The Federal Energy Regulatory Commission is considering issuing a preliminary permit for the Twentymile Pumped Storage Project, which would generate power during peak energy usage periods.
A Florida-based company is currently seeking a preliminary permit from Federal regulators to explore converting the caverns of Twentymile Mine into the lower half of a two reservoir, pumped storage power system with a generating capacity of 250 megawatts.
According to documents submitted to the Federal Energy Regulatory Commission in March 2023, the proposed project would pump water that is already in the tunnels and galleries of the mine to a new reservoir on a nearby bluff during off-peak energy usage times. When energy demand is higher, that water would then be released back into the lower reservoir while passing through a pair of generating turbines.
The application submitted last year is known as a Preliminary Permit Application, which would allow developers to do a feasibility study on the project and exclusive rights to pursue a full permit for the project in the future. After requests for more information, the application was accepted by FERC on May 24 and is currently in the public comment period.
The application was submitted by a Florida-based company called Twentymile Pumped Storage LLC, which has almost no online presence. The West Palm Beach address on the application however matches the address of the corporate headquarters of Rye Development, a company that boasts itself as “a new generation of pumped storage leaders.”
“The sole purpose of a preliminary permit, if issued, is to grant the permit holder priority to file a license application during the permit term,” FERC wrote in a notice of the preliminary permit application published on May 31. “A preliminary permit does not authorize the permit holder to perform any land-disturbing activities or otherwise enter upon lands or waters owned by others without the owners' express permission.”
The applicant contact listed in documents is Ushakar Jha, a vice president of project engineering for Rye Development. Jha did not immediately respond to a call seeking comment on Thursday.
The Federal Energy Regulatory Commission is currently accepting public comment on this project until Tuesday, July 23. The only comment submitted as of Friday morning came from the Routt County Commissioners, who noted the project would need to pass through the county’s development process and would require a Special Use Permit.
Twentymile Mine, which is owned by Peabody Energy, is still mining coal, though that is expected to curb as regional power plants shutter at the end of the decade. A timeline included in the application indicates a full permit application could be submitted four years from now.
Based on the application, each reservoir would be 1,550 acre-feet in capacity, with the upper reservoir sitting on a nearby bluff at an elevation of 7,600 feet. The mine’s elevation is roughly 6,000 feet, according to the application. The project would also require a nearly two-mile stretch of transmission line extending from the system to a power substation.
The application estimates it could generate power for about six hours each day and has the potential to generate 547,500 megawatt hours of power each year.
Caption: A graphic included in the application shows where the upper reservoir of the pumped storage system would be located. (Federal Energy Regulatory Commission/Courtesy)
Paul Bony, the energy and transportation director for the Yampa Valley Sustainability Council, said Colorado’s power grid needs more backup capacity as it adds more wind and solar generating projects to its power mix.
“Pumped hydro has been around a long time. It’s relatively rare because there are not a lot of good sites,” Bony said. “We do need to offset the intermittency of renewables, so it fits that. It’s non-carbon so it’s not consumptive. I like that.”
The project is being proposed to federal regulators and not Colorado’s Public Utilities Commission, which is an indication to Bony that they intend to sell the power they generate on the market.
“Who would buy the power will be interesting,” Bony said. “They went to FERC and didn’t come through with a bid into Xcel or Tri-State, [which] tells me that they are going to try to sell that off as an independent power producer.”
The application details various studies that will commence over the next four years, if the preliminary permit is approved. The application estimates it could cost as much as $6 million to complete the required studies, which will be paid for with “private funds.”
“Upon issuance of a Preliminary Permit, the Applicant proposes to conduct detailed studies to determine the feasibility of the project and potentially support the application for license,” the application to FERC reads. “The feasibility study will be designed to evaluate various Project concepts, layouts, and equipment arrangements to optimize the Project configuration, while considering potential environmental impacts.”
In addition to offering the grid more power during peak usage periods, the application says the project will “reduce volatility of electricity prices,” “provide a method to store intermittently generated energy” and is “sustainable development with direct investment into the local and regional economy.”
Rye Development’s website argues their projects support local economies by creating hundreds of jobs during the construction period and by paying property taxes to local governments annually once operational.
On its website, Rye Development notes other pumped-storage projects it has in the works, including one in Kentucky and two in Oregon. The Kentucky project, called Lewis Ridge, is also converting a former mine site into a pumped storage system, though that is an open-air pit mine. Rye Development received $81 million from the U.S. Department of Energy for construction on Lewis Ridge in March.
Top Photo Caption: Twentymile Mine, as seen from a Southwest Airlines flight in 2023. A proposed pumped storage project would add a reservoir on a bluff north of the mine site (left of picture) and generate power by letting it flow down into the caverns of the mine. (Dylan Anderson/The Yampa Valley Bugle)