FARGO – Metro Diversion Authority officials received a “high-level update” Thursday about forthcoming – and potentially significant – changes that might be recommended this fall for the $1.8 billion Red River diversion project.
Earlier this year, Fargo-Moorhead consultants embarked on seven post-feasibility studies. They sought to make the project more efficient and to assess alternatives for the southern portion of the 35-mile channel, where the project is most controversial due to its impacts on rural residents.
Diversion Authority leaders received an initial briefing Thursday on what those months of study found, a presentation that “set the stage for future meetings where we will be taking action,” Chairman Darrell Vanyo said.
The authority’s consultant team will unveil their final recommendation on Sept. 13, which will likely be a combination of the various study proposals board members heard about on Thursday.
Diversion officials will then have a month to gather public input before voting on the final plan in early October.
In embarking on the post-feasibility studies, the authority’s consultant team used the federally approved plan as their baseline, said Bruce Spiller, technical services manager for the authority.
Spiller cautioned that any significant changes to the alignment would likely require further approval by the U.S. Army Corps of Engineers.
None of the proposals are final yet, he added.
Each will be evaluated on implementability , cost, risk and impacts to property, the flood plain, the environment and transportation.
“Implementability is No. 1,” Spiller said. “We’re not going to recommend something that we don’t believe we can implement or build.”
Here is a look at the seven proposals the Diversion Authority is considering:
- “Value Engineering proposal 13, Option A”
This proposal calls for moving the southern tieback levee about 1 mile north, which would shift about 50,000 acre-feet of water storage to the south.
This would allow officials to eliminate what’s called “Storage Area 1” within the diversion channel, while adding to the larger water staging area to the south.
As originally planned, “Storage Area 1” is a 4,360-acre area that would be formed by 12 miles of embankments. That area – coupled with the 150,000-acre-foot water staging area south of the channel and tieback levee – were designed to offset downstream impacts from the Red River diversion.
Shifting “Storage Area 1” into the water staging area would reduce water levels in the staging area by only 0.16 feet – but it would allow officials to eliminate the storage area feature and the Wolverton Creek control structure in Minnesota, which could mean a cost-savings.
- “Value Engineering proposal 13, Option C”
This proposal calls for moving the southern tieback levee even farther north than Option A. Similarly, though, doing this would eliminate “Storage Area 1” and the Wolverton Creek control structure.
But the benefit would be greater: Reducing water levels by nearly 3 feet in the temporary water staging area south of the tieback levee.
The “Value Engineering 13” options were briefly considered by the Army Corps during the corps’ feasibility study, but the alternatives weren’t pursued as deeply as the Diversion Authority is looking at them now.
- “North of the Wild Rice River Alignment”
This proposal would move the diversion’s starting point significantly farther north, putting the tieback levee above where the Red and Wild Rice rivers meet.
The benefits of this change would mean eliminating “Storage Area 1,” and the control structures on Wolverton Creek and the Wild Rice River.
It could also reduce the staging area water levels by about 5 feet, a notable benefit to upstream communities affected by the project.
However, “technical analysis on this one is really ongoing,” Spiller said. “It’s not fully fleshed out yet, but this is the stage we’re at.”
He added: “Since this was not done as part of the value engineering during feasibility, it would require more permitting changes and additional federal review.”
- “South of Oxbow Alignment”
In similar fashion, this proposal could also drastically change the starting point of the Red River diversion. This alternative would shift the tieback levees south of Oxbow and provide protection to Oxbow, Hickson and Bakke.
All three cities stand to be displaced by the corps’ approved project, which threatens to inundate the cities with up to several feet of water in the temporary water staging area.
The “South of Oxbow” alignment comes with greater risk and impact, though, Spiller said.
“It does cause more upstream impacts at a higher level and pushes them further upstream,” he said.
It would also mean increasing the length of the tieback levees by at least half. Increasing the length of the levee by such an extent would mean more maintenance and a higher risk of levee failure, Spiller said.
Even more so than the Wild Rice alignment change, this proposal would require “significant permitting challenges and additional federal approval,” Spiller said.
- “Flows through town”
This proposal is one officials have discussed with almost certainty for several months.
It calls for increasing the allowable flows of the Red River up to 17,000 cubic feet per second – or about 35 feet on the Fargo gage – before the diversion’s protection would kick in.
In comparison, the approved project sets the bar at 9,600 cfs , or about 31 feet on the Fargo gage.
Increasing the Red River’s flows through downtown Fargo-Moorhead would reduce how often the diversion would need to be used, likely from every three to four years to as infrequently as every 10 years.
That would benefit upstream communities by impacting them less often and for a shorter amount of time, but the magnitude to which they’d be affected by stored water shouldn’t change, Spiller said.
This proposal would also eliminate the need for fish passage mitigation on the control structures for the Wild Rice and Red rivers.
To accommodate the higher flows through town, Fargo and Moorhead would both need additional permanent levees that protect to a minimum level.
A prime example of where such a levee would be needed is Second Street North near Fargo’s City Hall.
- “Diversion inlet gates vs. fixed weir”
The current plan calls for a fixed structure to form the start of the diversion channel, where the tieback levee ends near Cass County Road 17 south of Horace.
Once water reached the weir’s height, the water would naturally spill into the diversion channel, offering protection.
Having inlet gates instead of a weir would give officials flexibility to manage when the diversion is in operation, Spiller said.
“That would allow you to respond differently to different flood events as they occur,” he said.
- “Oxbow, Hickson and Bakke Levees”
This proposal would mean building permanent levees around the three communities, in order to protect them from the water staging area.
However, this proposal would only be possible “if the staging elevations can be lowered significantly,” Spiller said.
“This would only work in conjunction with another alternative that would lower those staging elevations,” he said.
This proposal could also have impacts to how the tieback levees are designed and whether the project would need additional federal approval, Spiller said.