A Polk County judge has stopped a riverfront construction project from moving forward after agreeing with plaintiffs that an apartment complex proposed for a bluff in Osceola, Wis., would be visible from the St. Croix River in violation of environmental protections.

The legal skirmish over the proposed 95-unit complex, called the Osceola Bluffs Development, has emerged as the most recent test of the 55-year-old Wild and Scenic Rivers Act, the federal legislation co-written by former U.S. Sen. Walter Mondale that designated the St. Croix and Namekagon rivers as part of the National Park System.

Thursday's court order was the second time in recent weeks that a judge has halted a development project along the St. Croix due to river protections. In late February, a St. Croix County judge ruled in favor of plaintiffs who said some elements of a four-story, mixed-use housing project slated to rise on a city block in downtown Hudson, Wis., violated longstanding St. Croix River protections.

The Osceola development, proposed by Gaughan Cos. of Forest Lake, would sit on the former site of a medical center at River Street and 3rd Avenue. That's a block west of Osceola's main business district and within the village's River Town Management Zone, where town code protects the natural and scenic qualities of the river.

The Wisconsin Department of Natural Resources, the National Park Service and neighbors of the project raised concerns to village officials about the building's height and potential conflicts with the Wild and Scenic Rivers Act, according to the suit.

Supporters of the plan say it would provide much-needed housing for the area, but opponents say materials provided by the developer suggest the building would be visible from the river. That would violate state standards for the Lower St. Croix National Scenic Riverway, which say buildings should be "difficult to see, or not readily noticeable, in summer months as viewed from at or near the mid-line of the Lower St. Croix River."

In a lawsuit filed last year, the St. Croix Scenic Coalition and eight other petitioners asked the court to review two decisions made last summer by the Osceola Village Board. The board reversed the village's Historical Preservation Commission's denial of a certificate of appropriateness for the project and then, two weeks later, approved the developer's final site plans.

The plaintiffs countered that the building's river-facing wall would stand 51 feet, 3 inches high, enough to make it "visually conspicuous" from the river's center.

In an order handed down Thursday, Circuit Judge Daniel J. Tolan affirmed the Village Board's decision not to deny a certificate of appropriateness for the project. But when it came to the board's approval of final site plans, the judge said the evidence showed the board "could not have reasonably approved" the plan because, in fact, the project would be easily visible.

A drone video shot by Gaughan as part of its application was intended to show tree heights on the property; the plaintiffs said the drone video also showed how the building's occupants would have clear river views. The developer said the building would stand 44 feet, 6.75 inches tall, just under the 45-foot height limit approved by village officials, but plaintiffs argued that measurement is faulty.

"The board's finding of visually inconspicuous was contrary to the drone footage, surrogate balloon test, failure to comply with code and public outcry," Tolan wrote. The drone footage and balloon test were used to determine if the proposed building would be visible from the river in violation of federal protections for the scenic riverway.