The Lower Duwamish Waterway is a five-mile stretch of industrial river in Seattle, Washington. The EPA added it to the National Priorities List in September 2001 after more than a century of industrial activity, stormwater runoff, and wastewater left the riverbed heavily contaminated. The site entered active remedial construction in January 2024, but cleanup is not complete and human exposure is not under control.
The river sediment contains more than 50 chemicals of concern. The main ones are polychlorinated biphenyls (PCBs), arsenic, carcinogenic polycyclic aromatic hydrocarbons (cPAHs), dioxins, and furans. These chemicals also show up in fish tissue. PCBs are the greatest health risk to people. Eating resident fish and shellfish is the primary exposure route because these chemicals build up in species that live in the river year-round and cannot be removed by cleaning. The Washington State Department of Health advises against eating crab, shellfish, and resident fish other than salmon. Salmon spend only a short time in the river and accumulate less contamination. Direct contact with contaminated sediment also poses a risk.
On March 4, 2026, the EPA, U.S. Department of Justice, and the state of Washington reached a settlement with more than 100 potentially responsible parties. The Lower Duwamish Waterway Group, made up of Boeing, the City of Seattle, and King County, agreed to design and carry out the cleanup. One source estimates cleanup cost at $342 million for the 177-acre sediment area addressed in the 2014 Record of Decision. A separate source estimates total cleanup cost at $668 million with at least 10 years of work ahead. Both figures appear in the source materials and reflect different scopes of the project. The consent decree is subject to a 30-day public comment period open until April 13, 2026, and requires final court approval. Prior to the main cleanup, five Early Action Area projects completed by the end of 2015 removed about 50 percent of PCB contamination.
Season 2 of construction in the Upper Reach began October 1, 2025, and runs through February 2027. Work includes dredging, capping, and enhanced natural recovery on weekdays and Saturdays, day and night. The South Park Bridge will close periodically for equipment access, except during peak commute hours, and Metro Route 60 will be rerouted during closures. The main remedial action is estimated to finish between March and May 2028.
Zoning restrictions limit land uses that do not match current cleanup levels, and a community-based healthy seafood consumption program is in place. Cleanup documents are available in English, Spanish, Vietnamese, Khmer, Korean, Chinese, Russian, Tagalog, Lao, and other languages at the Washington State Department of Ecology Northwest Regional Office in Shoreline and at the Seattle Public Library South Park Branch. Community members can reach the outreach team at 1-888-561-5394 or info@ldwg.org, or contact the EPA staff assigned to the site.
