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05 January 2006 <br /> AGE-NC Project No 97-0326 <br /> Page 5 of 5 <br /> I detected in all HUs <br /> • Concentrations of analytes generally decreased in all wells this quarter, especially in HU6 <br /> well MW-9D,in which analyte concentrations decreased ten-fold to within historical levels <br /> • Historically, the highest concentrations of contaminants were centered around the tank-pit <br /> and dispenser areas At the time of the fourth quarter 2005 monitoring event, the highest <br />' TPH-g concentration was centered around the southeastern dispenser area, whereas the <br /> highest MTBE concentration was at the tank-pit location (Figures 4 and 5) <br /> • Ethanol and methanol have never been detected in ground water wells since initial <br />' monitoring for these products began In December 2000 <br /> • The lateral extent and vertical extent of petroleum hydrocarbon-impacted ground water have <br /> Inot been defined <br />' 5.0. RECOMMENDATIONS <br /> • Based on the findings of this Investigation, AGE recommends <br /> • Continuation of the quarterly ground water monitoring program, but remove the analysis for <br />' ethanol and methanol The next monitoring event is scheduled for March 2006 <br /> • Complete the installation of off-site monitoring wells,pending resolution of permitting and <br />' bond issues, to date, AGE has installed three of the eight monitoring wells proposed in the <br /> AGE-prepared Additional Monitoring Wells Work Plan, dated 26 July 2002 <br />' As directed by the San Joaquin County Environmental Health Department by letter dated 28 <br /> September 2005, AGE has prepared and submitted Soil Vapor Extraction Feasibility Work Plan, <br /> dated 20 November 2005, for Interim remediation of petroleum-impacted soil and ground water <br />' 6.0. LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br />' environmental consultants practicing in this or similar localities The findings were based upon <br /> analytical results provided by an independent laboratory Evaluation ofthe hydrogeologic conditions <br /> at the site for the purpose of this investigation was made from a limited number of available data <br />' points(I e ,ground water samples)and subsurface conditions may vary away from these data points <br /> No other warranty,expressed or implied,is made as to the professional interpretations,opinions,and <br /> recommendations contained in this report <br /> Advanced GeoEnvironmental,Inc <br /> I <br />