Annual report of monitoring at Morrill, Kansas, in 2010.
- Environmental Science Division
Carbon tetrachloride contamination in groundwater at Morrill, Kansas, was initially identified in 1985 during statewide testing of public water supply wells for volatile organic compounds (VOCs). High levels of nitrate were also present in the wells. The city of Morrill is located in Brown County in the northeastern corner of the state, about 7 mi east of Sabetha. The population of Morrill as of the 2000 census was approximately 277. All residents of Morrill now obtain their drinking water from the Sabetha municipal water system via a pipeline constructed in 1991. Starting in 1922, eight different public wells formerly served the Morrill municipal system at some time. Because of poor water quality, including high nitrate levels attributed to numerous animal feeding operations in the vicinity and application of fertilizer on agricultural lands, use of the local groundwater from any public well for municipal supply purposes was terminated in 1991 in favor of obtaining water from the Sabetha municipal water system. Investigations of the carbon tetrachloride and nitrate contamination by the Kansas Department of Health and Environment (KDHE) in 1989, 1994, and 1996 (KDHE 1989; GeoCore 1994a-e, 1996) identified a localized plume of carbon tetrachloride in groundwater extending downgradient from a grain storage facility located in the northwestern section of Morrill. The facility was formerly operated by the Commodity Credit Corporation (CCC), an agency of the U.S. Department of Agriculture (USDA), from 1950 to 1971. Since termination of the CCC/USDA grain storage operations in 1971, the property and existing grain bins have been used for private grain storage up to the present time. Prior to 1986, commercial grain fumigants were commonly used by the CCC/USDA, as well as private and commercial grain storage operations, to preserve grain. Because the identified carbon tetrachloride contamination could in part be linked to historical use of carbon tetrachloride-based fumigants at its former facility, in 2003 the CCC/USDA assumed responsibility for the site investigation of the carbon tetrachloride contamination. The CCC/USDA involvement began with development and implementation of a work plan for a Phase I expedited site characterization (Argonne 2003). That investigation and subsequent investigations (Argonne 2004, 2005a) were performed by the Environmental Science Division of Argonne National Laboratory. Argonne is a nonprofit, multidisciplinary research center operated by UChicago Argonne, LLC, for the U.S. Department of Energy (DOE). The CCC/USDA has entered into an interagency agreement with DOE, under which Argonne continues to provide technical assistance to the CCC/USDA with environmental site characterization and remediation at its former grain storage facilities. The initial investigation by the CCC/USDA in 2003 determined that soils at the former facility have not been impacted by grain fumigation activities. Neither carbon tetrachloride nor chloroform was detected in near-surface soils or in subsurface soils collected to bedrock or to a depth of 15 ft below ground level (BGL). Therefore, no identifiable human health risk is associated with either carbon tetrachloride or chloroform in shallow soils, which additionally pose no further threat of contamination to groundwater. High carbon tetrachloride concentrations in groundwater (maximum 390 {micro}g/L in a sample collected from monitoring well MW3S - located on the former CCC/USDA property - in 1995) have declined significantly during long-term monitoring by the KDHE and currently by the CCC/USDA. Maximum levels within the plume of < 50 {micro}g/L at present confirm that no continuing soil source remains at the former CCC/USDA facility. Nevertheless, carbon tetrachloride concentrations exceeding the KDHE Tier 2 risk-based screening level of 5.0 {micro}g/L remain. In September 2005, the CCC/USDA initiated periodic sampling of groundwater at Morrill, in accord with a monitoring program approved by the state (KDHE 2005), to monitor carbon tetrachloride concentrations in the groundwater. Under the KDHE-approved monitoring plan (Argonne 2005b), groundwater was initially sampled twice yearly for a period of two years. The samples were analyzed for VOCs, as well as for selected geochemical parameters to aid in the evaluation of possible natural contaminant degradation (reductive dechlorination) processes in the subsurface environment. The data have been inconclusive overall, possibly because of the relatively low contaminant concentrations in the plume. Nevertheless, consistently low levels of dissolved oxygen (DO) and oxidation-reduction potential (ORP) at monitoring well MW1D (in the deepest portion of the contaminated aquifer) and the presence of chloroform (the primary degradation product of carbon tetrachloride) suggest that some degree of reductive dechlorination is occurring.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDA
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1023154
- Report Number(s):
- ANL/EVS/AGEM/TR-11-06; TRN: US201118%%890
- Country of Publication:
- United States
- Language:
- ENGLISH
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