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' 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 the presence of reduced levels of <br /> gasoline and gasoline constituents in water collected from monitoring well MW-lA. The <br /> levels reported indicate the continuation of a significant decline that began following <br /> 1 completion of the remedial excavation. A minor increase in the reported level of ethyl <br /> benzene was obtained from this sampling event. <br /> Minor increases in MW-6 petroleum hydrocarbon constituent levels were observed <br /> during this sampling event with the exception of toluene and gasoline, which exhibited no <br /> changes from the previous sampling results. <br /> 7.0 RECOMMENDATIONS <br /> The next sampling event is scheduled to take place in mid June, 1999, The June <br /> 140 sampling event will be the fourth sampling event conducted since the conclusion of the <br /> remedial soil excavation. Based on the significant reduction of contaminant mass <br /> ' indicated by the sampling events conducted since the completion of the remedial <br /> excavation, American Geological Services makes the following recommendations. <br /> AGS recommends that if the results obtained at MW-1A and MW-6 in June indicate <br /> either no significant increases or a continued decline in constituent levels, the remaining <br /> wells, MW-S, MW-7 and MW-9, should be immediately sampled. The sampling of these <br /> ' three wells would be conducted as part of the closure confirmation sampling event. <br /> Should the results of the two June sampling events indicate that site closure is warranted, <br /> AGS will prepare a case closure request in accordance with the requirements established <br /> in the Tri-Regional Guidelines, Appendix B. <br /> Following approval of the closure request by the San Joaquin Public Health Services, and <br /> 1 the Regional Water Quality Board, the ground water monitoring wells would be <br /> scheduled for destruction in accordance with California State Water Well Standards. <br /> 1 <br /> American Geological Services, Inc. <br /> ' CA95 DE-029 <br /> 10 <br />