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Weekly Update: West Seattle High-Rise Bridge Stabilization

West Seattle Bridge at sunset. Photo Credit: Madison Linkenmeyer

Every Monday, we’re posting a blog to keep you informed about our progress to stabilize the bridge, our efforts to address traffic and mobility, and other items related to the West Seattle High-Rise Bridge closure. 

In this week’s update: 

West Seattle High-Rise Bridge Stabilization 

The East entrance of the Low Bridge with Seattle Police Department enforcement..
The East entrance of the Low Bridge with Seattle Police Department enforcement. Photo Credit: Tim Durkan.

This past week, we reached a significant milestone by starting to stress the installed post-tensioning system.

This coming week, the contractor is planning to:

  • Release the restrained bearing at Pier 18
  • Begin constructing a new bearing for Pier 18
  • Perform the final 100% stressing of the post-tensioning system
  • Begin the final phase of carbon fiber exterior girder strengthening

Stabilizing the High-Rise Bridge is necessary to preserve public safety and the integrity of the bridge so that all options remain on the table with the approaching repair or replace decision. Stabilization puts us on the right path if repair is determined to be the best option and helps prevent further crack growth. Stabilization is also necessary for safe demolition if we choose to replace the bridge.

Kraemer North America, our contractor for the stabilization work, is working every week, Monday through Saturday from 6 AM to 4:30 PM, to stabilize the bridge.  We expect to complete stabilization work by the end of this year.

Photo Gallery | Recent Stabilization Work

Details | Recent and Upcoming Stabilization Work

Recent and Upcoming WorkDetails
The stabilization work we expect to be complete by the end of the year includes: 
Carbon fiber wrapping weakened areas of the bridge, adding post-tensioning inside the girders, and injecting epoxy into cracks wider than 0.3mm. (The epoxy injections don’t stabilize the bridge; they help prevent further deterioration by protecting the post-tensioning steel inside from corrosion.) Monitoring and inspection activities will continue after stabilization work is complete, in both the repair and replacement scenarios. 

As mentioned above, this coming week, the contractor is planning to:  

Release the restrained bearing at Pier 18; begin constructing a new bearing for Pier 18; perform the final 100% stressing of the post-tensioning system; and begin the final phase of carbon fiber exterior girder strengthening.

Upcoming work includes:
After the Pier 18 release and post-tensioning are complete, Kraemer North America will do other stabilization work, including applying the final layers of carbon fiber wrap to the girders and rebuilding the lateral bearing at Pier 18. Once all stabilization work has been finished, we will lower the work platforms onto barges and remove other temporary work structures – likely before the end of the year.

In the coming weeks:
The Mayor will make a final determination as to whether we will move forward with repairing the current bridge or replacing it with a new structure. With our replacement consultant HNTB on board, we are ready to pivot to designing the demolition and replacement structure.  

Over the past few weeks, we have:
Stressed the post-tensioning system to 10%; poured concrete for the deviator blocks, which will keep the post-tensioning strands from touching the bottom of the girder as they travel between anchor locations; installed the post-tensioning brackets; begun Pier 18 work, including core drilling and wire sawing; and continued monitoring and inspection efforts.

Since we closed the bridge in March, we have:
Installed an intelligent monitoring system to better understand what type of stabilization and repairs would be needed and to monitor the bridge during this work; designed and started to install stabilization measures; built and hoisted custom work platforms; completed the first phase of carbon fiber wrapping; and completed the cost-benefit analysis (CBA) that will help inform the decision to repair or replace the bridge. 

During daily work, you will see:
Some crews working on top and under the bridge, as well as scaffolding and crews working on platforms suspended under the bridge. You may also see large equipment and vehicles delivering, moving, and storing materials.

There is work taking place inside the bridge that you will not be able to see, including:

Monitoring cracks and installing the additional post-tensioning strands.

Traffic Impacts:

While we do not anticipate significant impacts to traffic below the bridge, you may see some traffic control signs and devices. These signs and devices are meant to keep the workers and traveling public safe. Please obey the signs and do not move them. 

While the majority of the traveling public will see little to no traffic impacts during Pier 18 work, there may be lane reductions on Klickitat Ave SW and SW Klickitat Way on the west and south sides of Harbor Island. Please obey the traffic control signs and devices and do not attempt to move them. Our teams are coordinating closely with the Port of Seattle to mitigate traffic impacts. 

Rapid Replace Option for the West Seattle High-Rise Bridge

This rendering shows the rapid replace option proposed by HNTB. Credit: HNTB. The span is shown in the Duwamish waterway.
This rendering shows the rapid replace option proposed by HNTB. Credit: HNTB.

Some of the opportunities Rapid Replace presents include using the existing pile foundations of the West Seattle High-Rise Bridge and shortening the existing piers. New twin arch spans made of steel and efficiently fabricated in tandem with superstructure demolition would rise above the refurbished, shortened bridge piers. 

Optimistically, this approach could shave up to three years off the time to open a bridge replacement from the traditional, conservative, linear delivery method and timeline used in the CBA for Alternative 4 (superstructure replacement), which could mean an opening date sometime in 2023.

Learn more about the Rapid Replace option in this blog post.

Recap of Wednesday’s West Seattle Bridge Community Task Force Meeting

The West Seattle Bridge Community Task Force met for the 12th time on October 28 to discuss the cost-benefit analysis (CBA) and talk again with Mayor Durkan. The Community Task Force discussed their thoughts about the CBA after their thorough review.

Watch the recording of the October 28 meeting.

The next Task Force meetings will take place on November 18 and December 2 at 12 PM. We will post links to watch those meetings live in these weekly updates posted every Monday.

Vegetation Work at SW Roxbury St and Olson Pl SW

This past Sunday, November, 1, SDOT crews worked again in the medians at the intersection of SW Roxbury St and Olson Pl SW. Crews completed the vegetation trimming, cleanup, and mulching that started last Sunday.

Upcoming Community Outreach Activities

Our outreach team is continuously connecting with the community to gather your input and hear about day-to-day experiences in West Seattle and the Duwamish Valley. 

  • Monday, November 2 (today): West Seattle Bike Connections meeting
  • Thursday, November 5: Washington Trucking Association meeting
  • Tuesday, November 10: Maritime Town Hall meeting
  • Tuesday, November 10: South Park Neighborhood Association meeting