July 2008 Monitoring Results for Barnes, Kansas.

The Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) operated a grain storage facility at Barnes, Kansas, during most of the interval 1949-1974. 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 characterize this contamination. Those results were reported previously (Argonne 2008a). 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 2008a). 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 and the subsequent monitoring events in November 2007 (Argonne 2008b) and March 2008 (Argonne 2008c) demonstrated the presence of carbon tetrachloride contamination in groundwater at levels slightly exceeding the Kansas Department of Health and Environment (KDHE) Tier 2 risk-based screening level (RBSL) of 5.0 {micro}g/L for this compound. The contaminant plume appears to extend from the former CCC/USDA property northwestward, toward the Barnes public water supply wells. Information obtained during the 2006-2007 investigations indicates that at least one other potential source might have contributed to the groundwater contaminant plume (Argonne 2008a). This current report presents the results of the third monitoring event, conducted in July 2008. During this third monitoring event, low-flow sampling methods were used to purge and sample all wells. This was the second event at Barnes during which low-flow sampling methods were used