White washing the i-35W bridge collapse: though it fell almost four years ago, questions still remain about the exact causes of the tragedy--and the National Transportation Safety Board's report has clone little to provide real answers for the worried public.

• Author: Lepatner, Barry B.
• Position: Infrastructure

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ON AUG. 1, 2007, the I-35W Bridge collapsed during rush hour, killing 13 people, injuring 145, and bringing massive economic disruption to the Twin Cities area. The November 2008 National Transportation Safety Board (NTSB) report, which followed 15 months of investigation, advised the public and transportation officials around the country that the bridge collapse was a one-time occurrence, caused by a design error that had gone undetected at the time of construction. In short, the collapse was a one-off from which no lessons could be learned to avoid future failures. That simply is not the case, as there is a desperate need for reform in the way we fund and maintain the nation's infrastructure.

NTSB tellingly ignored a host of critical factors that were not disclosed to the public or other state bridge operators, thus delegitimizing the efficacy of the report, which masked far more than it revealed about how the bridge was maintained, funded, and operated. NTSB claims that the bridge's collapse was the result of the under-design of certain gusset plates (metal plates used to connect structural members of a truss and hold them in position at a joint) at six nodes of the deck truss. These should have been an inch thick but, instead, were only half that.

Adding to the stresses on the too-thin gusset plates, the report states, were increases to the bridge's load. According to the NTSB, had all the gusset plates met design standards at the time of construction, then--even with the increased weight from the bridge's additions, the increase in traffic, and the weight of the construction materials and machinery--the collapse would not have occurred.

The reality is that the NTSB's findings virtually ignored 16 years of inspections by the Minnesota Department of Transportation that reflected the steady decline of the bridge. Widespread evidence of corrosion for critical steel members, frozen bearings that locked the structure in place, and cracks throughout the bridge and approach spans rendered its condition "poor," requiting that some of its Waffle lanes to be closed.

All of these critical factors were highlighted in several outside engineering reports commissioned by the Minnesota DOT. These reports, which detailed the frailties of this fracture-critical bridge--meaning the failure of one structural member would trigger the collapse of the bridge--made a series of recommendations, which went completely unheeded, for...