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Excavation took place over a period of several days in mid-to-late November 1995 During the work, it became apparent that the extent of soil contamination was greater than previously anticipated, and personnel from Upgradient Environmental, using a portable photo-ionization detector(PID), screened the excavated soil and directed the excavator Excavation was terminated when no further evidence of contamination was detected At completion, the excavation measured approximately 50 feet wide by 80 feet long by 40 feet deep (at the north end) A crane was used to lower a geologist from Upgradient Environmental into the excavation, and twenty samples were collected from the floor and sidewalls of the excavation to confirm that the contaminated soil had been removed Residual hydrocarbons were detected in two of the sidewall samples from the west wall, where further excavation was precluded because of the proximity of the service station building The excavated soil (approximately 4,000 cubic yards)was transported to REMCO, Inc in Richmond, California for treatment The excavation was backfilled with imported soil, which was compacted in accordance with County regulations After all laboratory work was complete, Upgradient Environmental submitted the Site Remediation Report in December 1995 Total Petroleum Hydrocarbons (gasoline) were detected at 9 mg/kg (parts per million) in sample JL-P-13 in a clay layer at a depth of 22 feet and at 4,200 mg/kg in sample JL-P-15 in a sand layer at 12 5 feet No hydrocarbons were detected in samples below the clay layer, and because organic vapor concentrations (PID readings) declined rapidly below this layer, Upgradient Environmental interpreted the clay as a confining layer that inhibited downward migration of gasoline No further work was performed until mid-2001, when Mr Fisk requested the CVRWQCB to close the case and issue a No Further Action letter,After contacting San Joaquin County PHS/EHD, the CVRWQCB denied Mr Fisk's request and recommended that he conduct a preliminary investigation of the groundwater to determine whether it was impacted This led to the first phase-of drilling in November 2001, which confirmed that groundwater had been impacted by both hydrocarbons spanning the gasoline-diesel range 3.0 PROCEDURES Drilling took place on February 13, 2003 V&W Drilling of Isleton, California mobilized a Brainerd-Kilman BK-81 hollow-stem auger rig to drill two vertical borings and a Geoprobe® direct-push rig to drill two shallower vertical borings and two slant borings The locations for borings JLM-6, JLM-7, and JLM-8 were selected to assess the extent of groundwater contamination in the vicinity of the former underground storage tanks, and the locations of borings JLM-9, JLM-10, and JLM-11 were selected to determine the extent of groundwater contamination in the vicinity of the former dispenser islands, where the original gasoline release was detected (Figure 2) A secondary purpose was to locate the western limit of the soil contamination that had been observed in excavation sidewall samples JL-P-13 and JL-P-15 and boring samples JLM-2-10', JLM-2-15', JLM- 20', and JLM-25' This required that borings JLM-9 and JLM-10 be drilled as slant 3