In 2015, Mark Powell swam from the headwaters of Green-Duwamish River in the Cascade Mountains to the river’s end in the saltwater of Puget Sound. From June to October, he swam 85 miles from the meandering, pristine start of the river to the polluted superfund end of the river. This site chronicles his journey. 

Drawing on communities, people and wildlife along the river, Swim Duwamish tells the story of the threats and opportunities facing the Duwamish River watershed.
Pollution and industrial impacts jeopardize the health of its ecosystems and economies, but the resilient river can – and must – be restored. As Mark swam the river, he connected people with the river and empower communities to speak up and advocate together for a restored river and ultimately a cleaner Puget Sound.


read blog posts from the river  /  watch underwater videos from the swim   explore photos chronicling the swim


We can’t protect and restore Puget Sound when one of its main tributaries continues to pollute its waters each day, simply by flowing into it. It’s time to bring the Duwamish River back to health by bringing communities, stakeholders, and partners together to restore the river. It’s time to prevent further degradation of Puget Sound and promote a watershed-wide vision for tackling pollution.

We can’t restore the river and protect Puget Sound without everyone doing their share. King County and the City of Seattle have teamed up to coordinate river recovery and plan for a healthy future through their Green-Duwamish Watershed Plan. The EPA’s Cleanup Plan for the river tackles existing toxic pollution that threatens fish and people, and many local groups and industries have cleanup projects underway throughout the watershed.


Together, we can return the Duwamish to health, but not without support from communities along the every mile of the river – families, school groups, local governments, tribal nations, and people like you. Here’s what you can do today:

  • Update your yard to be beautiful AND fight pollution through the Rain Wise program that provides homeowners with rebates to transition lawns into rain gardens. More info here.
  • Prevent dirty water from running into the river by washing your car at a designated car wash. Find one near you.
  • Keep pollution off the roadway by checking for oil leaks in your car. Learn how here.


blog posts
Watch video and read Mark’s blog posts from the river!

Mark was the Puget Sound Program Director at Washington Environmental Council. He has a long history in ocean and fish conservation, including nearly a decade leading Ocean Conservancy’s fish conservation efforts and three years leading the World Wildlife Fund’s global seafood program based in Switzerland. He is a marine biologist and his work has taken him from salmon streams to the halls of Congress to fish farms in rural China and Vietnam. He is a northwest native who enjoys our ocean, coasts, rivers, and mountains and he finds Seattle’s seafood to be the best in the world. Mark swam around Bainbridge Island in 2008 & 2009.

Seattle’s only river, the Duwamish, has been straightened, dredged, dammed, developed, polluted, and reduced in size by the re-direction of major tributaries.

The river has lost 70% of its flow, 97% of its estuary, and 90% of its floodplain. Most of its banks are covered in concrete or riprap and most of its shorelines have been developed. One major tributary, the Black River, no longer exists. The thriving industrial corridor created by these changes produces billions of dollars per year in income, but not without a cost.

Anyone can see the industrial development and pollution that plagues the river, but few people know the full story of what’s been lost. The Duwamish was once home to rich salmon runs, shellfish, and other food sources found in the productive estuary and floodplains. The river, and its waterfowl and fish, has sustained the Duwamish Tribe (Dkhw’Duw’Absh”) that lived around the watershed and along Elliott Bay for over 1,000 years. Today, the Duwamish Tribe continues to celebrate their culture along the river and in their local traditional longhouse.

More than the river is at stake. The Duwamish River is an important tributary to Puget Sound, as well as one of the biggest sources of pollution into the Sound. We will never see a truly healthy Puget Sound until we clean up the Duwamish and the other rivers that sustain the Sound. The lower Duwamish contains a Superfund site, an indicator of hazardous pollution but also an opportunity for restoration and transformation. More than ever, local governments and community groups are working together to restore and protect the Duwamish.


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.

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 designated 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.