The National Transportation Safety Board got the cause of the Interstate 35W bridge collapse wrong, the lead attorney for most victims of the disaster claimed Wednesday.
Attorney Chris Messerly said experts from the engineering firm Thornton Tomasetti Inc. told survivors and families of victims Tuesday night that the "initiating event" wasn't the fracture of a key gusset plate in the bridge, but the failure of a horizontal beam called a chord. The firm was hired by a group of attorneys who are representing 117 families of victims and survivors for free.
Messerly said the experts concluded that the "L9-L11 west" chord buckled because of heat stress on the bridge that day, the weight of construction materials on it, and frozen roller bearings that prevented the bridge from expanding as it should have to handle the heat. The engineers said the chord failure then caused the "U10 west" gusset to fail, Messerly said.
The firm has yet to produce a report on its findings, which Messerly said show that URS Corp., an engineering consultant that analyzed the bridge before it fell, is partially to blame for the collapse. Messerly said the families' attorneys have photographic evidence that the state of Minnesota and URS knew the roller bearings where the bridge sat on its concrete supports were corroded and couldn't move.
The bridge collapsed Aug. 1. 2007, killing 13 people and injuring 145.
The NTSB concluded last November that the bridge collapsed because the gusset plate was half as thick as it should have been, due to a flaw in the original design from the 1960s. Board members also criticized Minnesota officials for allowing 287 tons of construction materials to be stockpiled on the bridge's center on the day of the collapse.
The NTSB's conclusion pointed to the bridge's designer, Sverdrup & Parcel, which can't be sued because the firm has dissolved and the statute of limitations on design errors has run out.
Messerly said his legal team plans to use the Thornton Tomasetti study when they file suit, probably in May, against URS and Progressive Contractors Inc., which was resurfacing the bridge when it collapsed.
They can't sue the state, which owned the bridge, because their clients gave up that right when they accepted compensation from a $36.4 million fund set up by the Legislature, though other victims have until April 16 to decide whether to take the state money.
NTSB spokesman Terry Williams declined to comment, as did URS. Kyle Hart, an attorney for PCI, expressed skepticism about Thornton Tomasetti's conclusions.
"Obviously I'm interested in hearing anybody else's theories but I would tend to doubt the validity of that one," Hart said.
Four other victims have already sued URS and PCI. PCI is seeking to add the state and Jacobs Engineering Group Inc., the successor company of the bridge's designer, as defendants in that lawsuit.
Messerly said PCI piled construction materials on the bridge that weighed as much as a Boeing 747, when it should have stored the materials for the resurfacing project elsewhere.
Hart said PCI doesn't accept all the NTSB's findings, but that the company contends it's not at fault.
"It's not surprising that they're going to name everybody — that's to be expected," Hart said. "But the key thing is nobody has demonstrated the amount of weight we had on the bridge was improper. ... If the bridge had not been improperly designed everybody says it would have held up that weight easily."
For now, Messerly said, the survivors and attorneys are calling for a nationwide inspection of roller bearings on all similarly designed bridges, and say that any roller bearings found to be frozen should be fixed.