15th Ave NE Bridge Seismic Retrofit

Updated: February 2, 2023

What's happening now?

Early design project timeline graphic

We're in the final design phase of this project and are preparing for construction as soon as spring 2023.

We'll be in touch with individual property owners and neighbors in the coming months about any specific property impacts and permissions that may be needed for access during construction. Thank you for your patience!

Project overview

Earthquakes could have a detrimental effect on Seattle's infrastructure. To address seismic risks to city infrastructure, the City of Seattle established a bridge seismic retrofit program to assess the seismic vulnerability of the City's bridges and to prioritize limited funding to reduce this transportation infrastructure vulnerability.

As part of the Levy to Move Seattle, 16 bridges were selected for seismic retrofits, including the bridge at 15th Ave NE and NE 105th St. The 15th Ave NE Bridge is a 480 feet long concrete bridge designed by Homer Hadley and constructed in 1949 using innovative techniques, but prior to the modernization of the seismic design code. Spanning a forested ravine over Thornton Creek and connecting to Northgate Way area, it carries both vehicular and pedestrian traffic and is supported by five concrete piers. SDOT strengthened the original concrete box girders, added new abutments, and made other improvements to the bridge in 2011. 

The planned seismic retrofits to the 15th Ave NE Bridge build on the previous strengthening and include several modifications to seismically strengthen existing bridge piers and reduce the bridge's vulnerability to earthquakes. 

Graphic showing cross section of bridge structure and where our proposed work is located.


Project area

Project map showing project area on 15th Ave NE Bridge between NE 106th St and NE 104th St.

Schedule and construction

Project schedule graphic showing currently in design phase.

Planning: October 2018 - April 2020

Design: January 2021 - December 2022

Construction: Spring 2022

Once construction begins, it is scheduled to last approximately 9 months. To complete the work as safely and efficiently as possible, partial and full bridge closures are anticipated. The construction detour routes will be evaluated in design and finalized once a contractor is selected and we are closer to the construction start date. We understand this closure will impact everyone who uses the bridge regularly and will do what we can to minimize impacts. Once we have a contractor on board, we will have more information about the project timeline and construction impacts.

We currently anticipate the following impacts:

  • Work in the public right-of-way near your home or business
  • A temporary full bridge closure with detours for people walking, biking, and driving to get you safely around work zones
  • Occasional traffic or lane restrictions, including side street closures
  • Temporary on-street parking restrictions, with "no park" signs placed 72 hours in advance
  • Typical construction equipment, materials, noise, dust, and activity in the work area
  • Typical weekday work hours are 7 AM - 5 PM, Monday through Friday


The total project estimate is $6 million and is currently funded through 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.



Greg Spotts, Director
Address: 700 5th Ave, Suite 3800, Seattle, WA, 98104
Mailing Address: PO Box 34996, Seattle, WA, 98124-4996
Phone: (206) 684-7623

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The Seattle Department of Transportation (SDOT) is on a mission to deliver a transportation system that provides safe and affordable access to places and opportunities for everyone as we work to achieve our vision of Seattle as a thriving, equitable community powered by dependable transportation.