments becoming contaminated again.  
  • King County and Seattle Public Utilities’ contamination control efforts through their combined sewer overflow control programs, source tracing programs, business inspections, and storm drain line cleaning. 
  • The EPA-led Superfund project near the mouth of the Duwamish River called the Harbor Island Superfund Site cleanup. In May 2024, EPA issued the cleanup plan for the final portion of that Superfund Site, calling for removal of contaminated sediment from the East Waterway of the Duwamish River.  

“This work is an important step forward in our efforts to restore the Duwamish River and protect the people and fish that depend on it,” said Laura Watson, Director for the Washington State Department of Ecology. “Bringing the Duwamish back to health is a long-term endeavor that couldn’t happen without partnerships and collaboration.”  

“The cleanup of the Duwamish River represents a critical step towards healing both the environment and the communities,” said Duwamish River Community Coalition Executive Director, Paulina López, LLM. “This is not just about restoring a very important local body of water but is also a commitment to environmental justice for the communities that have borne the brunt of pollution for far too long. Ensuring a full cleanup with the highest health standards is essential for the well-being of those historically impacted by cumulative injustices and pollution in the Duwamish River Valley.” 

Neighbors who live, work, and play along the river are encouraged to stay informed about the project and any construction impacts by signing up for email updates. A project email and a phone line at 1-888-561-5394 for the Lower Duwamish Waterway Group are also available to submit questions or concerns.

Multimedia

Resources

Quotes

The Muckleshoot Tribe has been fishing in the Duwamish River for thousands of years. For generations, salmon have sustained our way of life. The cleanup of the Duwamish River is an important step to removing sediment contamination and restoring the river for our culture and future generations.

Jaison Elkins Chairman of the Muckleshoot Indian Tribe

We are glad to see these important steps towards clean-up of the Duwamish River, where the Suquamish Tribe has treaty fishing rights as guaranteed by the 1855 Treaty of Point Elliott. We look forward to continued progress in reversing the damage done by years of pollution and destructive land use, and hope to see the full recovery of salmon and other marine species.

Leonard Forsman Chairman of the Suquamish Tribe

The start of Duwamish River sediment cleanup marks a major step in our commitment to take on historic pollution impacting this essential waterway. Restoring the Duwamish will require all of us working together in good-faith partnerships among local, state, and federal governments, private partners, industry, and the people who live and work here. King County’s investment in this project and others on the waterway reflects our vision of a revitalized Duwamish River, supporting a healthy environment and community for generations to come.

Dow Constantine King County Executive

EPA is very pleased that the remaining phase of the cleanup of the Lower Duwamish Waterway is finally moving forward. While previous efforts have reduced sitewide PCB levels by half, this work signals the start of a new and critical chapter of cleanup and will further reduce risks to people and the fish and wildlife in the Duwamish River valley.

Casey Sixkiller Regional Administrator, Region 10, U.S. Environmental Protection Agency

Since time immemorial, the Duwamish River has been foundational to the people and communities of this region and the natural ecosystem it supports. This cleanup of Seattle’s only river is a much-needed investment in our city and for communities who have been burdened by legacy pollution. We have an obligation and responsibility to care for our natural environment, and through deep partnerships between our residents and businesses, the leadership of the U.S. EPA and Washington State Department of Ecology, and dedication of the City of Seattle, King County, and Boeing, we are building Seattle’s healthy and sustainable future.

Bruce Harrell Seattle Mayor

As a proud member of the South Park community, Pacific Pile & Marine views the Lower Duwamish cleanup as a transformative project with lasting economic and environmental benefits. By restoring this vital waterway, we are creating jobs, developing local skills, and fostering a sustainable environment for businesses and residents. Guided by our commitment to safety and quality, we are honored to be part of an effort that unites people to build a healthier and more resilient future.

JC Clark Chief Operating Officer of Pacific Pile & Marine

For more than a decade, we’ve embraced our commitment to the health of the Lower Duwamish Waterway and surrounding communities in Seattle by investing in cleanup activities and habitat restoration. Boeing partners with businesses, tribes, the local community and government agencies to find and implement the workable and sustainable solutions to restore and protect human and environmental health.

Jill Graftenreed Vice President, Global Enterprise Sustainability, Boeing

This work is an important step forward in our efforts to restore the Duwamish River and protect the people and fish that depend on it. Bringing the Duwamish back to health is a long-term endeavor that couldn’t happen without partnerships and collaboration.

Laura Watson Director, Washington State Department of Ecology

The cleanup of the Duwamish River represents a critical step towards healing both the environment and the communities. This is not just about restoring a very important local body of water but is also a commitment to environmental justice for the communities that have borne the brunt of pollution for far too long. Ensuring a full cleanup with the highest healthy standards is essential for the well-being of those historically impacted by cumulative injustices and pollution in the Duwamish River Valley.

Paulina López, LLM Executive Director, Duwamish River Community Coalition

Contact

Akiko Oda, King County Wastewater Treatment Division, 206-263-4190
Brad Wong, City of Seattle, Seattle Public Utilities, 206-446-8267
Connor Greenwood, Boeing, 571-243-0262  

Visit our Newsroom for additional resources

expand_less