STILLWATER, Minn. (AP) -- The governors of Minnesota and Wisconsin have written a joint letter to President Obama urging him to quickly sign the legislation that clears the way for a new bridge over the St. Croix River.

In a letter dated Tuesday, Republican Gov. Scott Walker of Wisconsin and DFL Gov. Mark Dayton of Minnesota say the two states have been working for decades to replace the current bridge, built in 1931.

An exemption from the Wild and Scenic Rivers Act passed the U.S. Senate in January and the House last week. That legislation was needed to advance the project.

An updated estimate from the Minnesota Department of Transportation pegs the project's cost at about $626 million -- down from an earlier projection of $633 million. With the president's signature, construction of the bridge could start in 2014.

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STILLWATER, Minn. (AP) -- Minnesota transportation officials have readjusted the cost of the new bridge over the St. Croix River at Stillwater.

The Department of Transportation now estimates the cost of the project at about $626 million -- down from an earlier projection of $633 million. MnDOT's Adam Josephson says some slight design changes and eliminating some work around a railroad helped lower the cost estimate. Josephson tells the St. Paul Pioneer Press some assumptions regarding inflation were also reworked.

MnDOT plans to build and test sample bridge foundations in the river this summer. Construction of the bridge, which replaces the aging lift bridge connecting Minnesota and Wisconsin, could start in 2014.

The project has finally gotten an exemption from the Wild and Scenic Rivers Act with passage by the U.S. House last Friday.