Characterization and Remediation of Carbon Tetrachloride Site Contamination
Argonne's Environmental Science Division has performed extensive site characterizations, feasibility studies, remedial investigations, and remedy implementations for the Commodity Credit Corporation of the U.S. Department of Agriculture (CCC/USDA) at more than 40 former grain bin storage sites in Kansas and Nebraska. In the 1940s and 1950s, the CCC/USDA treated grain in hundreds of leased bin sites across the Midwest with a commonly accepted fumigant containing carbon tetrachloride. When carbon tetrachloride was later suspected to be a carcinogen, and was found to have infiltrated the local groundwater, the first priority of the CCC/USDA was to identify immediate threats to drinking water and to provide clean water to the local residents. In developing processes and technologies for this large program, Argonne became a leader in expedited site characterization, streamlining the traditional site characterization and saving millions of dollars for the CCC/USDA. The process developed at Argonne became the basis for the ASTM standard D6235-04, Standard Practice for Expedited Site Characterization of Vadose Zone and Ground Water Contamination at Hazardous Waste Contaminated Sites.
Argonne operates two cone penetrometer (CPT) units as a primary means of data acquisition during site characterization. The 40-ton vehicle is capable of exerting 40 tons of push force, while the track-mounted "crawler" unit can exert 20 tons of push force and is uniquely suited to typical farm field conditions in Kansas and Nebraska. Argonne has developed and improved CPT technology, using CPT boring to replace conventional drilling for monitoring well installation in many cases. Several patents have been approved or are pending for CPT tools and technologies developed at Argonne for this program. The program has also benefited from Argonne's continued refinement of fast-turnaround analytical capabilities and methods and advances in nonintrusive sampling and analytical techniques such as vegetation sampling, for which Argonne was granted another patent. All sites where there were immediate threats to drinking water have been characterized, and no one is drinking contaminated water. The emphasis in the program has now moved into the remedial phase. Two of Argonne's innovative remedial programs at former CCC/USDA grain bin storage sites have recently received national recognition at the 2005 White House Conference on Cooperative Conservation, St. Louis, August 29-31. In the first, a phytoremediation project in Murdock, Nebraska, Argonne planted more than 2,000 trees to take up contaminated water and break down carbon tetrachloride. At the same site, Argonne restored a wetland to intercept traces of the chemical and installed trails and interpretive signs throughout the project site that enhance recreational and educational opportunities. In the second project, at Utica, Nebraska, Argonne is helping to treat contaminated groundwater with a spray irrigation system that provides beneficial reuse of the groundwater to restore the North Lake Basin Wildlife Management Area that lies in a critical migratory waterfowl flyway in south-central Nebraska. Argonne has provided technical support for the CCC/USDA Former Grain Bin Storage Program since 1989. The work continues with a new emphasis on innovative remedial technologies.
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