It is impossible to look at the death of a Boston-area – woman caused by a falling slab of concrete – and not wonder from a mechanical and structural perspective, just what broke to cause this tragedy.
It seems impossible for the politicians not to wonder, also. So far, the science of tunnel-building has made up the bulk of what investigators and local officials have been discussing in public as they try to piece together what happened.
As with all major investigations into large-scale projects like these, it will take time for the truth to finally come out, but when the answers Milena Del Valle’s family is looking for do emerge, there will be a lot more to blame than just rivets and epoxy, according to local engineering experts.
Stephen G. Banzaert is an instructor at the Massachusetts Institute of Technology, specifically teaching the history of engineering failures. If anyone could guess what went wrong with the Big Dig, it’s him, but even Banzaert can’t say at this stage until the specs on the ill-fated tunnel system are revealed.
Banzaert says everyone, from investigators to the contractors to the general public, is paying too much attention to the mechanical elements – like when Massachusetts Gov. Mitt Romney drew pictures on television and explained how he hung 8,500 lb from support bolts, and the memo from Bechtel-Parsons complaining that Romney weakened the bolts by doing that.
These arguments are important, Banzaert says, but it seems no one, at least from the public perspective, is paying enough attention to the all-important human element that surely bears a portion of the blame.
Without seeing the plans himself, Banzaert admits he can only guess at what the contractors and designers had in mind, something an engineer is not comfortable doing.
What seems certain is that this project, like any complex construction undertaking, should have had multiple fail-safes to protect against falling concrete panels, not to mention a secure system of monitoring to make sure the tunnel was safe. The fact that a panel collapsed on a passing car suggests a large number of errors, both mechanical and human, are to blame.
“There’s a long chain of ‘whys,” he said. “It usually goes back far from the original (problem).”
Banzaert used highway signs — those 20 x 8-ft green placards that hang over some of the very highways feeding into the new I-93 tunnels — as an example. For years, signs such as those all over the state have been held in place not by one, or two, but many rivets – a series of redundancies to account for the inevitable lack of perfection.
But when things do break down, Banzaert says highway workers don’t wait for all the rivets to give way before doing something.
“The first sign (of a problem) isn’t that the sign comes crashing down. It’s that you see a few busted rivets,” he says.
Dr. Matt Litman, an environmental engineer and adjunct professor at a Boston-area university, has done design work for a consulting firm that worked on multimillion-dollar wastewater treatment plants for New York City’s Department of Environmental Protection.
Litman agrees with Banzaert that the end-result of any investigation into a tragedy involving a project with the scope of the Big Dig will be not one, but many failures, on many levels.
“It’s not one thing. It’s usually many, many things that go wrong together,” he says.
Litman notes the five elementary phases of any massive construction undertaking: The concept, initial design, specified structure, or what it was supposed to be, the as-built structure, or what it actually wound up being, and finally maintenance and inspection of the structure as it is used.
No investigation, Litman says, will be complete until each phase is gone over with a fine-toothed comb.
“My guess is, you’ll find fault in all five,” he says.
Litman says each of the five phases of construction is run by one of three basic groups of people. Concept, design and the specified structure are all the responsibility of the designers and engineers who thought up the project in the first place.
As-built structure results, he says, are the responsibility of the contractors and construction workers who actually built the tunnels to specifications.
Lastly, the client – in this case the state’s highway department – was responsible for maintenance.
Just as all five phases of the construction process are likely to have flaws, Litman says it is likely all three groups of people will bear some weight of responsibility for Del Valle’s death.
Banzaert, speaking to the project’s design, says Big Dig engineers would have had to have redundancies involved when deciding to use massive concrete panels suspended over the road as the tunnels’ ventilation system.
“It’s a decision you make with your eyes open,” he says.
But in the connector tunnel where Milena Del Valle was killed, Banzaert says, if there were multiple fail-safes, they all failed, and no one noticed until it was too late.
“The first sign of (trouble) that we saw was 12 tons of concrete coming down,” he says.
Regarding maintenance, Banzaert says there must have been a plan created, along with the tunnel, to hand over to government officials upon completion, a kind of “owner’s manual” that would describe how the tunnels should be maintained and inspected, and what sort of warning signs could foresee an accident.
That plan, Banzaert says, can help pinpoint who should have been watching the roof tiles in the I-90 connector tunnel.
Investigators should also look to who was overseeing the design of the project. Banzaert said even the best engineers need proper oversight to check their work, otherwise the results can be disastrous.
An example Banzaert teaches in his class is the USS Princeton, an 1844 screw-powered warship, the first of its kind, which also had a first-of-its-kind deck-mounted cannon.
During a ceremony that included the secretary of state and the secretary of the navy, the gun misfired, killing both of them and at least one other spectator. It would have killed President John Tyler, too, had he not elected to watch from the crowd.
Banzaert said the problem was eventually traced to a flaw in the gun’s design, a flaw that was missed because no one dared insult the well-known designer at the time by checking his work.
The lesson: No one is above review or scrutiny.
“Even the best mathematicians might forget to ‘carry the 1’ someday,” he said.
Litman agrees that no project should be designed without supervision, especially where multi-ton ceiling panels suspended over highways are concerned.
“You have a serious, egregious breakdown of the engineering process when somebody is left on their own,” he says.
Banzaert says no one can possibly know yet whether it was a miscarried “1,” a weakened series of support bolts, a lack of proper inspection and maintenance, or a combination of failures that led to Milena Del Valle’s death, but Banzaert says the engineering community, the public and Del Valle’s family shouldn’t be satisfied until they have their answers, and until all three categories are properly explored.
“Even visionary geniuses need review panels,” he says.
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