An oversize truck caused the Interstate 5 bridge collapse into the Skagit River, the Washington State Patrol said Friday.
The truck, which was hauling drilling equipment, made it across the bridge and the driver remained on scene, cooperating with investigators. Two vehicles plunged into the Skagit River in the Thursday evening bridge collapse. Three people were rescued and are recovering.
"For reasons unknown at this point in time the semi struck the overhead of the bridge causing the collapse," Washington State Patrol Chief John Batiste said.
The collapse occurred at about 9 p.m. CT, or 7 p.m. local time in an area between Burlington and Mount Vernon, Wash.-- about 60 miles north of Seattle.
The trucking company said it received a state permit to carry its oversized load across the bridge, and their equipment-hauling plans were approved by the Washington Department of Transportation.
I-5 BRIDGE DESIGN 'FUNCTIONALLY OBSOLETE'
The bridge design is not similar to the old Interstate 35W bridge that collapsed in Minneapolis. The design is described as a "through-truss" bridge, which is similar to the Stillwater Lift Bridge.
The bridge is not considered structurally deficient but is listed as being "functionally obsolete" -- a category meaning that their design is outdated, such as having narrow shoulders are low clearance underneath, according to a database compiled by the Federal Highway Administration.
STATE OF WASHINGTON BRIDGES
The I-5 bridge was built in 1955 and has a sufficiency rating of 57.4 out of 100, according to federal records. That is well below the statewide average rating of 80, according to an Associated Press analysis of federal data, but 759 bridges in the state have a lower sufficiency score.
According to a 2012 Skagit County Public Works Department, 42 of the county's 108 bridges that are 50 years or older. The document says eight of the bridges are more than 70 years old and two are over 80.
Washington state was given a C in the American Society of Civil Engineers' 2013 infrastructure report card and a C- when it came to the state's bridges. The group said more than a quarter of Washington's 7,840 bridges are considered structurally deficient of functionally obsolete.
It also was not known what caused the collapse of the bridge about 60 miles north of Seattle in Skagit County, which stretches from the North Cascades National Park to a cluster of islands off the Washington coast.
'JUST A LOUD BANG'
"It's not something you see every day," said Jimmy O'Connor, the owner of two local pizza restaurants who was driving on another bridge parallel to the one that collapsed. "People were starting to crawl out of their cars."
He said he and his girlfriend were about 400 yards away on the Burlington Bridge when they heard "just a loud bang."
"Then we looked over and saw the bridge was down in the water," he said.
He pulled over and saw three vehicles in the water, including a camping trailer that landed upside-down, he said.
Xavier Grospe, 62, who lives near the river, said he could see three cars with what appeared to be one person per vehicle. The vehicles were sitting still in the water, partially submerged and partly above the waterline, and the apparent drivers were sitting either on top of the vehicles or on the edge of open windows.
"It doesn't look like anybody's in danger right now," Grospe said.
Helicopter footage aired by KOMO-TV in Seattle showed several rescue boats at the bridge collapse scene with several ambulances waiting on the shore. One rescue boat left the scene with one person strapped into a stretcher.
A damaged red car and a damaged pickup truck were visible in the water, which appeared so shallow it barely reached the top of the car's hood.
Information from the Associated Press was used in this report.