Estimates of Groundwater Age from Till and Carbonate Bedrock Hydrogeologic Units at Jefferson Proving Ground, Southeastern Indiana, 2007?08

During 2007?08, the U. S. Geological Survey, in coopera-tion with the U. S. Department of the Army, conducted a study to evaluate the relative age of groundwater in Pre-Wisconsinan till and underlying shallow and deep carbonate bedrock units in and near an area at Jefferson Proving Ground (JPG), southeastern Indiana, which was used during 1984?94 to test fire depleted uranium (DU) penetrators. The shallow carbon-ate unit includes about the upper 40 feet of bedrock below the bedrock-till surface; the deeper carbonate unit includes wells completed at greater depth. Samples collected during April 2008 from 15 wells were analyzed for field water-quality parameters, dissolved gases, tritium, and chlorofluorocarbon (CFC) compounds; samples from 14 additional wells were analyzed for tritium only.