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i October 13 , 1988 Page 4 Chevron U. S . A . 16000-105-03 E The headspace samples were manually injected into a Photovac Model IOS55 portable gas chromatograph for analysis . Before machine use and after every three sample analysis runs , the Photovac was calibrated using a solution of a known concentration of Benzene . # Each of the boring locations were backfilled with the 5 auger cuttings , and sealed with a cement plug flush to the I existing grade . a For more detailed information regarding the results of each sample screening , please refer to the chromatograms which have been included at the end of the text . t DISCUSSION OF FINDINGS y A total of eight subsoil samples were obtained at various locations at the subject property for soil vapor analysis . One sample was obtained at an approximate depth of three feet below the existing grade at each soil boring location Three of the soil vapor survey points were located • around the underground tank burial location ( VP-1 , VP-Z , and VP-8 ) , three soil vapor survey points were located at the eastern end of each of the three dispenser island locations ? (VP-5 , VP-6 , and VP-7 ) , and the two remaining soil vapor survey points were located along the northern planter bed locations (VP-3 and VP-4 ) . The soil vapor survey locations were selected based upon the most likely areas at which a potential release of petroleum products may occur. During the course of our field study, a station attendant informed the field personnel of his recollection of a recent surface spill of about 14 gallons of unleaded gasoline . The spill was purported to have occurred in the vicinity of the eastern end of the northernmost island . The results of the soil vapor analysis conducted in the field on samples obtained from the subject property had shown all but one of the samples as non-detected levels of those constituents analyzed for , with exception of location VP-7 The VP-7 sample location had shown the presence of Benzene , Toluene , and other unidentified chromatographic peaks Benzene was calculated at an approximate relative concentration of 4 parts per billion , and Toluene was calculated at an approximate relative concentration of 11 Parts per billion . The VP-7 sample location was situated in the general area of the recent purported surface spill of gasoline .