The Commodity Credit Corporation (CCC), an agency of the U.S. Department of Agriculture (USDA), formerly operated a grain storage facility approximately 1,100 ft north of Centralia (Figure 1.2). The CCC/USDA operated this facility from 1949 until 1971. None of the CCC/USDA structures remain. Two additional grain storage facilities currently exist in and near Centralia: the Nemaha County Co-op, approximately 4,000 ft south of the former CCC/USDA facility, and a private grain storage facility near the Don Morris residence, 3,500 ft north of the former CCC/USDA facility. Prior to 1986, commercial grain fumigants containing carbon tetrachloride were commonly used by the CCC/USDA and the grain storage industry to preserve grain. In April 1998, the Kansas Department of Health and Environment (KDHE) sampled the domestic well at the Don Morris residence near Centralia (Figure 1.2) as part of the CCC/USDA Private Well Sampling Program, which was initiated to determine whether carbon tetrachloride was present in domestic wells located near former CCC/USDA grain storage facilities in Kansas. Carbon tetrachloride was detected in the Morris well at 19.3 mg/L and confirmed at 25.4 mg/L, both concentrations above the maximum contaminant level (MCL) of 5 mg/L for carbon tetrachloride in drinking water. On the basis …