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22 December 1995 AGE-NC Project No 95-0101 Page 2 of 5 In January 1994, four soil borings were drilled a* the site by Geological Audit Services, Inc (GAS) Two of the bonngs were completed as monitoring wells MW-5 and MW-6 to a depth of 85 feet Borings B7 and B8 were advanced to a depth of 65 feet and backfilled in the entire depth with Portland cement No petroleum hydrocarbons were detected in any of the 14 soil samples collected and analyzed from the bonngs or monitoring wells In April 1995, two bonngs were drilled at the site Boring B9 was advanced to a depth of 75 feet, boring BIO was advanced to a depth of 80 feet Organic vapors were detected in soil samples collected from boring B9 from depths of 25 to 70 feet at concentrations of up to 646 ppm No organic vapors or hydrocarbon odors were detected in boring B10 TPH-g was detected in sample B9-35 at a concentration of 9,100 ppm Benzene and xylenes were detected in sample 139-45 at concentrations of 0 006 ppm Petroleum hydrocarbons were not detected in any other soil samples analyzed Ground water samples were collected from the bottom of both bonngs TPH-g was detected in the water sample collected from boring B9 at a concentration of 300 ppb Only xylenes were detected in the water sample collected from boring B 10 at a concentration of 0 83 ppb Boring B9 was backfilled from 50 to 80 feet with Portland Cement and bentonite The boring was then completed as vadose zone well VW-1 using 2-inch diameter, 0 020 slotted PVC casing from 30 to 50 feet Boring B 10 was backfilled in the entire depth with Portland Cement 2 3 GROUND WATER MONITORING Ground water monitoring at the site has been performed by AGS, Nations Groundwater Associates (NGA), GeoAudit and AGE on eleven occasions between June of 1987 and May 1995 Ground water flow direction has been consistently to the southwest Analytical results of past and current ground water samples are included in Table 2 24 UST REMOVAL Four USTs were removed from the site in March of 1990 Low concentrations of volatile aromatics were detected in soil samples collected beneath the tanks According to records in file with the San Joaquin County Public Health Services -Environmental Health Division (PHS-EHD), approximately 800 cubic yards ofgasohne-contaminated soil were removed from the tank excavation and stockpiled on-site In anticipation of future cleanup requirements, four-inch diameter slotted PVC casing was installed around the bottom of the excavation Approximately 5 inches of pea gravel were placed in the