Low-Level Outlet Retrofit at Lake Lure Dam

Lake Lure Dam, a concrete multiple-arch buttress dam located in western North Carolina, was found to have critical deficiencies in its hydraulic capacity, structural stability, and lack of a low-level outlet. To address these dam safety concerns, the owner adopted a rehabilitation approach that began with the addition of a low-level outlet while planning for a replacement dam. Maintaining a full reservoir during construction, a project objective important to the owner, posed challenges in both design and construction of the retrofit low-level outlet and required innovative solutions. As part of this project, divers installed a steel bulkhead with an O-ring seal to a precast concrete portal on the upstream arch face, withstanding 80 feet (24.4 meters) of head pressure without leakage. After placing a mass concrete buttress downstream, a penetration for a 72-inch (1.83 meters) pipe was cored through the arch. Once downstream piping and valves were installed, the system was activated successfully. The project improved dam safety, enhanced reservoir control, and will support future rehabilitation. The information in this paper offers valuable insights for dam retrofits, especially involving underwater construction and complex sealing conditions.