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1 <br /> ti <br /> f� <br /> C A M B R I A <br /> i <br /> Blaine will gauge and sample the site wells per the existing sampling schedule and tabulate the <br /> data Cambria will prepare a groundwater monitoring report <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> The analytical results of groundwater samples collected this quarter were generally within the <br /> historical norm for this site Again, one exception to this is an increase in the methyl tertiary <br /> butyl ether (MTBE)concentration to well MW-14, which is located southwest of the subject site <br /> Based on prevailing groundwater flow direction and the fact that MTBE is not detected in wells <br /> MW-6 and MW-2, which are located in the southwest corner of the subject site, it appears that <br /> the MTBE in MW-14 may originate from an offsite source The groundwater flow direction in <br /> the shallow zone is generally to the east at a gradient ranging from 0 003 to 0 005 <br /> The laboratory report notes that where total petroleum hydrocarbon as diesel (TPHd} was <br /> detected, that the chromatogram does not match the labs diesel standard Therefore these TPHd <br /> detections 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 ranging from 0 003 to 0 005 The <br /> vertical gradient was downward this quarter <br /> SAMPLE REDUCTION REQUEST <br /> Cambria recommends lead scavenger (1,2-dichloroethane [1,2-DCA] and ethelyne dibromrde <br /> [EDB]) analysis be discontinued in selected wells where these compounds have been historically <br /> not detected This request was previously made by Cambria (December 19, 2003) and it was <br /> denied by San Joaquin County Environmental Health Department (January 7, 2004) because the <br /> detection lints for these compounds were elevated More recent analytical data (with <br /> acceptable detection limits) shows lead scavengers are not present in several wells at the site <br /> We propose that lead scavenger analysis be discontinued in wells MW-1 through MW-8, <br /> MW-13, MW-15, MW-17,MW-18-120 and MW-19-120 <br /> Cambria also recommends discontinuing analysis for tertiary butyl alcohol (TBA) in wells <br /> MW-2, MW-6, MW-7, MW-8, MW-13, MW-15, and MW-17 Groundwater analytical data from <br /> these wells indicate TBA is not present and continued TBA analysis is not warranted <br /> 1399 2 <br />