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reportedly used for servicing buses and trucks during the operation of a former labor camp (GTI, <br /> 1995) An excavated UST was also observed on the property during the assessment It was <br /> I <br /> unknown if the UST was excavated at the property or simply being stored on the property <br /> Radian's review of San Joaquin County Environmental Health Department (SJC-EHD) files did <br /> not identify any documented UST removal at this site <br /> The Phase II work performed by GTI consisted of drilling two soil borings (SB-1 <br /> and SB-2) within the areas of concern identified during the Phase I work The borings were <br /> advanced to depths between 35 and 37 feet below ground surface and soil samples were obtained <br /> for laboratoryanalyses In Bonn SB-2, an attempt was made to obtain a grab groundwater <br /> Y g P <br /> sample with a bailer A groundwater sample could not be obtained, however, a dark oily <br /> substance was present on the bailer upon retrieval (GTI, 1995) A wipe sample of this substance <br /> was obtained for laboratory analysis The approximate locations of the borings are shown on <br /> i <br /> Figure 3 <br /> • n Bonn <br /> Analytical results for the soil samples obtained from o g SB-1 showed <br /> nondetection at the laboratory detection limits Analytical results for the soil samples obtained <br /> from Boring SB-2 showed concentrations ranging between 11,800 and 17,200 mg/kg of total <br /> i <br /> petroleum hydrocarbons-diesel (TPH-D) at depths between 12 feet and 315 feet Analytical <br /> results also detected a heavier petroleum hydrocarbon on the wipe sample from the bailer <br /> retrieved in Boring SB-2 at a concentration of 167,000 mg/kg <br /> Because of the detection of these two different TPH types in Boring SB-2, It was <br /> concluded that these constituents may have originated from two different sources Possible <br /> source areas include the former pump station/pipeline areas and former labor camp area (GTI, <br /> 1995) On the basis of the analytical results obtained to date, it appears that the vertical and <br /> lateral extent of impacted soils is undefined It is also unknown whether any dissolved <br /> petroleum hydrocarbons potentially associated with the TPHs detected in soil have impacted <br /> Preliminary Site investigation Work Plan-Draft June 30, 1998 <br /> Roberts Property(Former Vernalis Pump Station) <br /> Vernalls,California <br /> 6 <br />