To provide the residents of Carroll County, Georgia, with an adequate supply of raw water, Carroll County Water Authority (CCWA) turned to its long-time professional services provider Schnabel to design a dam. We designed the Snake Creek Dam, which was approved for construction in 2001 as a high-hazard dam by the Georgia Safe Dams Program, and have since worked on subsequent projects related to its operation.

The dam has a structural height of nearly 65 feet and impounds a reservoir on the order of 640 acres. Its principal spillway consists of a 13-ft by 52-ft interior dimension riser structure and twin 6-ft by 6-ft box conduits. The auxiliary spillway system, which was designed using the SITES computer program to evaluate erosion potential, consists of two 200-ft-wide open channels, one in each abutment.

When Snake Creek Dam was tested by a storm event in 2009, the spillway performed as anticipated by the SITES model when using the original design and the event’s rainfall data. Exceeding 33% of the probable maximum precipitation (PMP), the storm swelled discharges through the auxiliary spillways, resulting in erosion to the left abutment spillway while damage to the right abutment auxiliary spillway, which contained a significant amount of rock, was limited. The predicted erosion was nearly identical to the erosion that occurred. Repairs to the spillway, which we designed and the Georgia Safe Dams Program again approved, were completed in 2012.

In addition to the design of the dam and repairs to the left auxiliary spillway, we have also provided ongoing on-call consulting services to CCWA. These services include inspection, evaluations of instrumentation data, preparation of Emergency Action Plans, and training of CCWA staff on dam safety. Recently, we provided professional engineering support to CCWA on the planning of the next water supply reservoir. Services for this project include safe-yield modeling, downstream flow impairment modeling, preliminary design of the planned new dam, development of conceptual cost estimates, and assistance with financial planning for the project.

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