The Duwamish River functions as an industrial waterway, charting a human-engineered course through historic wetlands and floodplains. The final five miles of the river is one of the busiest ports in the Pacific Northwest and, thanks to its history of commercial use, also one of the most polluted stretches of river in the United States.  

A map of Harbor Island showing the outline of the Harbor Island Superfund Site

Harbor Island, an entirely human-constructed island, was built at the mouth of the Duwamish River after the river was dredged and channelized in the early 1900s. The island is currently home to shipyards, railyards, marinas and port facilities. The Environmental Protection Agency (EPA) added Harbor Island to its National Priorities List (aka Superfund) in 1983, a necessary decision given the level of pollution on site. Since then, EPA, Washington State, and the local community have worked to clean up the area’s toxicity.  

EPA addressed multiple “operable units” within the Harbor Island Superfund site since its 1983 listing. The East Waterway unit is the last remaining area without a cleanup plan in place. Now, after 40 years, community members have an opportunity to participate in the final planning phase of Harbor Island Superfund cleanup, via public comment.  

Harbor Island Superfund Site 

The East Waterway is bound by Elliott Bay to the north, Port of Seattle infrastructure to the east and west and, after passing under the West Seattle Bridge to the south, by the main stem of the Duwamish River.  

EPA identified several contaminants of concern (COCs) in the East Waterway and specified polychlorinated biphenyls (PCBs), arsenic, carcinogenic polycyclic aromatic hydrocarbons (cPAHs), and dioxins/furans as posing the greatest risk to human health and wildlife. Some of the COCs in the Duwamish River bioaccumulate in fish and shellfish posing a human health hazard and an environmental justice threat for the many people who fish for subsistence, commercial, and ceremonial purposes.  

A Living Waterway 

Duwamish Valley residents have little waterfront access or green space, yet they continue to make the most of the river through recreation and fishing. Additionally, the East Waterway is part of the treaty-protected fishing grounds for the Muckleshoot Indian Tribe, the Suquamish Tribe, and the Yakama Nation.  

The Green-Duwamish watershed connects Elliott Bay to the Cascades, linking Seattle’s industrial maritime corridor to critical wildlife habitat and salmon migration routes. People and wildlife use the river despite the legacy toxics in the sediment, and ongoing pollution from surrounding industrial infrastructure. 

Cleanup Options 

The EPA released a cleanup proposal earlier this year, detailing several potential cleanup plans. Puget Soundkeeper supports EPA’s “preferred alternative,” that is, the cleanup plan that the EPA itself recommends. This plan includes some initial stormwater regulation, which is critical for holistic river management and true, sustainable, long-term remediation.  

Duwamish River Community Coalition (DRCC) leads the larger Seattle community in a movement toward a healthy, resilient Duwamish River. Puget Soundkeeper and DRCC suggest a few improvements to the preferred alternative, including:  

  1. Addressing ongoing toxic “hotspots” in the river, including areas that receive high volumes of polluted stormwater from outfalls, and which overlap with areas heavily used by the community, including for fishing. This should help address the environmental justice issue of toxic fish and shellfish, especially given the Duwamish River’s limited water access for fishing and recreation space.  
  1. Updating the preferred alternative to include upstream stormwater management. This should treat and control polluted stormwater entering the Duwamish River upstream of the Harbor Island site so that the EPA’s cleanup effort works holistically across the watershed. Protecting the East Waterway from upstream sources of contamination is just as important as protecting it from buried legacy pollution within the site.  
  1. Accelerating remediation so EPA continues to see this project through to completion as quickly as possible. After 40 years, the East Waterway ecosystem needs remediation now, and the communities that live, work, and fish around Harbor Island cannot wait another 15 years for the EPA to finish this planned remedy.  

Source Control 

Full remediation of this site will not be possible until ongoing impacts from municipal, commercial, and industrial pollution are also controlled and, ultimately, stopped. 

Addressing and controlling these ongoing sources requires comprehensive stormwater management across the entire watershed. It’s vital that the entities responsible for historic pollution collaborate with those responsible for today’s toxic stormwater management.  

Comprehensive management is a key element in the long-term sustainability of the watershed, and would address much of the preventable pollution entering the Duwamish River. Ongoing pollution threatens EPA’s forward progress on behalf of the East Waterway and the entire river.  

Over the coming years (though Soundkeeper and its partners will push for sooner!), EPA will look to broaden its East Waterway cleanup plan and address this part of the pollution problem.