The 400MW Gordon Butte pumped storage hydropower project is located in Central Montana, US. Image courtesy of Absaroka Energy.
The Gordon Butte pumped storage project will source water from Cottonwood Creek, a tributary of the Musselshell River. Image courtesy of Jamie Rothwell.
The electricity generated from the Gordon Butte project will be interconnected to the Colstrip twin 500kV transmission lines in Montana. Image courtesy of arif_wic.

Gordon Butte pumped storage project is a 400MW hydroelectric facility planned to be developed in Meagher County, Montana,US.

The closed-loop pumped storage hydro facility will be built and operated by GB Energy Park (GBEP), a subsidiary of Absaroka Energy.

The US Federal Energy Regulatory Commission (FERC) granted GBEP the license to construct and operate the facility for 50 years, in December 2016.

Absaroka Energy secured equity investment capital for the project from Copenhagen Infrastructure Partners (CIP) in July 2019.

Construction works on the project are expected to begin in 2020, while commissioning is expected in 2023.

The Gordon Butte pumped storage facility will operate as a peaking plant by using excess renewable power generated in the region to produce up to 1,300GWh of clean energy a year during periods of peak demand for electricity.

The project is estimated to create approximately 350 construction jobs and up to 36 permanent jobs during operations.

Location and site details

The Gordon Butte project site is located on approximately 3,840 acres of private land on the Gordon Butte, in the Meagher County in Central Montana, approximately 5km west of Martinsdale.

The pumped storage facility will utilise water from Cottonwood Creek, a tributary of the Musselshell River.

Gordon Butte pumped storage plant make-up

The Gordon Butte closed-loop pumped storage facility will comprise an upper and lower reservoir with an elevation difference of 312m, and an underground power house equipped with four 100MW reversible pump-turbine units from GE Renewable Energy.

The 915m-long and 305m-wide upper reservoir will be impounded by a 2.3km-long and 27m-high concrete-faced rockfill dam, while the 701m-long and 580m-wide lower reservoir will be created through excavation as well as two 18m-high concrete-faced rockfill dams.

The reservoirs will be connected through a 225m-long underground vertical shaft tunnel and a 915m-long underground concrete and steel-lined penstock tunnel, which will terminate at the underground power house near the lower reservoir.

Designed to cycle 4,000 acre-feet of water back and forth between the reservoir for energy storage and generation, the facility is intended to quickly respond to electricity demand and generation fluctuations.

It will pump water from the lower to the upper reservoir for storage when the energy is available in excess, while the same water will be discharged to the lower reservoir for power generation during peak electricity demand. It can generate power continuously for an estimated 8.5 hours.

Power transmission

The pumped storage power plant will be interconnected with the Colstrip twin 500kV transmission lines through a 9km-long, 230kV transmission line, which will connect the project substation with a new step-up station at the interconnection site.

The Colstrip twin transmission line in Montana is co-owned by NorthWestern Energy, Puget Sound Energy, Portland General Electric, Avista Corp, and PacifiCorp.


Water required to initially fill the reservoirs will be sourced from the Cottonwood Creek via 71-Ranch’s existing irrigation system.

A trashrack and a 1.2m x 1.2m flow control slide gate will be installed at the terminus of the irrigation canal, from where the water will be sent to the lower reservoir through a 45.7m-long and 1.2m-diameter pipeline.

The lower reservoir will be accessed via a 965m-long access road from Montana Highway 294, while the upper reservoir will be accessed by the existing road running between the highway and the Gordon Butte wind farm.

Contractors involved in Gordon Butte pumped storage project

Ames Construction and Black & Veatch have been engaged for the engineering, procurement, and construction (EPC), while GE Renewable Energy will supply the turbine and pump equipment for the project.

Consultants invoved in the project include McMillen Jacobs Associates, Garcia and Associates, DOWL, Stanley Consultants , Pascoe Energy, Acelerex, and Energy+Environmental Economics (E3).