Continued: Lanes close on Blatnik Bridge in Duluth for gusset plate repair

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Minnesota bridges rated: An interactive map of bridges that are "structurally deficient," "functionally obsolete" or have gusset plates like those on the I-35W bridge.

More information about the Blatnik Bridge and the work can be found at www.mndot.gov.

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Duluth is the latest Minnesota city with gusset plate troubles: Two traffic lanes on its main bridge to Superior were closed Tuesday because of concerns about the steel connector plates.

Emphasizing that the Blatnik Bridge is safe, the Minnesota Department of Transportation said the gusset plates are in good condition, but a review of engineering calculations found "less safety factor than we normally expect and want to achieve," said Dan Dorgan, state bridge engineer.

The plates, 16 in all, will be bolstered with additional steel over the next few weeks, with all work and inspections expected to be completed by mid-June. The lane closures will reduce loads on the bridge and provide room for contractors to work, Dorgan said. Two lanes remain open.

In January, federal investigators said undersized gusset plates played a role in the Aug. 1 collapse of the Interstate 35W bridge in Minneapolis. Gov. Tim Pawlenty ordered load recalculations of 25 steel truss bridges in Minnesota, including the Blatnik Bridge and the recently closed DeSoto Bridge on Hwy. 23 in St. Cloud. The review is expected to be finished by July 1.

The plates on the Blatnik Bridge were properly designed, Dorgan said. But when the bridge's deck was replaced in the early 1990s, the addition of 2 inches of concrete increased the weight.

Even so, "the bridge is safe," said Transportation Commissioner Tom Sorel, who traveled to Duluth on Tuesday with Dorgan. "In taking this action, we're erring on the side of caution," he said.

The bridge opened in 1961 and continues Hwy. 53 and Interstate 535 across the St. Louis River south of downtown Duluth. The bridge is co-owned by Minnesota and Wisconsin. Minnesota is coordinating the repair, and the two states, which conferred on the work, are splitting the cost, Sorel said.

Carrying about 29,500 vehicles a day, the Blatnik Bridge is the busier of the two highway bridges connecting Duluth and Superior. The Bong Bridge, about 2 miles upstream, sees about 17,700 vehicles a day, and its four lanes will remain open.

Jim Foti • 612-673-4491

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