FERC seeks input on 800-MW pumped storage project in South Dakota

The Federal Energy Regulatory Commission said Sept. 25 that it will take 60 days of comment on a July 30 application by the Western Minnesota Municipal Power Authority on an 800-MW pumped storage hydro project in South Dakota.

The authority is proposing feasibility work on the Gregory County Pumped Storage Project, to be located on Lake Francis Case on the Missouri River, near the township of Lucas, in Gregory, Charles Mix and Brule counties, S.D. The sole purpose of a preliminary permit, if issued, is to grant the permit holder priority to file a license application during the three-year permit term.

FERC is taking 60 days of public comment, during which time parties can intervene in the case and/or submit a competing preliminary permit application.

The proposed project would include:

  • a new earthen embankment (upper reservoir) having a total storage capacity of 47,000 acre-feet with an operating elevation level of between 2,045 feet msl and 2,080 feet msl;
  • a new 340-foot-long by 200-foot-wide by 100-foot-high concrete powerhouse containing eight new 100-MW turbine units for a total plant rating of 800 MW;
  • the existing Lake Francis Case (lower reservoir) with a storage capacity of 5,494,000 acre-feet at normal maximum operation elevation of 1,355 feet msl;
  • a new 120-foot-long, 340-foot-wide tailrace from the powerhouse to Lake Francis Case;
  • a new substation on top of the powerhouse containing step-up transformers; and
  • a new 21-mile-long, 230-kV transmission line extending from the project substation to the existing Lake Platte substation (the point of interconnection).

The estimated annual generation of the Gregory County Pumped Storage Project would be 3,000 gigawatt-hours.

The company said the project is to be built in two phases. The powerhouse, one penstock, the release-intake structure, and the leveed upper reservoir will be constructed in the first phase. Four turbine-pump units will be placed into operation and the transmission will be built to serve the 400 MW generation-load. The second phase will complete the second penstock, install the remaining four turbine-pump units, and build out the transmission to support the 800 MW level. Construction of the second phase will start within ten years of commercial operation of the first phase.

“The purpose for constructing this Project in two phases is due to the limited transmission in the region,” the application noted. “Significant wind energy resources are available in the upper mid Nebraska and mid to eastern South Dakota region but have not been developed primarily due to limited transmission. The pumped storage will be an ideal backup for the developed wind energy in the region.”

The applicant contact is: Raymond Wahle, Missouri River Energy Services, 3724 W. Avera Drive, P.O. Box 88920, Sioux Falls, SD 57109; phone: (605) 330-6963.

Notable is that the County Commission of Gregory County, S.D., filed a July 3 application with FERC for a preliminary permit on the 1,200-MW (net) Gregory County Energy Project, a pumped storage facility on the Missouri River. The application, from consultant Schulte Associates LLC, said this is one of the prime sites in the western U.S. for a pumped storage project. The idea is to integrate this project with intermittent wind power in the region, evening out the power output in the region.

The upper reservoir for this project would be on the Missouri Plateau, about 700 feet above Lake Francis Case on the Missouri River, which would form the lower reservoir. The project would include four 300-MW (net) turbines and a 20-mile, 345-kV line that would interconnect with existing transmission for the Fort Randall Generating Station. Projected output for the Gregory County Energy Project is 3,120,000 MWh/year.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.