T.Y. Lin International

T.Y. Lin International New bridge features extradosed design. renderings courtesy of ty lin international

When the Minnesota and Wisconsin transportation departments first tried to build a bridge across the St. Croix River near Minneapolis in 1995, the Sierra Club thwarted them. Over a decade later, the Sierra Club is trying to stop them again.

The Sierra Club  filed suit in U.S. District Court in Minneapolis on June 5 against the U.S. Dept. of Transportation, the U.S. Dept. of the Interior, the National Parks Service, and the Federal Highway Administration. It seeks an injunction to stop a project that it claims violates the Wild and Scenic Rivers Act.

It echoes a 1996 lawsuit in which the Sierra Club sued to force the parks service to conduct an evaluation under the same act. The service determined that the proposed segmental steel or concrete bridge would significantly damage “the scenic and recreational value” of the river, barring FHWA from funding the project.

The new preferred alternative, chosen through stakeholder involvement, has an extradosed design, a hybrid cable-stayed and segmental box structure (ENR 2/19 p. 14). The four-lane, 106-ft-wide, 4,893-ft-long bridge is designed by San Francisco-based T.Y. Lin International and was chosen in part because it only will use five piers to span the 2,840-ft-wide river, says Nick Thompson, Minnesota Dept. of Transportation area manager.

The extradosed design will allow for a tower height of only 60 ft above the deck, which would reach a maximum 159-ft clearance above the river. Construction is estimated at $484 million, if it begins in 2010. The two states also plan to spend $16.5 million on environmental mitigation and $7 million to convert the old lift bridge, now carrying some 60,000 daily vehicles, into a pedestrian structure.

The design and mitigation package has satisfied all 28 stakeholders, except the Sierra Club. “We took extraordinary steps to develop a mitigation process that meets the demands,” says Thompson. Adds Tom Bradley, superintendent of the St. Croix National Scenic Riverway: “The last proposal was in a context that was very different than today. The old design was pretty much off the shelf.” The new design is “much more elegant.”

But the Sierra Club sees the mitigation package as insufficient. “None of the mitigation proposals will reduce the visual impact of this project,” says Mat Hollinshead, transportation committee chairman of the group’s North Star Chapter.  “From our perspective, it doesn’t matter what type of superstructure you put on the bridge—it eliminates the expanse of the view.”

MinnDOT officials note that President George W. Bush in 2002 issued an executive order to streamline environmental reviews for seven projects nationwide, including the St. Croix bridge.