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' 15 January 2001 AGE-NC Project No 96-0232 ' Page 19 of 20 ' The elevated petroleum hydrocarbon concentrations detected in water samples collected from well MW-1 (screened between 9 and 24 feet bsg) suggest this well may be screened within or near the dissolved petroleum hydrocarbon"core area"ofthe plume Substantial decreases of dissolved MTBE ' were reported at MW-1 between August 2000 and December 2000 sampling events, the reported decrease may be due to pump and treat extraction activities ' AGE roughly calculates that the arithmetic average concentration of MTBE in ground water extracted between 09 November and 31 December 2000 was approximately 494 µg/1 The total volume of water processed through the ground water pump and treat system was recorded at ' 1,005,045 gallons (equivalent to 8,643,760 pounds) of water extracted yields 4 27 pounds of MTBE (equivalent to 1,937 grams) removed from the plume of impacted ground water (Appendix L), or approximately 64 grams per day ' Analytical results from the December 2000 quarterly monitoring event indicates the most intense on- site q Y g site MTBE Impact is in the First Zone of MW-1 (1,800µg11), the most intense off site MTBE impact is in Rocky's Upper Zone of MW-11B (260µg11),probably influenced by the pumping operation of RDW-1 lopThe greatest off-site MTBE was detected in the area of Flag City Chevron wells MW-11A, MW-7 and Three B's Truck Plaza well MW-4, significant concentrations of MTBE were also quantified in the area of Three B's Truck Plaza wells MW-6 and Flag City Chevron well MW-13A, low concentrations of MTBE were detected at Three B's Truck Plaza wells MW-1 an MW-2 which is suggestive of separate MTBE plumes being pulled towards domestic dnnking water wells RDW-1 (Rocky's Restaurant) and DW-1 (Three B's Truck Plaza) Between the August and December 2000 monitoring events, significant TPH-g and TPH-d decreases ' were quantified in MW-11B (Rocky's Upper Zone), conversely, a significant increase was observed at MW-6B 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 200, however ground water elevations ' did show an increase from August 2000 to December 2000 (Appendix M) ' 110 RECOMMENDATIONS ' Based upon data collected from the site, AGE recommends • Continued quarterly ground water monitoring and sampling of monitoring wells MW-1 ' Advanced GeoEnvtronmental,Inc