SDOT continuing planning for eventual West Seattle Bridge replacement

SDOT continuing planning for eventual West Seattle Bridge replacement

Thu, 06/10/2021

information from Seattle Department of Transportation

As we continue to work to repair the West Seattle High-Rise Bridge (high bridge), we are also continuing to plan for an eventual high bridge replacement so that we are ready when the current bridge nears the end of its service life around 2060. 

For over a year, we have been making ongoing progress to repair the West Seattle Bridge. In late 2020, we completed emergency stabilization measures that successfully halted cracks from growing larger and kept the bridge standing by installing 10 miles of steel cable inside the bridge, repairing deformed bearings in the Pier 18 support structure, and wrapping the structure in carbon fiber. Since then, we have been extensively monitoring the bridge, which has confirmed that the bridge is behaving as expected and allowed us to plan for the final phase of repairs in the near future.    

With all this progress underway, now is the time to continue to plan for future replacement, explore location options, and anticipate future mobility needs of this critical corridor. Doing this work now allows us to carry forward what we have learned from the current closure about the importance of keeping people and goods moving across and through the Duwamish Valley. Exploring future replacement options now also allows us to work in close coordination with agency partners as they prepare to make investments in the bridge vicinity.  

Historically, the high bridge is the city’s most-used major roads, carrying more than 100,000 travelers every day, including 19,000 bus riders.  

In  November 2020,  Mayor Durkan made the decision to repair the high bridge after close consultation and analysis from SDOT’s structural team, members of the West Seattle Bridge Community Task Force, SDOT’s Technical Advisory Panel composed of leading experts in their fields, and countless others. This continued work that had been happening on, under, and inside the bridge since March 2020. This pathway provides the highest degree of certainty for a safe and rapid restoration of travel with the lowest level of impact to communities in and around the Duwamish Valley, the city, region, and state.  

At that time, the Mayor also directed SDOT to continue planning for an eventual replacement of the bridge. While we are confident that the scheduled repairs will ensure the repaired bridge’s service for up to 40 more years, it is important that we start to consider where an overall replacement might fit in this constrained corridor. 

The high bridge closure presents an opportunity to study future replacement concepts to ensure we will be ready when it’s time for an eventual replacement.  

Replacing an existing bridge is difficult to do while it is open to travelers. Based on recent experience, maintaining mobility during construction will be a critical goal. As we develop and evaluate concepts for where to locate a replacement bridge, we will consider ways to improve and connect the existing corridor while leveraging previous and planned investments.   

Another part of being prepared includes advancing a contingency plan should we need to respond quickly in the unlikely event of another emergency. This work builds on the findings of the Cost Benefit Analysis. Advancing this contingency plan will save us time and money and put us in a better position to expedite permitting and identify funding if needed.  

We will explore four replacement concepts in a range of locations near the bridge.  

Bridge corridor

Long-range planning for replacement concepts will consider potential locations on or near the high bridge to reduce delays and impacts to communities and travelers during construction. Photo Credit: SDOT. 

These replacement concept locations are just north and south of the bridge, in alignment with the existing bridge, as well as below in a tunnel.  

During the process of defining and evaluating these concepts, we will: 

  • Continue working with the community to confirm our understanding of the mobility needs throughout West Seattle and the Duwamish Valley. 
  • Coordinate closely with adjacent projects to consider potential impacts and opportunities for collaboration. 
  • Develop criteria to evaluate the replacement concepts, much like we did during our Cost Benefit Analysis 
  • Evaluate the opportunities and challenges of our replacement concepts based on the criteria 
  • Analyze the need for including space for people walking, biking, or taking transit on a future high bridge replacement and, if there is a need, conduct a feasibility analysis to determine if it can be done   
  • Provide a summary of the feasible replacement locations to consider in future planning  

At key milestones of the study, we will be sharing our progress with community members and the public to keep everyone informed and help answer questions. 

Simultaneously, we continue our work to Reconnect West Seattle. This work started with a community-led process in summer 2020 to learn how we could help reduce the impacts of the bridge closure and increased traffic in nearby neighborhoods.  

Last summer, we collected survey responses from over 17,000 people to learn more about how they travel to, from, and around the West Seattle peninsula. Together, this outreach helped us prioritize immediate needs and plan projects over the next year that will better serve the community in the long run.  Read our most recent update on Reconnect West Seattle. 

You can expect to hear more about what we learn in September as we study the replacement concept locations .  

At the end of this year, we will share the full report of what we’ve learned and make recommendations as to which location would be preferred for our future replacement. 

Learn more: 

Robinson Papers
West Seattle Herald