Using innovative technology to protect salmon habitat
Can compost prevent toxic roadway runoff from reaching salmon streams?
Tire dust and other chemicals in roadway runoff are deadly to salmon, so Long Live the Kings is working with multiple partners to test a compost-based biofiltration system to collect and clean stormwater before it reaches Ohop Creek.
Protecting Critical Waterways through Biofiltration
Coho salmon are dying from stormwater runoff
In 2020, researchers at Washington State University Puyallup and University of Washington Tacoma determined that a chemical called 6PPD-quinone was responsible for the harmful effects.
6PPD-quinone is formed when particles of tire dust react with ozone from the atmosphere. When it rains, this new chemical washes into stormwater and can end up in streams where it is a huge threat to coho survival: between 20% and 90% of coho die within hours of exposure to contaminated stormwater. Recent studies found that it is harmful to Chinook and steelhead as well.
While policymakers and scientists are working with the tire industry to find safe alternatives, 6PPD-quinone will be present in stormwater for years to come. In the Nisqually Watershed, some of the most important coho habitat occurs in Ohop Creek. Current traffic deposits around 12 pounds of tire dust on the road crossing Ohop Creek each year, washing potentially lethal amounts of 6PPD-quinone into the water.
Partnering Up
The Nisqually Indian Tribe has teamed up with Long Live the Kings, Cedar Grove, Herrera, and other partners to install and test a biofiltration system to filter stormwater and protect the salmon of Ohop Creek.
Biofiltration is a method that uses living material – such as plants, mulch, and compost – to remove pollution from contaminated water. Rain gardens and bioswales are examples of biofiltration systems which capture runoff and allow it to slowly filter through vegetation and layers of mulch and soil, removing pollutants. Because Ohop Creek is a sensitive habitat restoration site, constructing a large traditional bioswale below ground wasn’t a good option. Instead, our partners at Cedar Grove developed a mobile biofiltration unit to treat runoff. The unit collects stormwater from over 13,000 square feet of roadway in Ohop Valley and filters it through layers of compost-based filtration media to remove toxic compounds. Because compost can add excess nutrients to the water, this system includes a final, external polishing layer to remove phosphorous before the water is discharged to the wetlands near the creek.
Promising Results
During the first year of this pilot project, Long Live the Kings sampled water moving through this system during three storm events in the spring of 2022. The samples were sent to a lab for chemical analysis, comparing the levels of contaminants in the runoff before it entered the system, at the midpoint, and when it was discharged. Despite the small sample size, the results are promising: the system appears to be effective in removing over 90% of the 6PPD-quinone from untreated stormwater, reducing it to levels safe for coho salmon.
The biofiltration system is currently on site and operational, collecting and filtering stormwater before it reaches salmon habitat. Long Live the Kings is seeking funding to conduct more sampling in future years. Our goal is to collect enough data (from at least 15 qualifying storms) so that this system can be approved for use in projects across Washington to protect critical streams for salmon recovery.