Bridge Seismic Program

What is the Bridge Seismic program? 

Earthquakes could have a major impact on Seattle's bridges. To address this risk, the City of Seattle established a bridge seismic program to assess how vulnerable the City's bridges were to earthquakes and reinforce bridges to withstand the potential impacts of an earthquake.  

As part of the Levy to Move Seattle, we committed to seismically reinforcing 16 vulnerable bridges.  

What is a Bridge Seismic Retrofit? 

In a seismic retrofitting project, SDOT modifies a bridge’s components and reduces its vulnerability to earthquakes. We do not change the current use and operation of the bridges.  

Typical modifications include: 

1. Repairing cracks and damaged concrete
2. Installing concrete blocks and supportive shells for the bridge's columns and crossbeams
3. Strengthening the existing arch with a concrete infill wall
4. Installing carbon fiber wrapping to the bridge's crossbeams, columns, and arches
5. Replacing the expansion joints at both ends of the bridge  

Possible modifications SDOT can make during a bridge seismic improvement. 

A bridge seismic retrofit is a critical process for ensuring the safety and resilience of our city's infrastructure. With Seattle being located in an earthquake-prone region, it is necessary to take proactive measures to protect our bridges from potential damage.

During a seismic retrofit, SDOT (Seattle Department of Transportation) makes modifications to a bridge's components in order to reduce its vulnerability to earthquakes. It is important to note that these modifications do not change the current use or operation of the bridges.

Some typical modifications include repairing any existing cracks and damaged concrete, installing concrete blocks and supportive shells for the bridge's columns and crossbeams, strengthening the existing arch with a concrete infill wall, and using carbon fiber wrapping on key areas such as crossbeams, columns

Bridge Seismic Retrofit Locations

To learn more about an individual project, click on the project name below to visit its project webpage:

Active Seismic Retrofit Projects: 

• • Delridge Pedestrian Bridge
  • 15th Ave NW/Leary Way Bridge
  • N 102nd St/Aurora Ave N Pedestrian Bridge
  • SW Admiral Way North & South Bridges
  • 15th Ave NE/NE 105th St Bridge
  • McGilvra Blvd E Bridge
  • 13th Ave NW/Holman Rd NW Pedestrian Bridge
  • N 41st St Pedestrian Bridge 
  • Lower Spokane St Swing Bridge Silt Removal

Completed Seismic Retrofit Projects: 

• 8th Ave NW/NW 133rd St Bridge
• NE 45th St Pedestrian Bridge
• Cowen Park Bridge 
• McGraw St Bridge
• SW Andover St Pedestrian and Bicycle Bridge
• W Howe St Bridge  

Materials

Fact Sheet (December 2023) 

Funding 

From 2016 through 2024, the Bridge Seismic Program is funded by $67 million in Levy to Move Seattle dollars, as well as an additional $14 million of other funds. 

Translations

If you need this information translated, please call (206) 771-0481.  

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Odeeffannoon kun akka siif (206) 771-0481. 

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