Nisqually Tribe’s system shows promise in fighting threat to salmon

Last year, the Nisqually Indian Tribe and partners piloted a new biofiltration unit they hoped could alleviate devastating impacts of toxic roadway runoff, particularly a tire-dust chemical that’s deadly to coho and serve as a model to the region for a scalable system

After more than a year of data collection and follow-up study, the results of the project are out, and show that the device, properly sized, may protect salmon from 6PPD-quinone’s fatal effects.

The tribe cautions that more study is needed before the device’s benefits can be approved for expansion, and large-scale action to end 6PPD’s effects is still urgently needed. But with a 90% reduction in tire dust through the device’s use, they and their partners are excited to seek more funding for the tool.

“It certainly seems to have a measurable result on the chemical we’re interested in reducing. As a proof of concept, it worked really well,” said Chris Ellings, the Tribe’s salmon recovery program manager.

The tribe teamed up with Long Live the Kings, Herrera Environmental Consultants and Cedar Grove, among others, to place a newly developed biofiltration unit at Ohop Creek on property owned by the Nisqually Land Trust. The creek is a tributary to the Nisqually River and home to a large salmon habitat recovery project. It’s also near Highway 7, a busy road that sees vehicles deposit 12 pounds of tire dust on its surface every year—tire dust that rainstorms can wash into nearby habitat.

Developed by Cedar Grove, the biofiltration device applies the concepts of in-ground biofiltration to a mobile unit. Filtering stormwater through two layers—compost and a layer that removes phosphorus—the unit captured stormwater from three storms last year, with its results at leaching out harmful chemicals from that stormwater closely studied.

While the results of the unit’s effectiveness at filtering out harmful metals such as zinc and copper also were tested, partners were keenly interested in its effects on 6PPD. Researchers at Washington State University Puyallup and University of Washington Tacoma recently determined that the chemical, which is formed when tire-dust particles react to ozone when they wear off on roads, is a deadly threat to coho; it’s also been determined to be harmful to steelhead and chinook. 

The tested stormwater from the pilot program saw a 90% reduction in 6PPD, enough of a reduction that the water was made safe for coho. 

“We need to get these chemicals out of the system, but that’s going to take a long time. We can’t wait for politicians and the tire industry to make changes. This is an interim solution,” Ellings said.

Ellings cautioned that the study also reinforced how toxic stormwater can be a threat even in rural areas.

“The amount of contamination going into the system was eye-opening. There was a significant amount of 6PPD-quinone as well as metals and other pollutants. It’s alarming that this pollution has been going on for decades and decades in our watersheds. We’ve come to think of this as an urban issue but this highlights that this is a global issue,” he said.

Although more study is needed—and the tribe and its partners seek funding for a year-long use of the biofiltration unit—Ellings said the unit’s use could be an important tool as the campaign against 6PPD’s deadly effects continues.

“It has a ton of promise,” he said. 

A July 2022 visitor gets a tour of the biofiltration Nisqually Tribe and partners piloted. The results were promising, meaning such units may be a valuable tool to fight the threat posed by 6PPD, a chemical found in tires that poses a deadly threat to salmon. Photo and story: Trevor Pyle