WEST SEATTLE LOW BRIDGE: New information about what’s wrong, what’ll be done to fix it, and improvements to bicycle detour

(‘Live’ image from SDOT traffic camera)

More updates this afternoon from SDOT on the West Seattle low bridge, a week and a half after mechanical trouble closed it to drivers, riders, and pedestrians. Still no estimate, though, on how much longer the closure will last. First, key points from the repair-related update, followed by the detour-related update:

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.

Here’s what SDOT says went wrong:

1) 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.

2) 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 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 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. … 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.

As for the bicycle detour, SDOT says it’s taking these major steps:

This week, we are converting sections of W Marginal Way SW and 1st Ave S curb lanes to temporary protected bike lanes using cones, barrels, paint, and signs. The temporary bike lanes will remain until the Spokane St Swing Bridge reopens. We continue to procure traffic control devices and finalize the traffic control plan. We expect to complete the bike lane installation by the end of the day on Wednesday, Jan. 4. …

While the temporary bike lanes are in place, 1st Ave S will have one general-purpose traffic lane in each direction, a center turn lane, and one bike lane in each direction. As possible, existing on-street parking will remain but be restricted near driveways to help people biking and driving more easily see each other. In two instances at the north and south ends, people on bikes will have to use the sidewalk-see map above. You may wish to get off your bike and walk it through these areas with pedestrians.

We will also convert the southbound general-purpose travel lane at the northern segment of West Marginal Way SW to a temporary protected bike lane. We expect this to have a minimal impact on people driving, as this is not a through-lane.

We will check the detour twice daily to reset cones, barrels, or signs that may have shifted while the temporary bike lanes are in operation.

As noted in our daily preview, the detour will be discussed at tonight’s 6:30 pm online meeting of West Seattle Bike Connections.

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