The following is excerpted and edited from: Final Feasibility Report and Environmental Impact Statement, July 2011. (Large download)
STUDY AUTHORITY AND HISTORY
The Fargo-Moorhead Metropolitan area is significantly prone to flooding. The Red River has exceeded flood stage in 49 of the past 110 years, every year from 1993 through 2011, and again in 2013. A 500-year event would flood nearly the entire city of Fargo and a large portion of the city of Moorhead, as well as a major portion of West Fargo and several surrounding communities in the area.
As a result, The St. Paul District of the Corps of Engineers, and the sponsor cities of Fargo and Moorhead, began the Fargo-Moorhead Metro Feasibility Study in September 2008. The study was authorized by a September 30, 1974, resolution of the Senate Committee to Public Works.
Before 2008, the Corps had conducted numerous studies and projects in the study area. The Fargo-Moorhead metropolitan area was included in the Red River Reconnaissance Study approved in 2002. However, that study was not to a sufficient level of detail to recommend a feasibility study specifically for measures in Fargo and Moorhead. A supplemental reconnaissance report recommended the current Feasibility Study and was approved by the Mississippi Valley Division on April 8, 2008.
Based on the study’s findings, the city of Fargo, the city of Moorhead and the federal government entered into a Feasibility Cost Share Agreement on September 22, 2008. The study cost share was 50/50 between the federal government and the two non-federal sponsors. The Corps of Engineers issued a notice of intent to prepare an environmental impact statement in the Federal Register on May 5, 2009. The Draft Feasibility Report and Environmental Impact Statement (DEIS) was published in the Federal Register for a 45 day public review period on June 11, 2010. The review period closed on August 9, 2010, after being extended by 14 days. In response to comments and to more fully study upstream and downstream impacts, the Corps made the decision to prepare a Supplemental DEIS. The notice of intent to prepare a Supplemental DEIS was published in the Federal Register on December 27, 2010.
PURPOSE AND SCOPE
The purpose of the feasibility study was to investigate flood issues in the Fargo-Moorhead Metropolitan Area, identify flood risk management measures that could be implemented, document findings and, if appropriate, recommend implementation of a federal project. The planning objectives were specified as follows:
- Reduce flood risk and flood damages in the Fargo-Moorhead metropolitan area.
- Restore or improve degraded riverine and riparian habitat in and along the Red River of the North, Wild Rice River (North Dakota), Sheyenne River (North Dakota), and Buffalo River (Minnesota) in conjunction with other flood risk management features.
- Provide additional wetland habitat in conjunction with other flood risk management features.
- Provide recreational opportunities in conjunction with other flood risk management features.
The feasibility study investigated measures to reduce flood risk and analyzed the potential for federal participation in implementing a flood risk management project in the Fargo-Moorhead Metropolitan Area. The feasibility study team collected pertinent engineering, economic, social and environmental information needed to accomplish the study objectives. Interagency and public stakeholders and potentially affected landowners were identified. Potential issues and opportunities were defined. An array of possible flood risk management plans was considered and screened to define the costs, benefits, and impacts to the study area.
The study analyzed a number of possible types of measures and alternative plans that could reduce the flood risk in the Fargo-Moorhead metropolitan area. The St. Paul District Engineer recommends that the Locally Preferred Plan, the North Dakota East 20,000 cfs diversion channel with upstream staging and storage, and associated features described in the Corps’ reports, be authorized for implementation as a federal project.
LOCATION OF STUDY AREA
The geographic scope of analysis for the environmental impacts of the proposed action and alternatives encompasses the Fargo-Moorhead Metropolitan area plus areas in the floodplain of the Red River from approximately 300 river miles north of Fargo near Emerson, Manitoba to approximately 30 miles south of Fargo near Abercrombie, ND. The Wild Rice, Sheyenne, Maple, Rush and Lower Rush Rivers in North Dakota and the Buffalo River in Minnesota also cross the study area.
The Fargo-Moorhead metropolitan area is located within the area from approximately 12 miles west to 5 miles east of the Red River and from 20 miles north to 20 miles south of Interstate Highway 94. The metropolitan area is approximately 600 square miles, encompassing several smaller communities within ten miles of the Red River from Hickson, North Dakota to Georgetown, Minnesota. The metropolitan area has a population of approximately 200,000. Fargo-Moorhead is a gateway to the west and a hub of educational and health-related industries. The metropolitan area is the largest urban area in North Dakota and a principal regional economic and social center.
Figure 1 shows the location of the study area.
Because of its relatively low elevation and flat topography, the majority of the study area is located in the regulatory floodplain. Flooding in Fargo-Moorhead typically occurs in late March and early April. The Red River has exceeded the National Weather Service flood stage of 18 feet in 49 of the past 110 years, every year from 1993 through 2011, and again in 2013.
The flood of record at Fargo-Moorhead was the 2009 spring flood with a stage of 40.8 feet on the Fargo gage. With an estimated peak flow of 29,200 cubic feet per second (cfs), the 2009 flood was approximately a 2-percent chance (50-year) event. Equivalent expected annual flood damages in the Fargo-Moorhead metropolitan area are estimated to be over $194.8 million in the future without project condition. Although emergency measures have been very successful, they may also contribute to an unwarranted sense of security that does not reflect the true flood risk in the area.
The study analyzed a number of possible types of measures and alternative plans that could reduce the flood risk in the Fargo-Moorhead metropolitan area. These measures and plans included:
- No Action – Continue emergency measures
- Non-structural measures
- Flood barriers (including levees)
- Increase conveyance (including diversion channels)
- Flood storage
The alternatives went through an initial screening that used the following criteria: Effectiveness, Environmental Effects, Social Effects, Acceptability, Implementability, Cost, Risk, Separable Mitigation, and Cost Effectiveness.
The initial screening analysis was published in the Alternatives Screening Document dated December 2009. The analysis resulted in two diversion concepts being carried forward: a diversion in Minnesota and a diversion in North Dakota. Diversion channel alternatives following alignments primarily in either Minnesota or North Dakota were considered. Channels ranging in capacity from 20,000 to 45,000 cubic feet per second (cfs) were analyzed in detail. The alternatives were named for their location and capacity, for example, the 20,000 cfs channel located in Minnesota was named the “MN20K plan.”
For the DEIS, the designs, alignments, and features of several diversion channel alternatives were refined, and cost estimates for each alternative were completed. The expected future without project conditions were assessed and compared to the expected future conditions with each alternative in place. The hydraulic and associated economic effects of each alternative were quantified so that the alternatives could be compared. The various alternatives were compared on their ability to meet the goals of the non-federal sponsors as well as cost-effectiveness and environmental impacts.
Table 1 summarizes the results of the economic cost-effectiveness analysis.
Table 2 summarizes the estimated flood stages at the Fargo gage that would be delivered by each of the alternatives if they were operated during a 1-percent chance event or a 0.2-percent chance event.
Prior to release of the May 2010 DEIS, the study identified three plans of significance to decision makers:
- The National Economic Development plan (NED)
- The Locally Preferred Plan (LPP)
- The Federally Comparable Plan (FCP)
The NED plan was the MN40K diversion. The NED plan provides the greatest net national economic benefit consistent with protecting the Nation’s environment.
The LPP was the ND35K diversion. The LPP is the plan that, in the opinion of the non-federal sponsors, best meets the needs of the local community. The cities of Fargo and Moorhead, Cass County, North Dakota and Clay County Minnesota jointly requested that the ND35K plan be pursued as the LPP on March 29, 2010. The request to designate the LPP as the tentatively selected plan was approved by the Assistant Secretary of the Army for Civil Works on April 28, 2010.
The FCP was the MN35K diversion. Normally the NED plan establishes the basis for federal cost sharing of a locally preferred plan, but in this case the LPP provided fewer total annual economic benefits than the NED plan. Therefore, the FCP was used as the basis for federal cost sharing instead of the NED plan. The FCP is a plan that provides comparable total annual economic benefits to the LPP.
The May 2010 DEIS was released for public review on June 11, 2010. In September 2010 hydraulic modeling indicated that the ND35K plan would have more extensive downstream impacts than previously anticipated. Because of that, the decision was made to conduct additional analyses to identify ways to minimize downstream impacts from the LPP.
Beginning in September 2010, several concepts to minimize downstream impacts of a North Dakota diversion plan were considered and studied. The final LPP and tentatively recommended plan was a revised version of the North Dakota diversion channel following the same basic alignment as the ND35K plan, but including additional features to minimize downstream impacts. The primary changes included reducing the diversion channel capacity, raising upstream tie-back levee elevations, adding a 50,000 acre-foot storage area and a 150,000 acrefoot staging area, and compensating most affected landowners within the storage and staging areas. The revised LPP minimized downstream impacts, caused upstream impacts, and provided the same level of risk reduction to the Fargo-Moorhead Metropolitan area as the original LPP (ND35K).
The NED plan was the MN40K plan, and the FCP was the MN35K plan, as discussed above.
Following the public comment period on the SDEIS, the Corps considered all of the comments received from agencies, individuals, and other entities. Revisions were made to the SDEIS to incorporate additional analyses and data, and to address the comments received. The NED plan, FCP, ND35K plan, and LPP remain the same as described in the SDEIS.
Source: Final Feasibility Report and Environmental Impact Statement, July 2011 (large download), pages ES-1 – ES-7.
The St. Paul District Engineer, after considering the environmental, social, and economic effects, the engineering feasibility, and comments received from the other resource agencies, the nonfederal sponsors, and the public, has determined that the selected plan presented in this report is in the overall public interest and is technically sound, environmentally acceptable, and economically feasible. The St. Paul District Engineer recommends that the North Dakota East 20,000 cfs diversion channel with upstream staging and storage, and associated features described in this report, be authorized for implementation as a federal project. This plan is being recommended with such modifications thereof as in the discretion of the Commander, HQUSACE, may be advisable.
For further details on the selected plan, see section 3.13, Description of the Selected Plan, in the Final Feasibility Report and Environmental Impact Statement, July 2011 (large download), beginning on page 118.
Figure 1: Study Area