NE 40th Street Stormwater Treatment Retrofit

Graphic of NE 40th SW Treatment location - aerial photo

Project Overview

This project will construct a water quality treatment facility adjacent to the Overlake Technology Light Rail Station. The facility will serve one of Redmond’s highest traffic volume (and highest pollutant load) areas by intercepting flow from SR 520 and NE 40th St and discharging cleaned water to the existing drainage path, which eventually flows to Villa Marina Creek and Lake Sammamish. 

Untreated water will be pumped from the existing storm trunkline in NE 40th Street to the surface, then drained through a filterra bioscape to remove oils and grease, sediment, dissolved metals and phosphorous prior to discharging into the existing drainage path. The filterra bioscape will include native plantings landscaped to enhance the aesthetic value of the light rail station. Discharging cleaned water into Villa Marina Creek will help protect Chinook, Kokanee, Coho and Sockeye salmon that inhabit these waters.

Microsoft, as part of their commitment to environmental sustainability, is providing funding for this project through a Community Facilities District. Additional funding comes from a Department of Ecology Stormwater Financial Assistance Program Grant and a King County Waterworks Grant.