Stormwater Outfalls Water Quality Retrofit Project

Project Overview

This project will improve the water quality of roadway runoff discharging into the Green-Duwamish River by retrofitting four City-owned and operated stormwater outfalls with water quality devices. The Duwamish River is classified as a Category 5, 303(d)-listed waterbody due to impairments from pH, temperature, polychlorinated biphenyls (PCBs), and other industrial pollutants. The U.S. EPA declared the Duwamish River a Superfund site and administers the clean-up efforts. The Green River has eight water quality parameters on the 303(d) list including dissolved oxygen (category 5) and temperature (category 4A). The Green-Duwamish River is also home to threatened Chinook salmon, steelhead and bull trout, as well as other species of anadromous fish, resident trout and other aquatic species. Roadway runoff contributes substantially to the pollutant load in the Green/Duwamish River.

The City completed 90% design of four outfall sites with a Washington State Department of Ecology (DOE) grant.  The City has acquired construction grant funding from King County’s Waterworks grant and is seeking additional construction funding from the DOE. The two sites being advanced are along Tukwila International Boulevard and Interurban Avenue South.

Contact Information

For specific questions, contact Mike Perfetti at 206-433-7192 or email at mike.perfetti@tukwilawa.gov

Project Photos