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Feasibility study for the Gregory County pumped-storage project, USA

Stantec, USA, has been selected by Missouri River Energy Services (MRES) to conduct a feasibility study for the 1800 MW Gregory County pumped-storage project in the midwestern US state of South Dakota.

As part of the feasibility study, Stantec will develop the project to five per cent design and perform technical and cost evaluations covering alternative layouts for the principal structures, their types, and basic designs to provide a more specific indication of the technical feasibility of the site, the company announced on 22 Sep­tember.

The proposed project, which is planned to be located on Lake Francis Case on the Missouri river, is designed as an open-loop pumped-storage station, with an upper reservoir, which will cover 5.5 x 106m2 and be impounded by a 19 m-high earth embankment levee. Lake Francis Case and the Missouri river would act as the lower reservoir. The project could provide important energy services in a multi-state region and play a vital role in integrating wind and solar resources, according to the developer.

A preliminary permit to study the project was awarded by the Federal Energy Regulatory Commission (FERC) to Western Minnesota Municipal Power Agency (WM­MPA), part of MRES, in Sep­tember 2018. WMMPA provides financing for generation and transmission facilities that are used to serve the wholesale electricity needs of the 61 MRES member municipalities.

The project concept dates back to 1977, when the US Corps of Engi­neers completed a study of water resources along the Missouri river, with the Gregory County site having been identified as the best location for a pumped-storage project. The state of South Dakota applied for a permit to study the idea in 2002, although a feasibility study in 2004 conducted for the Depart­ment of Environment and Natural Resources concluded that the economic conditions were not fav­ourable at the time.

Stantec previously worked with MRES as owner’s engineer and designer for the 55 MW Red Rock hydro project on the Des Moines river near Pella, Iowa. That project, which was commissioned earlier this year, is now producing power for 61 MRES communities in four states. The Red Rock dam was originally built by the US Army Corps of Engineers in the 1960s for flood control and recreation purposes.

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