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ATTACHMENT A <br /> FIELD PROCEDURES AND LABORATORY ANALYSIS <br /> Groundwater Sampling Procedures <br /> The groundwater sampling procedure consisted of first measuring the water <br /> level in each well with an electronic water level indicator, and checking each <br /> well for the presence of separate-phase hydrocarbons using a clear Teflon <br /> bailer. None of the wells contained separate-phase hydrocarbons, and all <br /> wells were then purged of approximately four casing volumes of water, or to <br /> dryness, using a 2-inch diameter centrifugal pump. During purging, <br /> temperature, pH, and electrical conductivity were monitored .in order to <br /> _ document that these parameters were stable prior to sample collection. After <br /> purging, the water levels were allowed to partially stabilize. Groundwater <br /> samples were collected using a Teflon bailer, plamii into appropriate EPA- <br /> approved containers, labelled, logged onto chain-ofcustody documents, and <br /> transported on ice to a California State-certified laboratory. The chain-of- . <br /> custody documentation is attached. <br /> } r <br /> Laboratory Analysis <br /> Groundwater samples were analyzed in the laboratory for the presence of <br /> total petroleum hydrocarbons calculated as gasoline (TPH-gasoline), and <br /> benzene, toluene, ethylbenzene, and xylenes (BTEX compounds). Extraction <br /> was performed by the purge-and-trap technique, EPA Method 5030. Analysis t <br /> for TPH-gasoline was performed according to the DHS LUFT method, and <br /> analysis for IiTEX compounds was by EPA Method 8020. Final detection was <br /> by gas chromatography using a flame-ionization detector and a photo- <br /> ionization detector. Groundwater samples were also analyzed for semi- and <br /> non-volatile hydrocarbons calculated as diesel (TPH-diesel) by the DHS <br /> LUFT method. All analyses were performed by a California State-certified <br /> laboratory. <br /> 3100104/1Q92 March 24,1992 <br />