The Tompkins County Hillview Landfill was located on the site of an older landfill that had no containment and partially overlay permeable glacial deposits. After its use by the County it was capped and monitored in accordance with NYS Department of Conservation regulations, but there still remained the possibility that leachate could escape downward into local aquifers and from these into major aquifers underlying Cayuga Inlet Valley. Following closure, a number of test and monitoring wells were drilled around the periphery of the landfill, most of which showed little or no leachate migrating from the site. A review of well data by the Hillview Landview Citizens’ Committee determined, however, that the DGC-2 well cluster, at the northeastern corner of the landfill, did show significantly elevated levels of volatile organic compounds and dissolved metals. Together with a presumed northward groundwater flow gradient, based on water elevations in existing wells, this information suggested the possibility of a contaminant plume escaping from the landfill.