I-35W Bridge Collapse Findings Released


Although the NTSB previously cited too-thin gusset plates and construction project weights as factors in the collapse, yesterday’s update included drawings and tables that pinpointed the locations of those heavy loads on the structure. According to news reports this afternoon:

The Interstate 35W bridge over the Mississippi in Minneapolis collapsed last August after construction workers had put 99 tons of sand on the roadway directly over two of the bridge’s weakest points, according to a National Transportation Safety Board report.


More than 191 tons of construction material had been piled over the weakest areas of an interstate bridge that collapsed last August, according to federal investigators.

In a followup to a preliminary report released in January, the National Transportation Safety Board report that the piles of rock and sand were placed over steel plates that were thinner than they should have been.

Calculations by the agency have determined that the bridge in Minneapolis was carrying a 630-ton load at the time it fell into the Mississippi River. About half of that load was sitting on the center span.


The NTSB has uploaded investigative reports, photos and information submitted by the parties involved in the collapse here. Go to that link and check out all the data and reports.

I’m really fascinated by the photos in this particular report (pdf) especially with all the plates labeled and aerial (satellite?) photos of the bridge just hours before the accident.

Btw, where did those photos come from? Am I being photographed right now?

1 Comment so far

  1. mninvestmentproperty on March 21st, 2008 @ 11:40 pm

    That is just a amazing graphic. Nice article.

    So is anyone/any company going to be held liable for the damage?

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