The National Transportation Safety Board has calculated that the Interstate 35 bridge in Minneapolis was carrying a total load of about 1.26 million pounds, or 630 tons, at the time of its collapse, with a little more than half of that sitting on the center span.
Thirteen people were killed and 145 injured when the bridge collapsed on Aug. 1, 2007.
The agency didn’t cite the weight as the cause of the collapse, but noted that the weight was concentrated directly above steel gusset plates that were found to be structurally deficient.
Stress at one of the two weakest points was 83 percent more than it could have handled, according to an interim report released earlier by the Federal Highway Administration.
The NTSB expects to reach a final conclusion on the cause of the collapse by the end of the year.