MINNEAPOLIS -- The chairman of the House Transportation Committee criticized federal investigators Sunday after a published report said they have determined an original design flaw is the most likely reason for the collapse of the Interstate 35W bridge in Minneapolis.
National Transportation Safety Board investigators believe the bridge's original designers probably neglected to calculate the size of key gusset plates -- devices that help connect steel beams -- that eventually failed, the Star Tribune of Minneapolis reported.
Investigators also determined that corrosion of certain gusset plates, extreme heat and shifting piers did not contribute to the bridge's collapse, the newspaper said, citing unnamed sources with direct knowledge of the probe.
Rep. Jim Oberstar, a Minnesota Democrat, was skeptical of earlier suggestions from the NTSB that gusset plate design was responsible for the bridge collapse, and on Sunday held to that view.
"It stretches both credibility and past experience with bridge structural failure to find causation through a single factor," Oberstar said, also criticizing the NTSB for what he said "appears to be a selective leak."
"I can't recall a previous leak of critical information in so serious an investigation as this one," he said.
Kevin Gutknecht, spokesman for the Minnesota Department of Transportation, said his agency would wait for the official release of the report before commenting.
The bridge collapsed during the evening rush hour Aug. 1, 2007, killing 13 people, injuring 145 and leading to a closer examination of bridge safety in Minnesota and throughout the country.
NTSB chairman Mark Rosenker has indicated previously that flawed gusset plates were a focus of investigators' efforts. According to the Star Tribune's sources, investigators believe that if key steel gusset plates been designed properly at an inch thick instead of half an inch thick, the bridge would have held up under tons of concrete and steel that were added in two renovation projects -- and under the 287-ton construction load on the bridge the day it collapsed.
The NTSB is scheduled to discuss a draft report of investigators' findings at a public hearing in Washington on Nov. 13. Oberstar also criticized the NTSB, as he has previously, for what he believes has been an overly secretive approach to the investigation.
"The board chairman persists refusing to subject the NTSB's investigation to an open hearing," he said.