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Lawmakers and local leaders in Wyoming escalated scrutiny on May 28 after a Utah developer unveiled plans for a nearly $3 billion pumped-hydro project at Seminoe Reservoir, raising fresh questions about water, wildlife and community input. The dispute now centers on potential effects to the North Platte River watershed and whether state and federal reviewers have fully weighed those risks.
The proposal, led by rPlus Hydro, would create a 972-megawatt pumped-storage facility that stores energy by moving water between the existing Seminoe Reservoir and a newly built upper basin. During periods of excess wind generation the plant would pump water uphill; when grid demand rises, the stored water would flow back through turbines to produce electricity. Company materials estimate construction would take about five years.
What the project would look like
The developer describes the plan as largely subterranean, with most equipment sited belowground to limit surface disturbance. rPlus has told officials the project could add several hundred construction jobs and that a recent draft environmental review by the Federal Energy Regulatory Commission (FERC) recognizes the facility’s role in meeting grid needs.
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Seminoe Reservoir $3B energy project draws sharp pushback from Wyoming lawmakers
- Capacity: 972 megawatts
- Estimated cost: about $3 billion
- Water movement: up to roughly 13,400 acre-feet pumped to an upper reservoir holding about 10,800 acre-feet
- Construction timeline: roughly five years (developer estimate)
- Jobs: company projects 300–500 construction positions
- Design: proposed open-loop system — drawing from and returning water to the reservoir
But the hearing in Casper made plain that the proposal is far from settled. The Wyoming Legislature’s Travel, Recreation, Wildlife and Cultural Resources Committee spent hours hearing from county and city officials, conservation groups and state wildlife managers — many of whom accused the developer of inadequate outreach and warned of significant environmental costs.
Community objections and procedural concerns
Local leaders said they were blindsided by limited contact from the developer. Casper’s mayor told the committee the city depends on the river for drinking water, wastewater services and tourism, and said the municipality had not been adequately briefed or consulted.
Conservation advocates pressed technical objections to the federal review process, noting the environmental analysis relied on a short modeling window that they said did not capture extreme drought conditions. Representatives from Trout Unlimited warned repeated pumping and releases could change water temperatures and increase turbidity, with downstream impacts for the Miracle Mile trout fishery.
Public comments filed in the FERC record were overwhelmingly negative, according to speakers at the meeting — an indicator of local opposition that lawmakers flagged as they prepared their response to regulators.
Wildlife at stake
The proposed infrastructure falls inside crucial seasonal ranges for the Ferris-Seminoe bighorn sheep, which state biologists describe as one of Wyoming’s healthiest herds and an important source population for relocation work. Officials from Wyoming Game and Fish expressed alarm about continuous, multi-year construction activity and the herd’s strong fidelity to established habitat.
Wildlife advocates cautioned that blasting, round-the-clock truck traffic and new transmission corridors could push animals into risky areas — exposing them to disease, predation or, under current policies, forced removal. The project’s transmission line route also intersects core habitat for the greater sage-grouse, where towers and dust could disrupt nesting and increase predator pressure.
Biologists pointed to broader big-game concerns as well. Winter ranges for mule deer, elk and pronghorn overlap the development footprint; developers anticipate tens of thousands of heavy truck movements to move rock and concrete, which officials say raises the chance of vehicle collisions and long-term displacement of animals from critical foraging areas.
rPlus has proposed mitigation measures — nightly speed reductions, wildlife fences and adjustments to spoil placement to shorten haul distances — but conservation groups contend those steps do not adequately offset the cumulative impacts. One conservation leader noted the company estimated a multibillion-dollar price tag to meet stringent wildlife protections, and questioned whether economic trade-offs should outweigh biological losses.
Lawmakers’ response and next steps
The TRWC committee voted unanimously to draft a formal letter to FERC and the developer documenting local concerns about communication and environmental risk. Committee members also signaled interest in exploring state-level policy changes, including stronger bonding requirements for large infrastructure projects and incentives that favor closed-loop pumped storage systems over open-loop designs that draw directly from natural water bodies.
FERC’s draft environmental impact statement remains under review, and the agency will accept comments and additional data before issuing a final determination. State officials said they will continue submitting technical input to the federal process while weighing legislative remedies.
For residents and stakeholders, the immediate questions are practical: will water quality or recreational access at Seminoe State Park change, how will construction affect municipal water supplies, and what protections can be guaranteed for key wildlife populations? Those issues, lawmakers said, should be resolved in transparent, evidence-based reviews before the project advances.
With FERC moving forward with its environmental review and local officials prepared to press their case, the Seminoe proposal now enters a contested period where regulatory findings, additional studies and political pressure will determine whether the project proceeds as currently planned.
