Holden Natural Drainage Systems Project

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.

Location

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.

What's happening now?

The project team reached final design in March 2025. The team is working with partners at SPU and SDOT on reviewing the final design and permitting necessary to advertise the bid to construction contractors. We expect to award the construction contract in summer 2025 and begin construction around the end of 2025.

Preparation for construction:

In advance of this project, Puget Sound Energy (PSE) is relocating a portion of their gas line nearby the intersection of SW Holden St and 17th Ave SW in late March and early April 2025. PSE will notify customers of any impacts anticipated. 

The SPU Team will provide advanced notice before SPU project construction begins near the end of 2025. 

Design updates: 

Below are key updates the project team made between mid-design and final design. 

• Dumar Substation update- In September 2024, the City of Seattle's Office of Housing announced that Homestead Community Land Trust was selected as the partner to develop the former Dumar Substation at SW Holden St and 16th Ave SW for affordable housing. Both projects will continue to coordinate with each other.
• Emergency route prioritization- As part of our ongoing coordination with Fire Station 11, the Seattle Fire Department (SFD) requested the removal of the existing speed cushion on SW Holden St (an emergency route) between 16th Ave SW and 17th Ave SW. The removal of the speed cushion will improve SFD the ability to respond to emergencies. This project will also provide new pavement marking by the fire station to allow for emergency vehicle route improvement
• Addressing localized flooding- The project team was made aware of a localized flooding issue at the intersection of SW Holden St and 17th Ave SW during the project’s mid-design phase outreach.  As a result, the project will install new drainage infrastructures and new underground water quality treatment facility at the north side of the intersection. The new infrastructure will address both the flooding issue and provide additional water quality treatment for Longfellow Creek.  
• Tree removal and replacement– The project team will need to remove two trees that conflict with where the underground water quality treatment facility will be installed. Due to site constraints, the project team will plant one tree back in the project area. SPU will provide funding to SDOT for planting five additional trees as mitigation for removing the two trees.

Spring Drop-In Session: 

Please join us for a final design drop-in session on Saturday, May 31 from 11 am to 1 pm. The drop-in session will provide an opportunity for community members to learn about the final design, what to expect during construction, and ask questions and share comments with members from the project team.

Anticipated Construction Impact:

We understand that SW Holden St 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.  Our project team will provide more details on construction timing and impacts after we hire a contractor by the end of 2025. The contractor is responsible for obtaining construction permits which include traffic control planning. Our project team will provide more details on construction timing and impacts after we hire a contractor.

What to expect: 

• Coordination: An SPU resident engineer (RE) or inspector will be working with the contractor during construction. The SPU Project Manager will also be available to address issues. In general, for efficiency and faster response, the RE and the Contractor will be working with the community to address day-to-day issues while the Project Manager will address broader community concerns.
• Work hours: Construction typically takes place Monday through Friday from 7 am to 5 pm with some work potentially occurring during evenings or weekends. More details will be provided when a Contractor is onboard, and the construction permit is finalized/obtained.
• Road and sidewalk closures: Roads and sidewalks may be partially or fully closed, with posted detour signs. Pedestrian detours that meet permit requirements will be provided.
• Parking restrictions: Parking may be restricted near construction zones.
• Noise, dust, and vibrations: Construction can produce noise, dust, and vibrations.
• Access to homes and businesses: The Contractor is expected to work with the property owners to maintain access to their homes and businesses.  If the Contractor needs to close your driveway temporarily, they will work with you ahead of time for a workable solution. The Contractor will also coordinate for garbage pick-up and mail delivery as needed.
• Bus stop relocation: The bus stop at SW Holden St and 16th Ave SW may be temporarily relocated. 

Pedestrian access and access to essential services (i.e. emergency vehicles, mail delivery, garbage pickup) will be maintained.

Temporary access to driveways will be communicated in advance by the construction team. 

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

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 depends on other factors, such as:

• Regulatory requirements
• 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
• Construction and long-term operation and maintenance costs

Community engagement

The project team will continue to engage with community members. Look for an invitation to attend our neighborhood drop-in session later this spring. The drop-in session will provide an opportunity for community members to learn about final design, what to expect during construction, and ask questions and share comments with members from the project team.  

Please sign up for our project mailing list to stay up to date on these opportunities.