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- -- - C3eoln real?ec&x�res Inc- -- -_ - - - - -- -- - -- - - --Page 5 - - - - - 8 Groundwater Monaonng Report Project No 425 2 February 17, 2000 1 BSK sent the samples to Castle Analytical (Department of Health Services Certification No 2079), of Atwater, California, for analysis The samples were analyzed using the following methods • EPA method 602 —BTEX EPA method 503018015(m) - TPH-Gasoline The detection limits for the above analyses are listed in Table 4 of Appendix A and the lab data is presented in Appendix B 2.0 FINDINGS AND DISCUSSION The laboratory analytical data from the September and December 1999 monitoring events shows that TPH-G & BTEX compounds have been detected in the following monitoring wells MWA, MW-2, MW-4, MW-5 & MW-202 in September and MW-1, MW-2, MW-4 & MW-5 in December The results from the latest rounds of sampling are comparable with the results from the f previous monitoring events The following observations are made o Concentrations in MW-1 fluctuate significantly from event to event and showed a significant decrease during the September event but then increased to the highest levels observed in this well during the December event See Figure 3 for graph of Benzene and TPH-G versus time in MW-1 C Concentrations in MW-2 showed a significant increase during the September event but then decreased to normal levels during the December event The reason for this large increase is not known It is possible that floating product is again impacting this well, however none was observed in September Droplets of gasoline were observed in December See Figure 4 for graph of Benzene and TPH-G versus time in MW-2 • Concentrations in MW-4 showed increases in BTEX and TPH-G during the September and December events The levels are within those observed during previous events • MW-5 showed a decrease in BTEX and TPH-G during the September event However during the December event the BTEX levels decreased while TPH-G showed a fairly significant increase, to the second high levels observed in this well • MW-102 was non-detect for both the September and December events o MW-202 showed only the presence of low levels of Benzene during the September event ' and was non-detect for all compounds during the December event All of the domestic wells were non-detect during both events Domestic well 1600"A" ' Durham Ferry showed the presence of low levels of Benzene during the April 28, 1999 event but it was non-detect during both the September and December events