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"The Lexington Bridge [I-35E over the Mississippi River], that was a fracture-critical bridge. MnDOT moved that up pretty aggressively. What was happening on the Lexington Bridge was crack migration in the steel in the I-beam."
Dorgan said no open dissension existed.
"It was talked about whether replacement was needed, whether we could keep it in service," Dorgan said. "That was the whole point of those studies. There was engineering discussion of that, but I'm not aware of anyone who was rankled, or a heated discussion."If there was a strong opposition, it was not voiced," he said.
MnDOT said Thursday that about 8 percent of all bridges in Minnesota, including the I-35W bridge, have been listed by the federal government as "structurally deficient," compared with 13 percent nationally. The label doesn't necessarily mean a bridge is unsafe, but in the case of the 1,907-foot bridge, inspections were increased from once every two years to once every year, officials said.
According to findings from the most recent inspection in June 2006, inspectors noted various cases of corrosion and cracking, but found no evidence of growth in pre-existing cracks, Dorgan said. Another inspection began early this year but was put on hold when work began on a $9 million contract to patch and improve the bridge's driving surface. Dorgan said he has seen no link between the surface work and the collapse.
"We considered the bridge fit for service," he said.
Still, as recently as December, MnDOT indicated a desire to reinforce the bridge by 2008 with steel plates. According to a newsletter distributed in January 2007 by the Minnesota chapter of the Associated General Contractors, MnDOT was intending to take bids in late 2007 on a project that would "retrofit some of the chord members on the steel deck truss of [the I-35W bridge over the Mississippi River]."The Department is looking for feedback and advice from contractors regarding the project staging and constructability," the newsletter said.
But Dorgan told the Star Tribune Thursday that plans changed. "We decided to handle it with inspections instead," he said. Gary Peterson, MnDOT's assistant bridge engineer, said plating would have required drilling thousands of holes in the bridge.
"If you take a look at drilling all of those holes in a bridge that is already fracture critical you could initiate flaws that might initiate a fracture," Peterson said.
The option to monitor through inspection was one of two suggestions given to the department in 2006 by URS Corp., a San Francisco-based construction management consultant.
Some close observers of MnDOT continued to speculate Thursday that the decision to monitor instead of fix deficiencies in the bridge was driven by financial concerns. Dave Semerad, CEO of the Minnesota chapter of the Associated General Contractors, said everything MnDOT does is based on cost-benefit analysis.
"Let's face it. They don't have any money," Semerad said. "At the end of the day, that's the issue. This is indicative of a long-term pattern."
Asked whether a lack of money was behind MnDOT's decision not to reinforce the bridge, MnDOT Metro District Engineer Khani Sahebjam said: "No, we would never do that because of money."