Spokane St Swing Bridge update: Flooded power conduit repaired as we prepare to remove a damaged hydraulic cylinder
Related Updates:
We’re also working to enhance the safety and convenience of the detour routes with temporary protected bike lanes and improvements for freight. Read more.
This is part of a series of updates about our urgent response to the ongoing Spokane St Swing Bridge closure. Click here to see all updates on this topic. Click here to see all updates on this topic
Summary:
- Status at-a-glance:
- Complete: Developed repair plan
- Complete: Repaired flooded electrical conduit
- Underway: Preparations to remove leaking hydraulic cylinder
- Ahead: Reprogram eastern bridge span to operate on one cylinder
- Read more: Click on the links below for additional details:
Bridge engineers are making progress on repairs to Spokane St Swing Bridge and getting ready for the biggest challenge yet
Over the past ten days, our team of bridge engineers, maintenance crews, and technical experts have been continually working to repair the Spokane St Swing Bridge (Low Bridge) as quickly as possible. The bridge has been stuck since December 23, when the mechanical and electrical systems were damaged during a severe ice storm. We have made significant progress on repairs, including replacing 500 feet of damaged underground high-voltage power cable. However, there is still a lot to do as we prepare for the mammoth task of removing a significantly damaged 15,000-pound hydraulic turning cylinder, one of the two cylinders responsible for turning the 14 million-pound eastern side of the moveable bridge.
Last week we estimated that the bridge would be closed for a minimum of 2 weeks. We have made steady progress since then and will know more about the remaining timeline after we remove the cylinder.
Detour route updates:
In addition to the engineers working to repair the damaged bridge, we also have a team addressing the closure’s impact on freight movements and people who bike, walk, and roll. We are working to enhance the safety and convenience of the bike detour route and will build temporary protected bike lane segments on West Marginal Way SW and First Ave S. We’re also adjusting traffic signals to help keep freight moving. Read more about the improvements to the detour routes here.
How the bridge equipment was damaged
Our engineers determined problems arose and intensified with two critical bridge systems:
- A 15,000-pound hydraulic cylinder that moves the eastern side of the bridge is leaking fluid. We will need to remove and completely overhaul this cylinder as part of our repairs.
- While we were addressing other electrical and mechanical issues last week, high tides and heavy rain flooded an underground power conduit causing an electrical short to over 500 feet of high-voltage power cables. (We completed repairing and replacing these power cables at 3 a.m. Saturday, December 31st).
The bridge uses multiple hydraulic systems to lift and rotate the bridge spans. The damaged cylinder is one of four similar cylinders (two on each side of the water) responsible for turning the 14-million-pound eastern span of the bridge to open for passing ships.
The recent ice storm created a power outage to the bridge. After we restored power using the backup generator, we attempted to open the bridge and it was immediately apparent there was a problem. The eastern bridge span would only rotate a portion of the way and then stall, and we had to make several attempts to swing open the bridge. We soon discovered the cylinder had developed an intensified leak, and it could not safely operate in its current condition.
We staff this bridge 24/7 and were closely monitoring this cylinder. We know its current condition is not the same as the manageable issue which existed before the storm.
What we’ve completed and what we have left to do
We started preparations several months ago to overhaul all four hydraulic turning cylinders (including the damaged one) as part of our ongoing comprehensive bridge rehabilitation program. Click here to read more about our recently completed work to strengthen the bridge structure and replace several other hydraulic pump arrays.
The work we’ve already completed allowed us to jump into developing a response plan almost immediately after the damage occurred and will likely mean we’ll able to complete this rehabilitation faster than if we had started from scratch.
The cylinder will need to be temporarily removed and overhauled off-site. Over the past 10 days, we built and assembled some of the equipment necessary to move the massive cylinder. Once the cylinder is removed, we will re-engineer the bridge’s eastern span to temporarily operate on the single remaining turning cylinder. This work requires reprogramming the control system and testing it to ensure the new configuration is reliable and safe. While the eastern bridge span is running with one cylinder, opening and closing the bridge for passing ships will take about 10 minutes longer than usual.
Over the coming months, there will be additional bridge closures to reinstall the cylinder and to complete other projects in our comprehensive Spokane St Swing Bridge Rehabilitation Program. Occasional bridge closures were already planned for 2023 to complete proactive refurbishment and repair work planned this year.
Stay informed:
- Email: westseattlebridge@seattle.gov
- Phone: (206) 400-7511
- Sign up for email updates: https://public.govdelivery.com/accounts/WASEATTLE/subscriber/new?topic_id=WASEATTLE_270
- Web: https://www.seattle.gov/transportation/projects-and-programs/programs/bridges-stairs-and-other-structures/bridges/west-seattle-bridge-program/spokane-st-swing-bridge-improvement-projects
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