Thursday, May 23, 2013, the Interstate 5 bridge over the Skagit River at Mount Vernon, state of Washington, collapsed. The immediate cause was a truck carrying an oversized load hitting the bridge. But a federal database had listed the bridge as “functionally obsolete.” This suggests that the feds knew that the bridge ought to have been repaired or replaced.
As someone who works on environmental problems, I am frequently asked what assurances we can have that an environmental problem will actually be solved, even when we know both the problem and the solution. My general answer is that, unfortunately, with most aspects of life that pose risks, we tend to muddle through — we fix things after they are broke, not when we know they are about to break.
This new bridge collapse happened close to the 6th anniversary of the August 21, 2007 collapse of the Interstate 35W bridge across the Mississippi River at Minneapolis, during evening rush hour, killing 13 people and injuring 145 others. The National Transportation Safety Board reported that the I-35W bridge collapsed because gusset plates broke, and they broke because they were too thin. Gusset plates are steel sheets used to connect beams and girders to columns or other weight-bearing structures on a bridge. The I-35W gusset sheets were ½" thick, said to be too thin. I would expect that somebody knew this beforehand, but haven’t found that evidence.
It may surprise you that people leaving bridges untouched that need fixing until they collapse has a very long history. A fascinating, small book published in 1897, titled English Wayfaring Life in the Middle Ages, tells the same story way back in those Middle Ages. Then, few people “wayfared” — actors, traders, brigands, soldiers, religious pilgrims, Lords and their retinues.
At first they would come to a river they needed to cross that did not have a bridge, and they would persuade the local farmer, whose land abutted the river, to row them across, for a small fee. If and when those wanting to cross became a crowd and made a good job in itself, the farmer would arrange to have a toll bridge built, typically out of stone. He would make a living off that bridge, and his sons and grandsons would inherit it.
A generation or two after its construction, pieces of the bridge would begin to fall off, and worrisome people would complain and say that the bridge would need to be repaired. But the typical answer was “It’s stood there for a century, so it’s still good.” And then the bridge would collapse, there would be a hew and cry, and people would get busy rebuilding it.
Having directed a number of projects whose goal was to solve an environmental problem, or at least find out from a scientific basis what was needed to solve it, I often reflect on the history of bridges and the long-standing human tendency to don’t fix ‘um until they’re broke. It’s muddling through. I hope that we can do better about our environmental problems, but this history isn’t exactly encouraging.
(The book is: Jusserand, J.J., ENGLISH WAYFARING LIFE IN THE MIDDLE AGES (XIVth Century). 1897, London: Paternoster Square, London: T. Fisher Unwin.)