Seminoe Pumped Storage Project Has Wildlife Experts Concerned

MAY 5, 2025 |

Photo – Seminoe Dam – Bigfoot99 file photo

Officials at the Wyoming Game and Fish Department are concerned about the potential impact the proposed Seminoe Pumped Storage Project will have on local wildlife.

Last June, representatives from rPlus Energies, a Utah-based energy development company, met in Sinclair to discuss plans for a pumped storage facility at the Seminoe Reservoir.

If built, the Seminoe Pump Storage facility would require the construction of a 10,000-acre-foot upper reservoir in the Bennet Mountains, located approximately 1.9 miles east of the Seminoe Dam.

At the June meeting, Theresa Foxley, Chief of Staff for rPlus Energies, explained that the pumped storage facility will serve as a giant water battery. When electricity is abundant, water is pumped roughly 1,000 feet up from the lower Seminoe Reservoir into the higher storage lake. When energy demands outpace production, Foxley said the water is allowed to flow downhill through an underground hydroelectric turbine, generating electrical power.

The project is expected to cost between $2.5 and $3.5 billion.

If the facility is completed, the water level in the Seminoe Reservoir is expected to rise or fall by 6 to 18 inches as the pumped storage facility is drawing water from the reservoir into the upper storage lake or releasing the stored water to generate electricity.

The fluctuating water level in the reservoir—the rising and falling like bathwater in a tub–that concerns official at Wyoming Game and Fish.

Casper Regional Fisheries Supervisor Matt Hahn told Bigfoot 99, that the project has the potential to alter the water temperature in the Seminoe Reservoir. The fluctuating water temperature could have a negative impact on the nearby Miracle Mile. The nationally-renown trout-fishing area is located downstream of the corporate project.

Hahn said the Miracle Mile may be harmed by the reservoir project. Changes to the important natural resource must be examined, he said.

Additionally, pumping water into and out of Seminoe Reservoir may alter the oxygen content of the water, further impacting the fish population. Game and Fish Fisheries Supervisor Hahn said changes in oxygen levels are unlikely to impact the downstream ecosystem as significantly as potential temperature shifts and increased sediment levels.

Game and Fish Casper Region Public Information Specialist Janet Milek said fish aren’t the only wildlife that may be impacted by the Seminoe Pumped Storage Project. Milek said the state agency is also concerned about how construction of the facility will affect local populations of game animals.

The actual impact of the facility on the ecosystem will remain uncertain until the project is completed. Public Information Specialist Milek said Game and Fish is not providing an opinion on the project itself. Instead, the state agency is simply outlining the potential effects on local wildlife.

The Seminoe Pumped Storage Project is still in the early stages of development and requires many more studies to determine its viability and potential impact on the environment.

In a written statement to Bigfoot99, rPlus Energies Communications Associate Maile Resta stated that, as of March, the Federal Energy Regulatory Commission was in the process of drafting an Environmental Impact Statement for the project. Resta wrote that an Environmental Impact Statement evaluates the project’s effects on the environment, wildlife, recreation, and other resources while also reviewing alternatives and strategies to mitigate potential challenges. Once the Federal Energy Regulatory Commission releases the draft statement in September, the public will be given another opportunity to share their feedback on the project.

At the June meeting, rPlus Hydro representatives said they expected construction to begin next summer.