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27 May 2004 AGE-NC Project No 96-0229 ' Page 5 of 7 MTBE was detected by EPA Method 8260B In seventeen ground water samples collected from wells MW-1 through MW-4,MW-6,MW-7,MW-9,MW-10(A and B),MW-15A,MW-16 (A-C), MW-17A,MW-18(A and B)and MW-19A at concentrations as high as 400 pg/1(MW-6), 1,2-DCA ' was detected in nine ground water samples collected from wells MW-1, MW-2, MW-10B, MW-13D,MW-15A,MW-16C,MW-17A,MW-18C and MW-19A at concentrations up to 140 gg/l, TAME was detected in one ground water sample collected from MW-1 OB at a concentration of 1 1 ' gg/l, TBA was detected in two ground water samples collected from MW-13D and MW-17A at concentrations of 170 pg/l and 49 µg/l ' No other constituents of concern were detected above laboratory reporting limits in the analyzed samples Previous and current analytical results of ground water monitoring well samples are summarized in Tables 3 and 4 The laboratory reports(Castle Analytical Laboratory Reference No ' 6371) and chain-of-custody forms are presented in Appendix B ' 4.0. SUMMARY AND CONCLUSIONS 1• The implications from the findings of the November 2003 ground water monitoring event are • Generally,depth to ground water at the site vaned between 3192 feet and 33 45 feet below ' the top of well casings, ground water elevations ranged between 19 45 feet (MW-4 and MW-5) and 21 52 feet (MW-18D)below mean sea level First Zone ground water flow direction at the site was inferred to be towards the northeast at an approximate gradient of 0 006 fl/ft or less(Figure 4),offsite and towards the northeast, ground water gradient appeared to be much flatter at an approximate gradient of 0 002 ft/ft or less • Second Zone ground water flow direction at the site was inferred to be towards the east- southeast at an approximate gradient of 0 007 ft/f1 or less (Figure 5) ' • Due to the low hydraulic gradient at the site, slight variations in ground water recharge/discharge could greatly modify the inferred ground water flow direction • The most intense TPH-g-impacted ground water was reported in the area of First Water Zone wells MW-2 and MW-6 at concentrations as high as 100,000 gg/l (Figure 6) ' • The highest concentrations of on-site dissolved MTBE were detected from deeper screened well MW-1 (screened 48 to 53 feet and in the First Confining Unit), lesser on-site MTBE concentrations were detected from shallow screened wells MW-2 (screened 25 to 45 feet), MW-3(screened 29'/2 to 49%2 feet)and MW-4(screened 30 to 50 feet,Figure 5) The vertical . extent of on-site MTBE appears to be approximately between 53 feet (MW-1) and 62 feet I Advanced GeoEnvironmental,Inc