MOUNT VERNON, Washington — Officials with the National Transportation Safety Board said Saturday that when a truck carrying an oversize load hit the Interstate 5 bridge over the Skagit River, the concrete surface of the bridge deck “slid off the girders, like frosting sliding off a cake.”
At a Saturday afternoon news conference, NTSB Chairman Deborah Hersman said from the visible damage, investigators have identified compression buckles, compound fractures, and bending in the bridge frame that’s now in the water.
“The bending and buckling of the bridge is telling our investigators where the failure originated and how it propagated,” she said.
Hersman said investigators have interviewed the truck driver, and he described that his first indication of anything being wrong was when he heard and felt contact with the bridge. The driver pulled over and was told by another motorist that a portion of the bridge had fallen.
The 41-year-old driver said he had met the driver of the pilot car at the Canadian border and made arrangements with her to notify him of any problems via radio communication. He said he followed the pilot car and both were in the right lane as they crossed the bridge.
“The truck driver also reported that there was another commercial vehicle, traveling in the left lane, as he was on the bridge,” Hersman said.
Hersman added the truck driver had a permit for a load measuring 15 feet, 9 inches and he reported measuring the height of his load multiple times along the route.
But Hersman said the bridge portal is higher in the middle than it is on the outside corners near the shoulders.
“The permit was for 15 feet, 9 inches. This bridge, at its lowest point, the clearance is 14 feet, 6 inches. The bridge clearance, at its lowest point, that’s on the outside of the bridge near the shoulder — and as I mentioned, it’s an elliptical bridge, so you have more clearance towards the middle of the bridge — those clearances, those heights, are not posted on the bridge, and so it is the responsibility of the operator, solely to determine if they can clear through all of the structures on their route,” Hersman said.
Washington state does not require vertical clearance to be posted unless the clearance is 14 feet, 4 inches or less, Hersman noted.
Officials plan to interview the driver of the pilot car.
Despite the holiday weekend, they will have investigators out for several days, although they're not sure how long the investigation could take.
Officials are looking for a temporary, pre-fabricated bridge to replace the 160-foot section that failed. If one is found, it could be in place in weeks. If not, it could be months before a replacement can be built.
An average of 71,000 vehicles a day use the stretch of highway on the main route between Seattle and Vancouver, British Columbia.
Department of Transportation spokeswoman Kris Olsen said Friday they are working to get traffic running smoothly.
"We've been working really closely with the city of Mount Vernon to re-time signals, we've had our maintenance crews out here adjusting the detours," she said. "We're trying to find the right combination of what works for folks to keep traffic moving."
"We're never going to get it at free-flow at this point, but hopefully we can at last get it moving at a pace that's reasonable."
Olsen suggested that people traveling in the area allow for extra time.
"The area is still open; you just need to plan for it," she said.
Drivers are facing two, even three-hour delays because of bridge detours. Some companies are offering travelers an alternative to driving.
Amtrak said it plans to add one daily round-trip between Seattle and Bellingham.
In a statement, Amtrak, WSDOT, Sound Transit and BNSF Railway said they're working together to add the service. It would involve a morning departure from Seattle to Bellingham with an early evening return to help those who normally drive the route. Spokesmen said more details will be released as they become available.
Amtrak said its Amtrak Cascades service provides four trips each day over the Skagit River Rail Bridge, which remains fully functional.