Boone Dam is located above the South Fork Holston River's confluence with the North Fork Holston River. The Watauga River joins the South Fork Holston almost immediately upstream from the dam, creating a V-shaped reservoir that extends for up the South Fork Holston and for up the Watauga. The Sullivan-Washington county line follows the reservoir for most of its Watauga span. Boone Dam is downstream from South Holston Dam and upstream from Fort Patrick Henry Dam.
Capacity
Boone Dam is a concrete gravity-type dam high and long, and has a generating capacity of 81,000 kilowatts. While the main section of the dam is a concrete structure, the northern half of the dam consists of a earth-and-fill structure that seals off the floodplain adjacent to the main river channel. The dam's overfall spillway has five radial gates with a combined maximum discharge of. Boone Lake has of shoreline and a flood storage capacity of. The reservoir's operating levels vary by about in a typical year.
Background and construction
Both public and private entities were aware of the hydroelectric potential of the South Fork Holston River in the early 1900s, although other than Wilbur Dam on the river's Watauga River tributary, no major dam projects were attempted. In the 1920s, the Holston River Power Company surveyed the river basin with plans to build four dams, and identified the present Boone site. In the 1930s, when the Tennessee Valley Authority assumed oversight of flood control operations in the Tennessee River watershed, the agency suggested the Boone site as a potential dam site. As Watauga Dam and South Holston Dam neared completion in the late 1940s, the Spurgeon Island site was the next logical step in development of the South Fork Holston. The project's primary purpose was to provide flood control in the region, especially for Kingsport, which had suffered major flood damage in 1901 and 1940. The dam would also add hydroelectricity to TVA's energy grid, which by 1950 had been maxed out by increasing demands from consumers and from Atomic Energy Commission facilities at Oak Ridge. Work on Boone Dam began August 29, 1950. The construction of Boone Dam and its reservoir required the purchase of of land, of which had to be cleared. 152 families, 104 graves, and of roads had to be relocated, and three new bridges were built. The outbreak of the Korean War brought increased support from federal entities, and work progressed without interruption. Boone Dam was completed and its gates closed December 16, 1952. The dam's first generator went online March 16, 1953, its second generator went online June 12, 1953, and the third went online September 3, 1953. The total cost of the Boone project was $27.7 million.
Sinkhole
On October 20, 2014, during an informal inspection, a sinkhole was discovered at the toe of the dam that allowed water to seep through. Consequently, a decision was made to start lowering the water level in the lake earlier than normal as a cautionary measure. On July 30, 2015, a media briefing was held discussing the results of a formal inspection of the dam. Internal erosion was found to be the cause of the seepage. A wide range of methods of repairing the dam were considered. A composite seepage barrier was the preferred option. After impact studies have been conducted, work is likely to begin on the repair in early 2016 and may take 5 to 7 years to complete. The repair will cost two hundred to three hundred million dollars.
