The I-35W Bridge Collapse

At six oh five in the evening on August first, two thousand seven, the Interstate Thirty-Five West highway bridge over the Mississippi River in Minneapolis dropped into the water during the evening rush hour. It took about five seconds. The bridge was carrying one hundred forty thousand vehicles per day.

Thirteen people died. One hundred forty-five were injured. A school bus carrying sixty-three children was on the bridge; it stopped at the edge of a collapsed section. All the children survived.

The National Transportation Safety Board investigation determined the cause: the steel gusset plates connecting structural members at a critical joint in the bridge were only half an inch thick when they should have been at least an inch thick, a design flaw that had been present since the bridge was built in nineteen sixty-seven. In the forty years the bridge stood, inspectors had rated it structurally deficient multiple times. The Federal Highway Administration had put it on a watch list. Corrective action had been deferred. On the evening of August first, construction equipment and materials added to the usual traffic load exceeded what the inadequate gusset plates could bear.

The bridge was replaced within thirteen months. The replacement opened in September two thousand eight. At the site of the collapse, a small memorial park marks where the structure came down, with a granite ledger listing the names of the thirteen people who died.

The collapse produced a national conversation about deferred infrastructure maintenance that produced legislation, bridge inspections, and new standards. Whether that conversation produced adequate resources to address the accumulated deferred maintenance across the country's bridges and highways is a question that remains genuinely open.