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31 January 2005 <br /> AGE-NC Protect No 96-0232 <br /> Page 7 of 9 <br /> through the First Zone and upper Second Zone to the area of the former Rocky's Restaurant domestic <br /> water well, at which point it may have migrated vertically through the Rocky's Upper, Secondary <br /> Aquifer and Primary Aquifer Zones <br /> The vertical extent of Flag City Chevron MTBE-impacted ground water was interpreted to be <br /> between 25 feet bsg and 45 feet bsg Relative to the inferred source area near the Flag City Chevron <br /> UST area(EW-1), the Flag City Chevron plume previously extended westward for approximately <br /> 200 feet, where vertical migration appeared to have reached depths as great as 75 feet bsg <br /> (MW-11B), the maximum westward extent of the Flag City Chevron plume was most likely in the <br /> area of the former Rocky's Restaurant domestic drinking water well (RDW-1), where the plume <br /> appeared to converge with that of a Three B's Truck Plaza MTBE ground water plume Figures 8, <br /> 9 and 10 depict two,distinct MTBE-impacted ground water plumes that previously converged near <br /> the vicinity of the former Rocky's Restaurant domestic well RDW-1 <br /> Recently, a third, distinct MTBE ground water plume has been defined north-northeast of Flag City <br /> Chevron in First Water Zone on Banner Avenue (Figure 8), this third plume extends through the <br /> First Water Zone at the McDonald's Restaurant,to Second Water Zone near the Flag City Chevron <br /> UST/fuel dispenser areas (Figure 9) Analytical results from the December 2004 quarterly ground <br /> water monitoring event indicated the highest concentrations of on-site MTBE occur in the Second <br /> Zone sample collected from MW-8A at 290 µg/1 (Figure 9) Based on this current data, and based <br /> on previous ground water elevation data collected during the Flag City Chevron investigation(x e <br /> induced ground water depression in the areas of ground water pump-and-treat extraction), the <br /> migration of the third MTBE-impacted ground water plume would explain the consistent MTBE- <br /> impact at well MW-8A between March 2002 and December 2004 AGE suspects this third MTBE- <br /> impacted ground water plume was influenced by the ongoing Flag City Chevron pump-and-treat <br /> ground water extraction activities, the third MTBE-impacted ground water plume appears to have <br /> been drawn onto Flag City Chevron property and towards the ground water extraction induced cone <br /> of depression The migration of the third plume is further substantiated by the P-36, P-37 and P-38 <br /> grab ground water samples collected in First Zone and Second Zone (October 2002) that were <br /> previously non detect for MTBE <br /> A significant detection of MTBE was observed from Flag City Chevron well MW-2 during <br /> December 2004, the increase may be related to the suspension of the ground water pump-and-treat <br /> activities (17 August 2004), in effect causing MTBE-impacted ground water located near the Flag <br /> City Chevron UST/fuel dispenser area to migrate east-southeast relative to the natural ground water <br /> 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 /> Advanced GeoEnvironmental,Inc <br />