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15 October 2001 AGE-NC Project No 96-0232 ' Page 13 of 17 ' MW-1 radially inward in all directions at an approximate gradient of 0 01 fUft or less (Figure 3) Outside the area of influence of MW-1, First Zone ground water flow direction was inferred west to northwest at an approximate gradient of 0 003 or less ' + Second Zone ground water flow direction was inferred to be generally toward the west- northwest at an approximate gradient of 0 002 ft/ft or less (Figure 4) ' • Secondary Aquifer Zone ground water flow direction was inferred to be generally toward the west at an approximate gradient of 0 001 ft/ft or less (Figure 5) + Primary Aquifer Zone ground water flow direction was variable and generally oriented radially inward toward the area of the Rocky's Restaurant domestic drinking water well (RDW-1) at an approximate gradient of 0 001 ft/ft or less (Figure 6) ' • First Zone and possibly Second Zone ground water flow direction and gradient during the Flag City Chevron monitoring event appeared to be influenced by the remedial ground water extraction • Primary Aquifer Zone ground water flow direction and gradient during the Flag City Chevron monitoring event appeared to be influenced by ground water pumping at RDW-1 Due to the low ground water gradient at the site, small variations in ground water measurements or changes of recharge/discharge of the local ground water could greatly modify the inferred ground water flow direction Y Decreasing ground water elevations have been reported at the site between March 2001 and September 2001 monitoring events, the overall decrease of ground water elevation is probably due to seasonal fluctuation Hydrographs depicting recorded ground water elevations at wells MW-2, MW-6A and MW-6B vs time are in Appendix I + On-site, the greatest concentration of dissolved MTBE was detected in the sample collected from First Zone extraction well EW-5 at a concentration of 35 ,ug/l (Figure 8), low concentrations of on-site MTBE were detected in water samples from First Zone monitoring well MW-1 and extraction wells EW-2, EW-4, EW-6, EW-8 and EW-9, from Second Zone monitoring well MW-9A, and from Primary Aquifer monitoring well MW-9C (Table 6, Figure 9) + Off-site,the greatest concentration of MTBE was detected in Rocky's Upper Zone water near the Rocky's Restaurant domestic water well in MW-11B at a concentration of 130 ug/l, in First Zone water from Flag City Chevron monitoring well MW-7 at a concentration of 47 µg/l, and in Three B's Truck Plaza monitoring well MW-4 at a concentration of 110 ,ug/l (Figure 7) Low concentrations of off-site MTBE were detected in First Zone water in samples collected from well MW-13A, Three B's Truck Plaza monitoring wells MW-1 and • MW-6, and Second Zone water from well MW-11A (Figure 8) Advanced GeoEnvironmental,Inc