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groundwater and at monitor wells MW 11 and MW12 the top of groundwater has been above the top <br /> of the screened interval since January 1995. <br /> The most recent groundwater quarterly sampled all wells (MW 1 through MW12). These samples <br /> were analyzed for Total Petroleum Hydrocarbons as gasoline (TPHg), Benzene, Toluene, <br /> Ethylbenzene, Xylenes and Methyl tertiary Butyl Ether (MBTEX) using EPA method 8020, see <br /> Table 1. <br /> The groundwater plume of dissolved gasoline range hydrocarbons has been reduced in size and <br /> concentrations; the following figures historically display the plume reduction/stability. <br /> Figures 8A, 8B and 8C represents TPHg measurements obtained in January 1990, December 1992, <br /> and May 1998 respectively. <br /> Figures 9A, 9B and 9C represents Benzene measurements obtained in January 1990, December 1992 <br /> and May 1998 respectively. <br /> Table 1 represents groundwater chemical results showing TPHg MBTEX and DO. <br /> Charts have been developed for MW1, MW2, MW3, MW8, MW10 and MW12 that show the <br /> continued decline in concentrations of TPHg in the groundwater. These charts are located with <br /> Table 1. A computer generated averaging trend line demonstrates the decline of gasoline range <br /> hydrocarbons in the groundwater for all wells except for MW12, which is currently showing a stable <br /> trend. <br /> For the most part the MCLS for Benzene, Toluene, Ethylbenzene and Xylenes have not exceeded the <br /> primary MCLs for drinking water standards for the State of Calfironia. And the perimeter wells, <br /> except MW12, have tested below or at laboratory lower detection limits for TPHg, BTEX and <br /> MTBE, showing plume stability. <br /> Of the wells that do test positive for gasoline range hydrocarbons (MW1, MW2, MW3, MW8, <br /> MW10, MW12 and MW13) the following MCLS have not been exceeded with the exception of the <br /> December 1997 sampling which contain elevated levels for BTEX due to residuals in the pump. <br /> Compound Primary MCL Secondary MCL <br /> Benzene 1.0 ug/L none <br /> Toluene 150 ug/L 42 ug/L <br /> Ethylbenzene 700 ug/L 29 ug/L <br /> Xylenes 1750 ug/L 17 ug/L <br /> MW1, which contained free product until August 1992 has not exceeded the primary and secondary <br /> MCLs since December 1993. <br /> 5 R603 Update##52/CLOSURE RV 7198 <br />