West Seattle High-Rise Bridge Repair

Updated July 26, 2021

What's Happening Now?

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Thanks to everyone who joined us for the West Seattle Bridge Program virtual public meeting on Wednesday, July 21. More than 250 community members joined the meeting to ask questions and hear updates about the ongoing repair effort on the West Seattle High-Rise Bridge (high bridge), expanded access on the Spokane St Swing Bridge (low bridge), and our work to improve access to and around West Seattle through the Reconnect West SeattleHome Zone, and neighborhood travel options programs.

Couldn't attend the meeting? Here are other ways to learn more and connect with us:   

RECENT NEWS 

  • The West Seattle High-Rise Bridge (high bridge) is on track to reopen in mid-2022.
  • We've selected the contractor who will construct the next phase of rehabilitation, which is scheduled to begin later this year.
  • We've reached the intermediate design milestone for rehabilitation of both the high and low bridges. The design for both bridges calls for using several tried-and-true construction methods for rehabilitation (learn more below). We anticipate reaching final design later this summer/fall.
  • We're also doing rehabilitation projects on the Spokane St Swing Bridge (low bridge) simultaneously to keep it operating for emergency vehicles, transit, heavy freight, and people walking and biking.    

Project overview 

In 2020, we closed the high bridge in the interest of public safety. We made this decision based on regular inspections of the bridge, which showed rapidly growing cracks. Since the closure, we've wasted no time, working to repair the high bridge and to plan and build projects across affected neighborhoods that will reduce impacts on local communities.

We announced that we would repair the bridge instead of replacing it with a new span. The decision was based on input from the community, speed of traffic restoration, minimizing impacts, and cost effectiveness. 

Project background

Historically, the West Seattle High-Rise Bridge is the City's most used street, typically carrying more than 100,000 travelers every day. The concrete bridge was built in 1984 and has since been a major route for moving people and goods to and from West Seattle and providing connections with neighboring communities, such as the Duwamish Valley and SODO. Rising 140 feet above the Duwamish Waterway at its peak, the high bridge is approximately 1,300 feet long across three spans. It is a cantilevered and segmental concrete bridge, which means that the bridge was constructed on site, with crews building segments on either side of the piers until the segments all connected.

The closure has been a challenge to travelers and businesses in West Seattle, South Park, Georgetown, SODO, and Seattle as a whole. We have appreciated the patience and community spirit that is helping us all get through this challenging closure together. Alternate routes and signed detours include the 1st Ave S Bridge and South Park Bridge. With public safety as our top priority, the Spokane St Swing Bridge (low bridge) is restricted to authorized users only to ensure efficient emergency vehicle passage.

Graphic showing the project area.

Project Schedule - Phase 2 rehabilitation

  • 2020: Phase 1 stabilization
  • 2020-2021: Phase 2 rehabilitation planning and design
  • 2021-2022: Phase 2 rehabilitation construction, monitoring, and reopening
  • We plan to reopen to traffic the bridge in mid-2022. 

Project schedule for high bridge repair

Bridge rehabilitation details

We've already begun rehabilitation efforts on the bridge - no time has been lost. We're following an aggressive schedule to design and complete the high bridge rehabilitation work.

In December 2020, we we completed early repairs to stabilize the high bridge. Thanks to those stabilization efforts, the bridge is performing as expected and we've made significant progress on the overall repairs needed for traffic to return to the bridge in 2022. In May, we selected the contractor who will construct the next phase of rehabilitation, which is scheduled to begin later this year. Our contractor selection approach is just one part of our effort to expedite the repair process. Traditionally, a contractor is selected once the design is complete, and there is minimal interaction between the construction and design teams. With this approach, the contractor is on board much earlier during design, and when the designer and contractor work collaboratively, there are more ways to ensure schedule predictability.

We are continuing to approach rehabilitation work carefully, with ongoing monitoring and inspection. The data we've collected on how the newly stabilized bridge is behaving in response to seasonal temperature changes is helping to confirm our approach as we finalize design for phase 2. 

Phase 1: High bridge stabilization

phase 1 stabilization graphic

During phase 1 stabilization (shown above), we installed new post-tensioning, carbon-fiber wrapping, and an intelligent monitoring system. Diagram is not to scale.

Phase 2: High bridge rehabilitation

During phase 2 rehabilitation, we will build on the same tried-and-true construction methods we used in phase 1, including more epoxy injection crack filling, post-tensioning, and carbon-fiber wrapping in the main span, as well as strengthening work on the bridge's side spans (between bridge columns Pier 15 and Pier 16 and between Pier 17 and Pier 18). Diagram is not to scale.

phase 2 stabilization graphic

Rehabilitation methods   

Our team is using multiple construction methods in our efforts to rehabilitate the high bridge. We've already used epoxy injection crack filling, carbon-fiber wrapping, and post-tensioning on the central span to stop the progression of the cracking and stabilize the structure.

Full bridge rehabilitation will include more epoxy injection crack filling, post-tensioning, and carbon-fiber wrapping in the main span, as well as on the side spans (between bridge columns Pier 15 and Pier 16 and between Pier 17 and Pier 18). We'll continue to refine many of these details as the project moves towards final design. Through phases 1 and 2, we're also using intelligent monitoring techniques to assess how the bridge is responding to these measures, which is informing our design of phase 2 (rehabilitation).      

Side span graphic

Post-tensioning

As with many long-span concrete bridges, when the high bridge was constructed, engineers built high-strength cables into its concrete girders to support the concrete. These post-tensioning cables compress, or tighten, the concrete before vehicles travel on it, allowing the bridge to carry heavier loads.

The high bridge has two kinds of post-tensioning:

  • Original cables running through pipes in the concrete, which were built during bridge construction in the 1980s

  • Newly installed cables running along the floor inside the hollow bridge girders, which are held in place by post-tensioning brackets or anchors

Post-tensioning steel cables reinforce the bridge structure and help prevent it from cracking. When we post-tension the high bridge, we are adding more cables inside the hollow bridge girders (not within the concrete walls of the girders) so the bridge can better support itself and respond to other environmental factors such as weather, vehicle loading, or other external forces.

how postensioning works

We completed an initial phase of post-tensioning on the high bridge in 2020 in the main span, and will do additional post-tensioning work on the center and side spans to fully rehabilitate the bridge in phase 2.

Graphic showing the high bridge has hollow girders (bridge supports) where we can access the post-tensioning

The high bridge has hollow girders (bridge supports) where our team can access utilities and support systems, such as post-tensioning.

Photo looking down the row of tensioned cables (or strands) inside a high bridge central span girder. Photo credit: WSP

Looking down the row of tensioned cables (or strands) inside a high bridge central span girder. Photo credit: WSP

Carbon-fiber wrapping

Wrapping sections of the bridge with carbon fiber reinforced polymer helps support the now-stabilized bridge. We wrap sections of the bridge with carbon- fiber wrapping to strengthen the bridge, much like putting a cast on an injured arm or leg. When we add carbon-fiber wrapping to surfaces of the bridge, it's working in tandem with the steel already inside the bridge to increase bridge strength.

We will do additional carbon fiber wrapping in phase 2 rehabilitation. The wrapping will include sections of the center span and the end spans. Carbon-fiber wrapping can be added both outside of the bridge girders, and within the hollow girders for added strength. When we add carbon-fiber wrapping, we do so in phases, alternating with tightening the post-tensioning to ensure that the bridge continues to strengthen as the girders get more compressed.

carbon fiber wrapping graphic

A cross-section of one of the bridge's hollow girders (which span between bridge supports). The hollow girders allow our team to access inside the box for inspection and maintenance purposes, install utilities and the monitoring system, and rehabilitate the bridge.

Carbon-fiber wrap, with anchors that are bolted through the bridge girders to support the post-tensioning system, are attached in sections on the underside of the bridge’s central span and can be seen from the ground below. Photo credit: WSP

Carbon-fiber wrap, with anchors that are bolted through the bridge girders to support the post-tensioning system, are attached in sections on the underside of the bridge's central span and can be seen from the ground below. Photo credit: WSP

Crack filling and monitoring

In phase 1, stabilization, we installed interim measures to slow the spread of cracks, including epoxy injections coated with carbon-fiber wrap at the distressed locations.

We also installed a new monitoring system of additional movement sensors, crack monitors, and monitoring cameras throughout the bridge. These monitors are improving our understanding and tracking of the health of the high bridge, with greater precision and real-time data.

We'll continue around-the-clock monitoring and regular visual inspections of the bridge. As we continue phase 2 rehabilitation, we'll also expand the system to include an even more sophisticated, long-term monitoring system that will allow us to continue to monitor the in-service bridge.

Additional improvements

We're also working to make smart use of our contractor team after they are brought on board. As the project moves forward through design, we'll continue to look at opportunities to make improvements to the foundation of the high bridge's Pier 18 and identify other possible roadway and paving improvements along the West Seattle Bridge corridor to take advantage of while the bridge is out of service.

Planning for the future

As we move forward with bridge rehabilitation, we are continuing to plan for an eventual bridge replacement. Learn more here.

Community engagement

We are committed to working with the community to keep you informed of progress and milestones as we rehabilitate the bridge. We will seek your continued feedback on how to improve mobility and safety for West Seattle, as well as the South Park and Georgetown neighborhoods. Thank you to everyone who has helped us make this project better with your ongoing engagement.

  • Learn more, get involved, and tell us what you think: Invite us to meet virtually with your neighborhood group, local business, or place of worship.

  • Email or call us at WestSeattleBridge@seattle.gov or (206) 400-7511 to let us know how to improve safety and mobility in your neighborhood.

  • Sign up to receive regular program update emails.