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tl *V <br /> C A M B R I A <br /> i <br /> Blaine will gauge and sample the site wells according to the existing sampling schedule and <br /> tabulate the data Cambria will prepare a groundwater monitoring report <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> The groundwater sample analytical results this quarter are generally within the historical norm <br /> for this site Again, one exception to this is an increase in the methyl tertiary butyl ether <br /> (MTBE) concentration in well MW-14, which is located southwest of the subject site Based on <br /> prevailing groundwater flow direction and the fact that MTBE is not detected in wells MW-6 and <br /> MW-2, which are located in the southwest corner of the subject site, it appears that the MTBE in <br /> w� <br /> MW-14 may originate from an offsite source The groundwater flow direction in the shallow <br /> zone is generally to the east at a gradient ranging from 0 003 to 0 007 <br /> The laboratory report notes where total petroleum hydrocarbons as diesel (TPHd) was detected, <br /> the chromatogram does not match the lab's diesel standard Therefore these TPHd detections } <br /> may be anomalous <br /> Groundwater flow directions in the 80- and 120-foot zones during this quarter were generally <br /> toward the southeast, at approximate hydraulic gradients of 0 004 The vertical gradient was <br /> downward this quarter <br /> SAMPLE REDUCTION REQUEST <br /> As discussed in the Third Quarter 2004 Groundwater Monitoring Report, Cambria recommends <br /> discontinuing analysis for lead scavenger (1,2-dichloroethane [1,2-DCA] and ethylene dibromide <br /> [EDB]) in selected wells where these compounds have been historically not detected as well as <br /> discontinuing analysis for tertiary butyl alcohol (TBA) in wells MW-2, MW-6, MW-7, MW-8, <br /> MW-13, MW-15, and MW-17 Groundwater analytical data from these wells indicate TBA is <br /> not present and continued TBA analysis is not warranted <br /> Well MW-14, as previously mentioned, appears to contain gasoline constituents from an offsite <br /> source Cambria recommends discontinuing all sampling and gauging activities in this well as it <br /> appears the gasoline constituents detected in this well are not associated with the release that <br /> occurred at the former Texaco-branded site <br /> These sampling program changes will be implemented upon approval from the San Joaquin <br /> County Environmental Health Department <br /> 1399 2 <br />