The Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) formerly operated a grain storage facility (during most of the interval 1949-1974) at Barnes, Kansas. Carbon tetrachloride contamination was initially detected in 1986 in the town's public water supply wells. In 2006-2007, the CCC/USDA conducted a comprehensive targeted investigation at and near its former property in Barnes to investigate this contamination. In November 2007, the CCC/USDA began quarterly groundwater monitoring at Barnes. The monitoring is being conducted on behalf of the CCC/USDA by Argonne National Laboratory, in accord with the recommendations made in the report for the 2006-2007 targeted investigation (Argonne 2007). The objective is to monitor the carbon tetrachloride contamination identified in the groundwater at Barnes. The sampling is presently conducted in a network of 28 individual monitoring wells at 19 distinct locations, 2 public water supply wells, and 1 private well (Figure 1.1). The results of the 2006-2007 targeted investigation demonstrated the presence of carbon tetrachloride contamination at levels slightly exceeding the Kansas Department of Health and Environment (KDHE) Tier 2 risk-based screening level of 5.0 {micro}g/L for this compound, in a plume that appears to extend from the former CCC/USDA property northwestward, toward the Barnes public …