U.S. Warns States After Potential Flaw Found in Minn. Bridge Design

August 10, 2007

Federal officials cautioned transportation authorities across the U.S. to re-examine bridges after investigators probing a deadly interstate bridge collapse in Minnesota said they found a potential design flaw.

The National Transportation Safety Board said that it found issues with the collapsed bridge’s gusset plates — the steel plates that tie steel beams together.

U.S. Transportation Secretary Mary Peters also advised states to consider the additional stress placed on bridges during construction projects. An 18-person crew was working on the Interstate 35W span when it collapsed last week during evening rush hour, killing at least five people and injuring about 100.

“Given the questions being raised by the NTSB, it is vital that states remain mindful of the extra weight construction projects place on bridges,” Peters said.

In an update of its work, the NTSB said helicopter observations had found several “tensile fractures” in the superstructure on the north side of the bridge, but nothing that appeared to show where the collapse began. Investigators were verifying loads and stresses on the beams, as well as materials in the plates.

NTSB investigators have also been looking into reports of wobbling before the Aug. 1 collapse.

The company that was doing the construction work, Progressive Contractors Inc., rejected a report that a worker noticed unusual swaying of the bridge in the days before its collapse. The company said it did not believe any of its work contributed to the bridge failure but hadn’t responded directly to claims of wobbling.

Officials of the Minnesota Department of Transportation would not comment on the significance of the gussets in the bridge’s collapse.

Even as the federal warning was issued, Navy divers continued probing the wreckage of the collapsed bridge for bodies, and officials said they expected removal of heavy debris to begin later than expected to give the divers more time.

At least eight people are missing and presumed dead. At least eight more were still hospitalized, one in critical condition.

Separately, President George W. Bush dismissed raising the federal gasoline tax to repair the nation’s bridges at least until Congress changes the way it spends highway money.

Bush’s comments came a day after U.S. Representative Jim Oberstar, the chairman of the House Transportation Committee, proposed a 5-cent increase in the federal gasoline tax to establish a new trust fund for repairing or replacing structurally deficient highway bridges. The idea was also quicly dismissed by the committee’s senior Repubilcan.

“Before we raise taxes, which could affect economic growth, I would strongly urge the Congress to examine how they set priorities,” Bush said in a news conference.

At the dive site, two large cranes were ready to go. But they sat idle as divers returned to the water doing “a very meticulous, hand-over-hand search of the scene,” said their spokesman, Senior Chief Dave Nagle.

Navy and FBI dive teams are trying to go deeper into the debris of the bridge than the local dive teams that have been working since the Aug. 1 collapse, police Capt. Mike Martin said. He expects it to be at least a week before cranes start regularly hauling out large pieces of debris.

The water where the divers are working ranges from 2 to 14 feet (4.3 meters) deep.

Debris removal had been expected to begin this week. The State Patrol said 88 vehicles have been located at the collapse site, including those in the Mississippi River.


Associated Press writers Chris Williams and Steve Karnowski in Minneapolis and Frederic J. Frommer in Washington contributed to this report.

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