The Skagit River Bridge was listed as "functionally obsolete" by the Federal Highway Administration last year. NBC's Ayman Mohyeldin
The bridge that collapsed on Interstate 5 in northern Washington this week has a documented history of being struck by oversize trucks, federal investigators said Sunday.
The collapse of the bridge Friday night over the Skagit River in Mount Vernon, about 60 miles north of Seattle, left only three people with non-life-threatening injuries, but the National Transportation Safety Board called it a warning for the entire nation. Washington officials announced plans for a temporary replacement Sunday afternoon.
NTSB Chairwoman Deborah Hersman said Sunday that in addition to records listing previous so-called oversize hits — the most recent just seven months ago, on Oct. 22 — there is also visible evidence on the bridge of damage from years past.
Investigators said that when the truck hit the bridge Friday night, the concrete surface of the bridge deck slid off the girders, like frosting sliding off a cake.
Hersman said the 41-year-old driver told investigators that his first warning of a problem came at the moment of contact.
"He described hearing a boom and feeling contact in the vehicle," she said.
Investigators said this weekend that the driver had a proper permit for a load measuring 15 feet, 9 inches. He said he had rechecked the height of his load several times along his route.
But the bridge, at its lowest point, is only 14 feet, 6 inches high — which isn't posted anywhere, the NTSB said. That's because Washington state law doesn't require the clearance height to be posted unless it's less than 14 feet, 5 inches.
Gov. Jay Inslee said in a statement Sunday that the collapsed segment could temporarily be replaced within a few weeks by a pre-built four-lane bridge carrying traffic at reduced speed and capacity. If everything goes according to plan, a permanent replacement could be in place by late fall, he said.
The Federal Highway Administration last year listed the Skagit River Bridge as "functionally obsolete" — meaning it was structurally sound but had an outdated design. Tens of thousands of U.S. bridges have the same classification, in addition to about 66,000 that are labeled as even worse risks: "structurally deficient."
"This is a really significant event, and we need to learn from it, not just in Washington but around the country," Hersman said Saturday.
"The results can be very catastrophic," she said. "We're very fortunate in this situation."
This story was originally published on Sun May 26, 2013 5:34 PM EDT