Seattle Public Utilities

Thornton Natural Drainage

  • Established_NDS A natural drainage system project a few years after installation.
  • Installed_NDS A natural drainage system before plants are installed.

What & Why

We will construct approximately 45 blocks of natural drainage systems in the Thornton Creek basin. The work will be in three phases. Natural drainage systems are low areas in the right-of-way or “planter strip.” They are planted with deep-rooted plants, and temporarily hold and clean stormwater from streets and sidewalks.

Natural drainage systems can only be built on blocks that have the right technical requirements.

Thornton Creek is a salmon-bearing, urbanized creek with degraded water quality. Rain washing pollutants off streets is part of the problem; it brings pollution into the creek through ditches or pipes. This project will remove pollutants from the stormwater before it reaches the creek.

Please see the project's FAQ for more information on natural drainage systems.

What's happening now?

We are currently working to determine:

  • Where we can partner with other city departments on related projects
  • Which blocks will be eligible

We want your input to help choose specific blocks and locations for this project. While SPU can only build these systems where it is technically feasible, we would like to incorporate community input into the final decision. Please see our map for some of the potentially feasible areas in your neighborhood (pdf)

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


Luis Ramirez, project manager
(206) 684-3660

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