MnDOT Considers Eliminating One Pier from St. Croix River Crossing

MnDOT is considering the possibility of reducing the number of piers in the water for the St. Croix River Crossing Project from six to five.

“We’re still assessing the possibility of going from six to five spans—eliminating a pier—so that would eliminate some of our environmental impact, make the design more efficient, reduce construction time and would definitely be a cost savings,” said Wednesday afternoon.

MnDOT will be making a decision about eliminating a pier in the next month or so, Chiglo said. When the decision is finalized, more information—including  diagrams of the design—will be made available to the public.

“The designers we have selected have experience working with this type of bridge in the U.S. and Canada,” Chiglo said, “and are looking at ways they can make this more efficient—eliminating a span is one of them.”

A design with six spans would have about 475 feet between each pier, Chiglo said. With a five-span design there would be about 570 feet between each pier.

The total span of the river crossing is about 5,080 feet.

One benefit of the five-pier design would be that is “defiantly eliminates having an (expansion) joint in the middle of the span,” Chiglo said. That would mean less noise.

A lot of the concern associated with this bridge is noise, Chiglo said. The noise from the bridge isn’t going to come from the deck, but rather the slapping of tires on the joints.

Expansion joints allow the bridge to move. When tires hit those joints, it makes a clicking noise.

“With the way the configuration is now, and the number of piers, I wouldn’t say there is definitely going to be a joint in the middle, but it is more likely with six piers than if we go down to five,” Chiglo said.

If MnDOT is able to go down to five piers, there will be one joint on the Minnesota side and one on the Wisconsin side, Chiglo said. But for the majority of the span there will be very few joints, in turn, reducing noise from the bridge.

“There is still going to be noise,” Chiglo said. “But this bridge type is going to be more conducive to minimizing that noise than others.”