Holden Natural Drainage Systems Project

Example of a natural drainage system project a few years after installation
Example of a natural drainage system project a few years after installation

Project description

Improving creek water quality, increasing landscaping diversity, and providing roadway and pedestrian safety improvements

More than 12 million pounds of pollution are carried into our water bodies through stormwater runoff each year. Stormwater that falls on the roofs, streets, and parking lots in your neighborhood can pick up harmful pollutants before entering Longfellow Creek, which flows into Puget Sound. The pollutants can harm fish, wildlife, and our ecosystems. The Holden Natural Drainage Systems (NDS) Project plans to build natural drainage systems, also known as roadside rain gardens or bioretention, on SW Holden Street between 16th Avenue SW and 17th Avenue SW. The NDS will capture and treat stormwater runoff before it reaches Longfellow Creek and Puget Sound.

The NDS will be built in the space between the existing sidewalks and edge of the road. The project will include roadway and pedestrian safety improvements such as curb bulbs and ADA ramps, in addition to new landscape plantings.

This project will affect street parking. SPU knows that parking and access from the street to homes and properties are very important to community members. We carefully consider the impacts to parking in every potential project location. More detailed information will be provided as the project progresses.


The Holden NDS Project area is along SW Holden Street west of 16th Avenue SW and half a block west of 17th Avenue SW. The map shows the project area.

Aerial view of project site on SW Holden St between 16th Ave SW and 17th Ave SW


What's happening now?

The Holden NDS Project reached the mid-design phase, also known as 60% design, in October 2023. Please view our 60% design plans and narrated presentation to learn about the latest design updates and what the next steps are as we move forward with the design. 

Mid-Design (60%) Project Update

The following updates were made between 30% and 60% design:

  • 17th Avenue SW - Initially, we planned to build natural drainage systems on a portion of the east side of 17th Avenue SW. After further analysis, we have eliminated the natural drainage systems from 17th Avenue SW from the project because the 17th Avenue SW system does not provide enough treatment to justify the construction and long-term maintenance investment. While we understand that there is a lot of community interest in additional natural drainage systems in the neighborhood, the current project focus is to plan and design natural drainage systems on SW Holden Street.
  • Roadway & Pedestrian Safety - We’re retaining the speed cushions and formalizing the curb bulbs on SW Holden Street.
  • Landscape plantings - We appreciate the comments we received during early design on the types of plantings community members are interested in seeing in the project area. We have incorporated that feedback into the landscape areas where feasible. The plantings used in the natural drainage systems are pre-approved to support the system’s proper functioning.
  • Traffic impacts - We understand SW Holden Street is a busy street for residents, businesses, and commuters. We will work to minimize construction impacts to the extent possible and will keep you informed before and during construction so you know what to expect.

There will be additional in-person and online engagement opportunities as we move forward with the project’s design. Please sign up for our project mailing list to stay up to date on these opportunities. We will continue to gather feedback from the community, permitting agencies, and other impacted parties as we finalize the design in 2024 and tentatively start construction in early 2025.

Community benefits

The Holden NDS Project will offer multiple benefits to local neighborhoods and ecosystems, including:

  • Improved pedestrian safety
  • Improved roadway elements
  • Increased landscaping diversity
  • Improved stormwater/drainage water quality
  • Healthier creek ecosystems

Community engagement

Community feedback, alongside technical evaluations, will be important to this project during each phase. The project team will continue to engage with community members to understand important issues in the neighborhood throughout design and construction. Community members can share their feedback through a variety of online and in-person activities.

If you are interested in learning more about the project and upcoming community engagement opportunities, please sign up to receive project email updates.

  • Planning: 2022
  • Early Design (30%): Winter 2022 – Spring 2023
  • Mid Design (60%): Spring – Fall 2023
  • Late Design (90%, final design): Winter – Spring 2024
  • Construction: early 2025

This schedule will be updated as the project progresses.
Holden NDS project timeline showing Mid Design phase

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 aquatic life and people. SPU is planning to build NDS in the Longfellow Creek watershed to improve water quality in the creek and Puget Sound.

If you are interested in learning more about how stormwater harms our ecosystems, watch this video produced by the Nature Conservancy, which highlights Longfellow Creek.

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." To learn more about the Holden Natural Drainage Systems Project, please view this presentation from the Highland Park Action Coalition’s (HPAC) October 2022 meeting. 

NDS helps restore functions of the land to natural condition.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.