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' 26 May 2004 AGE-NC Project No 96-0229 ' Page 4 of 6 ' wells MW-1, MW-9 and MW-14A at concentrations of 170 gg/1 , 14 µg/1 and 0 59 µg/l, respectively 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 (McCampbell Analytical Inc Work Order ' 0308418) and chain-of-custody forms are presented in Appendix B ' 4.0. SUMMARY AND CONCLUSIONS On 24 March 2004,a state of California state-licensed survey engineer from Morrow Surveying Land ISurveyors (MSLS) surveyed the top of well casings from newly installed wells MW-13 through MW-19, and re-surveyed the top of well casings from wells MW-1 through MW-12 to the nearest 0 01-foot utilizing GPS techniques and relative to vertical datum point NAVD88 (North American IVertical Datum 1988) The results of the monitoring well survey are contained in Table 1 The original elevation survey for wells MW-1 through MW-12 was relative to vertical datum point NGVD29(National Geodic Vertical Datum 1929),which off-sets NAVD88 by approximately 2 feet The implications from the findings of the August 2003 ground water monitoring event are C Ground water flow direction at the site was inferred to be towards the northeast at an approximate gradient of 0 004 ft/ft, this appears to be the prevailing flow direction for the area(Figure 3),offsite and towards the northeast,ground water gradient appeared to be much steeper at an approximate gradient of 0 02 ft/ft Due to the low hydraulic gradient at the site, slight variations in ground water Irecharge/discharge could greatly modify the inferred ground water flow direction • The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-1, MW-2, MW-3 and MW-6 indicate that these wells are within or near the dissolved petroleum hydrocarbon"core area" of the plume (Figure 4) • TPH-g,BTEX and MTBE were reported for the ninth consecutive quarter in water samples i v11 lid J.1 1vi1TV-9, 3uggiStiil�that ilii,PIU111V vfpCtrvliruiii-1t11PaiJtCd SIvuiid waL%,i 111a'y have shifted eastward towards MW-9 (Table 3) • The highest concentrations of on-site dissolved MTBE were detected from deeper screened well MW-1 (screened 48 to 53 feet bsg), lesser on-site MTBE concentrations were detected from shallow screened wells MW-2 (screened between 25 and 45 feet bsg) and MW-3 (screened between 29%2 and 49%2 feet bsg (Figure 5) 1 Advanced CeoEnvironmental,Inc