State transportation departments in Minnesota and Wisconsin on Friday named Ames/Lunda Joint Venture as the apparent low bidder to build the superstructure for the new St. Croix River Bridge.

The $380 million bid substantially exceeds state engineers' estimates, but that's because contractors were required to bid both the price of bridge construction and place a dollar value on their time spent to complete the project.

Requiring contractors to submit costs for both establishes responsibility for timely completion of the work, said Jon Chiglo, the Minnesota Department of Transportation (MnDOT) engineer in charge of the project.

Chiglo said the amount of money bid on each of the two components will remain confidential until a contract is awarded in December, and MnDOT will pay only the construction portion of the bid.

MnDOT has estimated that the superstructure portion of the project will range from $285 million to $310 million.

Overall, the bridge project includes new approach highways in Minnesota and Wisconsin, environmental work and a loop trail through both states at a cost reaching $676 million.

Construction of highways on the Minnesota side of the St. Croix and foundations for the bridge began this summer.

Ames/Lunda was one of three contractors bidding on the superstructure under the requirement known as A + B bidding, Chiglo said. The same requirement was used to choose a contractor for the new Interstate 35W Bridge in Minneapolis, he said.

"It adds a different dynamic to the bidding process," he said.

The bid will undergo a review in coming weeks to determine whether Ames/Lunda should be awarded the work, but Chiglo said he doesn't expect any surprises.

"We're comfortable where we're at in terms of price," he said.

Other construction in the superstructure contract includes:

• The ramp bridge from Hwy. 95 to the river crossing (south of main bridge).

• The ramp bridge from the river crossing to Hwy. 95 (north of main bridge).

• The Hwy. 36 box girder approach bridge.

• A connecting structure between the river bridge and the Hwy. 36 approach bridge.

An extradosed bridge design (a cross between a girder bridge and a cable-stayed bridge) uses wire cables and box girders to carry the load. When completed, the St. Croix bridge will be the second extradosed bridge in the United States; the first is in Connecticut, MnDOT said.

Construction will take about three years to complete, with the bridge opening to traffic in fall 2016. Construction would start in December or early January, Chiglo said Friday.