Martin Falbisoner / Wikimedia Commons
Why It Matters
A massive energy storage project proposed for Carbon County, Wyoming, moved significantly closer to reality this month after federal regulators released a critical environmental review. If approved, the facility could reshape how Wyoming manages electricity supply — but conservation groups warn the project’s construction plan puts sensitive wildlife and a prized trout fishery at risk.
Supporters say the project could deliver $200 million in annual savings to electricity ratepayers, a figure that carries particular weight as Wyoming families already face mounting pressure from rising utility costs. Ratepayers across the state have seen proposals for significant rate increases in recent years, making large-scale energy investments a closely watched issue.
What Happened
The Federal Energy Regulatory Commission issued an environmental impact statement for the Seminoe pumped-water storage hydroelectric project, advancing it toward potential final approval. Utah-based developer rPlus Hydro is behind the proposal, which would construct a 13,400-acre-foot reservoir in the Bennett Mountains above the existing Seminoe Reservoir in Carbon County.
The project carries an estimated price tag of $4 billion and would require roughly five years to build. Pumped-storage hydroelectric facilities work by moving water uphill during periods of low electricity demand and releasing it downhill through turbines when demand peaks — functioning effectively as a large-scale battery for the grid.
Earlier this year, the Wyoming Department of Environmental Quality issued a Section 401 water quality certificate for the project. The Environmental Protection Agency subsequently reviewed those findings and agreed with Wyoming DEQ’s conclusions and stipulations, giving the project additional regulatory momentum heading into the FERC review.
Opposition from Conservation Groups
Despite that regulatory progress, several conservation organizations have raised pointed objections to how the project handles wildlife protections. The revised construction plan retains multiple waivers that would allow rPlus Hydro to bypass seasonal restrictions designed to limit harm to wildlife during sensitive periods.
Trout Unlimited and Friends of the North Platte both argue that current protections for the Miracle Mile stretch of the North Platte River fall short. That renowned fishing corridor faces potential harm from rising water temperatures that could trigger fish kills during construction and operation.
Patrick Harrington, Wyoming Government Relations Director for Trout Unlimited, did not mince words in response to the final environmental impact statement. “I’m very disheartened by the final EIS,” he said.
The Wyoming Wild Sheep Foundation also opposes the waivers, specifically those tied to the Ferris-Seminoe bighorn sheep herd — one of the state’s notable wild sheep populations. Executive Director Katie Cheesbrough pointed out that the wildlife restrictions were not a surprise to the developer. “Those wildlife restrictions were publicly available, and they knew that going into it,” she said.
By the Numbers
- $4 billion — estimated total cost of the Seminoe pumped-storage facility
- $200 million — projected annual savings to electricity ratepayers, per rPlus Hydro
- 13,400 acre-feet — proposed reservoir storage capacity in the Bennett Mountains
- 5 years — estimated construction timeline
- Multiple waivers retained in revised plan to bypass seasonal wildlife-protection construction limits
Zoom Out
The Seminoe project is part of a broader national push to expand energy storage capacity as Western states work to maintain reliable electricity delivery. Pumped-storage hydroelectric facilities are considered one of the most proven large-scale storage technologies available, and Wyoming’s geography makes it a candidate for such development.
At the same time, Wyoming lawmakers and utility regulators have been grappling with rising electricity costs. Rocky Mountain Power’s recent request for a $71 million rate increase has put pressure on policymakers to find ways to reduce long-term electricity expenses — a tension that makes the claimed $200 million in annual ratepayer savings politically significant, even as wildlife concerns remain unresolved. Separately, Wyoming legislators have explored new generation taxes as part of broader efforts to manage the cost of electricity for residents.
What’s Next
The environmental impact statement marks an important milestone, but FERC must still issue a final license before construction can begin. Conservation groups opposing the current wildlife waiver provisions are expected to continue pressing regulators and the developer to strengthen protections for both the North Platte fishery and the Ferris-Seminoe bighorn sheep herd before any final approval is granted.
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