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As a result of the proximity of groundwater to the contaminated soils, the installation of groundwater monitoring wells was required. These wells were installed prior to the excavation of the contaminated soil at the site and have been monitored for the past year. Laboratory analysis of the groundwater samples has consistently detected hydrocarbon contamination in one of the up- gradient wells (MW-2: most notably benzene; detected at 660 to 8000 ug/1) . Figure 2 shows the layout of the site, the area where the contaminated soils were removed, location of the monitoring wells, and the area where the bio-remediation of the soils is occurring. Copies of reports which documented the procedures used and results of each of the tasks mentioned above are on file with the Regional Water Quality Control Board: Central Valley Region (CVRWQCB) and the San Joaquin Local Health District (SJLHD) - (Preliminary Report on Underground Storage Tank Investigation at Stockton Scavenger Association: (BMI, 1989) ) & (Proposed Remediation Plan for Contaminated Soils at Stockton Scavenger Trucking Facility (BMI, 1988) ) . Discussions with staff of the CVRWQCB indicated that the levels of contamination in the up-gradient well were high enough to warrant additional investigation into their extent and to subsequently evaluate the risks posed to the surrounding area. GROUNDWATER INVESTIGATION The procedures to be implemented in the investigation of groundwater contamination at the Stockton Scavenger facility will employ a phased approach. Phase I involves obtaining a qualitative measure of the extent of groundwater contamination by using a Hydro-Punch attachment to the drilling rig which will allow for the procurement of groundwater samples without the expense of installing wells. After this data has been evaluated and a conceptual idea of the extent of the groundwater contamination formulated, an addendum to this report will be submitted to the CVRWQCB which shows the proposed locations of monitoring wells to be installed at the site. The installation of these wells will constitute Phase II of the investigation. Phase III involves the performance of rising and falling head slug tests on selected wells to determine hydraulic properties of the saturated sediments. Phase IV involves the analysis and reporting of the data obtained from the investigation and also an assessment of the risks posed by the contaminated groundwater. The report will also contain information pertaining to possible remedial actions that could be implemented at the site if necessary. Phase I: Oualitative Assessment of Groundwater Contamination To obtain a conceptual definition of the extent of groundwater contamination at the site, a Hydro-Punch groundwater sampling 2