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s WEISS ASSOCIAM VIA Jack Fiori 27 may 1987 11 representing 18 March water levels, shows a gradient somewhat more northeasterly than that of 30 January. TABLE 3. Water Level Data, San Joaquin Mosquito Abatement, Lodi Facility Top-of- 30 January 1987 _ 18 March 1987 Casing Depth to Water Depth to Water Elev. Water Elev. Water Elev. (ft above (DTH) (ft above (DTH) (ft above Well No. HSL) (ft) HSL) (ft) MSL) MW-1 54.11 38.21-• i5.90 MW-2 54.28 37.92' 16,36 37.91 16.37 V-3 54.03 38.50* 15.53 38.50 15.78 * - DTW measured prior to well development. CONCLUSIONS »- During Phases 1 and 3 of this project TFHC were detected at concentrations of up to 3,600 ppm in soil beneath the 1,000-gallon gasoline tank. The concentrations increased with depth down to 31 ft below ground surface but there was no evidence that either the gasoline tank or the weed oil tank or associated piping had leaked. It appears that these hydrocarbons constitute a slug of indeterminate origin and a finite areal extent below the excavated gasoline tank. The soil samples collected from borings drilled a. during Phase 2 and the soil samples collected during Phase 4 were all below detection limits. The soil and ground water analyzed during Phase 5 were also below dwtettion limits, indicating that this material is bound in the soil and has not migrated to the ground water table at this time. WA concludes that hydrocarbons are present in unsaturated soil down to 31 ft. At approximately 30 and 32 ft below ground surface there is a lower-permeability layer which may retard and alter the direction of the hydrocarbons' vertical- movement. Continued migration vertically downaaxd is probable in the future.