U.S. federal and state authorities have reached a $668 million settlement agreement to support the long-term cleanup of the Lower Duwamish Waterway Superfund site in Seattle, marking a major step toward addressing decades of industrial contamination in the river system.
The agreement between the U.S. Environmental Protection Agency (EPA), the U.S. Department of Justice, and the state of Washington involves more than 100 potentially responsible parties. The cleanup effort is expected to take at least 10 years to complete.
Under the terms of the settlement, the Lower Duwamish Waterway Group—comprising The Boeing Company, the city of Seattle, and King County—will lead the design and implementation of the EPA-selected cleanup plan for the in-water portion of the site. The strategy includes dredging, capping, and additional measures to address the most heavily affected sections of the waterway.
To support the work, approximately $130 million will be contributed by other responsible parties, while federal agencies will provide about $140 million.
“This settlement finally ensures full-scale cleanup of the Lower Duwamish Waterway,” said EPA Office of Enforcement and Compliance Assurance Assistant Administrator Jeffrey A. Hall. “The cost-sharing agreement resulting from negotiations among many parties shows that this Administration will make good on its promise to expedite cleanup of hazardous pollutants while ensuring responsible parties are held accountable and the public is not left with the bill for the cleanup.”
The Lower Duwamish Waterway forms the final five miles of the Duwamish River, Seattle’s only river, before the water reaches Elliott Bay and Puget Sound. Historically, the river flowed through tidal marshes and mudflats that provided habitat for fish, birds, and other wildlife and supported Native American communities.
During the early 20th century, dredging, channelization, and land reclamation reshaped the river to accommodate industrial development. Activities such as aircraft manufacturing, timber processing, steel production, and chemical operations—along with sewage and stormwater discharges—contributed to contamination in river sediments.
EPA has identified 41 hazardous substances in the sediments, including polychlorinated biphenyls (PCBs), arsenic, carcinogenic polycyclic aromatic hydrocarbons, dioxins, and furans. The site was placed on the federal Superfund list in 2001.
The consent decree has been lodged with the U.S. District Court for the Western District of Washington and will undergo a 30-day public comment period before final court approval.
