Great Falls Dam at Rock Island State Park is 100 years old.
Tennessee Electric Power Company began construction of the dam in 1915 for the purpose of power generation. It was complete in 1916, started generating power on Jan. 1, 1917, and was named for the falls that plunge into the Caney Fork River below it.
Great Falls Dam is considered an engineering triumph. It utilizes mostly underground conduit to carry water from the reservoir to the power house, which is .75 miles away.
The dam was redesigned in 1925, which resulted in its height being raised 35 feet. It now stands 92 feet tall and is 800 feet long. The one-lane wooden road atop Great Falls Dam, which allowed motorists to drive across it, was closed in 2009.
At the time of the redesign in 1925, a second tunnel was augured, and a newer high-capacity generator was placed in the power plant.
Floods in 1929, while devastating to many, were controlled by the men at the Great Falls plant, and the dam’s usefulness as a flood control unit was revealed.
The dam creates a reservoir of the water at the confluence of the Caney Fork and Collins rivers. It is essentially a concrete, non-overflow structure which includes an emergency spillway in its design. It looks, essentially, as it appeared after the redesign in 1925.
Purchased in 1939 by Tennessee Valley Authority, Great Falls Dam was one of seven acquired by the company from private companies, and it’s the only TVA dam located outside the Tennessee River watershed. It has two generating units with a net dependable capacity of 36 megawatts.
Great Falls Dam was purchased by TVA in a package of four dams purchased from Tennessee Electric Power Company.
“Great Falls was one of four dams we purchased from Tennessee Electric Power Company in 1939,” said Robby Floyd, plant manager for Watts Bar and Great Falls. “It’s one of the oldest dams in our system. In fact, Great Falls features one of the oldest vertical generating units in the country.”
The dam had one unit when first constructed. A second until was added in the early 1920s and the powerhouse was rebuilt to accommodate it. The two generating units have a net dependable capacity of 36 megawatts. Net dependable capacity is the amount of power a dam can produce on an average day, minus the electricity used by the dam itself.
Facts: Great Falls Reservoir is 22 miles long and has 120 miles of winding shoreline and about 1,830 acres of water surface. Great Falls has a flood-storage capacity of 30,500 acre-feet. The dam is 92 feet high and stretches 800 feet across the Caney Fork River.
Great Falls Hydroelectric Station was added to the National Register of Historic Places in July 1990 and TVA gives great care to preserve its historical significance.
“TVA takes its significance into account whenever we do projects at Great Falls so as not to impact the historical integrity there,” said Pat Ezzell, TVA historian. “Our Cultural Resources Department works hard to make certain that cultural integrity is maintained.”
For its 100th year, TVA will undertake an initiative to rehab the windows at Great Falls Dam without damaging its standing on the National Register of Historic Places.