FARGO, N.D. — Opponents of a planned project to divert the Red River around Fargo, N.D., and Moorhead, Minn., have sued the U.S. Army Corps of Engineers in federal court.

The lawsuit filed by opponents south of the metro area accuses diversion leaders of unnecessarily expanding the scope of the flood protection project. The Richland-Wilkin Joint Powers Authority claims the expansion has boosted the diversion's estimated cost to $1.8 billion and will damage farmland.

Nathan Berseth, a spokesman for the Joint Powers Authority, called the lawsuit "the last straw," and an effort to protect areas upstream of the north-flowing river from irreparable damages to their tax bases and property values.

"We were pushed against a wall and we had no alternatives," Berseth told The Forum newspaper (http://bit.ly/171Kibq ).

The lawsuit alleges the corps failed to provide Congress with several suitable alternative plans, presenting lawmakers in Washington, D.C., with "the false choice between building a vastly overpriced, unnecessarily expansive project, or providing no protection at all."

The lawsuit also alleges that the supposed flooding impact on rural land south of Moorhead would violate Minnesota laws that put strict prohibitions on permitting or authorizing projects that "significantly affect the quality of the environment."

Gerald Von Korff, the Joint Powers Authority's attorney, said the goal is to either get the corps to the negotiating table to find a cheaper plan that better protects farmland south of Fargo, or to get a judge to order the corps to do so.

"This suit is not about trying to stop a flood control project," Von Korff said. "It's about trying to get to the point where there is a flood control project that doesn't flood Richland and Wilkin counties."

Richland County is on the North Dakota side of the river; Wilkin County is on the Minnesota side.

Aaron Snyder, a corps project manager for the diversion, declined to discuss the lawsuit other than to say it is under review.

Diversion Authority Chairman Darrel Vanyo said the lawsuit doesn't surprise him. He disputed any potential impacts on farmland and said the corps' current plan is the only approach that will protect against a major flood.

Marty Johnson of rural Horace, whose farmland is near the line of the proposed diversion channel, welcomed news of the lawsuit.

"At least it slows everything down," he said.

The U.S. Senate authorized the project earlier this year but has not approved any funds for its construction. The project is still awaiting authorization in the U.S. House.