"This is a really significant event and we need to learn from it, not just in Washington but around the country," Debbie Hersman said after taking a boat ride on the Skagit River below the dramatic scene where a truck bumped against the steel framework, collapsing the bridge and sending two vehicles and three people falling into the chilly water.
Investigators need to find out what happened in Washington and if it could be repeated at similar bridges around the country, Hersman said.
"At the end of the day it's about preventing an accident like this," she said.
Her team will spend a week to 10 days looking at the bridge, talking to the truck driver whose vehicle hit it, and examining maintenance documents and previous accident reports.
Other over-height vehicles struck the Skagit River bridge before the collapse on Thursday, she noted. Investigators are using a high tech 3-D video camera to review the scene and attempt to pinpoint where the bridge failure began.
Hersman does not expect the investigation to delay removal of debris from the river or work on a temporary solution to replace or repair the I-5 span. State and federal officials can, and will, work together on the investigation, she said.
They'll be watching for safety issues that could affect other bridges.
"The results can be very catastrophic," Hersman said. "We're very fortunate in this situation."
Washington state officials said Saturday that it will take time to find both short- and long-term fixes for the bridge that collapsed on Interstate 5.
While, the National Transportation and Safety Board finishes its inspection, state workers will begin removing debris from the river. Next, a temporary solution will be put in place to return traffic to Washington state's most important north-south roadway.
Inspectors are working to find out whether the disintegration on Thursday of the heavily used span over the Skagit River, 60 miles north of Seattle and 40 miles south of the Canadian border, was a fluke or a sign of bigger problems.
"These things take time. We want to make sure it's done right, done thoroughly," Washington Transportation Department spokesman Bart Treece said.
A trucker was hauling a load of drilling equipment Thursday evening when his load bumped against the steel framework over the bridge. He looked in his rearview mirror and saw the span collapse into the water behind him.
Motorists should not expect to drive on I-5 between Mount Vernon and Burlington for many weeks and possibly months, Treece said.
Treece asked people to plan for an extra hour to make their way through detours around the collapsed bridge. There are three detour options northbound and two options southbound.
About 71,000 vehicles use that stretch of highway every day. Late Saturday morning, traffic was moving freely through the detours.
"We're expecting it to get worse as the day progresses," Treece said, noting that at 11 a.m., the cloudy skies and cool weather could be keeping Memorial Day weekend travelers at home.
State transportation officials began working on both a temporary solution and a permanent fix within hours of the bridge collapse, he said.
The goal is to get I-5 open as quickly as possible, while making sure the solution is as safe as possible, he added.
Officials were looking for a temporary, pre-fabricated bridge to replace the 160-foot section that failed, Gov. Jay Inslee said Friday. That option could be in place in weeks. Otherwise, it could be months before a replacement can be built, the governor said.
Inslee said it will cost $15 million to repair the bridge. The federal government has promised $1 million in emergency dollars and more money could come later, according to Washington's congressional delegation.
State officials approved Mullen Trucking in Alberta to carry a load as high as 15 feet, 9 inches, according to the permit released by the state. However, the southbound vertical clearance on the Skagit River bridge is as little as 14 feet, 5 inches, state records show. That lowest clearance is outside of the bridge's vehicle traveling lanes, Transportation Department communications director Lars Erickson said Friday. The bridge's curved overhead girders are higher in the center of the bridge but sweep lower toward a driver's right side.
The bridge has a maximum clearance of about 17 feet, but there is no signage to indicate how to safely navigate the bridge with a tall load.
At a news conference later Saturday, Hersman said Washington state does not require signage unless the clearance is 14 feet, 4 inches or less.
The permit specifically describes the route the truck would take, though it includes a qualification that the state "Does Not Guarantee Height Clearance."