EPA Superfund Site

LOWER DUWAMISH WATERWAY

WA | EPA ID WA0002329803

About this site’s exposure pathways: As of November 2024, the Lower Duwamish Waterway Superfund site is considered "Current Human Exposure Not Under Control" (HENC). The exposure pathways include direct contact (sediment ingestion) and consumption of contaminated seafood, due to Polychlorinated Biphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), arsenic, and dioxins/furans in sediment. These exposure pathways, primarily the latter, are unacceptable based on EPA risk-based criteria.

Five early PRP-led cleanups, most completed before 2015, have reduced the levels of PCBs in the Lower Duwamish Waterway by approximately half. Direct contact risks will be addressed through sediment cleanup. While cleanup will also reduce risks from seafood consumption, this pathway must also be addressed through institutional controls. Public Health Seattle & King County implements an institutional controls program required by the Record of Decision. The program is funded by the PRPs and uses culturally appropriate community-based methods to reach key (mostly immigrant) fishing communities with the health message that: salmon is the only safe seafood choice.

Remedial design and remaining cleanup will be phased and includes a combination of dredging, capping, and enhanced natural recovery. Design of the first phase was completed in 2024, with construction starting in late 2024. The design of the second phase is underway. Construction activities will take place annually between October 1 and February 15 to avoid impacts to juvenile salmon. Construction is anticipated to require at least 10 construction seasons, addressing direct sediment contact risks. Monitored natural recovery will continue to assess sediment changes. Community members can get up-to-date information related to construction by visiting the Potentially Responsible Party (PRP) webpage at https://ldwg.org/construction-news/.

Periodic seafood monitoring every five years will assess changes in contamination levels in fish, crabs and clams as cleanup progresses. The most recent monitoring was conducted in 2023. The institutional controls program will continue as long as necessary to protect community members from exposure to contaminated seafood.