Some aspects of the design and construction of the Bear Creek Reservoir, Jackson County, Georgia

In response to the severe drought conditions experienced throughout the State of Georgia in the mid-1980's, four counties in the Piedmont region of Northeast Georgia, including Athens-Clarke, Oconee, Barrow and Jackson recognized the need for additional water storage to minimize the impact of future drought conditions in their area. To address that need, the four counties adopted resolutions approving passage of state legislation and in the 1994 Sessions of the Georgia General Assembly, the Upper Oconee Basin Water Authority was created as a political subdivision of the State of Georgia and a public corporation. Subsequent passage of a 1996 intergovernmental agreement between the Authority and the four counties began the process of the development, design and construction of the 505-acre Bear Creek Reservoir which is permitted to yield 52 million gallons of water per day. Based on previous studies, investigations and evaluations made by the Authority, the Bear Creek Reservoir site, located in the southwest comer of Jackson County, was selected as the preferred site for the water supply reservoir. The project involves the construction of an embankment dam on Bear Creek to form a reservoir with a capacity of 4.8 billion gallons of water, an intake pump station situated at the Middle Oconee River, a 0.6 mile long raw water pipeline extending from the pump station to the Bear Creek Reservoir, to fill the reservoir during periods of high flows in the Middle Oconee River, an intake in the reservoir and a raw water treatment plant and ancillary facilities situated adjacent to the dam. The project also involved relocating an existing road to extend across the crest of the dam and construction of a new bridge spanning the emergency spillway. This paper describes the design and construction of the Bear Creek dam and spillway. One of the main challenges was to restrict flood levels to the available property, while providing the required storage volume and at the same time providing a safe structure that did not exceed the budget that was raised by bonds sold by the four counties. Consideration of these issues led to the final design which included a 1,000 ft. long, 90 ft. high zoned earthfill embankment, a 75 ft. high water inlet tower and an overflow "stair-stepped" emergency spillway with its invert founded entirely within rock. A 14 ft. high, 310 ft. wide Ogee weir is located at the upstream end of the spillway and a 180 ft. wide "roller bucket" energy dissipator is located at the downstream end of the spillway. The emergency spillway is designed to activate when the water level in the reservoir exceeds 1/2 ft. above the normal pool elevation. 12 pp., 2 references.