Identification of potential water-bearing zones by the use of borehole geophysics in the vicinity of Keystone Sanitation Superfund Site, Adams County, Pennsylvania, and Carroll County, Maryland

Abstract

Between April 23, 1996, and June 21, 1996, the U.S. Environmental Protection Agency contracted Haliburton-NUS, Inc., to drill four clusters of three monitoring wells near the Keystone Sanitation Superfund Site. The purpose of the wells is to allow monitoring and sampling of shallow, intermediate, and deep waterbearing zones for the purpose of determining the horizontal and vertical distribution of any contaminated ground water migrating from the Keystone Site. Twelve monitoring wells, ranging in depth from 50 to 397.9 feet below land surface, were drilled in the vicinity of the Keystone Site. The U.S. Geological Survey conducted borehole-geophysical logging and determined, with geophysical logs and other available data, the ideal intervals to be screened in each well. Geophysical logs were run on four intermediate and four deep wells, and a caliper log only was run on shallow well CL-AD-173 (HN-1S). Interpretation of geophysical logs and existing data determined the placement of screens within each borehole. INTRODUCTION The Keystone Sanitation Superfund Site was an active landfill that accepted household, municipal, and some industrial and construction wastes from before 1966 until April 1990. In 1982, the Pennsylvania Department of Environmental Protection discovered volatile organic compounds (VOC’s) in an on-site monitoring well and a nearby spring. Subsequent sampling by the U.S. Environmental Protection Agency (USEPA) in 1984 confirmed the presence of VOC’s in off-site residential wells. In 1987, the Keystone Site was added to the National Priorities List. The USEPA took the lead on the Remedial Investigation/Feasibility Study (RI/FS) in 1989. The purpose of the RI/FS was to evaluate the nature and extent of hazardous contamination and determine cost-effective remediation alternatives for the Keystone Site. In 1990, a Record of Decision (ROD) was signed by USEPA that specified a landfill cap and ground-water withdrawal and treatment as the remedies for contamination from the landfill site (Operable-Unit 1). In addition, the ROD provided for further study of off-site Operable-Unit 2 (OU-2) contamination. An RI/FS for OU-2 is currently being conducted by Haliburton-NUS, Inc. (NUS), to characterize the nature and extent of hazardous contamination and determine cost-effective remediation alternatives for off-site contamination.