A long-simmering fight between Minnesota and North Dakota has broken wide open now that Gov. Mark Dayton has drawn a line down the middle of the Red River by refusing to allow a massive flood diversion project to go forward on his side of the border.

Residents and local leaders in Fargo are outraged at what they say is his administration's cavalier advice to keep sandbagging in the face of ever higher threats of flooding. The U.S. Army Corps of Engineers and even the mayor of the Minnesota city Moorhead came out swinging last week, vowing to press ahead with the $2.1 billion project.

While proponents say they want to keep talking with Minnesota, the depth of the disagreement about the value and safety of the diversion project is so profound that, other than a legal battle, there is no apparent resolution in sight.

"If there is a confrontation, there will be a confrontation," said Darrell Vanyo, executive director of the Fargo-Moorhead Diversion Authority. He said the U.S. Army Corps of Engineers has all the authority it needs to build a high-hazard dam and flood thousands of acres of mostly farmland on the Minnesota side of the river in order to protect the Fargo-Moorhead urban areas.

But attorneys for residents who have been fighting the project in federal court say that decision would have to be made in Washington, D.C. And riding roughshod over Minnesota, they say, would require strong congressional support.

"The Army Corps, thankfully, is not the king of the United States," said Jerry Von Korff, the attorney representing upstream communities that would be flooded if the project went forward as planned.

And so far, while Congress has approved the project, it's only provided $5 million of the $450 million in federal funds that are part of the deal.

"Just the fact that you've got a lawsuit going on is going to make it difficult to get federal money," said U.S. Rep. Collin Peterson, whose district is bordered by the Red River. "It's hard enough to get things funded without having controversy."

But project supporters didn't seem to heed clear warnings, going back more than a year, that Minnesota was unlikely to grant them the permit they need.

A year ago, Peterson met with diversion officials.

"I asked them, 'What is your Plan B if Minnesota denies the permit?' " he said. "And they said, 'There is no Plan B.' "

51 floods in 113 years

There is widespread agreement that Fargo needs protection from floods — the question is how.

The Red has flooded 51 of the past 113 years, causing millions of dollars in damage to homes and businesses around Fargo and the region. Across the river, Moorhead sits 4 feet higher and is protected by $130 million worth of walls, dikes and levees that Minnesota has put in place over the years.

After the most recent flood, in 2009, local North Dakota governments asked the U.S. Army Corps of Engineers to come up with a long-term plan. And it came up with a big one.

The Corps would carve a 36-mile ditch around Fargo and build flood control dams across the Wild Rice and Red rivers. In the event of a flood, water from the Red and its five tributaries would be diverted away from Fargo — the region's bustling economic hub — and into miles of North Dakota and Minnesota farmland and prairie.

North Dakota would pay $1.2 billion of the cost and Minnesota would pay $100 million.

If the project goes ahead, a net increase of 2,000 acres in Minnesota would be at risk of flooding. But across the river, many more thousands of acres would be left high and dry and ripe for construction of homes, schools and businesses.

A crucial piece: Construction of what Minnesota officials describe as a "high-hazard" dam across the Red — the kind that would cause catastrophic damage if it fails.

Minnesota officials have been critical of the project for years. They even joined a federal lawsuit to stop preliminary work from going forward while they completed their own environmental review, which was finished last spring.

Then last week Tom Landwehr, commissioner of the Department of Natural Resources, announced that the state would not grant a permit for the dam on Minnesota's side of the project. It didn't meet Minnesota's environmental laws or standards, he said. Instead, Minnesota suggested that current and planned flood mitigation projects around Fargo, in combination with emergency measures like sandbagging and evacuation, were more likely to be in the public interest.

'Shifts the burden'

Vanyo said the Diversion Authority and the Army Corps will keep talking with Minnesota officials to try and resolve differences. But the document Landwehr provided to support the DNR's decision suggests they may be insurmountable.

More than half the area that would be protected by the dam and diversion channel is now flood plain that would be open to development in the future, the document says. But dams "can, and do, fail," the DNR said. "Allowing development in vulnerable areas would increase the consequences of a dam failure. ..."

The DNR said the corps has underestimated the number of potential deaths if the dam were to fail and exaggerated the time Fargo would have to evacuate in such an event.

Peterson pointed out that Minnesota hasn't approved a new high-hazard dam in decades. "It's one thing when you've got a flood and it comes up slowly and you can deal with it," he said. "But it's another if you're behind a 20- or 30-foot-high dam and it breaks and water rushes through."

The DNR also noted that the Diversion Authority would be financially liable for a dam failure but questioned whether the quasi-governmental organization has sufficient financial wherewithal to pay.

In addition, the DNR argues that the Army Corps overestimated the financial benefits to the community by at least $41 million. The claimed benefits are "misleading" because they include flood control projects that would occur with or without the diversion project and improperly include temporary economic impacts of constructing the project itself.

In short, the DNR said, "The proposed Project … simply shifts the burden of flooding from one sparsely developed rural area to another."

Melissa Samet, an attorney with the National Wildlife Federation familiar with the Army Corps, said Congress has expressly discouraged projects that alter the natural processes of rivers, result in the unwise use of flood plains, or encourage development into undeveloped areas.

"And this project absolutely does that," she said.

The DNR argues that the vast majority of Fargo's developed area is already protected by existing or planned flood projects and that remaining areas can be protected in an emergency the way Fargo has always done it — with evacuations and sandbagging.

But that's cold comfort to the people of Fargo, who look at every spring thaw with trepidation, said local officials. They say thousands of Fargo's buildings are at risk if rising flood projections come true and relying on a strategy of business as usual is dangerous.

"Are we going to flood this spring?" Fargo Mayor Tim Mahoney said, describing residents' mind-set in a radio interview this week. "We think people are tired of sandbagging."