A methodology is described that will allow the pollution potential of any hydrogeologic setting to be systematically evaluated anywhere in the United States. The system has two major portions: the designation of mappable units, termed hydrogeologic settings, and the superposition of a relative rating system called DRASTIC. Hydrogeologic settings are described for different regions in the United States. These settings incorporate the major hydrogeologic factors which affect and control ground water movement including depth to water table, net recharge, aquifer media, soil media, topography, impact of the vadose zone and hydraulic conductivity of the aquifer. These factors, which form the acronym DRASTIC, as used to infer the potential for contaminants to enter ground water. The relative ranking scheme uses a combination of weights and ratings to produce a numerical value, called the DRASTIC INDEX, which helps prioritize areas with respect to ground water contamination vulnerability.

Distributed to depository libraries in microfiche. "May 1985." Includes bibliographical references. "Cooperative agreement CR-810175-01." "EPA/600/2-85/018."

Development of the system and overview -- DRASTIC: A description of the factors -- How to use hydrogeologic settings and DRASTIC -- Impact risk factors -- HYDROGEOLOGIC SETTING OF THE UNITED STATES BY GROUND WATER REGIONS: Western mountain ranges -- Alluvial basins -- Columbia Lava Plateau -- Colorado Plateau and Wyoming Basin -- High Plains -- Non-glaciated Central -- Glaciated Central -- Piedmont and Blue Ridge -- Northeast and Superior uplands -- Atlantic and Gulf coastal plain -- Southeast coastal plain -- Hawaii -- Alaska.