Crews from the Minnesota Department of Transportation are working an aggressive schedule to complete a new bridge spanning the Mississippi River in St. Cloud by this fall.
The DeSoto Bridge, which runs over the river along Highway 23, was one of four bridges flagged for inspection by MnDOT following the collapse of the I-35W bridge in Minneapolis in August 2007, killing 13 people.
At that point, crews suspected bent gusset plates caused the 35W bridge to collapse. The DeSoto Bridge had a similar design, along with the Highway 123 bridge over the Kettle River in Sandstone, a bridge in Sauk Rapids, for which replacement was already underway at the time of inspection, and the bridge over the St. Croix River to Osceola, Wisconsin.
MnDOT spokeswoman Judy Jacobs says all four bridges looked fine at the time of inspection. Then in March of last year, crews found problems at the DeSoto Bridge during a routine inspection.
"They did find that the gusset plates on the St. Cloud bridge were starting to buckle," she said. "They were buckling just a tiny-it was essentially a quarter of an inch buckle, but for safety reasons they decided to close down the bridge because the 35W bridge had set a precedent."
So MnDOT accelerated plans to replace the St. Cloud bridge, which was tentatively scheduled for construction in 2010. Jacobs says they didn't want to take any chances.
Project inspector Jesse Hudec says the new bridge, dubbed the Granite City Crossing, is a redundant bridge, which means every aspect of the bridge is tied together with concrete and steel for a strong support system.
The previous bridge, like the 35W bridge, was not, which meant if one aspect of it failed, all of it would fail.
"It had two main support structures that were tied together with pins and plates with various cross bracing... had two main supports... versus this has six beams, girders across," he said.
Girders are the main support structure for the bridge deck. Hudec says they've built piers to allow an additional 8 to 10 feet on each side so crews can add extra traffic lanes in the future.
The new bridge will also feature a wider pedestrian walkway that will have outlook areas.
MnDOT officials say they are on budget and on schedule to open to traffic by November.