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' 15 October 2001 AGE-NC Project No 96-0232 ' Page 15 of 17 • Impacted ground water in the First and Second Zones migrates vertically to Rocky's Upper Zone, the Secondary Aquifer and Primary Aquifer via mixing in the RDW-1 casing and possibly along the filter pack ' During non-pumping periods, MTBE-impacted ground water migrates from the well casing g and/or filter pack laterally along the coarse-grained members of the lower hydrologic units ' Ground water extraction from theound water extractions stem on gr y the Flag City Chevron site has pulled back some impacted ground water, lowering MTBE concentrations in ground ' water in the general extraction area, and has prevented additional lateral and vertical migration of the impacted ground water ' Continued production of ground water from RDW-1 in combination with reduction of west- southwestward migration of impacted ground water has reduced the concentrations of MTBE ' in the lower hydrologic zones in the vicinity of RDW-1,however, RDW-1 can still serve as a vertical conduit from impacted ground water ' 6.0. CONCLUSIONS AGE interprets the results of all work completed to indicate a Flag City Chevron release of hydrocarbons and MTBE occurred in the areas of the fuel dispensers, UST pit and/or storm dram, migrated through the First Zone and upper Second Zone to the Rocky's Restaurant domestic well, at which point it apparently migrated vertically to the Rocky's Upper, Secondary Aquifer and Primary Aquifer Zones Between March and September 2001, concentrations of dissolved MTBE decreased substantially in samples collected from RDW-1, from monitoring wells MW-1, MW-9A, MW-11A, MW-11B, MW-11D, from extraction wells EW-2, EW-4, EW-6, EW-7, EW-8, EW-9, EW-10 and influent water samples collected between the third quarter 2001 monthly sampling events, the data implies that the decreases may be due to the overall MTBE mass reduction in First Zone and Second Zone ground water at the site AGE estimates the arithmetic average concentration of MTBE in ground water extracted between 01 July and 30 September 2001 was 15µg/1 The total volume of water processed through the ground water pump and treat system was recorded at 1,923,307 gallons (equivalent to 16,034,610 pounds) of water extracted yields 0 24 pounds of MTBE(equivalent to 110 grams)removed from the plume of impacted ground water (Appendix D), or approximately 12 grams per day Analytical results from the September 2001 quarterly monitoring event indicates the most intense I Advanced GeoEnvironmeatal,Inc