TVA teams have worked together to complete a multi-year, multi-division project that increases public safety, dam safety and nuclear safety if the most extreme of weather events ever hits the Tennessee Valley.
JUNE 26, 2018—The recent completion of a new seven-foot high concrete flood wall at TVA’s Fort Loudoun Dam marks the last in a series of major construction projects at five TVA dams to further protect Watts Bar and Sequoyah nuclear plants from a worst-case flood scenario.
The new Fort Loudoun flood wall is designed to temporarily contain the waters of the Tennessee River should it rises to unusually high levels during extreme weather events. Stretching about 1,200 feet and designed to hold back waters cresting at 837 feet above sea level, the wall is four feet higher than the old wall it replaces. Demolition and disposition of the old wall, which was built in 1989, will be completed by the end of April.
The Fort Loudoun work also included construction of a 1,400-foot long rolled compacted concrete section of the dam’s South embankment and modification of another section of the dam with post-tension anchors and steel bar reinforcement.
The work stems from TVA’s 2009 decision to modify Cherokee, Douglas, Fort Loudoun, Tellico and Watts Bar dams to provide extra protection for nuclear plants in the event of a worst-case scenario flood, also know as a probable maximum flood (PMF). Although a flood this extreme has never occurred and is highly unlikely, TVA took steps to lower the risk of flood damage ever occurring at its nuclear plants.
The initial modifications included temporary barriers made by stacking wire-mesh containers filled with sand to raise the flood wall height. The barriers are known as Hescos after the company that manufacturers them. About 18,000 feet of Hesco barriers filled with 30 million tons of sand were used. All have been replaced now with permanent concrete flood walls or earthen embankments, with the last removed recently at Fort Loudoun Dam. Sand from the discarded barriers is being used to maintain walkways and trails, and to support other work at TVA sites and facilities.
“While they added an effective extra measure of protection for our plants and the public, the Hesco barriers were only a temporary solution,” says Sam Vinson, principal project manager, Generation Construction, Projects & Services. “TVA made a commitment to the Nuclear Regulatory Commission to have the permanent flood walls and other work completed by June 2018. With completion of this work at Fort Loudoun, TVA has met and exceeded that goal.”
TVA’s Dam Safety, River Management and Nuclear, Generation Construction & Projects organizations worked together to calculate flood levels impacted by Fort Loudoun and other dams; determine modifications needed to protect nuclear plants in a PMF; perform detailed field investigation and stability analyses; and complete construction modifications at the dams.
“The teamwork, collaboration and expertise of the TVA groups who worked on this project over the years has been remarkable,” says Husein Hasan, senior program manager, Dam Safety. “Completion of these PMF modification at Fort Loudoun Dam is a major achievement that will greatly increase the safe and reliable operations of our dams and nuclear plants in the event of the most extreme adverse weather conditions.”
Fort Loudoun Dam is located on the Tennessee River near Lenoir City in Loudon County. It was built by TVA between 1940 and 1943, stands approximately 122 feet high and reaches 4,190 feet in length. Fort Loudoun Reservoir is connected to the Tellico Reservoir by a short canal, linking the two reservoirs in their joint functions of flood damage reduction, power production, recreation and navigation.