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PRELIMINARY EVALUATION AND INVESTIGATION OF HYDROCARBON CONTAMINATION 1 LERNER SERVICE STATION 521 N. CHEROKEE LANE LODI, CALIFORNIA BACXGROUND The site is a former gas station located in a flat, commercial/residential area ,Figure i - 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. Applied Geosystems (AGS) drilled four soil borings (B-1 to B-4) and collected 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 27 Septembe:r; 1.988. The` highest reading ..(538 ppm TPH), was recorded in boring H-4 at a,depth of. 3 40 feet: This boring was drilled down to 60 feet and converted to ground-water monitoring well-NW-1. The ground-Mater level at the time of completion was 40 feet. Gasoline was reportedly present floating.on:the .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 monitoring wells. This PIER reports the rasults of this work. PROCEDURES West Hazmat Drilling Corporation drilled monitoring wells MW-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 PVC liner was installed from total depth to 40 feet (five feet above the water table) . The well design is depicted in Figure 4. -. -- - - --- - - -- Samples-were-obtained--at-_5.-rfoot.._interval s_.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,Westerr, Environmental science and Technology for analysis of TPH-gasoline using EPA method 8015 and for aromatic hydrocarbons (BTE&X) using method 8020. The second tube wain extruded and described using the Unified Soil