Longfellow Creek Natural Drainage System (NDS) Project
Example of a natural drainage system.
Project description
Enhancing Our Communities with Natural Drainage Systems and Pedestrian Improvements
Seattle Public Utilities (SPU) is constructing natural drainage systems (NDS) at three 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:
- Reduced drainage issues
- Improve pedestrian access, safety, and traffic calming
- Increase landscaping and create urban habitat through vegetation and street trees
- Improve creek ecosystems
SPU has partnered with Seattle Department of Transportation (SDOT) on this project to provide pedestrian improvements at 24th Ave SW between SW 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've added artwork at the SW Kenyon St site. The artwork along with the pedestrian improvements and new natural drainage systems are 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 site 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.
Site Updates
- Sylvan Way SW Site: Construction here was postponed in 2022 due to technical issues on site. Construction is expected to resume in August 2025 and be completed by December 2025
- SW Kenyon St Site: Contractor crews have finished installing the majority of the natural drainage system and pedestrian improvements. Crews will complete minor underground drainage and landscaping work in late 2025.
- 24th Ave SW Site: Contractor crews finished installing the natural drainage system and roadway improvements in 2024
What to Expect During Construction?
Crews will be mobilizing at the Sylvan Way SW and SW Kenyon St sites to install underground drainage systems. After the underground drainage work, crews will install natural drainage systems in the roadway shoulder area. The final phase of construction will be roadway and landscaping restoration.
During construction, residents can expect the following impacts in their neighborhood:
- Contractor crews will generally work during weekdays and daytime hours
- Noise, dust, and vibrations typical of a construction site
- Temporary lane closures and parking restrictions near the work area
- Materials and equipment staged near construction activities
- Access to private property and businesses may be temporarily impacted
- King County Metro Bus stops may be temporarily impacted
- Pedestrian detours will be in place
In 2024, SPU installed natural drainage system facilities 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 partnered with SDOT to install a sidewalk along the west side of 24th Ave SW between SW Thistle St and SW Barton St.
Check out the Final Design for 24th Ave SW.
Post 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.
Maintenance and Care
SPU is responsible for all maintenance needs of the natural drainage systems. This 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, if needed. You will not be asked to perform any maintenance of 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. Work at the site began in October 2022. However, during early construction, crews encountered unanticipated groundwater impacts. Due to technical challenges from these impacts, work at the Sylvan Triangle site was postponed.
Construction on the Sylvan Way SW site is expected to resume in August 2025 and be completed by December 2025.
Check out the Final Design Sylvan Way SW.
SPU has partnered with SDOT and the Office of Arts and Culture to develop 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
The majority of this work has been completed. Construction will resume in late 2025. We’ll update the community when this work continues.
Check out the Final Design for SW Kenyon St.
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
Through the City's Public Art Program, Portland-based artist Brian Borrello developed an art installation for the SW Kenyon St site. The public art was installed at the corner of 24th Ave SW and SW Kenyon St in late spring 2025 in collaboration with Portland-based artist Brian Borrello and the City of Seattle’s Public Art Program.
The artist's goals wee 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.
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 funded through City of Seattle's Public Art Program.