An aggravated Gov. Mark Dayton fired off a letter to the U.S. Army Corps of Engineers, warning the agency not to rush ahead with a $2 billion project that would flood wide stretches of Minnesota to keep wider stretches of North Dakota safe and dry.

"This is not how we do business in Minnesota," the governor wrote in a Sept. 1 letter to the agency.

The scolding followed a cheery YouTube video the Corps posted in August that showed construction crews breaking ground on the first stage of the diversion — even though Minnesota has not yet given the project its blessing.

The Fargo-Moorhead Diversion is one of the largest public works projects on the federal drawing board. It would dig a 36-mile trench west of Fargo to divert floodwater away from the bustling city. A dam across the Red River would back even more floodwater away from Fargo — protecting the urban core by flooding rural Minnesota and North Dakota farmland and prairie instead.

But Minnesota regulators aren't sold on the idea, and the Department of Natural Resources has not yet issued the necessary permits to dam the Red. There is no guarantee that those permits will ever be issued, Dayton warned.

"Minnesota has not 'come together' with the Army Corps of Engineers and the State of North Dakota to advance the proposed project," Dayton wrote. "You should know that a favorable permit decision by Minnesota is by no means guaranteed, and I take exception to actions by the U.S. Army Corps of Engineers and its non-federal sponsors to suggest otherwise or attempt to advance project construction in the absence of the required Minnesota permits."

Floods, like this one in 1969, have plagued residents along the Red River for decades

The video features Lt. Gen. Todd Semonite, commanding general of the U.S. Army Corps of Engineers, visiting the diversion site, where construction crews have already begun work on the first stage of a project — an inlet channel on the North Dakota side of the river, funded by a $5 million federal grant. The inlet will connect to the 300-foot-wide diversion channel that will run west of Fargo, carrying spring runoff around the city instead of spilling into streets and homes.

The north-flowing Red River is prone to frequent, costly spring floods as meltwater to the south hits the still-frozen river in the north. The river has overflowed its banks 49 of the past 112 years. Supporters and foes of the diversion project agree that Fargo needs flood protection, but a recent DNR analysis raised concerns about the effect that flooding 2,000 acres of Minnesota that now sit above the flood plain would have on the state's residents and environment.

The video made no mention of Minnesota's concerns, or the fact that the DNR is still in the middle of its permitting process.

"We are racing with the local sponsors to get it done as quick as possible," diversion project manager Terry Williams explains on the video, holding up a sketch of the flood diversion project against a backdrop of earth-moving equipment. Semonite noted that the flood control project could be complete by 2023.

Not so fast, Dayton warned.

"In all my years of public service at the state and federal levels, I have never seen such a complete disregard for the process of a co-regulator," he wrote.

The corps has not responded to the governor's letter, or another he sent in July raising similar concerns about the start of construction on the inlet structure.

"We've been working with the DNR and we've gone through numerous scientific and technical studies that all have pointed to the same solution," said Aaron Snyder, chief project manager for the diversion project. "So I think we're confident in our path moving forward."

Jennifer Brooks • 612-673-4008