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Spokane St Swing Bridge (low bridge) will close October 25–27 for turn cylinder installation 

by on October 18, 2024

Blog stats: 1,100 words | 6-minute read 

At-a-glance: 

  • The Spokane St Swing Bridge (low bridge) will be closed on October 25-27 to people driving, biking, walking, and rolling. 
  • The closure is scheduled to start at 7 AM on Friday, Oct. 25 and is expected to continue until approximately 10 PM on Sunday, Oct. 27. 
  • The West Seattle High-Rise Bridge will remain open while the low bridge is closed, and is the primary option for people getting to and from West Seattle by car or bus. 
  • The closure will allow crews to re-install a refurbished bridge turn cylinder that was removed in April 2024. 
  • The turn cylinders are a key component that help the low bridge open and close when ships need to pass by on the Duwamish Waterway. 
  • This closure is part of our ongoing work to rehabilitate the low bridge’s systems. We have already completed bridge strengthening, earthquake safety upgrades, and modernization of the control and communications system. We are continuing our work to replace aging cylinders, hydraulics, and electrical components. 

The Spokane St Swing Bridge, commonly known as the low bridge, was built in 1991 and serves as a crucial link across the West Duwamish Waterway, especially for pedestrians and bicyclists.  

To keep the bridge reliably operating, we’re closing the low bridge on October 25-27 to people driving, biking, and walking. The West Seattle High-Rise Bridge will remain open while the low bridge is closed, and is the primary option for people getting to and from West Seattle by car or bus. 

During the low bridge closure, crews will reinstall a turn cylinder that we removed from the west side of the bridge in April 2024 for repairs. There are several types of cylinders which work together to lift and rotate the bridge.  

This is one of several aging cylinders which we are repairing over time to prevent issues like the 3-week bridge closure in January 2023. We will continue work to repair the remaining cylinders in 2025.   

Replacing the cylinders is part of a longer series of projects to repair, maintain, and upgrade the low bridge, including:  

  • Bridge strengthening (complete) – We completed our bridge strengthened work from 2020 to 2022. These efforts included injecting epoxy resin into cracks in the low bridge and adding carbon-fiber wrapping in several locations on interior and exterior surfaces.  
  • Earthquake safety (complete) – This past summer we finished removing silt that had built up around the western bridge foundations and replaced rusted steel collars around the support piers. This will allow the bridge to move as intended during an earthquake reducing force and stress on the foundations. This was one of 16 bridge seismic retrofit projects we are completing citywide thanks to the Levy to Move Seattle.  
  • Control system upgrades (complete) – Earlier this year we finished upgrading the bridge’s control and communications system that opens and closes the bridge. The previous system was over 30 years old.   
  • Component upgrades (ongoing) – Over the past few years we have been continually working to replace the bridge’s various cylinders, hydraulic pump systems, and electrical components which all work together to move the bridge. 
Our crew members guide the cylinder out of the bridge pier house. Jan 2023. Photo credit: SDOT
Our crews slowly and carefully manuevered the cylinder around the interior of the bridge before moving it outside and onto a truck. Jan 2023 Photo credit: SDOT
Example of a refurbished turn cylinder that was re-installed in 2023. It included new seals and a wearing band on the turn cylinder’s newly machined piston. Photo: SDOT

Crew members installing similar cylinders last year. This weekend’s work will be the third turn cylinder repair we have completed.

Additional phases of this bridge rehabilitation project are expected to continue through 2025. Over the next year, additional short-term closures will be required as part of our ongoing preventative maintenance work on this bridge. That means that in the future, the low bridge will be closed again to people walking, biking, rolling, and driving. 

How to get around during the closure

Although you won’t be able to travel using the low bridge during the closure on Oct. 25-27, we have compiled a list of other options and ways to get around: 

  • The West Seattle High-Rise Bridge will be open. This is the main detour route for people driving or taking the bus.  
  • People will not be able to bike or walk over the low bridge during this closure. Taking the bus or water taxi is a reliable option for people without a car. People may also use this bike map find other bike route options, and SDOT recently added permanent safety barriers to the protected bike lane on West Marginal Way SW.  
  • Harbor Island can still be accessed from the east via SW Spokane St. These detour maps show how to get between Terminal 5 using the West Seattle High Rise Bridge: Going to Terminal 5  / Leaving Terminal 5. 
The map shows different routes to enter Harbor Island and Terminal 5 during the low bridge closure. Graphic: SDOT
The map above shows different routes to enter Harbor Island and Terminal 5 during the low bridge closure. Graphic: SDOT
The map shows different routes to exit Harbor Island and Terminal 5 during the low bridge closure.
The map above shows different routes to exit Harbor Island and Terminal 5 during the low bridge closure.

We appreciate your patience and understanding as we complete this crucial work to keep the low bridge reliably operating today and in the future. To stay informed about the project, sign up to receive project updates and visit our website regularly. 

Filed Under: SDOT, Traffic and Construction