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1 <br /> in the slightly lower concentration found in the second run of MW-8 Also, petroleum <br /> hydrocarbons are not miscible in water and tend to separate from the water in the vial <br /> Variation in the analytical results from different vials is expected since homogenizing the sample <br /> prior to analysis is not appropriate for volatile parameters <br />' Analysts of the field decontamination sample, which was collected after sampling MW-8, <br /> indicated that there were no detectable compounds remaining in the field equipment after <br /> completion of standard field decontamination procedures <br /> TABLE 2 <br /> Groundwater Analytical Results <br />' San Joaquin County Human Services Building Site <br /> Third Quarter 1993 <br /> Sample Date: August 12 and 13, 1993 <br /> 1 <br /> Method <br />' Monitoring EPA 602 EPA 8015M Notes <br /> Well <br /> Benzene Toluene Ethylbenzene Xylene TPH-G <br />' Detection 1 00µg/L 1 00 ,ug/L 1 00µg/L 1 00 jug/L 50 ycg/L <br /> Limit <br /> MW-4 ND ND1 ND ND 37 J2 Primary Sample <br /> MW-5 ND ND ND ND ND Pnmary Sample <br />' MW-6 ND ND ND ND ND Primary Sample <br /> MW-7 ND ND ND ND ND Primary Sample <br /> MW-8 ND ND ND ND 1,700 Pnmary Sample <br />' MW-104 NA' NA NA NA 2,900 Duplicate of MW-8 <br />' <br /> MW_115 NA NA NA NA ND Decon Rinsate Sample <br /> (after sampling MW-8) <br /> 1 ND = Non-detectable at deter-hon limit shown at top of column Please refer to the explanation of Reporting <br />' Lints for BTEX in Appendix B <br /> 2 J = Present, below detection lint Please refer to the explanation of Reporting Lints for BTEX in <br /> Appendix B <br />' 3 NA = Not analyzed <br /> 4 MW-10 = Duplicate of MW-8 <br /> 5 MW-11 = Equipment decontamination sample collected after sampling MW-8 <br />' To assist in reviewing trends in the hydrocarbon concentrations found in the various wells at the <br /> site, Table 3 presents a historical chronological summary of the TPH-G concentration data to <br /> date The data presented for the time period before this sampling period was developed during <br />' the Phase lI Groundwater Investigation in 1991 The TPH-G concentration in MW-4 appears <br /> to be decreasing over time The TPH-G concentrations in MW-8 appear to be siable within the <br /> range of approximately 1,700 to 2,900 jig/L, including the analytical result of the duplicate <br /> sample from the third quarter 1993 sampling event <br /> IS K\RPrSWC 3RD WP 5 10/4! <br />