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iCAMBRIA <br /> 60, 75, and 80 fbg groundwater samples from CPT-3 to the 65, 73, and 80 fbg groundwater <br /> samples from CPT-6 it is apparent that petroleum hydrocarbon concentrations attenuate <br /> significantly east of CPT-3 These data suggest that CPT-6 provides adequate downgradient <br /> delineation of petroleum hydrocarbons in groundwater <br /> Boring CPT-7 was drilled approximately 100 feet upgradient of the suspected source area on the <br /> subject site The purpose of this boring was to determine if there is an upgradient source of <br /> petroleum hydrocarbons that is responsible for or contributing to the petroleum hydrocarbon <br /> plume beneath the site TPHg and benzene were detected in groundwater samples from CPT-7 at <br /> each depth interval sampled The petroleum hydrocarbon concentrations detected in <br /> r groundwater samples from this boring are not typical of those found 100 feet upgradient of a <br /> suspected source area CPT-7 is also located more than 60 feet west (upgradient) of any other <br /> potential source area at the subject site Soil samples collected from CPT-7 contained sporadic <br /> low concentrations of petroleum hydrocarbons at various depths This suggests that petroleum <br /> hydrocarbons detected in groundwater samples from CPT-7 do not originate from a shallow <br /> source in the vicinity of CPT-7 It is possible that petroleum hydrocarbons detected in <br /> groundwater samples from CPT-7 originate from an offsite source <br /> • Groundwater samples collected during this investigation did not contain MTBE with the <br /> exception of three low level detections These data are consistent with previous findings at this <br /> site, which indicate there is little MTBE in soil and groundwater beneath this site The absence <br /> of MTBE in the soil and groundwater suggests that the release at this site is old and likely <br /> occurred prior to the introduction of MTBE into gasoline <br /> RECOMMENDATIONS <br /> Based on the findings of this investigation, especially the upgradient detection of petroleum <br /> hydrocarbons in groundwater, Cambria recommends performing a file review to evaluate <br /> information from nearby UST sites Cambria proposes to review SJCPHS/EHD files to obtain <br /> recent information regarding the status of investigations or cleanup at several VST sites in the <br /> vicinity of the subject site Based on the findings of this review we will make a recommendation <br /> as to whether or not to prepare a Problem Assessment Report (PAR) for the subject site <br /> • <br /> 1399 6 <br />