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f <br /> e <br /> tested for total organic vapor, measured in parts per million as benzene (ppm: l <br /> volume/volume). The instrument was previously calibrated using a 1.00 ppm <br /> I :f isobutylene standard (in air) and a sensitivity factor of 0.7, which relates the photo- <br /> ionization sensitivity of benzene (10.0 ppm) to the ionization potential of isobutylene <br /> tt; '"' (7.0 ppm). Results of these tests were used to assist in selection of samples for <br /> „a <br /> laboratory analysis. <br /> r <br /> ;x Groundwater Sampling <br /> The groundwater sampling was performed using techniques approved by the Regional j S <br /> I Water Quality Control Board. The sampling procedure consists of first measuring the 1! <br /> `? F water Ievel in each well, and checkLig each well for the presence of floating petroleum { <br /> 1 64 product using an optic probe or a clear Teflon bailer. If no free product is detected,the <br /> wells are purged of a minimum of four casing volumes of water (or until dryness). <br /> t During purging, temperature, pH, and electrical conductivity were monitored until <br /> + ' stable in order to ensure that a representative -ample was obtained. After the water <br /> I` levels partially recover, groundwater :_:,iples were collected using a Teflon bailer and j <br /> w placed into appropriate EPA-approved containers. The samples were labeled, logged <br /> 4: <br /> onto chain-of-custody documents, and transported on ice to the laboratory using appro- <br /> priate chain-of-custody documentation. i <br /> Laboratory Analysis <br /> Selected soil and groundwater samples were analyzed in the laboratory for the presence �. <br /> of total petroleum hydrocarbons calculated as gasoline (7TH-gasoline), and benzene, <br /> G , 9 toluene, ethylbenzene, and xylenes (BTEX) compounds. Soil samples were also <br /> analyzed for semi- and non-volatile hydrocarbons calculated as diesel (I PH-diesel). <br /> The rrm.ethod of analysis for TPH-gasoline was by modified EPA Methods 8015, 8020, I <br /> kand 5030. Final analysis w-s performed by the purge-and-trap technique with final <br /> detection by gas chromatography using a flame-ionization detector and a photo- <br /> n ionization detector. The method of analysis for TP;-`-diesel was by modified EPA <br /> Method 8015. This method involves extracting the samples with solvent and examining ' <br /> the extract by gas chromatography using a flame ionization detector. All analyses were, <br /> 1 <br /> r , performed by a State-cert£ied laboratory. <br /> r <br /> i <br /> t <br /> t t <br /> f <br /> s t <br /> f t .. <br /> l a.. 310010/REPORT' A-2 Septcmber 30,1991 <br /> i <br />