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Published April 22 2010

Diversion impact analysis only half finished

The impact of a proposed Fargo-Moorhead flood diversion on downstream river levels may be greater than previously estimated, but a U.S. Army Corps of Engineers official cautioned Wednesday that the analysis is only half-completed and the numbers will likely change.

Aaron Snyder, project manager for the corps, wouldn’t say how much larger the downstream impact could be than the 10.4 inches estimated by the corps in February, but he said it isn’t as large as the 14.5 inches reported by one media outlet that cited a leaked report.

“We had some discussions about it during our internal team meeting,” he said. “The number we discussed was not 14.5.”

Fargo City Commissioner Tim Mahoney mentioned the figure on a radio talk show Tuesday. Mahoney told The Forum on Wednesday that he’d heard the figure when talking with Mayor Dennis Walaker and City Administrator Pat Zavoral. Zavoral said he heard it from engineers who heard it from the corps during a weekly conference call.

Snyder said it’s “not responsible to put numbers out there at this time.

“The numbers floating around are not accurate,” he wrote in an e-mail. “In essence, the numbers being discussed were not authorized for release.”

Snyder said the corps is updating two components for its analysis: hydrology, which is the amount of water at each location, and hydraulics, which is how water moves through the river system.

Hydraulic models have been updated with data from the 2009 flood, but the hydrology update isn’t finished, he said.

“We are basically saying we did half the analysis and we should not be putting much weight into those results until the analysis is completed,” Snyder said.

Estimates of the diversion’s impact will change in the near future, and for now the figures released in February are the best available, Snyder said. The corps should have new numbers to release at its next round of public meetings June 9 and 10, he said.

The corps will give an update today to the Metro Flood Study Work Group when it meets at 3:30 p.m. at Fargo City Hall. Members also will discuss local sponsorship of the diversion project and a joint powers authority.

Walaker said the potential for higher downstream impacts underscores the need for more water storage upstream.

“I will continue to be concerned,” he said, adding, “I just hope we have a project.”

Diane Ista, a manager of Minnesota’s Wild Rice Watershed District and a member of the Red River Downstream Impact Work Group pushing for a zero-impact diversion, said downstream communities are concerned about any rise in flood levels, but they realize the corps’ numbers will change with further study.

“There’s no use for us to be hyper about every little word that comes out,” she said.

Readers can reach Forum reporter Mike Nowatzki at (701) 241-5528