Collapsed I-5 bridge had a history of vehicle strikes, investigators say

By David Tanner, Land Line associate editor | 5/28/2013

The federal agency investigating the bridge collapse on Interstate 5 north of Seattle says the bridge had a history of being struck by over-dimensional vehicles. The National Transportation Safety Board says the overhead structure of the Skagit River Bridge had visible damage from strikes that occurred through the years.

“Our team has looked back at the last 10 years of inspection records, and from that we can tell that this bridge has a history of over-height vehicle hits,” NTSB Chairman Deborah Hersman told the media by video conference.

The 60-year-old Skagit River Bridge carried 71,000 vehicles, including 6,500 commercial trucks, per day prior to a section collapsing on Thursday evening, May 23.

The collapse occurred seconds after an over-height load guided by a pilot car struck bridge supports. The trucking company, Mullen Trucking of Aldersyde, Alberta, Canada, had a legal permit to haul the load on a designated route that included the I-5 bridge. The truck was piloted by William D. Scott, age 41, of Spruce Grove, Alberta.

Hersman said inspection reports show an over-height vehicle struck the bridge as recently as Oct. 22, 2012.

“You can see with the naked eye visible damage and deformed metal in the first frame and in subsequent frames along the bridge – and again, this is from the last hit, last year,” Hersman said, pointing to a photo of the supports on an otherwise intact portion of the bridge.

“As you walk the bridge, you can see visible damage on other spans that is not so recent,” she continued. “Our team is obtaining inspection records going back further, and we will continue to look into the history of the bridge.”

Hersman said the overhead bridge supports were 18 feet above the bridge deck toward the center of the two-lane southbound span, but arched down to a 14-foot, 6-inch overhead clearance at the narrow right shoulder.

The truck load was permitted at 15-foot 6-inches, giving it clearance toward the middle of the double lane but not enough clearance at the right shoulder.

A driver of one of two passenger vehicles that plunged into the Skagit River told KIRO 7 in Seattle that another semi “pinned” the oversized load in the right lane as the vehicles arrived at the bridge.

A reporter asked Hersman about the likelihood of a different outcome had the truck been centered on the bridge instead of being in the right lane.

“If this vehicle had been traveling in the left lane, we likely would not have seen the bridge strikes that we saw, but we need to take measurements all the way through,” Hersman said.

Hersman said the NTSB will compare eyewitness testimony with video evidence gathered from multiple cameras that captured the collapse and the moments leading up to it.

“There are a lot of statements that are going to be put out there,” Hersman said. “Some of those statements might be conflicting. That is not unusual in our investigations to have conflicting witness statements. People see different things from different vantage points.”

NTSB hopes to have a preliminary report in 30 days, but a final report could take months.

The U.S. Department of Transportation announced $1 million in emergency funds to help Washington State build a temporary span while waiting on a permanent replacement.

Washington Gov. Jay Inslee said a temporary span could be up and running in June and a permanent replacement built by September.

“We will install a temporary span on the bridge that will restore traffic while we build a safe and durable permanent span adjacent to it,” Inslee announced on his website. “This plan ensures the economic vitality of Washington state and the communities along this important corridor.”

See related story including detour information and a link to eyewitness testimony:
I-5 bridge north of Seattle collapses after being struck by wide load

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