U See U10, U Fix U10?

The ill-fated, warped U10 gusset plate on the I35W bridge.  June 12, 2003.
The ill-fated, warped U10 gusset plate on the I35W bridge. June 12, 2003.
The National Transportation Safety Board (NTSB) has concluded that the I35W bridge collapse was caused by undersized gusset plates and oversized construction load, and that corrosion did not cause the collapse. I’m as far from an engineer as you can get, but all of that makes logical sense to me.

But it strikes me that the NTSB made an error of ommission. It failed to explore why no steps were taken to address a gusset plate that was known to be badly warped, more than four years before the collapse.

Some terrific investigative reporters at the Star Tribune discovered that Minnesota Department of Transportation (MnDOT) bridge inspectors had a June 12, 2003 photo of a very warped U10 gusset plate in their inspection file. U10 is the plate that NTSB says failed.

That part of the process seemed to work well, and we should be comforted by that. Inspectors spotted and documented a major problem.

But then what? Did the inspector report the problem to superiors? Did the inspectors’ superiors discuss options for strengthening the warped plate? If strengthening or replacing was technically infeasible, did MnDOT consider closing the bridge, as they have in the face of similar problems in St. Cloud and Hastings?

Assuming the plate couldn’t be fixed, why didn’t someone at least warn against parking several tons of construction equipment — reportedly the largest load the bridge had ever borne, equal to the weight of a 747 jet — directly on top of the badly warped U10 gusset?

These are legitimate questions that the NTSB seems to have bypassed.

Think of it this way. Imagine if a doctor spotted a tumor, stuck a PET scan of it in the file, labeled the tumor an unfortunate biological design flaw, and took no further action to prevent further damage from the flaw. The doctor would be 100% correct; the tumor is a design flaw, and not her fault. But the doctor would still need to explore all options for removing, killing or slowing the tumor.

And so it goes with MnDOT. The NTSB seems to have done excellent work examining the strictly technical issues behind the collapse. But for whatever reason, it stopped short of delving into the human and process issues.

I have no interest in villifying MnDOT. They do amazing work that keeps us safe, and keeps our society and economy humming along. I just want to see a great agency get better. There was a gap between inspectors seeing the flawed U10 gusset plate and MnDOT doing anything about it. To prevent future catastrophes, NTSB needs to help us understand the reasons for that gap.

– Loveland

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Strib Gets Bent

The Star Tribune’s Tony Kennedy deserves some love for his story pointing out the bent I35W bridge gusset plates in photos that apparently were in the hands of the Minnesota Department of Transportation (MnDOT) five years prior to the I35W bridge collapse.

In mid-January of this year, the National Transportation Safety Board (NTSB) announced that flawed gusset plates were to blame for the collapse. The news that day read:

In a Washington news conference, NTSB Chairman Mark Rosenker also said there were no indications that Minnesota’s upkeep of the bridge played any role in its collapse — a statement that immediately unleashed political debate, with Gov. Tim Pawlenty scolding critics for leaping to conclusions and DFLers insisting that the full cause has yet to be found.”

The fact that these bent gusset plate photos were in state officials’ hands in 2005 seems to suggest that the bridge safety inspection could have been better.

Journalists have more digging to do, because we need to know what happened with these photos. Did inspectors not see the bending? Did they see them, but conclude it wasn’t a serious problem? Did inspectors conclude it was serious problem, but conclude that all potential fixes were more dangerous than the problem itself? Or did the safety inspectors recommend a solution that was shot down higher up the food chain? If so, did the leadership forgo repairs because of technical concerns or budgetary concerns?

For me, this kind of dispassionate questioning isn’t about blaming Pawlenty, Molnau or committed MnDOT employees. This is about learning from any mistakes, so we can build a better safety oversight system that keeps Minnesota bridges upright in the future.

The rest of us don’t have the time to schlep through hundreds of photos with straight edge rulers up against gusset plates. I’m grateful at least one newsroom in town does.

– Loveland

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