"The cleanup of the Duwamish River is an important step to removing sediment contamination and restoring the river for our culture and future generations."

— Muckleshoot Tribal Council Chairman Jaison Elkins

DUWAMISH RIVER — 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 (LDWG).

The U.S. Environmental Protection Agency (EPA) is overseeing the cleanup design and construction for the waterway, and the Washington State Department of Ecology (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 Muckleshoot Indian Tribal Chairman Jaison Elkins. “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.”

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 approximately 10 years. The members of 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 (PCBs), heavy metals like arsenic, lead, zinc, and other types of contaminants including dioxins, furans, and polycyclic aromatic hydrocarbons (PAHs).

“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.”