Rocky Mountain Hydroelectric Plant
| Company type | Joint venture |
|---|---|
| Industry | Energy |
| Founded | 1977 |
| Headquarters | Rome, Georgia , United States |
Area served | Georgia, United States |
| Products | Hydroelectric power |
| Owner | Oglethorpe Power (75%), Georgia Power (25%) |
The Rocky Mountain Hydroelectric Plant is a pumped-storage energy facility situated northwest of Rome, Georgia within the U.S. state of Georgia. It derives its name from Rock Mountain, the site of its upper reservoir. Construction commenced in 1977, with the plant becoming operational in 1995. After an upgrade in 2011, its installed capacity was enhanced to . The facility is jointly owned by Oglethorpe Power (holding 75%) and Georgia Power (holding 25%).
Background
In 1972, Georgia Power submitted an application for a Federal Energy Regulatory Commission (FERC) license and began the design phase alongside land procurement. Initial construction began in 1977, concentrating on tunnels, penstocks, roadways, and bridges, but work was halted at 20% completion in 1985. Two years later, in 1987, Oglethorpe Power expressed interest in developing a pumped-storage plant and entered negotiations with Georgia Power to finalize the project. On December 15, 1988, after obtaining a $706.8 million loan guarantee, Oglethorpe assumed operational control and acquired a 75% ownership share. Construction activities recommenced soon thereafter.
The plant reached completion with generator commissioning in 1995 at a total cost of $1 billion. The upgrade implemented in 2011 boosted each turbine-generator’s capacity from to , raising overall capacity from to 1,095 MW. Pumping power was also improved during this enhancement. This early modernization was possible because turbines, pumps, and inlet valves had been purchased prior to the initial construction suspension and stored until work resumed.
Design and operation
Operating as a pumped-storage facility, this plant employs two reservoirs to manage energy storage and generation. During periods of low electricity demand, water is stored in the upper reservoir; when demand peaks, it is released to generate hydroelectric power. Water flowing into the lower reservoir is then pumped back uphill during off-peak times to replenish the upper reservoir within approximately 7.2 hours. The turbine-generators function reversibly as pumps during this process.
The upper reservoir is created by an earth and rock-fill dam on Rocky Mountain that stands 120 ft tall and stretches 12,895 ft long. It holds up to 10,650 acre-feet of water over an area of 221 acres at an elevation of 1,392 ft. The lower reservoir lies at an elevation of 710.5 ft and impounds Heath Creek using two embankment dams plus a composite gravity/embankment dam standing 120 ft tall with a spillway equipped with two tainter gates. This reservoir contains up to 18,800 acre-feet across 600 acres. Additionally, two nearby auxiliary reservoirs—Auxiliary Pool I (400 acres) and Auxiliary Pool II (200 acres)—offer an extra storage capacity of 5,800 acre-feet during drought conditions while supporting recreational activities and wildlife habitats.
A penstock measuring 889 ft connects the upper reservoir to the powerhouse before dividing into three conduits that feed each of the three Francis pump-turbine units rated at 365 MW each. The elevation difference ensures a minimum net hydraulic head of 613 ft.