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' 5.2 Discussion of Analytical Results ' Analytical laboratory data indicate a significant decrease in detected constituent levels in monitoring well MW-1A. Benzene, toluene, total xylenes and gasoline levels dropped between 15% and 78% as compared with the previous sampling event results. MTBE levels were reported below the detection limit. These data indicate a continuation of a signi fcant decrease in contaminant mass since the performance of the remedial soil excavation. ' The sample collected from monitoring - p g w 1 e l MW 6 indicated decreases in gasoline and ' BTEX Ievels. Benzene decreased from 5.1 p,g/L to below detectable levels, and gasoline decreased from 0.4 mg/L to 0.12 mg/L. Toluene and MTBE levels were reported below their detection limits. No detectable levels of analyzed constituents were reported for monitoring wells MW-5, MW-7, MW-9, or the two water supply wells (North Well and South Well). These data ' are consistent with results reported for prior sampling events. Analytical laboratory data are summarized as reported by the laboratory in Table 2 below. ' Laboratory data sheets, the chain of custody document, and QA/QC data sheets are included in Appendix A. TABLE 2 ' Summary of Ground Water Analytical Results, March 24 and May 27, 2004 ' Anal to Sample Location Benzene Toluene Ethyl Total TBH-Gas MTBE (pg/L) (µg/L) Benzene Xylenes (mg/L) (µg/L) ' MW-IA 25 1.4 1 7.3 3.2 0.87 ND MW-6 ND ND 0.5 1.5 0.12 ND ' MW-5 ND ND ND ND ND ND MW-7 ND ND ND ND ND ND MW-9 ND ND ND ND ND ND ' North Well ND ND ND ND ND ND South Well ND ND ND ND ND ND ' ND = Not detected above the laboratory detection limit. Analytical values represent significant digit accuracy as specified by the analytical method and its detection limit. American Geological Service,Inc. CA95DE-029 9