West Seattle, Washington

06 Tuesday

67℉

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

January 3, 2023 3:37 pm
|      19 COMMENTS
 |   Transportation | West Seattle news

(‘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.

ADDED 4:15 PM: SDOT also says it’s working toward “temporary free transit rides on the bus & West Seattle Water Taxi.”

ADDED 6:37 PM: We asked SDOT on followup how soon they expect to remove the cylinder, since they won’t have a full timeline until after that: “Our goal is to remove the cylinder within the next week. We are currently working to identify suppliers for all the parts and equipment necessary to move the massive cylinder and to reprogram the control system to operate with one cylinder.”

Share This

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

  • Flivver January 3, 2023 (4:47 pm)

    WSB. Will the temporary free rides apply to everybody or only those with bikes?? 

    • WSB January 3, 2023 (7:09 pm)

      Yes, according to the SDOT reps in the WSBC meeting.

  • bolo January 3, 2023 (5:13 pm)

    Thanks for this. Even as the general situation is unpleasant, it helps to know more of what is going on “under the hood.”

    Disclosure: I am not a certified bridge or hydraulic systems engineer but do have experience working on smaller versions of each. My own observation of the swing bridge in action leads me to believe there were some design deficiencies in how the bridge operates. When the “14 million-pound eastern side of the moveable bridge” swings closed, when it reaches to within a few feet of closed, it abruptly stops and ricochets back and forth as it works its way (lower speed) to closed. That “14 million-pound eastern side of the moveable bridge” whipping back and forth as it abruptly drops into low-speed mode appears to put a large strain on the mechanism. Seems like they could have implemented a smoother transition that does not overly stress the system. (The west section operates similarly.)

    Also, related, apparently they also did not design for future maintainability if it is so difficult to access and overhaul the hydraulic cylinders. Well-known that they are not lifetime maintenance-free, and do need to be overhauled from time to time.

    Overall, pleased that SDOT has a plan and has been making steady progress, and is freely sharing information.

    • Question Authority January 3, 2023 (7:20 pm)

      The 14 milllion pound mass has sheer inertia and is basically floating on an oil film as it swings, in a simplistic explanation it’s going to wiggle.  You see exaggeration from being outside looking at the “moment” when at the cylinders it’s rather smooth. And, you do not simply remove 15,000 lb anything.

    • Question Authority January 3, 2023 (8:05 pm)

      You can research the hydraulic system and build out easily and will see the immense balancing act required of both bridge leafs.  The lift cylinders are 8’8″ in diameter weighing 15,000 pounds and most hydraulic cylinders/pistons only go in and out but these also rotate.  Therefore the seals do double duty while carrying 14,000,000 lbs while only raised 1″, that causes inevitable wear and tear so consider those dynamics in a cramped space and you’ll understand better.

  • Mj January 3, 2023 (5:52 pm)

    What is the number of bicyclists that cross the bridge per day this time of the year?  

  • Ben January 3, 2023 (7:07 pm)

    I had to take the detour today at about 6:15am. Surface road grime is pretty bad. Lots of glass and screws. Got a flat on the 1st Ave S section. 

  • Jim January 3, 2023 (7:08 pm)

    “working towards”?! How hard is it to just not charge a fare for a few days?

    • WSB January 3, 2023 (7:20 pm)

      They will be starting it later this week, according to discussion at tonight’s meeting. That was not specified in this afternoon’s release, so that’s about all I could say at the time.

    • Bus January 3, 2023 (9:04 pm)

      Metro is a county agency, not a city agency, so at the very least SDoT needs to ask before just telling everyone they can ride for free.

  • KSJ January 3, 2023 (7:26 pm)

    I’m very glad they are shifting quickly to take care of cyclists. But this does not seem to bode well for getting the low bridge back any time soon. 

  • Question Authority January 3, 2023 (8:16 pm)

    Will this bike lane force those multiple RV’s at 1st Ave and Hudson St to finally move, it’s only been years since they “parked” there.

  • Luke Campbell January 3, 2023 (8:27 pm)

    Hi Cyclists.  I live on Holden and 35th. Any tips for getting down the hill to West Marginal Way.  Going down highland park way does not seem great, but maybe its ok on the sidewalk.  Google suggests I ride my bike through trails in Riverview Park.  Might be a little muddy on the rainy days. 

    • Ben January 3, 2023 (9:10 pm)

      It might make sense for you to take the detour route from the bridge. I live in the same area. You probably know this route, but if not, it is low traffic: Ride North on the East side of Walt Hundley field, thru highpoint and down that Hill past Greg Davis Park, then parallel to Delridge on 26th to Andover. From there, the detour. It’ll add some time, but the Highland Parkway hill is treacherous. 

    • bolo January 3, 2023 (9:37 pm)

      Hi cyclist. I rode down HPW on the east/south sidewalk recently. Doable, not too bad. Expect the usual debris, broken glass, trash, fallen branches. Main danger were the upthrusting tree root protruding bumpy sections that lower braking performance on a steep downhill.

      Then I got lost trying to navigate to the 1st Ave. S Bridge bike lane. Somehow I didn’t see or maybe didn’t decipher the markings correctly? One or two wrong turns got me into some really hostile biking territory that was doubly dangerous to extract myself from. Now at least I know which way NOT to go!

  • Don Brubeck January 4, 2023 (2:49 pm)

    Here is a bike route from SW Spokane St to 1st Ave S Bridge and back north to S Spokane & East Marginal Way S.  Not the same as the city’s temporary detour route.  This route is a few minutes longer and has a lot less traffic. Try it in daylight first, if you can. The link has audio cues if you put it on a phone.   https://ridewithgps.com/routes/34419471If coming from Riverview or Highland Park, try using the south sidewalk.  A bit bumpy and steep, but doable  if you are on an e-bike or have low gears.

  • Don Brubeck January 4, 2023 (2:53 pm)

    Here is a bike route from SW Spokane St to 1st Ave S Bridge and back north to S Spokane & East Marginal Way S.  Not the same as the city’s temporary detour route.  This route is a few minutes longer and has a lot less traffic. Try it in daylight first, if you can. The link has audio cues if you put it on a phone.   https://ridewithgps.com/routes/34419471If coming from Riverview or Highland Park or White Center, try using the south sidewalk on Highland Park Way hill.  A bit bumpy and steep, but doable  if you are on an e-bike or have low gears.

Sorry, comment time is over.