15th Ave NE Bridge Seismic Retrofit
Updated: November 15, 2024
What's happening now?
Crews will begin potholing for utilities as soon as late November 2024 to prepare for seismic retrofit work next year. Potholing is expected to last through December. After the potholing is complete, work will stop until crews return as soon as early 2025 to begin work on retrofits to help the 15th Ave NE/NE 105th St bridge better withstand earthquakes. Visit the “What to expect during construction” section below to learn about how this temporary work could impact you.
Once construction begins next year, it is expected to take around 12 months to complete. During this time, there may be times when parts or the entire bridge will be closed. We will carefully plan alternative routes for pedestrians, cyclists, and drivers to use while the closures are in effect. These alternate routes will be finalized closer to the start of construction.
We understand that the bridge closure will inconvenience those who regularly use it, and we will do our best to minimize the impact. In the next couple of months, we will reach out to individual property owners and neighbors to discuss any specific impacts to their properties and any permissions that may be needed for access during construction. We appreciate your patience throughout this process.
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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.
What to expect during construction
Crews will start potholing work in late November 2024 to prepare for seismic retrofit construction which will begin in early 2025. During this potholing work, people can expect:
- Three phases of temporary one-lane, two-way operation on 15th Ave NE
- Phase One: The northbound side of 15th Ave NE will be closed between NE 103rd St and NE 104th St. Flaggers will be on-site to alternate traffic, as needed.
- Phase Two: The northbound side of 15th Ave NE will be closed between NE 104th St and NE 106th St. Flaggers will be on-site to alternate traffic, as needed.
- Phase Three: The southbound side of 15th Ave NE will be closed between NE 106th St and NE 104th St. Flaggers will be on-site to alternate traffic, as needed.
- Noise, dust, vibrations, and construction equipment staged within the project area
- Typical weekday work hours of 7 AM – 5 PM, Monday through Friday
As the start of seismic retrofit construction next year approaches, we will share information about what to expect during that work. Sign up for email updates and check this webpage to stay informed.
Project Area
Schedule and construction
Planning: October 2018 - April 2020
Design: January 2021 - December 2022
Potholing Work: Late November - December 2024
Construction: Early 2025
Funding
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.