Skagit River bridge collapse: Looking for a temporary fix (+video)

It may be months before the I-5 bridge over the Skagit River near Seattle is repaired. Until then, authorities are considering a temporary bridge of the type used in Europe during World War II.

By , Staff writer

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    Workers inspect a damaged beam on a section of bridge adjacent to a collapsed portion of the I-5 span at the Skagit River in Mount Vernon, Wash. A truck carrying an oversize load struck the four-lane bridge, sending a section of the span and two vehicles into the river.
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The I-5 bridge that got clipped by a truck and fell into the Skagit River in Washington State may have been old, its design officially “functionally obsolete.” But the temporary fix to get traffic moving again along this busy highway corridor linking Seattle north to Canada may be of a type that’s even older.

Authorities are considering a “Bailey Bridge” like the ones used in World War II to get Allied tanks and other military vehicles across rivers in Germany and Italy after D-Day. Such bridges are designed to be portable and temporary, constructed quickly then taken apart to be used elsewhere.

The Washington State Department of Transportation built a 180-foot Bailey Bridge over the Chehalis River in 2007, after a flood washed out a county bridge, the Seattle Times reports.

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For highway use, such bridges can clear spans up to 200 feet long, according to Bailey Bridges, Inc. in Fort Payne, Ala. The I-5 bridge over the Skagit River is 160 feet long, so the idea there is feasible.

For such a system to work, however, the existing concrete piers under the bridge’s road surface would have to be sound.

That’s just one of the things state and federal authorities need to investigate as they piece together what happened to send a portion of the bridge plummeting into the river Thursday evening, then figure out a permanent solution.

“Patience is going to be the watchword,” Gov. Jay Inslee said at a press conference Friday.

Gov. Inslee, a former member of Congress who won the governorship last year, says it will cost $15 million to repair the bridge, which averages 71,000 vehicles a day. Meanwhile, other bridges crossing the Skagit have backed up traffic through residential and business areas.

What’s known for sure so far is that a truck with a large load clipped one of the metal trusses that are part of the essential design holding up the bridge. That section of the bridge collapsed immediately, sending a pickup truck and an SUV into the river. No one was killed, and injuries to drivers and passengers were minor.

While the Federal Highway Administration lists the bridge as "functionally obsolete” because it’s an old design, it had not been classified as structurally deficient.

The bridge has a maximum clearance of about 17 feet – higher than the truck’s load in this case – but the clearance curves down to 14 feet 5 inches along the sides, where the collision occurred. The tractor-trailer was hauling drilling equipment southbound.

The truck’s owner – Mullen Trucking in Alberta, Canada – had a permit to carry the oversize load on the Interstate 5 highway. The driver has not been cited for any infractions.

It's not rare for trucks to strike bridges in Washington State, the Associated Press reports. The state Department of Transportation lists 21 bridge-strikes involving trucks last year, 24 in 2011, and 14 in 2010.

Officials performed a special inspection six months ago on the bridge that collapsed because there were indications it had been struck by a different vehicle.

A report released Friday said the checkup was done due to "impact damage," and inspectors identified tears, deformations, and gouges on the northbound side of the bridge.

In that Nov. 29, 2012, impact, an overheight truck struck a metal overhead truss on the bridge. An inspection crew determined the bridge to be safe, with only minor repairs required. Those repairs were added to an existing list of bridge maintenance items to be completed at a future date.

The collapse of the bridge north of Seattle highlights recent calls by President Obama and state officials to repair the nation’s infrastructure.

“Regardless of how this happened, the collapse of the Skagit River Bridge in Washington State is a timely reminder of our nation’s need to invest in critical infrastructure upgrades,” Ed Rendell, Co-Chair of Building America’s Future and former Governor of Pennsylvania, said in a statement. “Our nation’s bridges, roads and highways are deteriorating before our eyes, and today’s incident was a call to action,”

“According to our report ‘Falling Apart and Falling Behind,’ America currently has more than 69,000 structurally deficient bridges, many of which haven’t been updated in decades,” Mr. Rendell said. “If the US wants to remain competitive in the global economy and provide safe, efficient transportation systems for our nation, then I urge state and local officials to act now and find creative ways to fund these projects, so that future collapses and accidents can be avoided.”

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