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Tri <br /> 4 CONCLUSIONS AND RECOMMENDATIONS <br /> i ; <br /> 4 Results of Kleinfelder's soil assessment investigation and previous tank excavation <br /> sampling indicate that petroleum hydrocarbons are present in the soil in the vicinity of the <br /> two tank excavations. However the detected concentrations appear to be limited to the soil <br /> in and around the bottom or the tank excavations. <br /> f.{ <br /> 1000 Gallon-Waste Oil Tank <br /> A TPH concentration of 640 mg/kg was detected at the bottom of the 1000-gallon tank <br /> excavation during the tank removal, but TPH and volatile aromatic concentrations were <br /> not detected in the three borings advanced around the 1000-gallon tank excavation.: <br /> 500 Gallon-Waste Oil Tank <br /> u! `, A TPH concentration of 26 mg/kg was detected at a depth of 12 feet at the bottom of the <br /> 500-gallon tank excavation during the tank removal,and TPH concentrations ranging from <br /> 53 to 234 mg/kg were detected at a depth of 11.5 feet in one of three borings drill adjacent <br /> to the excavation. The TPH concentration decreased to 12 mg/kg at a depth of 21.5 feet in ; <br /> the boring. <br /> -+ Samples collected from the bottom of borings B-1 through B-4 drilled at both waste oil <br /> tank sites had detectable concentrations of chromium and zinc. The detected <br /> concentrations were well below the California Administrative Code's Total Threshold <br /> Limit Concentrations and appear to be consistent with background soil concentrations <br /> typical of the northern San Joaquin Valley. <br /> Based on the analytical results,Meinfelder does not recommend additional assessment of <br /> the two excavation areas. The lateral and vertical extent of petroleum hydrocarbon <br /> Enigration_from the two tanks appears to be limited to the general vicinity of the bottom of - <br /> the two excavations.. The deepest TPH concentration detected (12 mg/kg} was 35 feel <br /> above free water, which was first encountered at a depth of 56.5 feet. Some petroleum <br /> hydrocarbon concentrations are present at the bottom of the excavations, but given the . <br /> depth to water and. the limited extent.of lateral and vertical migration, kleinfelder <br /> 241-89-2196 7 <br />