Upgrading the NRCS Y-14 dam in Gwinnett County
Hudock, Gregg W.
Humphries, Richard W.
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Suburban development of Gwinnett County has surrounded many of the flood control watershed dams that were built in the mid-1900s. In many cases, the watersheds and downstream reaches have developed significantly since the time of construction. Development has changed the runoff characteristics of the watershed and many homes are now in the breach zones of these dams. The spillways of many of these dams cannot safely pass flood flows based on current design standards required by the State of Georgia Rules for Dam Safety or the NRCS design criteria for high hazard dams. The Yellow River Watershed Dam No. 14 (Y-14) is the first of the watershed dams to be upgraded in Gwinnett County. Y-14 was originally constructed in 1967 by the Soil Conservation Service (SCS – currently the USDA Natural Resources Conservation Service or NRCS) to control drainage from a 3.1 square mile watershed. The structure has a 40 feet high embankment dam, a traditional SCS principal spillway structure with a riser tower and outlet pipe, and a 50 ft. wide earthen auxiliary spillway through a saddle on the left abutment. In 2003, the dam was upgraded to bring it into compliance with modern standards by constructing a new Roller Compacted Concrete (RCC) Stepped Spillway on top of the embankment dam and decommissioning the original auxiliary spillway. This paper describes the evaluation of the original dam and the design of the upgrades to the dam.