Longfellow Creek Natural Drainage System (NDS) Project

Photo of a street with natural drainage system
Example of a natural drainage system.

Project Description 

Enhancing Our Communities with Natural Drainage Systems and Pedestrian Improvements 
Seattle Public Utilities (SPU) will construct natural drainage systems (NDS) at 3 sites in the Longfellow Creek basin. Natural Drainage Systems are built in the roadway shoulder (the space between the street edge and the property line) and are 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:

  • Increased landscaping
  • Reduced drainage issues
  • Creation of habitat along our streets
  • Healthier creek ecosystems
  • Traffic calming
  • More street trees
  • Pedestrian improvements

SPU is partnering with Seattle Department of Transportation (SDOT) on this project to provide pedestrian improvements at 24th Ave SW between Thistle and Barton streets and at the SW Kenyon St pedestrian bridge at 24th Ave SW. This project is funded in part by the Levy to Move Seattle. 

Through the City of Seattle's Public Art Program, we're adding artwork at the SW Kenyon St site. The artwork along with the pedestrian improvements and new natural drainage systems were designed to create space for the community to connect with neighbors and the surrounding habitat.

Location

This project includes three locations, which were selected based on a variety of factors that included community input, recurring drainage and flooding issues, and technical feasibility.

  • 24th Ave SW (between SW Thistle and SW Barton St)
  • Sylvan Triangle (Sylvan Way SW between SW Orchard St and Delridge Way SW)
  • SW Kenyon St (near the Longfellow Creek pedestrian bridge at 24th Ave SW)

Visit the site map to see where each of the sites is located in the Longfellow Creek area and see below for more information about the final design and anticipated construction impacts for each of the sites.

SPU will install a natural drainage system from SW Thistle St to SW Barton St, which will help improve stormwater drainage, slow down traffic, and remove pollutants from stormwater runoff to improve water quality in Longfellow Creek, a salmon-bearing creek.

We know that many residents highly value pedestrian safety and sidewalks, and as part of the project we are excited to partner with SDOT to install a sidewalk along the west side of 24th Ave SW between SW Thistle and SW Barton St.

To view the planned work near your home, please review the Final Design and Info for 24th Ave SW and visit the Online Open House.

What to Expect During Construction?

Construction for this site began in April 2022. Crews will work block by block and will begin by installing the underground drainage system and completing roadway work. After the underground drainage and roadway work is complete, crews will install the natural drainage systems and begin landscaping and planting.

Residents can expect the following once construction begins near their home:

  • Work will generally occur during weekday, daytime hours
  • Construction noise, dirt, dust, and vibrations
  • To minimize disruption, work will generally be done in segments moving along 24th Ave SW
  • Parking restrictions and temporary lane closures near the work area
  • Temporary blockage of driveway access during some construction activities. When possible, the contractor will work to reopen access during nights and weekends.
  • Materials and equipment staged along the road edge near construction activities
  • The contractor will work to maintain access for delivery services, garbage/recycling/compost pick-up, and emergency vehicles. In some instances, mailboxes may be temporarily relocated during construction to facilitate deliveries. 
  • Some residents may experience brief, temporary water service interruptions to facilitate water meter relocation. Advanced notice will be provided prior to planned water outages.
  • Removal of street trees in areas where NDS and sidewalks will be installed and installation of new street trees along 24th Ave SW in accordance with SDOT's Urban Forestry requirement to improve Seattle's tree canopy, which has many benefits, including improving air and water quality. 
  • Installation of curb and gutters and driveway aprons along 24th Ave SW as well as final street pavement restoration, which may require 24-hour/day closures to allow for curing

If you have items in the public right-of-way (e.g. plantings, rockeries, and/or fences) that you would like to keep, please remove them prior to construction.

What to Expect After Construction?

Natural drainage systems are living systems and their appearance will change over time. The grasses, shrubs, and trees installed will grow and change as the garden matures. It may take up to three years for plants and shrubs in the natural drainage system to reach full maturity, and possibly longer for trees. The examples below show what a natural drainage system may look like over time.

Example before construction

Example newly planted

Example growing phase

Example mature phase

Maintenance and Care

SPU is responsible for all maintenance needs of the natural drainage systems, which will include general upkeep of the natural drainage system plantings, checking that the natural drainage system is functioning properly, removing sediment, and replacing or removing plantings and trees in the natural drainage system, if needed. You will not be asked to perform any maintenance related to the natural drainage system.

SPU plans to install a large natural drainage system in the public right-of-way on Sylvan Way SW near Home Depot.

To view the planned work at this site, please review the Final Design and Info for Sylvan Way SW and visit the Online Open House.

What to Expect During Construction?

During construction, there will be increased construction traffic as well as materials and equipment in the project area.

While most of the work will be contained to the grassy area between Sylvan Way SW and the Home Depot parking lot, the contractor will require temporary traffic impacts to perform work near the road edge.

Construction at this site is expected to begin in Fall 2022. Crews will begin by installing the underground drainage system and completing roadway work. After the underground drainage and roadway work is complete, crews will install the natural drainage systems and begin landscaping and planting.

The project team will coordinate with other construction activities in the area to minimize impacts to the extent possible.

SPU has partnered with SDOT and the Office of Arts and Culture to develop planned improvements near the intersection of SW Kenyon St and 24th Ave SW. These improvements include:

  • New walkway, bridge, and boardwalk to make it easier for people to get to nearby schools, homes, and bus stops
  • Natural drainage systems to reduce pollution in Longfellow Creek
  • Art installation to enhance the space and connect community to the creek

To view the planned work at this site, please review the Final Design and Info for SW Kenyon St and visit the Online Open House.

What to Expect During Construction?

Construction at this site is expected to began in June 2022. 

You can expect the following during construction at this site:

  • Work will generally occur during weekday, daytime hours
  • Construction noise, dirt, dust, and vibrations
  • Parking restrictions and temporary lane closures near the work area
  • Closure of the pathway and bridge over Longfellow Creek at 24th Ave SW. This closure is anticipated to last through January 2023.
  • Pedestrian detours will be in place
  • The project team has notified local schools about construction impacts

What's Happening Now?

Construction on the Longfellow Natural Drainage System (NDS) project began in April 2022. Construction is ongoing and will go through late 2022/early 2023. At each site, the contractor will begin by installing the underground drainage system and completing roadway work. After the underground drainage and roadway work at each site is complete, crews will install the natural drainage systems and begin landscaping and planting.

Please sign up to receive project email updates to stay informed about this project throughout construction.

You can also visit our Online Open House to learn more about the final designs for each of the 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

Thank you to everyone who shared their valuable feedback throughout planning and design! We have finalized the project design and have begun construction. 

Please sign up to receive project email updates to stay informed about this project throughout construction.

You can also visit our Online Open House to learn more about the final designs for each of the sites.

Through the City's Public Art Program, Portland-based artist Brian Borrello developed an art installation for the SW Kenyon St site.

The artist's goals are to make this place interesting for the community to visit and for the art to offer something unexpected, thought-provoking, and perhaps a little magical. This site is where life forces are nourished by the creek, where neighbors can connect with each other while they pass through, and where community can experience the natural world and its often-unseen processes.

Below is the artist’s proposed concept. Visit our online open house to learn more about the proposed art.

rendering of proposed art

Past Work

  • Initial outreach to gather community input to inform site selection
  • Concept development for potential natural drainage systems sites
  • Design development for the three selected sites
  • Design phase community outreach, which included hosting an Online Open House, an online questionnaire, email list updates, mailers, meetings with residents, and more

Early to Late 2021

  • Finalize project design and perform the construction contracting process
  • Pre-construction outreach including anticipated impacts for each site as well as construction schedule and sequencing information

Spring 2022 to Late 2022/Early 2023

  • Construction on this multi-site project to occur
  • Provide ongoing construction updates to the community

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 the 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.

Funding Information

This project is paid for in part by the King County Flood Control District and the Levy to Move Seattle. Art at the SW Kenyon St site is through the City of Seattle's Public Art Program.