Nickajack Dam

Nickajack Dam is a hydroelectric dam in Marion County in the U. S. state of Tennessee. It is one of nine dams on the Tennessee River owned and operated by the Tennessee Valley Authority, which built the dam in the mid 1960s to replace the outdated Hales Bar Dam 6 mile (10 km) upstream. The dam impounds the Nickajack Lake and feeds into Guntersville Lake. Nickajack Dam is named for a Cherokee village once located just upstream from the dam (the site is now submerged). The village was the namesake for Nickajack Cave, which was partially flooded by the reservoir.

Nickajack Dam is located 424 mile (682 km) above the mouth of the Tennessee River, near the point where the states of Tennessee, Georgia, and Alabama meet. This stretch of the river marks a region where the river begins to exit the once treacherous Tennessee River Gorge en route to the flatlands around Guntersville, Alabama. The Sequatchie River empties into the dam's tailwaters, and the city of South Pittsburg is just over 5 mile (8 km) downstream from the dam. Nickajack Lake stretches northeast for over 46 mile (74 km), all the way to the base of Chickamauga Dam in Chattanooga. Tennessee State Highway 156 passes just south of Nickajack Dam, and Interstate 24 passes a few miles to the north.

Nickajack Dam is 81 feet (25 m) high and 3767 feet (1148 m) long. Its reservoir has 179 mile (288 km) of shoreline and of water surface. The dam's 10 spillway bays have a combined discharge of The electrical generating capacity of Nickajack is 104 megawatts. Nickajack is serviced by a auxiliary lock that can lift or lower as many as nine large barges at a time 41 feet (12 m) between Guntersville Lake and Nickajack Lake. The dam's original design allowed for an main lock beside the auxiliary, but it was never completed. This lock, as well as every lock on the Tennessee River, is operated and maintained by the U. S. Army Corps of Engineers. Hales Bar's weak limestone foundation— which hadn't been considered in the selection of the dam site— presented numerous obstacles from the outset, but the dam was finally completed in 1913. The dam had been leaking since its construction, and TVA immediately initiated a series of foundation improvements that by 1943 had succeeded in halting the leaks. In 1960, however, the leaks had returned, spilling at an alarming Around the same time, TVA began expanding locks on its dams to at least 600 feet (183 m) to accommodate the increase in traffic the river had experienced since World War II, and it was determined that expanding the Hales Bar lock would be "prohibitively" expensive. Rather than spend the necessary expenses to upgrade Hales Bar, a decision was made in 1963 to build a new dam altogether on a more solid bedrock a few miles downstream. The Nickajack Dam project was authorized January 9, 1964, and construction began April 1, 1964. Funding set aside for repair work on Hales Bar was transferred to the Nickajack project. The reservoir's construction— which basically involved extending the Hales Bar Reservoir 6 mile (10 km) downstream to Nickajack— required the purchase of , of which had to be cleared. 82 families and 8 mile (13 km) of roads had to be relocated. Two generators and several switchyard parts were moved from Hales Bar Dam to the new dam. Construction was completed on December 14, 1967, at a cost of $73 million (equivalent to $ in ). Operations at Hales Bar Dam were halted the following day, and by September 1968, Hales Bar Dam had been dismantled and its reservoir merged with Nickajack Lake.