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RESULTS OF LABORATORY ANALYSES Water samples collected from wells MW-1, MW-3, and MW-4 were analyzed for TPHg, TPHd, and BTEX using modified EPA methods 80151$020 These results and cumulative results of laboratory analyses are summarized in Table i The Cham of Custody Record and laboratory ' analytical reports are included in Appendix B Results of this quarter's laboratory analyses of water samples from wells MW-1, MW-3, and MW-4 indicate the following. • Concentrations of BTEX, TPHg, and TPHd were nondetectable in all wells ' CONCLUSIONS Based on the results of this quarterly monitoring and previous work performed at the site, ' RESNA concludes that the TPHg, TPHd, and BTEX concentrations in groundwater have remained nondetectable, consistent with the last monitoring episode in September 1994 ' Since monitoring was reinitiated 1n December 1992 the concentrations of TPHd, TPHg, and BTEX have steadily decreased to nondetectable levels and no longer appear to be impacted by petroleum hydrocarbons in soil beneath the site This is a result of the continued operation of the soil vapor extraction system which began operating in July 1993 The vapor extraction system has removed over 3,700 pounds of a total estimated 3,900 pounds of petroleum hydrocarbons from soil beneath the site (RESNA, March 1993) The system is currently ' extracting less than three pounds per day of TPHg and BTEX and has been effective in removing almost 95% of petroleum hydrocarbons from soil beneath the site (Table 3) ' Well MW-1 is located directly downgradient from the former USTs During the last four sampling events, well MW-1 contained no detectable concentrations of petroleum hydrocarbons ' Well MW-2, located downgradient from the former diesel UST and adjacent to the former gasoline UST, contained no detectable concentrations of TPHg and BTEX during the last four quarters in which it was sampled TPHd was detected once in September 1993, at 720 parts per ' billion (ppb), since sampling was reinitiated Well MW-2 was not sampled during the last two sampling events ' Well MW-3 is located downgradient from the former diesel UST and upgradient from the former gasoline UST Well MW-3 contained no detectable concentrations of TPHg or BTEX during the last three sampling events TPHd was detected once in March 1994 at 62 ppb ' Well -4 r located downgradient from both former USTs Well MW-4 contained no MW s g detectable concentrations of TPHg or BTEX during the last three sampling events TPHd was detected once in March 1994 at 110 ppb 54W561QUARTLYI4QMR1994 FNL 3 CanonteE nv 1 ron menta l