case study

Fremont Bioswale Project

"“We saw a video showing baby salmon being put in water runoff from the 520 bridge and instantly dying. And then we saw them surviving after they were put in water that had been passed through soil a few times.” "

The two new buildings capture runoff from the Aurora Bridge and pass it through soil cells, cleaning the runoff before it reaches Lake Union. The bridge’s runoff at this site impacts a critical migration route for salmon on their trip out to the Pacific Ocean as well as their return trip to the upper watershed spawning grounds. The developers chose to certify their projects through Salmon-Safe. Salmon-Safe conducted water quality testing from the downspouts of the bridge. Bridge runoff samples were taken in 2017 to determine what pollutants were in the water and provide a water quality baseline for testing bridge runoff and treatment over the next five years.

In the future, the developers aspire to go further by building a bioretention under the bridge across North 34th St., adjacent to Lake Union. When the biowale is complete, 1,835,000 gallons of runoff will be treated annually. Currently, 98 million gallons of polluted water drains from the six bridges that span the Lake Washington Ship Canal, so this project serves as an inspiration for future retrofits of all of these bridges. To date, the Aurora Bridge project has been supported entirely by private funding from landowners at Stephen C. Grey & Associates, Boeing, and an anonymous donor.

This project serves as an excellent example of the type of innovative partnership SPU and WTD would like to see more of and support.