Frequently Asked Questions

Is it safe to swim in the Duwamish River?

Yes, but cautiously. While many miles of the Green and Duwamish River are healthy and thriving, the lower five miles of the Duwamish River are designated a Superfund site and contain highly contaminated mud and sediment on the bottom and shorelines. King County has advised Mark of the locations of high levels of pollution and has confirmed that he will be able to swim the full length of the river without major concern.

Other advisories from King County include:

  • Wearing an insulating wetsuit and hood for protection from cold water
  • Avoiding areas near Combined Sewer Overflow within 48 hours of heavy rainfall
  • Being aware of dangerous whitewater in the Green River gorge
  • Refraining from consumption of shellfish, crabs, and bottom-feeding marine life
  • Limiting salmon consumption, though they contain lower toxic levels as they do not spend their whole lives in the river
  • Avoiding contact with mud in contaminated areas, especially for children

Does Mark have experience with swimming? 

Yes! As an avid outdoorsman Mark has a great appreciation for the outdoors and our local waters, and he has decades of experience as a surfer and open water swimmer. In 2008, Mark completed another outdoor adventure: swimming completely around Bainbridge Island! This 41 mile swim helped raise awareness of the importance of protecting Puget Sound.

Learn more about Mark’s previous swim in this Seattle Times Article!

How long will it take?

Mark will swim about one day a week for the months of June through November.

Why is the Duwamish River a Superfund site?

Due to high levels of dangerous pollutants and contaminants from years of pollution, the last five miles of the lower Duwamish River are designaged as a Superfund Site by the Environmental Protection Agency. The past 100 years of industrial and urban use of the river resulted in hazardous levels of contaminants, such as PCBs and arsenic. Many of these contaminants are in the mud on the river bottom and threaten water quality, marine life, and people’s health. Fortunately, the Superfund program is leading cleanup and restoration the river, carried out by the entities responsible for the contamination, and is expected to take 17 years.

What pollutants are in the Duwamish River?

According to the EPA, several harmful pollutants are found in the lower Duwamish River. High levels of arsenic, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxin, and furans are all present in the lower Duwamish River, threatening both wildlife and the local communities. As a Superfund site, polluters are responsible for the efforts and costs of restoration.

How did they get there? 

For over 100 years the lower Duwamish River has received waste from the industrial area along its banks. Polluted stormwater from surrounding communities, the primary source of pollution into Puget Sound, and sewage overflows during heavy rains are also main contributors of pollution. Industrial waste yields high levels of PCBs and arsenic, and PAHs result from combustion of fossil fuels, wood, and garbage. Although PCBs were banned in 1979, the human-made chemicals remain in the river’s marine ecosystem. As a Superfund site, all polluters are responsible for the efforts and costs of restoration.

 What’s being done to restore the Duwamish River? 

The EPA has outlined strategies and priorities for cleaning up the Superfund hazardous areas. There are already sites along the river that have completed their “early action” cleanup, such as the Norfolk Area, Slip 4, and Duwamish Diagonal site. Other sites, such as Boeing Plant 2 and Terminal 117, are actively cleaning up their sites. Other industries and organizations are working to clean up the river as well as to control and reduce contamination at the source.

What other groups are working to clean up the Duwamish?

Environmental Protection Agency: Lower Duwamish Waterway Superfund Site Cleanup Plan 

In December 2014, the EPA released their official plan for restoration of the Duwamish River. The lower five miles of the river are a Superfund site, and the EPA is required to oversee the cleanup. The plan involves cleaning up 177 polluted acres of the river through several methods, including natural recovery, capping, and dredging. The restoration is projected to take 17 years, including ten years of natural recovery and seven years of active cleanup. By the end of 2015 it is expected that half of the Superfund cleanup will be completed.

Learn more about the EPA’s efforts here!

King County and the City of Seattle: Green-Duwamish Watershed Pla

King County and the City of Seattle have been making strides in addressing the environmental challenges of the Green and Duwamish Watershed as a whole. Together, they are working to control contamination at the source and prevent runoff and sewage overflows from entering the river. King County is acquiring land that is key in flood control, forest wetland conservation, and protecting vital habitat for salmon populations. By working with non-profits, businesses, and communities together, the City of Seattle and King County are working towards long-term goals and restoration of the Duwamish River.

Want to learn more about King County’s work on the Duwamish? Visit their website here!

Duwamish River Cleanup Coalition/Technical Advisory Group

Since 2001, the Duwamish Cleanup Coalition has joined neighborhoods and passionate Puget Sound residents together to clean up the Duwamish River. As the Community Advisory Group of the Duwamish Superfund site, DRCC manages outreach and educational programming about the Superfund cleanup and is the successor to the community, neighborhood, environmental, tribal and small business organizations that first came together as EPA’s community advisory group for the site. DRCC also works to restore the natural habitat of the Duwamish through their “Duwamish Alive” volunteer program.

Find more information, and involvement opportunities at the DRCC website!

What other effects does the pollution along the Duwamish River have on our communities?

Some of the industries along the Duwamish River produce air pollution, as well as water pollution. This air pollution has negative impacts on both families residing in the area and our natural environment. The poor air quality of the area has reduced quality of life for local residents of the Duwamish, particularly for communities of color and of low incomes. King County has worked to include these residents in their efforts of improving the Duwamish River as a whole without avoiding any negative consequences of the industrial neighborhoods.