Harbor Island (Lead)

Overview

Harbor Island is a 420-acre industrial island in Seattle's Elliott Bay. It has been contaminated by commercial and industrial activity dating back to the early 1900s. The site was added to the National Priorities List in 1983 and is managed under EPA oversight with cleanup divided into seven Operable Units, or OUs, to address different areas and types of contamination.

Contaminants of concern include PCBs (polychlorinated biphenyls), arsenic, lead, mercury, cadmium, copper, zinc, chromium, and other heavy metals found in soil, groundwater, and sediment. Organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), dioxins and furans, pesticides like chlordane and DDT, and volatile organic compounds including benzene and tetrachloroethene are also present. PCBs, arsenic, carcinogenic PAHs, dioxins, and mercury pose the greatest health risks. The biggest danger to people is eating resident fish, crabs, and clams from the East Waterway, where these chemicals build up in seafood year-round. The Washington Department of Health advises against eating resident fish, shellfish, or crab from the waterway. Human exposure is not currently under control at the site, though groundwater migration is under control and no unacceptable discharge to surface water is occurring.

The Port of Seattle, City of Seattle, and King County lead cleanup efforts under EPA oversight. Completed work includes removing contaminated soil and disposing of it off-site, capping remaining contamination, removing about 6,000 creosote-treated piles from shipyard areas, dredging nearshore sediments, and installing habitat-friendly soil layers. The Washington Department of Ecology approved cleanup for the Tank Farms OU. Five of the seven OUs have completed cleanup decisions, and those areas are now in long-term monitoring. The most recent five-year review was completed in September 2025. The East Waterway is the final OU. EPA issued an Interim Record of Decision for it in May 2024, with removal work estimated between February and August 2026 and completion expected between February and April 2028. Construction has not been completed across the entire site, and the site has not been deleted from the National Priorities List.

EPA offers free technical assistance to community groups through its Technical Assistance Services for Communities program. Tribal nations including the Yakama Nation, Muckleshoot Indian Tribe, and Suquamish Tribe consult with EPA on cleanup decisions, and tribal members hold treaty rights to harvest seafood around the island.