Raccoon Mountain Pumped-Storage Plant is a pumped-storage hydroelectric underground power station in Marion County, just west of Chattanooga in the U.S. state of Tennessee. Owned and operated by the Tennessee Valley Authority (TVA), the plant can generate a maximum of 1,652 megawatts of electricity. The reservoir at the top of the mountain covers 528 acre, with a dam that is 230 ft high and 5800 ft long, the largest rock-fill dam ever built by TVA. The plant serves as an important element for peak power generation and grid balancing in the TVA system. Construction was started in 1970 and was completed in 1978. The plant was idled in March 2012 due to cracks in the generators' rotors. The plant came entirely back on line in April 2014.

Operation

During periods of high electric demand, water flows from reservoir into a tunnel drilled through the center of the mountain, driving electric generators in the underground powerhouse. During periods of low demand and excess generation, the generators run in reverse and pump water from Nickajack Lake back up to the top of the mountain, where it is stored until needed later. This process repeats continuously, serving as peak power generation. The plant has a maximum power output of 1652 MW and can generate power for up to 22 hours.

Recreation

The TVA operates a visitor center, open year-round, that offers exhibits on the history of the generating facility as well as the TVA’s operations. The center also offers views of the Tennessee River gorge and surrounding mountains. Raccoon Mountain is used for hiking, walking, running, and road and mountain biking. It hosts a marathon, half marathon, double half marathon, relay, 5K and 10K race each year.