"Drastic" Mapping to Determine the Vulnerability of Ground-Water to Pollution
The Georgia Geologic Survey Branch of the Environmental Protection Division, Georgia Department of Natural Resources, in cooperation with the Georgia District of the U.S. Geological Survey, Water Resources Division, is conducting a project to map the relative susceptibility of Georgia's shallow aquifers to ground-water pollution. The DRASTIC method developed by the U.S. EPA is being used to develop the maps. DRASTIC is a methodology that allows the pollution potential of any hydrogeologic setting to be systematically evaluated. The system has two major portions: the designation of mappable units, termed hydrogeologic settings, and the superposition of a relative rating system (Aller, et. al., 1987). DRASTIC is an acronym for the hydrogeologic factors which influence pollution potential: depth to water (D), net recharge (R), aquifer media (A), soil media (8), topography (T), impact of the vadose zone media (I), and hydraulic conductivity of the aquifer (C). Each factor is incorporated into a relative rating scheme that uses a combination of weights and ratings to produce a numerical value called the DRASTIC Index (Aller, et. al., 1987). The higher an area scores on the index, the more vulnerable the specific area is to ground water pollution.