Limited disruption planned to bring replacement I-5 bridge online

By David Tanner, Land Line associate editor | 7/15/2013

Washington state’s bridge construction team has some big plans for just after Labor Day. That’s when they’ll bring their permanent replacement online for the Skagit River Bridge on Interstate 5 north of Seattle, and they’ll do it without disrupting traffic for more than a few days. Traffic has been using a temporary span since a few weeks after a bridge section collapsed May 23.

State DOT spokesman Travis Phelps said crews have begun driving piles next to the original and temporary portions of the bridge.

“Essentially what they’re building is a platform to build the new permanent span on,” Phelps told “Land Line Now.”

“Sometime after the Labor Day weekend, they will shut down I-5 and use a rail system to move the temporary span out of the way and the new span into place.

Officials were initially planning a two-week disruption to traffic, but Phelps says the contractor is now planning on “just a few days.”

“It’s pretty intense work and it involves lifting an entire bridge, or two entire bridges, moving them out of the way and one into place,” he said. “It’s a big challenging bunch of work, and we’ll get this done quicker than originally anticipated.”

In the early evening hours of May 23, a trucker hauling a permitted over-height load and accompanied by a pilot car was operating in the right lane of the southbound lanes when the load struck an overhead bridge support. Seconds later, a 160-foot section of the bridge collapsed into the Skagit River. The truck made it across, but two passenger vehicles ended up in the river. Fortunately, no one died, and three people were rescued from the river.

The bridge was functionally obsolete, but was also deemed fracture critical – an engineering term. It applies to a structure that is one incident such as an earthquake or strike by a heavy vehicle from collapsing.

According to state and federal investigators in an ongoing investigation, the driver of the over-height vehicle, William Scott of Alberta, Canada, said he was “crowded” over to the right by an unidentified tractor-trailer that was attempting to pass him as the vehicles arrived at the bridge.

The structure that collapsed had 18 feet of overhead clearance down the center, but had just 14 feet, six inches of overhead clearance at the right shoulder. The trucker’s company, Mullen Trucking of Alberta, possessed a permit for 15 feet, nine inches and had been cleared by the state DOT to travel the I-5 route on that day.

The permanent replacement bridge is costing about $7 million.

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