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• 29 July 2005 AGE-NC Project No 96-0232 Page 8 of 9 Chevron in First Water Zone on Banner Avenue (Figure 8), this third plume extends through the First Water Zone at the McDonald's Restaurant, to Second Water Zone at the Flag City Chevron UST/fuel dispenser areas (Figure 9) Analytical results from the June 2005 quarterly ground water monitoring event indicated the highest concentrations of on-site MTBE occur in the Second Zone sample collected from MW-8A at 610 µg/l (Figure 9) Based on this current data, and based on previous ground water elevation data collected during the Flag City Chevron investigation (I e induced ground water depression in the areas of ground water pump-and-treat extraction), the migration of the third MTBE-impacted ground water plume would explain the consistent MTBE- impact at well MW-8A between March 2002 and June 2005 AGE suspects this third MTBE- impacted ground water plume was influenced by the ongoing Flag City Chevron pump-and-treat ground water extraction activities, the third MTBE-impacted ground water plume appears to have been drawn onto Flag City Chevron property and towards the ground water extraction induced cone of depression The migration of the third plume is further substantiated by the P-36, P-37 and P-38 grab ground water samples collected in First Zone and Second Zone (October 2002) that were previously non detect for MTBE By March 2004, MTBE concentrations sampled from Flag City Extraction wells EW-1 through EW-10 all generally declined to either non-detectable(EW-1,EW-2,EW-3,EW-6,EW-7,EW-10) • or near non-detectable levels(EW-4,EW-5,EW-8, EW-9),which also could be argued were levels that could potentially warrant a site closure However, a general trend of significant `spikes' was evident between March and June 2004 from wells EW-5,EW-7,EW-8 and EW-10(northern trench line) and from well EW-9 (fuel dispenser island area) The March-June 2004 `spikes' may be attributed to the above referenced third MTBE-Impacted ground water plume being drawn towards the Flag City Chevron extraction wells Based on generally low MTBE detections (below 20 µg/1) in Influent samples since March 2004, ground water pump-and-treat operations were fully suspended at the site on 17 August 2004 Between November 2000 and August 2004,a total volume of approximately 27,086,201 gallons of MTBE-impacted water was treated at the site A significant detection of MTBE was observed from Flag City Chevron well MW-2 during December 2004, March 2005 and June 2005, the increase may be related to the suspension of the ground water pump-and-treat activities(17 August 2004),in effect causing MTBE-impacted ground water located near the Flag City Chevron UST/fuel dispenser area to migrate east-southeast relative to the natural ground water flow direction 5.0 RECOMMENDATIONS Based previous and current data collected from the site, AGE is in the process of preparing a site Advanced GeoEnvironmental,Inc