Thornton Natural Drainage

What & Why

We will construct approximately 12-15 blocks of natural drainage systems (NDS) in the 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.

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.

The project FAQ contains more information.

What's happening now?

The team has completed our technical analysis of potential sites for the Thornton Creek NDS project and selected sites that will 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 the two maps below. We are also partnering with the Seattle Department of Transportation’s Safe Routes to School sidewalk projects to install NDS along 12th Ave NE between NE 120th St and NE 117th St and N 117th St between Meridian Ave N and 1st Ave NE.

Map 1: Wedgewood, Olympic Hills, and Victory Heights

  • Sites 113, 138, 139, and 208

Map 2: Haller Lake and Northgate

  • Site 23

Over the next few months we will:

  • Begin designing the natural drainage systems for each selected site
  • Continue to engage with residents, businesses, and community organizations around individual sites

Our team will be hosting public drop-in sessions near site locations to speak with residents and get feedback on each site’s design. If you’re interested, please sign up to receive updates about upcoming drop-in sessions by clicking “sign up for project updates” on the far right of this webpage. We look forward to seeing you soon!

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