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PRELIMINARY EVALUATION AND INVESTIGATION OF HYDROCARBON CONTAMINATION LERNER SERVICE STPTION 521 N. CHEROKEE LANE LODI, CALIFORNIA BACKGROUND The site is a former gas station located in a flat, commercial/residential area (Figure 1 - Location Map, Lodi North 7.5 minute Quadrangle, USGS Topographic Series, 1976) . It is our understanding that RAMCON, Inc. removed five underground gasoline storage tanks and one waste-oil tank on 5 February 1988. Soil samples obtained by RAMCON from below the largest (10,000 gallon) tank indicated that an unauthorized release of gasoline had occurred, and Applied Geosystems, Inc. was subsequently retained to assess the extent of soil contamination. Aprnl.ied Geosystems (AGS) drilled four soil borings (B-1 to B-4) and 4olleected soil samples at 5-foot intervals in all four in August 1988 (Figure 2 -Site Plan) . These samples were not. submitted For laboratory analysis, but a portable photo-ionization detector was used to measure total petrolelum hydrocarbon (TPH) levels in the field. AGS reported the results of this investigation in a report dated 21 September 1988. The hi4l`est. reading (538 ppm TPH) was recorded in boring B-4 at a depth of, 4.0 feet: This boring was drilled down to 60 feet and converted to- ground-water monitoring well MW-1. The ground-water level at the time of completion was 40 feet. Gasoline was reportedly present floating on the r water in this well.. The property subsequently became involved in litigation, and no further �- work was undertaken until April, 1991, when Falcon Energy submitted a workplan to San Joaquin County Environmental Health to install two additional monitorinU wells. This PIER reports the results of this work. PROCEDURES West Hazmat Drilling Corporation drilled monitoring wells biW-2 and MW-3 on 17 May 1991 using 8-inch hollow-stem augers. The wells were drilled to a depth of approximately 60 feet, and slotted IVC liner was installed from total-depth-to 40-feet-(five-feet-above-the-watPr_table)_.___The_well_ design is depicted in Figure 4. Samples were obtained at 5-foot intervals from 10 to 45 feet, using a split-spoon sampler loaded with three brass tubes. The lead tube was sealed with aluminum foil, capped, taped, and preserved on ice. Samples at depths of 30, 35, 40, and 45 feet were later transmitted to Western -- Environmental Science and Technology for analysis of TPH-gasoline using EFA method 8015 and for aromatic hydrocarbons (BTE&X) using method 8020. The second tube was extruded and described using the Unified Soil .