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1.0 INTRODUCTION This report presents the results of a preliminary investigation of subsurface petroleum contamination conducted by Upgradient Environmental Consultants (Upgradient Environmental) in November 2001 The investigation was performed at 8125 South El Dorado Street, which is located one block east of Interstate Highway 5 at Mathews Road (Figure 1) Upgradient Environmental was retained by the property owner, Mr James Fisk, in July 2001 under contract number 21003 The scope of work was to prepare a Site Investigation Work Plan, perform an initial subsurface drilling investigation to determine whether groundwater, in addition to soil, is contaminated, and prepare this report The work plan was submitted to the lead regulatory agency (Central Valley Regional Water Quality Control Board (CVRWQCB) on August 29 and was approved on September 20 Drilling took place on November 12 2.0 BACKGROUND In November 1995, Bob Evans Trucking, under contract to Elite IV, Inc , removed three underground fuel storage tanks (USTs) and related product lines and dispensers from the site Two of the tanks were 10,000 gallons in capacity, and the third was 2,000 gallons in capacity All three stored unleaded gasoline Upgradient Environmental witnessed the removal and collected fourteen soil samples from beneath the tanks and product lines and five from the excavated soil that had been stockpiled Hydrocarbons were detected in only one of the nineteen samples (JL-P-3), and it appeared that a small petroleum release had occurred near one of the fuel dispensers (Figure 2) A work plan to remove the contaminated soil was prepared, and Elite IV was authorized by the local oversight agency (San Joaquin County, Public Health Services, Environmental Health Division [PHS/EHDj) to excavate the contaminated soil Excavation took place over a period of several days in mid-to-late November During the work, it became apparent that the extent of soil contamination was greater than previously anticipated, and personnel from Upgradient, 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 25 2