The latest report on a proposed Fargo-Moorhead flood diversion finds environmental hurdles can be cleared with a little creative design - and, in at least one case, a lot of money.
The estimated cost of the locally preferred North Dakota-side diversion plan includes $37.3 million to make it easier for fish to swim up and down the Red River and its tributaries.
Craig Evans, project manager for the U.S. Army Corps of Engineers, said staff put more effort into fish passage than probably any other issue addressed in the 382-page draft feasibility report and environmental impact statement (EIS) released last week.
The corps has worked closely with the Minnesota Department of Natural Resources and North Dakota Game and Fish Department, both of which have concerns about how the diversion's water control structures would affect fish movement.
"We're designing the project to have a minimal impact," Evans said.
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For example, the gates that will control water flow from the Red River into the diversion channel will be wider than originally planned -- at a cost of $5 million -- to slow down the water velocity and make it easier for fish to pass.
The wider gates were perhaps the most important change for fish passage, said Luther Aadland, a DNR river ecologist who has worked with the corps and area cities including Fargo-Moorhead to improve fish passage at Red River dams. State officials will continue to work with the corps to minimize the diversion's effects, he said.
"But until we're there, I can't say there are no concerns because there are," he said.
A diversion most likely wouldn't affect fish passage under most flow conditions, but it could limit fish migration during high river flows that have a 2 percent to 20 percent chance of occurring every year, the report states.
Fish passage would be "halted completely" for flows above a 2-percent-chance event, the report states, pointing out that those conditions have occurred only twice in Fargo in the past 108 years, for a total of nine days, all in late March and April.
To minimize the impact on fish during such large flood events, the diversion plan calls for a fish bypass channel measuring 30 feet wide and 3,500 feet long with an entrance as close as possible to the diversion inlet control structure.
While not as effective as a natural channel, the bypass channel "should provide another route for fish to migrate upstream past the control structure," the report states.
Bob Merritt, a DNR hydrologist in Detroit Lakes, said last week he hadn't yet had time to digest the draft EIS report and wasn't ready to comment on it.
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"It's going to take us a bit of time to review it," he said. "I'm sure there will be a response of some form."
Starting on Friday, the public has until July 26 to submit official comments on the draft EIS report, and Evans encouraged them to do so.
"If we've missed something, we want people to point that out, because it's going to be much more difficult for us to revise things after this," he said.
Here are summaries of the report's findings on various environmental components.
Wetlands
The diversion project area contains about 7.2 square miles of wetlands -- an area nearly the size of West Fargo, N.D.
Construction would directly affect wetlands, either through excavation or dumping the excavated dirt along the channel.
The diversion also may indirectly affect wetlands by cutting off drainage to the wetlands, or by creating a drainage pattern to the diversion, allowing the wetlands to drain.
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The 36-mile long North Dakota diversion would directly affect as much as 32.5 acres of wetlands and indirectly affect as much as 193 acres, while a 25-mile-long Minnesota diversion could directly impact about 17 acres of wetlands and indirectly impact 85 acres.
But, the wetland acres lost "would be more than offset" by wetlands created within the diversion channel's bottom, the report states.
The channel would intercept flows from agricultural drains, so its bottom would generally be wet -- especially downstream from where it would pick up flows from the Rush River and Lower Rush River, which wouldn't have river crossing structures such as the Maple, Sheyenne and Wild Rice rivers.
"From that point down, it's going to have a pretty large drainage area that is relying on that channel all the time," Evans said.
Groundwater
The two diversion options studied in the corps' report, both capable of carrying as much as 35,000 cubic feet of water per second, would be dug to a maximum depth of 29 feet in North Dakota and 30 feet in Minnesota.
And, since groundwater always flows to the lowest available area, some of it would end up in the bottom of the diversion channel.
That could lower the groundwater table near the diversion channel, but only to the depth of the channel and likely only in an area as wide as the diversion's outer spoil banks, the report states.
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The Buffalo aquifer east of Moorhead "is not expected to experience measurable effects" from a Minnesota diversion channel, and the West Fargo aquifer "appears to be deep enough to avoid adverse impacts" from a North Dakota diversion, the report states.
Riverbank stability
The diversion channel would prevent large rises in the Red River during flood events, but wouldn't affect it during normal conditions.
As a result, riverbank stability "would not be adversely impacted by any of the diversion alternatives." In fact, the lower flow during floods may actually reduce erosion on the primary riverbank, thus boosting its overall stability, the reports states.
Some slope stability issues could occur where the diversion channel empties into the Red River, but that's not a concern for this project because the outlet would be "armored" to protect against erosion, the report states.
The report's executive summary also touches on farmland, dwellings and recreational features.
n The Minnesota and North Dakota diversion options would remove about 5,700 and 5,400 acres of prime farmland from operation, respectively, in Cass and Clay counties.
n The diversion alignments would require the relocation of six homes or farmsteads in North Dakota and five in Minnesota.
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"Owners would be fairly compensated for their property and relocation," the report states.
n Recreational features may include multipurpose trails, interpretative signage, benches and trailheads with parking.
