Daniel L. Dorgan, Minnesota's chief bridge engineer, defends his staff's decisions, while Robert J. McFarlin, assistant to the MNDOT commisioner, looks on.
The Minnesota Dept. of Transportation knew that a $9–million project to replace concrete overlay, expansion joints, lighting and guardrails on the ill–fated I–35W bridge over the Mississippi River would delay for months critical weld inspections. The inspections are necessary to define future repairs.
The agency defends its decision, however, saying that it did not find any unsafe connections across the bridge's steel deck trusses before construction work began.
"We intended to go back and resume inspection this fall," says Daniel L. Dorgan, bridge engineer for Minnesota Dept. of Transportation. The mostly cosmetic repairs were set to wrap up Sept. 30.
Acting upon the advice of San Francisco–based consulting engineer URS Corp., MNDOT began an inspection program in May for "suspected" weld details at 52 fracture–critical truss members.
In a supplemental report in January to follow up its 294–page draft report issued in July 2006, URS recommended three options: retrofit the fracture–critical truss members with steel plating and bolts to add structural redundancy; inspect and repair suspect welds or do a combination of the two.
URS added in its supplement that the plating method's "relatively high cost may not be justified by the actual levels of stresses the structure experiences."
Knowing those exact levels would have been difficult, as the bridge was not undergoing a continuous electronic load–monitoring program.
"We were handling this through the inspection program," says Dorgan. "Monitoring would have been very difficult given all of the critical locations." "Our decision was to pursue the inspection of the critical welds," Dorgan adds.
Agency reports indicated that the bridge was safe to operate and undergo deck resurfacing, says Minnesota Lt. Gov. and MNDOT Commissioner Carol Molnau.
"Was there any malice or ill–intention? The answer is no," Molnau says. The bridge was scheduled to be replaced around 2020.
Meanwhile, investigators are not commenting on whether or not the construction activity played a role in the bridge's collapse. URS says in a statement that it "has not been involved in any of the recent work being performed on the bridge, nor was the recent work related to the company's recommendations."
What is certain is that the I–35W bridge's well documented problem structural areas are under heavy scrutiny by federal officials investigating the Aug. 1 collapse.
"We are going line by line in those bridge inspection reports," says Mark V. Rosenker, chairman of the National Transportation Safety Board.
Before it collapsed, the structure had been inspected every year since 1993.