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Well Closure Methods and Procedures Phase 2

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Historically, McClellan AFB has used a variety of hazardous materials as part of routine operations and maintenance activities. These hazardous materials have included industrial solvents, caustic cleaners, electroplating wastes containing heavy metals, jet fuels, and a variety of oils and lubricants Radian Corporation, 1990. In August 1979, the McClellan AFB Environmental Protection Committee created a special groundwater contamination task force to determine whether groundwater quality problems existed in the area. This voluntary action was prompted by concern that previous use of toxic chemicals, particularly trichloroethylene TCE, could have affected groundwater quality. Samples collected from several wells on and near the base during 1979 and 1980 confirmed the presence of TCE in certain wells. As a result, those wells were taken out of service. Since the discovery of groundwater contamination, investigations have been conducted at McClellan AFB under the Air Force Installation Restoration Program. Results of these investigations show that contamination is mainly confined to the uppermost groundwater zones beneath the base. Drinking water wells in the vicinity of the base draw primarily from deeper groundwater zones Radian Corporation, 1990. Heavy pumping from many of these wells has created a downward gradient of flow in the groundwater system beneath the base. However, concern mounted that existing inactive water supply wells at McClellan AFB may serve as conduits, allowing contaminated groundwater near the water table to migrate to deeper zones through the casing and gravel pack and potentially threaten downgradient drinking water supplies.

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  • Environmental Health and Safety

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