The Raccoon Mountain pumped-storage plant near Chattanooga in Tennessee is a breathtaking site featuring panoramic views of the Tennessee River Gorge and a vast network of challenging biking and hiking trails through scenic woods teeming with wildlife.

At the same time, this 3,000-acre site hosts a huge power plant, producing more than 1,600 megawatts of electricity from a spectacular feat of engineering.

Construction of this $300 million plant began in 1970 and took nine years to complete. It started with the creation of a manmade reservoir on top of the mountain which can hold more than 12 billion gallons of water!

To generate electricity, water from the upper reservoir is channeled through an intake structure to a 35-foot-diameter concrete-lined passageway called a penstock, down 1,000 feet through the centre of the mountain to an underground power plant.

Deep inside the mountain are tunnels leading to a space the size of an American football field, which was carved entirely out of solid limestone. This space houses the plants’ four pump turbines, which use the force of flowing water to turn the generators that create electricity.

The turbines are able to be reversed and the same penstock is used to pump water back to the upper reservoir from the Tennessee River below. It takes some 28 hours to refill the upper reservoir.

The Tennessee River Gorge as viewed from the top of Raccoon Mountain.

The upper reservoir which has a roadway all around it.

The slotted design of the intake structure prevents whirlpools from developing as water enters it.