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.

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Raccoon Mountain Pumped-Storage Plant
Tailrace (TN River) of RMPS (TVA photo)
Location of Raccoon Mountain Pumped-Storage Plant in Tennessee
Country	United States
Location	Marion County, Tennessee
Coordinates	35°2′54″N 85°23′48″W
Purpose	Power
Status	Operational
Construction began	July 1970 (1970-07)[1]
Opening date	1978 (1978)
Construction cost	$310 million (1978)[2][3]
Owner(s)	Tennessee Valley Authority
Operator(s)	Tennessee Valley Authority
Upper dam and spillways
Type of dam	Embankment dam
Height (foundation)	230 feet (70 m)[4]
Length	8,500 feet (2,600 m)[4]
Dam volume	10,000,000 cubic yards (7,600,000 m3)[1]
Upper reservoir
Total capacity	107,000,000,000 US gallons (4.1×1011 L; 8.9×1010 imp gal)[4]
Surface area	528 acres (214 ha)[4]
Maximum water depth	222 feet (68 m)
Normal elevation	1,672 feet (510 m)
Lower dam and spillways
Type of dam	Gravity dam
Impounds	Tennessee River[5]
Height (foundation)	81 feet (25 m)[5]
Length	3,767 feet (1,148 m)[5]
Elevation at crest	635.0 feet (193.5 m)
Spillways	10
Spillway type	Radial gate
Lower reservoir
Creates	Nickajack Lake[5]
Total capacity	252,297 acre-feet (311,204,000 m3)
Active capacity	32,132 acre-feet (39,634,000 m3)
Catchment area	21,870 square miles (56,600 km2)
Surface area	10,370 acres (4,200 ha)[5]
Maximum water depth	145 feet (44 m)
Normal elevation	633.5 feet (193.1 m)
Power Station
Operator(s)	Tennessee Valley Authority
Commission date	1978 (1978)
Type	Pumped-storage
Hydraulic head	1,040 feet (320 m)
Pump-generators	4 × 413 MW
Installed capacity	1652 MW
Capacity factor	20%[6]
Storage capacity	22 hours
2017 generation	-686 GW·h
Website Raccoon Mountain

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The facility is owned and operated by the Tennessee Valley Authority (TVA). Construction was started in 1970 and was completed in 1978.^[7]

Water is pumped from Nickajack Lake on the Tennessee River at the base of Raccoon Mountain to a storage reservoir built at the top of the mountain. The reservoir at the top of the mountain covers 528 acres (214 ha), with a dam that is 230 feet (70 m) high and 5,800 feet (1,800 m) long, the largest rock-fill dam ever built by TVA. It takes 28 hours to fill the upper reservoir. During periods of high electric demand, water can be released from the reservoir through a tunnel drilled through the center of the mountain, driving electric generators in an underground hydroelectric plant.^[7] The plant has a maximum power output of 1,652 megawatts (2,215,000 hp) and can generate for up to 22 hours. The plant is used most days and serves as an important element for peak power generation and grid balancing in the TVA system.^[8][9]

The plant was idled in March 2012 due to cracks in the generators' rotors. The plant came entirely back on line in April 2014.^[10]

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.^[11]