FARGO, N.D. — Supporters of a Red River diversion channel around the Fargo and Moorhead, Minnesota, area said they are determined to start on the $2.1 billion flood-control project even though the Minnesota Department of Natural Resources announced Monday it would not approve a permit that is considered to be the final hurdle for construction.

Fargo Mayor Tim Mahoney said he’s surprised by the state’s decision to turn down a dam to hold back water during serious flooding, but believes the U.S. Army Corps of Engineers has the authority to move forward.

“We need to proceed with the project, so we will work with the corps on the best way to do this,” Mahoney said. “We need this for the F-M area to protect our people.”

Minnesota DNR Commissioner Tom Landwehr said the permit was rejected primarily because there are better options for flood control, the state and local plans lacked “consistency” and the proposal doesn’t contain proper remedies for upstream impacts.

He added that it is “the position of the state that this is fundamentally a local project,” which should not proceed as proposed. He said the Fargo-Moorhead Diversion Authority can appeal the decision.

Mahoney said he’s not inclined to appeal because it could drag out for months and affect next month’s vote to extend local sales taxes to help pay for the project.

The 30-mile long diversion channel would have required a massive area upstream of the two cities that would be flooded in times of high water.

Corps officials said as recently as last month that they could resolve any issues with the Minnesota DNR. Col. Sam Calkins, commander of the corps’ St. Paul district, said Monday the agency needs time to digest the ruling before providing a detailed response.

“Right now, what I can say is that we are deeply disappointed with this determination after having worked with the state of Minnesota on this project for more than eight years,” Calkins said. “We will continue working with the sponsors to get this project completed.”

Landwehr said the decision should not have come as a surprise.

“I don’t want to speculate on whether there was a misreading, but certainly those concerns have been known for a long time,” Landwehr said.

Landwehr said 60 percent of the acres that would be flooded on purpose would be in Minnesota, while the state would receive 14 percent of the project benefits.

“This is a real transfer of risk and benefits that only gets more obvious when we look at the Minnesota side of this proposed project,” Landwehr said.