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, reducing drainage issues, 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 and on the half-block on the east side of 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. Additionally, the Project will include roadway improvements such as curb bulbs, ADA ramps, and landscape plantings.

Location

The Holden NDS Project area is roughly along SW Holden Street between 16th Avenue SW and 17th Avenue SW and along the east side of 17th Avenue SW between SW Holden Street and SW Kenyon Street.

View the Holden NDS project map.

What's Happening Now?

The Holden NDS project is currently in the planning phase which includes evaluation of various major design options and features, as well as community outreach. We are gathering early input from the community and permitting agencies. The project will begin design in early 2023. We will engage the community throughout all phases of the project — planning, design, and construction.

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
  • Reduced drainage issues
  • Healthier creek ecosystems

    Community Involvement

    Community input, alongside technical evaluations, will be essential to this project during each phase. The project team will work with neighbors and community members to understand important issues in the neighborhood and to identify feasible and appropriate locations for natural drainage systems. Community members will be able to share their input through a variety of online and in-person activities.

    During this initial planning phase, we will be conducting outreach to residents and businesses in the immediate project area. We will expand our outreach efforts to adjacent areas as we move forward in the process. Outreach will be ongoing through all phases of the project from planning to design to construction.

    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

    Design 2023 -2024

    Construction 2024 - 2025

     

    This preliminary schedule will be updated as the project progresses.
    Holden NDS project timeline

    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.

    How does SPU select locations for building NDS?

    SPU selects project locations by working with other city departments to identify locations where there is a need for addressing drainage issues and other community needs. The final project location will depend on other factors, such as:

    • How much water can be treated
    • Location of existing underground utilities
    • Existing soil conditions
    • Width of the public right-of-way
    • Presence of driveways
    • Availability of off-street parking
    • Potential impacts to mature trees
    • Location of nearby steep slopes
    • Community input
    • Cost of project construction and long-term operation and maintenance