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6.0 CONCLUSIONS <br /> 6 1 On-Site Monitoring Wells <br /> Dissolved hydrocarbon concentrations this quarter are generally similar to <br /> those reported from the previous sampling event Notable changes include <br /> the significant decreases of the TPH-G concentration in monitoring well <br /> MW-19 and the TPH-G, ethylbenzene, and total xylenes concentrations in <br /> recovery well RW-3 Additionally, the ethylbenzene concentration in <br /> monitoring well MW-5 increased further and ethanol was observed in <br /> MW-20 for the first time, at a concentration of 240 ppb <br /> The TPH-G concentrations in monitoring well MW-5 and recovery wells <br /> RW-2 and RW-3 exceeded the Water Quality Objectives (WQOs) as listed in <br /> RWQCB Cleanup and Abatement Order #R5-2003-0713 The MTBE <br /> concentrations in monitoring wells MW-13 and MW-16 exceeded WQOs <br /> Finally, the ethylbenzene concentration in monitoring well MW-5 exceeded <br /> its WQO <br /> 6 2 Domestic Wells <br /> • Five residential domestic wells are positioned south of the subject site <br /> During this quarter's sampling, two of these residences, 18142 and 18202 <br /> Airport Way, contained detectable concentrations of MTBE for the first <br /> time Both of these wells were re-sampled, and the presence of trace <br /> concentrations of MTBE was confirmed Due to the presence of MTBE in <br /> these two wells, the RWQCB has ordered our client to sample these wells o n <br /> a quarterly basis The next sampling event is scheduled for February <br /> 2005 <br /> MTBE and 1,2-DCP were also observed for the first time in the <br /> groundwater samples collected from the domestic well at 17717 Airport <br /> Way This well has historically only contained 1,2-DCA <br /> Frank's One stop Quarterly Report — December 2004 Sampling <br /> -4- <br />