(Looking east under the high bridge from Marginal Place)
By Tracy Record
West Seattle Blog editor
Ten days have now elapsed since the sudden, shocking news that the West Seattle Bridge was unsafe and would be shut down immediately. SDOT warns in a new online FAQ that “we anticipate a lengthy closure.” Monday’s City Council briefing suggested that means months, not weeks.
So, many questions remain.
We were able to ask a few of them in a brief conversation this morning with SDOT director Sam Zimbabwe (a West Seattle resident). Our allotted time was short so these are by no means all the questions that we (and you!) have – but it’s a start. (We also have questions, mostly technical, out to SDOT in writing.) Exact quotes are marked as such.
TR: What’s happening right now, today, regarding the work toward finding out what’s wrong and getting a temporary shoring plan?
SZ: “Our roadway structures division lead Matt Donahue has personally visited the bridge just about daily … we are still trying to understand what exactly is going on with cracking on the bridge … we are still inspecting every day after taking the live load off the bridge; we are still trying to understand what is causing the cracking to happen. Our repair and interim shoring plan has to respond to the structural issues that we are facing and so we still have to understand exactly what’s going on and make sure that our repair plan is responding to those issues. So we’ve got the same consultants [WSP] that have been part of this … going back to last year when we started analyzing this cracking in more detail have still been with us working on continuing to understand what’s been going on and what our repair strategy can and should be.” As for when they will know they have enough information to proceed with a temporary shoring plan, that’s dependent on their “modeling” matching “what we’re seeing in reality” during those daily inspections, to “understand where the stresses are appearing in the bridge and how we can address that.” The modeling involves analyzing how the bridge is reacting to forces including gravity, wind, load compared to how it “should be responding” to those factors, and what it can tell them about “where the bridge is going over time.”
TR: What has SDOT seen since the must-close-the-bridge-now discovery on March 23rd?
SZ: “We have still seen some crack growth.” They’re installing stress-monitoring instrumentation – real-time monitoring should be in place within a week – and are also “mapping” the cracks to see if they’re growing at the same rate as before the closure.
(Signage at west end of lower bridge, a small part of the white sheet covering the old green sign)
TR: The low-bridge restrictions are being ignored. When will a decision be made on enforcement? And when will the signage be improved?
SZ: “We implemented the detour plan [on March 23rd] extremely quickly and there are certain things that we have limited capacity, especially right now in terms of our public-health emergency response … We are working to improve the signage over the next week or so and increase some of the size, make sure there’s better signage, and hope that that in part can lead to better behavior. … Enforcing the restriction is not necessarily an easy task, and what we have been working on over the last week with the Police Department is … there has not been active enforcement of the prohibitions but police have been out there at various points, observing, having a presence, but then also figuring out… how we could safely and effectively enforce the restrictions.”
(Screengrab of SDOT camera, tweeted Sunday by @kazzmere)
TR: What about measures to keep people off the high bridge? We’ve received multiple reports of people seen walking, running, biking, skateboarding on it. Will there be better barricades (etc.)?
SZ: “There likely will.” Police were dispatched on Sunday to check out two reports of people on the bridge. “It is not … open to pedestrians, it is closed because it’s unsafe to be up there right now, for anybody; we don’t want anybody up there at all, it really is a hazard to people … We recognize that we may have to upgrade the fencing to make sure that people aren’t up there … we’ll do that as we need to.”
From there, we went back to the high bridge’s condition:
TR: Which side of the bridge are the worst cracks on?
SZ: “Both … the south side of the bridge [eastbound] is in a little bit worse condition … that’s potentially because it’s getting more solar exposure … hotter from the sun … but again, we don’t know exactly what all the causes of the deterioration are, but that could be one part of it.”
TR: Given the unique nature of the bridge, have you been in contact with anybody involved in building it?
SZ: Not sure about that but knows they’ve “reached out to folks who were part of SDOT over the years” and they’re also talking with WSDOT “and some of their bridge experts.” Part of what led to the discovery of this problem was consulting firm WSP bringing in some experts – “I believe from Toronto” – and some “academic bridge experts … so we’ve got a lot of eyes on it, and we’re looking for all the best advice and thoughts that we can get … Building a bridge like this, maintaining it, repairing it … there’s no one way to do it, and we’re looking for the best ideas of how to do it effectively.”
We were over our allotted window by then, but SDOT had indicated they wanted to clarify the pre-closure timeline a bit, so we asked about that last.
SZ: “The late February notification was an indication that we needed to think about reducing the number of lanes on the bridge by the end of 2020 – over time. It wasn’t an immediate ‘hey, do this right away’. March 19th was more of a ‘hey, this is a big issue'” and recommending full closure. That led to Donahue going to the bridge daily over that weekend and then Monday (March 23rd) morning, when he “went back inside the bridge – and a lot of this you can only see from inside the bridge – that takes some effort to actually (get) inside the bridge, make sure people can get in and out safely – so when he went back in with the WSP consultant and another one of our bridge engineers, that’s when he confirmed the growth of the cracks and also recommended full closure.”
TR: So the February 21st “think about reducing lanes by the end of 2020” wasn’t a life/safety matter?
SZ: No, and they knew what an effect even lane reductions would have on West Seattle, so they were talking about implementation, mitigation, “starting that conversation” but “in a month in the middle of our public-health emergency we had not been able to have a lot of those discussions that we would need to have to be able to implement even a lane reduction … and then it became a public-safety concern very quickly.”
As noted above, we have other questions pending with SDOT, and have requested an interview about the traffic plan – from monitoring of the detour routes to strategies that might be deployed when “stay-home” time is over and traffic starts getting back to something resembling a normal level. So watch for more followups.
Our ongoing coverage is all archived here, newest to oldest. SDOT’s project page is here, including the new FAQ.
I had the privilege of working on the West Seattle Bridge from 1982 to contract completion in 1985. I was a Seattle Engineering Department Civil Engineer assigned to work with the USACOE who was managing the construction contracts on behalf of the Federal Highway Administration. I was assigned to assist the COE field staff with the inspection of the construction. We inspected the construction to assure contractor compliance with the contract plans and specifications. My initial area of the work was the Main Span Superstructure from Pier 15 to Pier 18. This included the section crossing the river from Pier 16 to Pier 17 and the two back spans from Pier 15 to Pier 16 and Pier 17 to Pier 18. Besides the structural work, we also handled all of the other various elements of the work. The work was both challenging and difficult at times. With that stated, my opinion is that the current problem is a result of increasing loading beyond the design specifications or intent. Perhaps it is much like the Galloping Gertie of the Tacoma Narrows. The big busses and heavy trucks with long wheelbases are creating a dynamic load wave that acts much like an earthquake with peaks that exceed the design specifications. The Bridge is being slowly destroyed by overloading and overuse. The solution will require reducing the loads back to the original design plus stiffening the portion of the bridge that is deteriorating. It is flexing and twisting beyond the intent of the design. The City needs to bring back the design team and solve the problem. All is not lost, but the politicians may need to rethink budgets and priorities.
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