Municipalities have a legal obligation to take action on stormwater and salmon mortality.

Seattle, WA (June 16, 2022). The Cities of Seattle, Mukilteo, Normandy Park, Burien, and Seatac have failed to control and report stormwater discharges into three urban salmon streams—Pipers Creek, Big Gulch, and Miller Creek—despite conclusive evidence that road runoff carrying toxic chemicals like 6PPD-quinone kills coho salmon in these waterways.

On Thursday, Puget Soundkeeper sent Clean Water Act notices of intent to sue (the first step in any clean water litigation) to the five municipalities due to their failure to comply with permit notification requirements. Failure to control this stormwater and report it to the Washington Department of Ecology is a violation of the Clean Water Act and the cities’ state-issued Municipal Stormwater Permits, which regulate polluted stormwater discharges. Soundkeeper must now wait 60 days before it can file an enforcement action in federal court.

“Our salmon have been dying due to stormwater pollution for decades,” said Puget Soundkeeper Executive Director Sean Dixon. “6PPD-quinone is a solvable crisis, but only if we act without delay.”

Recent research conducted by the University of Washington, the University of Washington Tacoma, and Washington State University Puyallup identified 6PPD-quinone as the toxic tire chemical responsible for killing coho salmon before they’re able to spawn. This phenomenon, known as coho Pre-Spawn Mortality Syndrome, was observed for decades before pinpointing 6PPD-quinone as the cause.

Decades of companion studies have consistently shown that 6PPD-quinone’s toxic effects can be prevented through a host of best practices for stormwater management, including certain green infrastructure installations that filter polluted stormwater through mixtures of soils and sand.

“When it comes to stormwater and coho Pre-Spawn Mortality, we know the cause and we have a solution,” said Puget Soundkeeper’s Clean Water Program Director, Alyssa Barton. “We look forward to collaborating with regional municipalities as they implement green stormwater infrastructure solutions for new and existing development, ensuring our urban streams are clean and healthy for salmon and people.”

Research dating back well over 10 years consistently shows that salmon die after they enter Pipers Creek, Big Gulch, and Miller Creek to spawn. Data and modeling from a host of federal and state agencies show similar results for coho in waterways around the Sound and throughout the West Coast.

The City of Seattle owns at least nine stormwater outfalls that empty into Pipers Creek. Big Gulch receives stormwater discharge from approximately 12 outfalls owned by the City of Mukilteo, while Normandy Park, Burien, and Seatac together own dozens of outfalls that spill into Miller Creek.

“The permits are clear: municipalities must take action when they know about toxic pollution,” said Puget Soundkeeper Attorney Katherine Brennan. “Today’s notices give each of the five municipalities 60 days to come into compliance with their permits and take a step toward addressing the 6PPD-quinone crisis.”


Puget Soundkeeper protects and enhances the waters of Puget Sound for the health and restoration of aquatic ecosystems and the communities that depend on them. A founding member of the global Waterkeeper Alliance, Puget Soundkeeper has advocated for the public’s right to clean water for nearly 40 years.

Puget Soundkeeper is represented in these actions by Earthjustice.

Learn more about Urban Runoff Mortality Syndrome here.

Learn more about 6PPD, 6PPD-quinone, and tire pollution here.