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30 April 2005 <br /> AGE-NC Project No 96-0232 <br /> Page 8 of 9 <br /> December 2004 and during March 2005,the increase may be related to the suspension of the ground <br /> water pump-and-treat activities (17 August 2004), in effect causing MTBE-impacted ground water <br /> located near the Flag City Chevron UST/fuel dispenser area to migrate east-southeast relative to the <br /> natural ground water flow direction <br /> Ground water pump-and-treat operations were fully suspended at the site on 17 August 2004 <br /> Between November 2000 and August 2004,a total volume of approximately 27,086,201 gallons of <br /> MTBE-impacted water was treated at the site By March 2004, pump-and-treat operations at Flag <br /> City Chevron had effectively reduced influent MTBE concentrations to levels below 20 gg/l,which <br /> could be argued were levels that could potentially warrant a site closure However, a `spike' in the <br /> influent MTBE concentration was reported in the July 2004 influent sample (47 µg/l ), which may <br /> be attributed to the Banner Avenue MTBE-impacted ground water plume being drawn towards the <br /> Flag City Chevron extraction wells <br /> Since start-up of pump-and-treat operations, MTBE concentrations sampled from Flag City <br /> Extraction wells EW-1 through EW-10 all generally declined to either non-detectable(EW-1,EW-2, <br /> EW-3,EW-6,EW-7,EW-10)or near non-detectable levels(EW-4,EW-5,EW-8,EW-9),which also <br /> could be argued were levels that could potentially warrant a site closure However, a general trend <br /> of significant `spikes' was evident between March and June 2004 from wells EW-5, EW-7, EW-8 <br /> and EW-10(northern trench line)and from well EW-9(fuel dispenser island area) The March-June <br /> 2004 `spikes' may be attributed to the above referenced third MTBE-impacted ground water plume <br /> being drawn towards the Flag City Chevron extraction wells <br /> AGE has interpreted the data collected to date to represent a third,separate MTBE-impacted ground <br /> water plume that migrated from the First Zone near Banner Avenue to the First ZonelSecond Zone <br /> near the northern Flag City Chevron property boundary, influenced by the pump-and-treat cone of <br /> depression, the third MTBE-impacted ground water plume converged at the north trench-line of <br /> ground water extraction wells (EW-5, EW-7, EW-8 and EW-10) <br /> 5.0 RECOMMENDATIONS <br /> Based previous and current data collected from the site, AGE is in the process of preparing a site <br /> closure report, the closure report will include a ground water model with a fate-and-transport <br /> evaluation of the remaining contamination The site closure report will be submitted to the RWQCB <br /> by 01 June 2005 <br /> Advanced GcoEnvironmental,Inc <br />