Final report : groundwater monitoring at Morrill, Kansas, in September 2005 and March 2006, with expansion of the monitoring network in January 2006.

Field: Environmental Science (Physical Sciences)

This document reports the results of groundwater monitoring in September 2005 and March 2006 at the grain storage facility formerly operated at Morrill, Kansas, by the Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA). These activities were the first and second twice yearly sampling events of the two-year monitoring program approved by the CCC/USDA and Kansas Department of Health and Environment (KDHE) project managers. The monitoring network sampled in September 2005 consisted of 9 monitoring wells (MW1S-MW5S and MW1D [installed in the mid 1990s] and MW6S-MW8S [installed in 2004]), plus 3 private wells (Isch, Rillinger, and Stone). The groundwater samples collected in this first event were analyzed for volatile organic compounds (VOCs), dissolved hydrogen, and additional groundwater parameters to aid in evaluating the potential for reductive dechlorination processes. After the monitoring in September 2005, Argonne recommended expansion of the initial monitoring network. Previous sampling (August 2004) had already suggested that the initial network was inadequate to delineate the extent of the carbon tetrachloride plume. With the approval of the CCC/USDA and KDHE project managers, the monitoring network was expanded in January 2006 through the installation of 3 additional monitoring wells (MW9S-MW11S). Details of the monitoring well installations are reported in this document. The expanded monitoring network of 12 monitoring wells (MW1S-MW11S and MW1D) and 3 private wells (Isch, Rillinger, and Stone) was sampled in March 2006, the second monitoring event in the planned two-year program. Results of analyses for VOCs showed minor increases or decreases in contaminant levels at various locations but indicated that the leading edge of the contaminant plume is approaching the intermittent stream leading to Terrapin Creek. The groundwater samples collected in March 2006 were also analyzed for additional groundwater parameters to aid in the evaluation of the potential for reductive dechlorination processes. Preliminary screening of groundwater parameters provided inadequate evidence that reductive dechlorination of carbon tetrachloride is taking place at some locations on the former CCC/USDA property. Groundwater levels measured manually in October 2005, March 2006, and June 2006 were used to map the potentiometric surface at Morrill. The results were generally consistent with each other and with previous measurements, indicating a groundwater flow direction to the south-southeast from the former CCC/USDA facility. Data recorders installed in wells MW1S-MW8S in July 2004 are gathering long-term data on the groundwater elevation and gradient. Data downloaded in August 2004, March 2005, October 2005, and June 2006 indicate that two relatively upgradient wells near the former CCC/USDA facility responded distinctly to apparent rainfall/recharge events. In contrast, two downgradient wells south of the former facility showed virtually no response, probably because of the damping influence of the nearby surface drainages and shallow groundwater at their locations. The first two monitoring events of the planned two-year monitoring program for Morrill have demonstrated no clear pattern of changes in carbon tetrachloride concentrations, though the contaminated zone has expanded toward the intermittent stream. Argonne recommends that the monitoring program continue as approved and that surface water samples be collected in future monitoring events (September 2006, March 2007, and September 2007).