UPDATE: Feds look for temporary fix after I-5 collapse

“You cannot overstate the importance of this corridor to Washington state,” Gov. Jay Inslee said. Traffic on I-5 and surrounding roads was backed up for miles, a situation the governor said would continue indefinitely.

Officials were looking for a temporary, pre-fabricated bridge to replace the 160-foot section that failed, Inslee said Friday. If one is found, it could be in place in weeks. If not, it could be months before a replacement can be built, the governor said.

The spectacular collapse unfolded about 7 p.m. Thursday on the north end of the four-lane bridge near Mount Vernon, about 60 miles north of Seattle and 40 miles south of the Canada border.

“He looked in the mirrors and it just dropped out of sight,” Cynthia Scott, the wife of truck driver William Scott, said from the couple’s home near Spruce Grove, Alberta. “I spoke to him seconds after it happened. He was just horrified.”

The truck made it off the bridge, but two other vehicles went into the water about 25 feet below as the structure crumbled.

Dan Sligh and his wife were in their pickup heading to a camping trip when he said the bridge before them disappeared in a “big puff of dust.”

“I hit the brakes and we went off,” Sligh told reporters from a hospital.

Bryce Kenning, of Mount Vernon, said the bridge seemed to explode in front of him. The 20-year-old slammed the brakes and could see the edge of the pavement approaching, but there was nothing he could do.

“It was like time was frozen — like a roller coaster where you’re not attached to the tracks,” Kenning said in a phone interview. “I’m sure it was just one of the loudest sounds ever to hear this thing explode and fall into the water like that, but I didn’t hear a thing. I just witnessed it happening in front of me.”

The permit specifically describes the route the truck would take, though it includes a qualification that the state “Does Not Guarantee Height Clearance.”

It’s not rare for trucks to strike bridges in Washington state — it’s just that such accidents don’t usually cause the structures to collapse.

The state DOT said there were 21 bridge-strikes involving trucks last year, 24 in 2011 and 14 in 2010.

There were no signs leading up to the Skagit River bridge to warn about its clearance height. State Transportation Secretary Lynn Peterson said that under federal and state standards, the clearance is tall enough to not require signage.

Inslee said it will cost $15 million to repair the bridge. The federal government has already promised the state $1 million in emergency funding.

Traffic could be affected for some time. The bridge is used by an average of 71,000 vehicles a day, so the roadblock will cause a major disruption in trade and tourism.

The closest detour is a bridge about a quarter mile east of I-5, which is mostly used by local traffic between Mount Vernon and Burlington. Officials are also recommending detours using state Routes 20 and 9 that add dozens of miles to a trip.

The bridge that collapsed was inspected twice last year and repairs were made, Peterson said. It was not classified as structurally deficient, but a Federal Highway Administration database lists it as “functionally obsolete” — a category meaning that the design is outdated, such as having narrow shoulders and low clearance underneath.

The 1,112-foot-long bridge, with two lanes in each direction, has four spans, or sections, over the water supported by piers. It’s a steel truss bridge, meaning it has a boxy steel frame.

The span on the north side is the one that collapsed.

The mishap was reminiscent of the August 2007 collapse of an I-35W bridge in Minneapolis that killed 13 people and injured another 145 when it buckled and fell into the Mississippi River during rush-hour.

The National Transportation Safety Board determined that the Minneapolis bridge failed because steel gusset plates that connected the structure’s beams and girders were too thin.