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' 5.3 Discussion of Analytical Results <br /> ' <br /> Analytical laboratory data indicate a significant decrease in detected constituent t levels in <br /> monitoring well MW-1. Benzene, toluene and ethyl benzene levels dropped between <br /> 80% and 95% as compared with the previous sampling event results. Gasoline levels <br /> dropped approximately 54% from those obtained during the previous sampling event. <br /> ' Analytical data indicate a slight increase in xylene, however the change in this constituent <br /> level is not deemed significant. The changes are believed to reflect the removal .of <br /> ' contaminated soil in the vicinity of MW-1 that was a source of ground water <br /> contamination. <br /> ' The sample collected from monitoring well MW-6 indicated no changes in the Ievels of <br /> benzene or toluene which were below the detection limit. Ethyl benzene, xylenes and <br /> gasoline levels decreased slightly as compared with the results of the previous sampling <br /> event. The changes observed in ethyl benzene and xylene levels are not deemed <br /> significant. The gasoline level found during this sampling event represent the second <br /> lowest level obtained since gasoline was first detected. <br /> ' The remaining wells, MW-5, MW-7 MW-9 and the two domestic wells, North Well and <br /> South Well, each indicated non detectable levels for all analyzed constituents. These data <br /> ' are consistent with data obtained from past quarterly sampling events. <br /> 6.0 CONCLUSIONS <br /> The following conclusions and recommendations are based on the observations and <br /> analytical data collected to date. <br /> ' Laboratory analysis of ground water samples indicates theP resence of moderate levels of <br /> gasoline and gasoline constituents in water collected from monitoring well MW-1 and <br /> ' low Ievels in MW-6. The constituent levels obtained from monitoring well MW-1 are <br /> substantially lower than the Ievels obtained prior to the remedial excavation. Slight <br /> decreases in MW-6 constituent levels were observed during this sampling event. <br /> ' All other monitoringand domestic estic water supply well samples indicated non detectable <br /> levels for analyzed constituents. The ground water data support the conclusion that the <br /> vertical extent of contamination has not extended beyond the depth of 18 feet below <br /> grade as indicated during the remedial soil excavation. The two domestic water supply <br /> ' wells, and monitoring well MW-9 have not been impacted. <br /> ' American Geological Services, Inc. <br /> CA95DE-029 <br /> 9 <br />