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30th Ave NE Sidewalk and Natural Drainage System

Last updated: September 15, 2017

What's happening now?

We are currently working with individual property owners, providing details and information about individual property impacts. We expect to begin construction in Spring 2018.

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Project Background

The Seattle Department of Transportation (SDOT) Sidewalk Development Program is planning to build new sidewalks and a natural drainage system (NDS) along the east side of 30th Ave NE between NE 130th St and NE 137th St as soon as Spring 2018. This project will make it safer, easier, and more pleasant to walk along 30th Ave NE by replacing an existing dirt path with a new sidewalk. The NDS will be designed and constructed with Seattle Public Utilities (SPU), who will maintain the NDS.

Sidewalk improvements were selected for 30th Ave NE because many people in the area depend on walking as a form of transportation. The sidewalk improvements will make it easier to walk along the corridor and will create more defined intersections for safer crossings. This installation of natural drainage systems (NDS) was selected as part of SPU's Integrated Plan to provide treatment of polluted stormwater within the Thornton Creek basin. The projects were combined in order to capture efficiencies in design and construction and to foster better coordination between City departments. Project benefits include:

  • Improved pedestrian safety and access along busy 30th Ave NE;
  • Reduced polluted stormwater runoff to Thornton Creek;
  • More pleasant walking and biking.

Natural Drainage Systems


What are Natural Drainage Systems?

Natural drainage systems (NDS) are constructed depressions along the road in the right-of-way or "planter strip". They are a type of green stormwater infrastructure (GSI) and are built to capture runoff and filter pollutants. When it rains, large volumes of polluted stormwater flow into Thornton Creek, but NDS can help slow and clean the stormwater before it reaches the creek, improving water quality and reducing pollution in Lake Washington.

Figure 2 is a cross section of potential sidewalk and natural drainage system improvements. Project design may include elements shown in the cross section.

  1. New sidewalk
  2. Retaining wall
  3. Cell Wall
  4. Underdrain
  5. Natural drainage system area
  6. Driveway
  7. Stormwater runoff
  8. Curbless edge, no parking

Project Design

This project will build a new sidewalk along the east side of 30th Ave NE between NE 130th St and NE 137th St. The project will also incorporate new sidewalk infrastructure including retaining walls and new curb ramps. Natural drainage systems will be located adjacent to the new sidewalk.

What will happen to existing trees in the right of way? The planned improvements in the public right-of-way will affect some trees. Trees are important to reducing stormwater pollution and will be preserved where possible. Licensed landscape architects will conduct a full tree assessment on all blocks to determine which trees should be protected and which may be replaced or transplanted. It is a priority to retain and protect trees throughout the project area. Any tree removed will be replaced with two young trees in the project area, however, not necessarily in the same specific locations as the removed trees. SPU will also prune trees or shrubs located in the natural drainage system as needed. SDOT will maintain any new trees for two years after they are planted. After that time, homeowners are responsible for tree upkeep.

Who will be responsible for the maintenance of the natural drainage system? SPU is responsible for the watering, weeding, and general upkeep of the natural drainage systems to ensure proper function. Residents are not required to pay for or perform any maintenance. In fact, it is important for residents to stay out of the natural drainage system areas to maintain their function.

What kind of plants will I see? The project team selects plants that help the natural drainage system do its job: clean stormwater and allow it to slowly seep into the ground. We also select plants that are easy to maintain and able to withstand wet winters and dry summers. We will keep you updated on plant palettes throughout the design process.

Will this project cause me to lose parking in front of my house? We understand that parking is very important to residents. SDOT conducted a parking study over multiple time periods to estimate the number of parking spaces available and the use of parking space in your neighborhood. This project will remove on-street parking from the east side of 30th Ave NE, but there will be no changes to parking on private property and existing driveways will remain at their current location.

Will transit lines be impacted? The bus stop at NE 133rd St will be removed. We are working with King County Metro to determine the impacts project construction will have on Routes 64 & 65 that service this area. We will continue to keep you updated as we move closer to the project construction phase.  

Project Budget & Funding

This project is a partnership between SDOT and SPU. SDOT funding is through the Sidewalk Development Program, with funds from the Levy to Move Seattle. Approved by voters in 2015, the 9-year $930 million Levy to Move Seattle provides funding to improve safety for all travelers, maintain our streets and bridges, and invest in reliable, affordable travel options for a growing city. Learn more about the levy at

SPU funds are from the NDS Partnering Program, which uses NDS to improve water quality in three large creek watersheds. The NDS Partnering Program is part of the Plan to Protect Seattle's Waterways.

Project Map

Project Timeline

We have completed the design phase, and we anticipate construction will begin in Spring 2018.We are currently working with project area residents to on specific property impacts. Additional project activities may include outreach in your neighborhood to answer questions, provide information about the project, and provide construction updates.

This project is part of several improvements being made to 30th Ave NE. SDOT's Arterial Major maintenance will be repaving 30th Ave NE between 130th to 135th after the completion of this project. We anticipate this work to begin in 2018 and continue through 2019.

There are plans for a second phase of the project that would extend a sidewalk, but no Natural Drainage system, from 137th Ave NE to 143rd Ave NE. The project is currently in the planning phase. The design will be completed in 2019 with construction in 2020.

timeline graphic

Project Materials

Questions or Comments?

If you have questions about the project, please contact our outreach team directly at or (206) 727-3575. We stay up to date on the latest project details, schedule, and design. It's our job to answer your questions. We look forward to hearing from you!

Click here and sign up to receive regular email project updates.

Emily Reardon
Project Communications Lead
(206) 615-1485

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