NTSB: Thousands of U.S. bridges at risk of freak collapse

SEATTLE (AP) ? The collapse of an interstate highway bridge in northern Washington state should be a wake-up call that prompts an expansive safety review, according to the chairman of the National Transportation Safety Board.

Investigators need to establish a full account of what happened at the span over Interstate 5 about 60 miles north of Seattle and whether the same thing could happen elsewhere, Debbie Hersman said.

"At the end of the day, it's about preventing an accident like this," she said Saturday after examining the collapsed structure in the Skagit River.

The bridge came down last week after a truck bumped against the steel framework, prompting a collapse that sent two vehicles into the river. Three people involved escaped with non-life threatening injuries.

An investigation by The Associated Press suggests similar accidents could indeed happen elsewhere. Thousands of bridges around the U.S. are kept standing by engineering design, rather than sheer size or redundant protections. Such spans may be one freak accident or mistake away from collapse.

Bridge regulators call them "fracture critical" bridges, because if a single, vital component is compromised, they can crumple.

Hersman's team will spend about a week inspecting the I-5 bridge, talking to the truck driver whose vehicle hit it, and examining maintenance documents and previous accident reports.

Other over-height vehicles struck the Skagit River bridge before the collapse on Thursday, she noted. Investigators are using a high tech 3-D video camera to review the scene and attempt to pinpoint where the bridge failure began.

Hersman does not expect the investigation to delay removal of debris from the river or work on temporary replacement or repair plans. State and federal officials will work together on the investigation, she said.

They'll be watching for safety issues that could affect other bridges.

"The results can be very catastrophic," Hersman said. "We're very fortunate in this situation."

Washington state officials said Saturday that it will take time to find both short- and long-term fixes for the I-5 bridge.

While, the National Transportation and Safety Board finishes its inspection, state workers will begin removing debris from the river. Next, a temporary solution will be put in place to return traffic to Washington state's most important north-south roadway.

Inspectors say they are working to find out whether the collapse was a fluke or a sign of bigger problems.

A trucker was hauling a load of drilling equipment Thursday evening when his load bumped against the steel framework over the bridge. He looked in his rearview mirror and saw the span collapse into the water behind him.

Motorists should not expect to drive on I-5 between Mount Vernon and Burlington for many weeks and possibly months, said Washington Transportation Department spokesman Bart Treece.

About 71,000 vehicles use that stretch of highway every day.

Officials were looking for a temporary, pre-fabricated bridge to replace the 160-foot section that failed, Gov. Jay Inslee said Friday. That option could be in place in weeks. Otherwise, it could be months before a replacement can be built, the governor said.

Inslee said it will cost $15 million to repair the bridge. The federal government has promised $1 million in emergency dollars and more money could come later, according to Washington's congressional delegation.

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Contact Donna Blankinship at https://twitter.com/dgblankinship

Source: http://news.yahoo.com/ntsb-says-wash-bridge-collapse-wake-call-081218583.html

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