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13 July 2001 M AGE-NC Project No 96-0232 Page 14 of 15 I water pump and treat system was recorded at 2,395,645 gallons (equivalent to 19,972,492 pounds) of water extracted yields 154 pounds of MTBE (equivalent to 601 grams)removed from the plume of impacted ground water(Appendix D), or approximately 7 grams per day Analytical results from the June 2001 quarterly monitoring event Indicates the most intense on-site MTBE impact is in the First Zone near EW-4 (140µg/1), the most intense off site MTBE impact is I in Rocky's Upper Zone of MW-11B (190 ug/l), probably Influenced by the pumping operation of RDW-1 and beyond the immediate influence of the Flag City Chevron ground water pump-and-treat remediation system ISignificant concentrations of MTBE were quantified west of the site In the area of Three B's Truck Plaza wells MW-1,MW-2,MW-4,MW-6 at concentrations between 5 2,ug/l and 60,ug/l (Three B's Truck Plaza Quarterly Report -Second Quarter 2001, dated 09 July 200 1) and Flag City Chevron wells MW-7,MW-12A and MW-13A at concentrations between 2 4,ag/l and 20 Ezg/l which suggest the possibility of separate MTBE plumes being pulled towards domestic drinking water wells RDW-1 and DW-1 (Figure 7) Ground water elevations versus ground water monitoring dates (hydrograph) were plotted for monitoring wells MW-2, MW-6A and MW-6B, generally, all three plots depicted a trend of decreasing ground water elevations from May 2000 to August 2000 and June 2001, however ground water elevations did show an increase from August 2000 to March 2001 (Appendix 1) Figures 10 and 11 depict the approximate extent of MTBE-impacted ground water beneath the site in cross sectional views C-C' and D-D', Figures 7, 8 and 9 depict the estimated extent dissolved MTBE-impact in plan view These figures depict Flag City Chevron wells MW-1,MW-7, MW-9A, MW-1 IA,MW-12A, MW-13A and Three B's Truck Plaza wells MW-1, MW-2, MW-4 and MW-6 ' to be located within dissolved MTBE plumes The vertical extent of impacted ground water on-site appears to he between 15 feet bsg(estimated depth to ground water) and 50 to 60 feet bsg in the area ofMW-1 and MW-9 (Figures 10 and 11). Impacted ground water in the area at 40 to 50 feet bsg in ' MW-9 is underlain by two thin fine-grained units (Problem Assessment Report, dated 19 June 2000) that appear to have retarded the downward migration of the MTBE ' Going off-site toward the west,the plume may extend to as much as 75 feet bsg approaching the area of MW-11B, near Rocky's Restaurant domestic well (RDW-1) as the underlying fine-grained sedimentary units thin and pinch out Further westward from RDW-1, the plume of water impacted ' by MTBE appears to extend beyond Three B's Truck Plaza well MW-4, with a vertical extent from possibly 15 feet bsg to possibly 75 feet bsg The full westward extent of the FIag City Chevron ' plume is unclear at this time Contaminants in First Zone ground water at MW-12 and MW-13 include TPH-g,TPH-d,TPH-mo,benzene,toluene,xylene,MTBE and 1,2-DCA,which suggest that • most of the contaminants are from a source other than the Flag City plume It is not known if the IAdvanced GeoEnvironmental,Inc I