Work Begins on Temporary Span to Replace Collapsed I-5 Bridge

This story appears in the June 3 print edition of Transport Topics.

Crews in Washington state were constructing a temporary span last week to replace a section of bridge on Interstate 5 that collapsed May 23, apparently after it was struck by a truck carrying an oversize load.

Officials said they hope to complete the temporary span over the Skagit River by the middle of this month and finish a permanent bridge this fall.

“We will install a temporary span on the bridge that will restore traffic while we build a safe and durable permanent span adjacent to it,” said Gov. Jay Inslee (D). “This plan ensures the economic vitality of Washington state and the communities along this important corridor.”

An estimated 71,000 vehicles a day crossed the bridge, built in 1955, including more than 7,800 trucks.

Truckers and other motorists have been spending an additional hour to detour around the bridge, said Jim Tutton, vice president of the Washington Trucking Association.

About 1 million trucks cross the U.S.-Canada border on I-5 each year, and a large percentage of those also cross the Skagit River bridge, said Louise Yako, executive director of the British Columbia Trucking Association.

The bridge is about 60 miles north of Seattle and 50 miles south of the Canadian border.

The Washington State Patrol said a truck operated by Mullen Trucking, Aldersyde, Alberta, was responsible for the collapse.

Ed Scherbinski, vice president of Mullen, confirmed his company’s truck was involved but did not say whether the truck caused the collapse. He told Transport Topics the National Transportation Safety Board has asked the company not to speak publicly about the incident.

Three motorists were injured when their vehicles fell into the river. The truck driver drove across the bridge before the collapse.

“The load was equipment casing for a drilling rig,” Sgt. Kirk Rudeen, a WSP spokesman, told TT. “It’s kind of a big huge steel box . . . that has the four walls, but the inside is clear.”

The load was 15 feet, 9 inches tall, but the bridge’s clearance was as low as 15 feet, 6 inches at the outer edge, NTSB Chairwoman Deborah Hersman said.

The Washington State Department of Transportation said it granted Mullen a permit for the load, However, the permit does not guarantee the clearances along the route.

The flatbed carrier operates about 130 trucks. It is a unit of Mullen Group, which has a variety of trucking operations and ranks No. 51 on the TT Top 100 list of the largest for-hire carriers in the United States and Canada.

For the two years ended April, Mullen Trucking was involved in only three U.S. accidents, none of which involved fatalities or injuries, according to Federal Motor Carrier Safety Administration records.

Its scores in FMCSA’s Compliance, Safety, Accountability program are better than the average of similar companies in all categories visible to the public, including being in the top 3.1% of similar carriers in the unsafe driving category.

Washington state does not post signs for bridge clearances higher than 14 feet, 6 inches, so Mullen had to rely on the state’s clearance data, which is not guaranteed to be correct, Scherbinski said.

The truck was following an escort car with a pole raised to the height of the load. That’s car’s role is a subject of NTSB’s investigation, Hersman said.

NTSB also said in a May 28 statement the truck had one flaw that would have put it out of service, but that did not contribute to the incident.

Truss bridges built around the time of the 58-year-old I-5 bridge generally have no redundant systems to hold the bridge’s load if a truss is compromised, said Kirk Grimmelsman, a professor of civil engineering at the University of Arkansas.

The truck’s load damaged one of the truss’ pieces, also known as a member, Grimmelsman said.

“If you have a failure of one member, it can bring down the whole structure,” he said. “A lot of the failures of bridges in the past have been based on redundancy issues.”

Modern bridge standards include redundant systems, Grimmelsman said.

When the I-5 span opens, it will have a speed lower than the current 60 mph, WSDOT spokesman Travis Phelps said. The structure also will not accommodate trucks heavier than 80,000 pounds.

WTA’s Tutton said he was happy to see the state work fast to fix the bridge.

“It’s certainly much better than we expected in terms of the time delay. We’re certainly hopeful that the timeline put in place by the Department of Transportation holds true,” he said.

Meanwhile, Rep. Janice Hahn (D-Calif.), a member of the House Transportation and Infrastructure Committee, asked Chairman Rep. Bill Shuster (R-Pa.) for a hearing on bridge safety.

Hahn cited a May 26 bridge collapse in Missouri, which took place after two freight trains collided in Scott County, according to NTSB.