Longfellow Creek Natural Drainage System (NDS)

Project Description

Improving Our Communities with Natural Drainage Systems 
Seattle Public Utilities (SPU) will construct natural drainage systems (NDS) at 3 sites in the Longfellow 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 offer multiple community benefits, including:

  • Greener, more attractive neighborhoods
  • Lower risk of flooding
  • Healthier creek ecosystems
  • Calmer traffic patterns
  • And more

Seattle Department of Transportation is partnering with SPU on this project to provide pedestrian improvements at most sites, and this project is funded in part by the Levy to Move Seattle. 
The project FAQ contains more information.

Location

Seattle Public Utilities (SPU) will construct natural drainage systems (NDS) at 3 sites in the Longfellow Creek basin:

  • 24th Ave SW between SW Thistle St and SW Barton St
  • Sylvan Triangle (Sylvan Way SW between SW Orchard St and Delridge Way SW)
  • 24th Ave SW and SW Kenyon St

What's Happening Now?

The team has completed our technical analysis of potential sites for the Longfellow 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. Selected sites can be viewed on this site map.
Selected Sites for Design:

  • 24th Ave SW between SW Thistle St and SW Barton St
  • Sylvan Triangle (Sylvan Way SW between SW Orchard St and Delridge Way SW)
  • 24th Ave SW and SW Kenyon St

Throughout 2019 and 2020, we will:

  • Design the natural drainage systems and pathway improvements
  • Continue to engage with residents, businesses, and community organizations around individual sites

Community Benefits

This project will improve water quality in Longfellow Creek, as well as improve stormwater drainage, slow down traffic, provide pedestrian improvements, 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 by 2025.

Community Engagement

If you're interested in learning more and finding out about upcoming community engagement events, please sign up to receive project email updates.
 

Schedule

2017 - 2018

  • Concept development for potential natural drainage systems sites
  • Initial outreach to basin residents about potential blocks

2019 – Mid-2020

  • Design development for selected sites
  • Design phase community engagement

Late 2020 – 2021

  • Anticipated construction
  • Provide ongoing construction updates to the community

Background

Natural drainage systems slow stormwater and filter out pollutants before they can harm our creeks and other waterways. Keeping pollutants out of our water is important for fish, aquatic life, and people.

Building a natural drainage system in Longfellow Creek basin is part of the Plan to Protect Seattle's Waterways. SPU used to call these "roadside rain gardens" but now calls them "natural drainage systems" or "NDS."

Why Longfellow Creek? Longfellow Creek is a salmon-bearing urban creek with degraded water quality adjacent to where people live, work, and play. Stormwater picks up pollutants from streets-including oil, heavy metals, and fertilizers-every time it rains and flows into the creek through ditches or pipes. This project will remove pollutants from the stormwater before it reaches the creek.