Posted: 01/15/08 16:36
by Dave Mindeman
The NTSB report is focusing on a design flaw in the gusset plates. But before the administration's defenders go into a new series of "I told you so", let's look at the unanswered questions.
First of all, as an aside, I find it interesting that this "updated" report comes out less than a month before Minnesota's legislative session. With Pawlenty's hired investigation team collaborating with the NTSB, the timing is certainly interesting.
But aside from that, here are my questions:
I will concede that there is no way the current administration could have known about a design miscalculation going back to the construction of the bridge. But that was 40 years ago, and I refuse to believe that 13 people were simply destined to die because somebody didn't fine tune their slide rule.
Here are my concerns:
Going back to early inspections (Star Tribune, 10/18/07):
In 1993, a state inspector found that the half-inch gusset plate had lost nearly half of its thickness in some spots due to corrosion along an 18-inch line, but no repairs were ordered, according to Minnesota Department of Transportation records.
Granted, MnDOT was assuming that the original gusset plate was sufficient for bridge stability, but if this inspection saw a reduction in thickness to 1/4 inch in places, wouldn't that be cause for concern regardless?
The other item that has always raised a red flag to me:
MnDOT officials had long known from their inspections that the bearings were not working correctly because of corrosion and buildup of debris. And in July 2006, a consultant's report highlighted the problem. "The bearings are not allowing the structure to move linearly with changes in the ... temperature," the report said.
Roller bearings recovered from the river are stacked neatly in the NTSB's secure area for inspection. One of the structural engineers who asked not to be named said the bearings appear to be lacking marks of wear, indicating they may have been locked up or their movement restricted by debris and corrosion.
The gusset plates didn't just suddenly give. They reacted to stress. The NTSB has talked about the added weight from the construction and also the 91 degree heat playing a stress factor. Even if the plates were flawed, the roller bearings could have reduced that stress if they had been in proper working order. The inspection evidence suggests that those bearings were never repaired.
This bridge has been under scrutiny for some time. Officials could not have known that the design was flawed, but they could have made sure that the other problems outlined in the reports could have been fixed. Would working roller bearings have made a difference? Would the reinforcement recommended in 2006 have added some structural integrity? Should someone have asked more questions as gussets deteriorated from corrosion?
We don't know if any of these things could have prevented the disaster, but one thing is certain.... inspection reports revealed problems with this particular bridge for over a decade, yet there were no fixes, no reenforcement.
For 40 years that bridge held up. But in August of 2007, it fell. It looks like our state government is going to tell us there is nothing they could have done to prevent it. With so many other parts of our infrastucture aging and in need of repair..... is that the answer to the future of Minnesota transportation?
I hope not.
