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30 June 2004 <br /> . AGE-NC Project No 98-0433 <br />' Page 4 of 5 <br /> I Analytical results from ground water samples are summarized in Table 1 The laboratory report <br /> (CalTech ID CT214-040205 8),quality assurance and quality control(QA/QC)and chain-of=custody <br /> are Included in Appendix B The distribution of dissolved hydrocarbons is depleted on Figure 4 <br /> 4.0. SUMMARY AND CONCLUSIONS <br />' Based upon the data collected during the First Quarter 2004 monitoring event, AGE concludes <br /> I0 Ground water at the site was encountered at approximately 25 to 26 5 feet below the casing <br /> tops The prevailing ground water flow direction from the former UST area was generally <br /> toward the northwest at a gradient of 0 001 ft/ft <br /> • The highest concentration of TPH-g was in the area of monitoring wells MW-1 and MW-9 <br /> located adjacent to the former UST area and well MW-6 approximately 300 feet east of the <br />' former UST area TPH-g concentrations in ground water decreased in the samples from well <br /> MW8 The samples from MWI, MW6 and MW9 showed an Increase in TPH-g <br /> concentrations TPH-diesel concentrations increased in wells MW1 and MW-6 (Table 1) <br />' . Benzene was detected in the sample from well MW-6 at a concentration of 17 4g/l, which <br /> is above the DHS'Maximum Contaminant Level(MCL) MTBE was detected in wells MW- <br /> 1, MW-8 and MW-9 at concentrations as great as 2,200 µg/1, significantly above the DHS' <br /> Iprimary MCL (\,rn,UJ � <br /> • The lateral extent of TPH-g, BTEX in well MW-6 and lack of MTBE indicates an older <br /> Irelease,while the distribution of MTBE near the former UST area, Indicates recent release <br /> • The lateral extent of dissolved MTBE is generally defined by the current well network, <br /> Including the wells sampled at the Ripon Farm Service site directly south ofthe subject site <br /> The vertical extent of MTBE at the former UST area is not dened below a depth of 40 feet <br /> bsg <br /> • The lateral extent of TPH-g and BTEX was previously defined in the former UST area <br /> however, it is undefined in the area of MW-6 <br /> I <br /> 5.0. RECOMMENDATIONS <br /> Based on the results of this investigation, AGE recommends <br /> • Continued quarterly monitoring at the site, the next monitoring event should be scheduled <br /> for May 2004 <br /> I <br /> Advanced GeoEnvironmental,Inc <br /> I , <br />