South Thornton Natural Drainage Systems

What & Why

Seattle Public Utilities (SPU) will construct natural drainage systems (NDS) at 4 sites in the south Thornton Creek basin. NDS consist of shallow depressions in the public right-of-way, or “planter strip,” filled with deep-rooted plants and spongy soils that temporarily hold and clean polluted stormwater from streets and sidewalks before the stormwater enters our waterways.

Natural drainage systems can offer multiple benefits to local neighborhoods and ecosystems, including:

  • Greener, more attractive neighborhoods
  • Lower risk of flooding
  • Creation of habitat along streets
  • Healthier creek ecosystems
  • Calmer traffic patterns
  • More street trees

Why Thornton Creek? Thornton Creek is a salmon-bearing urban creek with degraded water quality. Stormwater picks up pollutants from streets—including oil, heavy metals, and fertilizers—and flows into the creek through ditches or pipes. This project will remove pollutants from the stormwater before it reaches the creek and reduce the quantity of stormwater going into the creek.

The project FAQ contains more information.

What's happening now?

We completed our technical analysis and selected sites to move into the design phase. We selected sites based on a variety of factors that included community input, recurring drainage and flooding issues, existing soil conditions, and availability of off-street parking. The project FAQ has a complete list of factors weighed.

Selected sites can be viewed on one of the maps below. 

Combination site map: view high level map with 4 sites shown (Northgate site: 23, Victory sites: 113 & 138, Wedgewood site: 139, and Meadowbrook site: 208)

Throughout 2020, our team will be hosting public drop-in sessions near site locations to speak with residents and get feedback on each site's design. We're looking forward to continuing to engage with residents, businesses, and community organizations around these selected sites. If you're interested, please sign up to receive updates.

Project goals and benefits

This project will improve water quality in Thornton Creek, as well as improve stormwater drainage, slow traffic, and beautify streets.

The project will also help the City of Seattle achieve its goal of managing 700 million gallons of stormwater runoff using green infrastructure.

Project Documents