A Computational Fluid Dynamics Approach to Assessing and Limiting Scour from Complex Spillway Flows

Mitchell Dam, which is owned and operated by Alabama Power Company (Alabama Power), is a 1,264-foot long concrete gravity dam on the Coosa River, in Alabama. The dam serves to generate hydroelectric power, and provides recreation on the impounded Mitchell Lake. Original construction of the dam and four-unit powerhouse began in 1921; three 17.5 MW generating units were brought online in 1923, with a fourth 20 MW generating unit brought online in 1949. As originally constructed, the spillway included 26 radial gates, each 30 feet wide and 15 feet tall, with the powerhouse located upstream of the spillway and the draft tubes discharging through the apron of 12 spillway bays. A substantial redevelopment of the project was completed in 1985, adding a second three-unit powerhouse along the west bank of the river. As part of the redevelopment of the project, three of the original spillway gates were removed to accommodate the construction of the second powerhouse. To offset the loss of discharge capacity, three larger (30 feet wide and 25 feet tall) radial spillway gates were added at the east end of spillway, replacing a portion of the original abutment section. The three new spillway bays are collectively known as the East Spillway.