Background

SPU originally decided to build a stormwater treatment facility in the 7th Ave S drainage basin because of the industrial nature of the lower (and northern) portion of the basin, and because the system drains into the Duwamish Waterway, which has poor water quality. Large-scale, centralized treatment of municipal stormwater is a new and emerging approach to addressing polluted stormwater runoff. At that time, SPU selected a treatment technology based on what was available and created a design for the combined water quality facility and pump station.

As more data became available about the performance and maintenance requirements of the treatment technology selected, SPU decided to take another look at other available and more effective treatment technologies. SPU is currently selecting a treatment technology for the water quality facility.

From the pump station, stormwater will be sent through the water quality facility, where it will be treated to remove a variety of pollutants that are common in urban stormwater runoff. The treated stormwater will then be released through the existing outfall to the Duwamish Waterway, resulting in cleaner water and a healthier Duwamish Waterway.