WEST SEATTLE BRIDGE CLOSURE: SDOT explains new monitoring system

One week after SDOT went public with some details of its emergency plan in case of West Seattle Bridge failure or imminent failure (WSB coverage here), it’s just published a close-up look at the new monitoring system. The graphic above is from the new SDOT Blog update, which also includes photos of some of the monitoring equipment. Also explained – the monitoring is also key to the biggest decision yet to be made. Three main purposes are listed:

*Keep us informed on how the bridge reacts to environmental changes, bridge stabilization measures, temporary shoring, and potential future repairs.

*Give us a better indication of bridge distress that could warn of impending failure.

*Guide us to a decision about the technical feasibility of repair or replacement.

SDOT says the system includes cameras, movement sensors, and crack monitors, noting:

The new intelligent monitoring system is already ‘talking’ to us and telling us that there is some potential for failure. What we don’t yet know is how great that potential is. The new system will help us better determine that.

SDOT adds that “after we collect a few weeks’ worth of data”:

Analytic modeling will interpret the data to gain a baseline understanding of the bridge’s behavior. If we observe stable behavior, the bridge will continue to be monitored during and after the temporary crack arrest measure installation and the Pier 18 restrained lateral bearings’ release, to see how the bridge reacts.

See the entire update here.

28 Replies to "WEST SEATTLE BRIDGE CLOSURE: SDOT explains new monitoring system"

  • Eric1 May 13, 2020 (1:02 pm)

    Yikes.   Never good when the testing equipment tells you that failure is an option.   The good thing is that if imminent failure becomes likely, they don’t have to risk lives checking on the bridge in person.  Hopefully they can shore it before it fails. But it is looking grim for the bridge. 

    • bolo May 13, 2020 (10:16 pm)

      Why do so many choose to react so negatively? The test results alternatively, could show that the failure risk is relatively minor, and simple* repairs may be all that is needed.

      *I know that nothing is simple as far as bridge engineering, but meaning simple as far as not requiring total demolition/rebuild or otherwise complex retrofits.

  • Railroaded May 13, 2020 (1:16 pm)

    West Seattle has always been out of the way. Sometimes more, sometimes less. Now, West Seattle has returned to its roots: way outta way.

    • JeffK May 13, 2020 (5:56 pm)

      Too bad WS can only seem to build more housing units which means more commuters.  A couple of office buildings here would help out.

      • max34 May 14, 2020 (7:44 am)

        and what offices would move here if they’re only source of workers are from Admiral to Burien? 

  • wetone May 13, 2020 (2:38 pm)

    To bad City officials and SDOT didn’t install proper systems to monitor and get proper consulting for bridge when issues were first noticed in 2013…. most likely would have different outcome than we have today. Really don’t see much difference today with City officials and SDOT  decisions, as their more interested in spending money on changing MPH signs, painting fancy cross walks, replacing ADA ramps that were per code, road diets, road closures and soooo much more. While still doing nothing or very little to fix real infrastructure issues if there related to motor vehicle usage…. Such as roadway surfaces, elevated roadways, bridges. Get ready for huge tax increases/levy’s to fix/repair needed areas of work due to our poor leadership.  

    • Blang May 13, 2020 (4:07 pm)

      Sooooo true.

    • Jon Wright May 13, 2020 (4:34 pm)

      That’s a revisionist narrative. SDOT did what any organization responsible for maintaining a concrete structure would have done, they monitored the cracks. In case anyone reading wasn’t aware, there are only two kinds of concrete: the kind that is cracked and the kind that is going to crack. When the cracking accelerated unexpectedly, SDOT began to take action. A recent Seattle Times article claimed a “design problem may have doomed it [the bridge] all along.” If a 1980s bridge was built with a design flaw, I don’t see how it is appropriate to pin that on contemporary (or even circa 2013) SDOT.

      • Chemist May 13, 2020 (7:12 pm)

        The inspection records SDOT has shared have mentioned “At Pier 18 the lateral restrainers have extruded the PTFE sliding surface. Continue to observe” as well as the same for Pier 15 continually since 2013’s report.  Those are the same bulging bearing surfaces that are now the first step of the repair to be done to the bridge.  Even if those weren’t signs of stuck bearings damaging the bridge, maybe addressing them or any other items labelled “continue to observe” might have meant the bearing isn’t stuck now.  I’d feel bad for an inspector who is visiting a location twice as frequently and documenting conditions when so few of the indicated problems actually progress into a repair.  That might be a fun exercise actually, see which issues in the reports appear to have been repaired over the past 7 years.

        • BBILL May 13, 2020 (9:43 pm)

          How do you pick and choose which “continue to observe” items to repair immediately? Be sure and justify every tax dollar you decide to spend when the recommendation was “continue to observe.”

      • Kate May 13, 2020 (7:13 pm)

        The 1980s potential design flaw and the 2013 response are 2 different things. There could have been a competent response to a previous error. A whole different engineering team than the one involved in the initial design should have been brought in when exceptional cracking was found in 2013. This was not done. Also, hindsight shows that the City should not have chosen to spend tax dollars such a cutting edge design. Something more conventional would have been a better bet. 

        • BBILL May 13, 2020 (9:40 pm)

          “Also, hindsight shows that the City should not have chosen to spend tax
          dollars such a cutting edge design. Something more conventional would
          have been a better bet. ” I’d like to see the supporting analysis for that.

    • FedUp May 13, 2020 (5:30 pm)

      @wetone    Exactly!  let’s close streets and lower speed limits. Ridiculous

    • StupidinSeattle May 13, 2020 (5:54 pm)

      Nailed it.  This was a major failure that should have been dealt with by SDOT years ago.  Still waiting to see the Mayor and City Council work on the solution.

    • Rick May 14, 2020 (7:23 am)

      The truth can be painful.

    • Jason May 14, 2020 (12:54 pm)

      This hits the nail on the head.  The “‘money grows on trees” spending of SDOT on trivial things like you said.  Lowering speed limits in an unreachable quest of zero traffic fatalities. Replacing curb ramps.  “Sharrows” every 200 feet.  Traffic “calming” and ridiculous striping our of corners on wide intersections.  Priorities weren’t set right.  And now the bill has come due. 

  • Sancho May 13, 2020 (2:48 pm)

    Larger forces at work in WSEA  to keep us safe in this covid  moment 

  • dsa May 13, 2020 (2:51 pm)

    Has SDOT said or published anything if they have determined (surveyed) a vertical sag for the bridge?  Reading in the Seattle Times the other day the theory  that concrete shrinkage is the now popular reason for the cracking.  Other bridges  in world with shrinkage experienced vertical sag.  If I recall correctly, one was saved, and one failed after repairs.  So I got curious if SDOT knows if this bridge has experienced a sag in it’s vertical alignment.

  • heyalki May 13, 2020 (3:40 pm)

    Great…soooo…how are they going to FIX IT?

  • Wild Willy May 13, 2020 (5:08 pm)

    Good to see that SDOT is being candid in their assessment of the data being collected by the new monitoring instruments. The sooner that the problems are determined, the sooner a solution can be implemented. With SDOT already saying failure of the bridge is possible, replacement is looking more probable.

  • John P Woods May 13, 2020 (7:56 pm)

    Assuming that the bridge is going to be replaced, are there any parts of the bridge that can be reused. Yes, I know that this is the same stupid question i asked when they decided that the the West Seattle Viaduct had exceeded its useful lifespan. However, I just want the answer on the record

    • bolo May 13, 2020 (10:51 pm)

      Still too early to assume that the bridge is going to be replaced.

  • Beech May 13, 2020 (10:16 pm)

    Maybe if people had not had a second vote on the monorail between Ballard/Seattle/WestSeattle and voted to trash it after the right of way was already purchased  things might not be so tragic. Typical Seattle, vote no. This was public transportation we need it. Times are different now with the virus. A good chance to think things through.

    • Chemist May 14, 2020 (12:39 am)

      Considering the monorail was supposed to be built on the high bridge, it wouldn’t help much with where we are now. mapI still wish SDOT would share some of the real-time readings from the sensors that have been installed for years and share the design concepts that the WSP consultant had referenced presenting back in February’s report.

      In summary, the process to repair the bridge needs to start now in order to complete repairs as
      soon as possible. It is our opinion that the work should be completed this calendar year. We
      have design concepts in mind that have been presented to the City. We need to begin the process
      of deciding which of those repair concepts the City would like to investigate further and
      subsequently implement. Once a repair concept has been selected, it should be possible to
      design and implement the repair in a reasonably short period of time. 

    • Revisionist history May 14, 2020 (9:33 am)

      Chalking that disaster up to NIMBY’s is way off base. There was either complete financial incompetence or outright grift depending on your perspective. The final ballot measure was pushed by the city in order to defeat it. Properties & businesses were lost due to eminent domain foreclosure and we all threw our money away. Hoping that measure had passed in conjunction with COVID and the current bridge condition is a head scratcher to say the least. 

  • Wild Willy May 14, 2020 (7:10 pm)

    One thing to remember is that the Spokane Street Bridge, a Seattle street and not a Washington State or United States highway, was built with Federal government funding, and was overseen by US Army Corps of Engineers. This came about because of Sen Warren G Magnuson and his position in US Senate. 

  • Duff C. Radke-Bogen May 15, 2020 (2:19 pm)

    20/20 hindsight of what shoulda been done doesn’t solve problems. It’s possible and probably a best practice to hope for the best and plan for the worst case.
    If repairs work out the best we’d have would be a patched up old bridge supporting over capacity traffic.
    If.sufficieht repairs can’t be made so that the bridge can be reopened we need to look at how to build a bridge that is more than just a replacement.

    The clearest option would be to add lightrail to the bridge and not dig a tunnel. Combining the two projects could be a net savings. An unanswered question is what is the state’s share in this roadway that connects highway 160 (The Vashon/Southworth Ferry route) to I-5. Should ferry traffic pay its way by sharing the cost of a new bridge.
    My sense is that these cracks are telling us to plan on building a new bridge and to start the discussion early.

  • Perry Cole May 15, 2020 (8:01 pm)

    Why don’t they just get started on a tunnel as a replacement for the High Bridge?

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