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1 <br /> Y S <br />' 09 July 1999 <br /> AGE-NC Project No 95-0184 <br /> Page 4 of 4 <br /> at the site <br /> I • Ground water is up to 24 feet above the screened interval in monitoring wells at the site <br /> Wells recharge rapidly, possibly preventing significant drawdown during purging The <br />' hydrocarbon concentrations detected in these `drowned' wells may not be representative of <br /> shallower ground water where the maximum hydrocarbon impact would be expected <br />' • Ground water is currently within the screened interval in one vapor well and near the top of <br /> the screened interval in two additional vapor wells The data collected from these wells <br /> should be representative of shallow ground water conditions in the immediate vicinity <br />' • The lateral extent of hydrocarbon-impacted soil at the site has not been delineated <br /> • MTBE was not detected during the March 1999 monitoring event, possibly due to the high <br />' detection limits MTBE has been detected at significant concentrations during previous <br /> monitoring events <br /> 5.0. RECOMMENDATIONS <br /> Based upon data collected from the site, AGE recommends the following <br />' • A soil vapor extraction/in-situ air sparging pilot test should be conducted to evaluate <br /> remediation options for this site Findings of the vapor extraction/air sparging test can be <br />' used to determine the spacings of potential additional vapor and sparging wells <br /> • Additional soil borings and monitoring wells should be installed to define the horizontal <br /> extent of hydrocarbon-impacted soil and ground water A work plan addendum should be <br />' prepared updating the locations and depths of the proposed wells An encroachment permit <br /> should be obtained from the City of Stockton for the well installations <br />' The next ground water monitoring event will be scheduled for July 1999 <br />' G.O. 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 Evaluations of the geologic/hydrogeologic <br /> conditions at the site for the purpose of this investigation were made from a limited number of <br />' available data points (i e monitoring wells), and subsurface conditions may vary away from these <br /> data points No other warranty, expressed or implied, is made as to the professional <br /> recommendations contained in this report <br /> Advanced GeoEmironmental,Inc <br /> 1 - <br />