The future of a proposed four-lane interstate bridge over the St. Croix River was in serious trouble Friday after the National Park Service, charged with enforcing federal laws on the river, turned thumbs down on the $700 million project.

The decision -- a reversal from Park Service support of the St. Croix River Crossing just five years ago -- rocked transportation advocates who had hoped to clear a recent court challenge and begin construction by 2013.

Building a bridge where one previously didn't exist would have "direct and adverse effects that cannot be avoided or eliminated," the Park Service said in its decision. The bridge at Oak Park Heights, south of Stillwater, also "would fundamentally change" the scenic qualities that existed when the St. Croix was designated a national wild and scenic river in 1972, the Park Service said. Because the Park Service administers federal laws on the river, Friday's decision probably means the bridge can't proceed unless Congress passes special legislation for it.

The Minnesota Department of Transportation (MnDOT), the lead agency in the bridge project, will review the decision and talk with federal highway administrators about the "best way to move forward," said engineer Todd Clarkowski, the project manager.

U.S. Rep. Michele Bach-mann, R-Minn., who represents Stillwater, expressed frustration that the long-stalled project has been delayed again.

"The determination by the National Park Service is extremely disappointing news after 20 years of planning for a new bridge," she said. "Minnesota and Wisconsin families would benefit by a new bridge to cross the St. Croix River in a safe and efficient manner, with minimal environmental impact. The current bridge is severely lacking in all of those qualities."

Bachmann said she would continue to support the St. Croix Crossing through a bill she introduced last March. It would give U.S. Interior Secretary Ken Salazar the power to approve the bridge. The bill has been referred to a subcommittee, but has drawn no cosponsors and no action has been taken.

"I'm very disappointed, really, really disappointed," said Gary Kriesel, a Washington County commissioner who represents Stillwater, where large traffic jams occur. "We are still going to continue to push until the bridge gets built."

But Chris Stein, superintendent of the Park Service's St. Croix National Scenic Riverway, said a new bridge "would forever change the look of the river." The U.S. Wild and Scenic River Act left the Park Service no choice but to reject the proposal, he said.

Planning for a new bridge to replace the 79-year-old Stillwater Lift Bridge began decades ago, but the Sierra Club challenged the latest attempt by contending in a lawsuit that the proposal violated federal law.

In March, U.S. District Judge Michael Davis blocked construction and wrote that a "massive" bridge south of Stillwater would have a "dramatic and disruptive" influence on the river's scenery.

Davis, who sits in Minneapolis, ruled that the Park Service couldn't authorize the bridge proposal or otherwise assist in construction until it better explained in a new evaluation why a new bridge wouldn't violate federal law.

The Sierra Club, chief foes of the plan, applauded Friday's announcement. The proposed bridge, which would allow semis to barrel through at 65 miles per hour, is a huge structure far different than what it would replace, said club spokesman Jim Rickard.

"Look, we're OK with a new bridge, but let's build one more in line with the one that's there today," Rickard said. MnDOT looked at several more modest bridge proposals that addressed the traffic needs while having less impact on the river, he said, but "unfortunately, for MnDOT, it was this alternative or nothing."

Besides the environmental concerns, the cost of the bridge project was out of line at a time when government budgets are short, Rickard added.

"Our argument all long is that the job of National Park Service is to preserve and protect our natural resources," he said. "We applaud them for sticking to their core mission."

Several stakeholders had combined efforts to better sell the bridge proposal with environmental additions, such as a loop trail, shoreline improvements and wetlands preservation. "We operated all along in good faith with this project," Stein said Friday. "We can only do what Congress says we can do."

Kevin Giles • 651-735-3342 Jim Anderson • 651-735-0999