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' 28 June 2004 <br /> • AGE-NC Project No 97-0300 <br />' Page 4 of 5 <br /> I4.0. SUMMARY AND CONCLUSIONS <br /> The implications from the findings of the January 2004, first quarter ground water monitoring event <br /> I are <br /> • Ground water flow direction at the site appeared to be oriented generally northwest at an <br />' estimated gradient of 0 002 (Figure 3) Due to the low gradient at the site, slight variations <br /> in ground water measurements or changes of recharge/discharge of the local ground water <br /> could greatly modify the modeled ground water flow direction <br /> I • The ground water elevation at the site was within the screened intervals of wells MW-1, <br /> MW-2 and MW-3 and yield samples fully representative of shallow ground water conditions <br /> • Since March 2001, ground water had not been encountered in monitoring wells MW-1, <br /> MW-2 and MW-3 and had been recorded as being `dry' <br /> I Ground water elevations at the site decreased an average 7 04 feet between the March 2001 <br /> and the January 2004 ground water monitoring events (Table 1) <br /> • Low concentrations of MTBE were detected for the first time (by EPA Method 8260) from <br /> wells MW-1 and MW-2 <br /> • No TPH-g, TPH-d, TPH-mo or BTEX compounds were detected by laboratory analysis, <br /> however very low concentrations of dissolved TPH-d have previously been detected in the <br /> area of monitoring well MW-1 indicating that there is only a mirror TPH-d-impact to ground <br /> water in the area assessed <br /> I <br /> I5.0. RECOMMENDATIONS <br /> Based upon the results of the first quarter 2004 investigation, AGE recommends <br /> I • Submission of a ground water monitoring well sample collected from MW-1 to a <br /> microbiological laboratory for microbial enumeration and physicochemical analysis to assess <br /> the potential for natural attenuation of petroleum hydrocarbons in ground water at the site <br /> • Due to the detection of significant TPH-d,TPH-mo, 1,2-DCA,benzene and MTBE in a grab <br /> water sample collected from P-9(65 to 68 feet bsg),installation of at least one on-site ground <br /> water monitoring well is warranted (near boring P-9) to provide repeatable ground water <br /> sampling locations,determine site-specific ground water flow direction and gradient and to <br /> document petroleum hydrocarbon concentration trends <br /> • Advanced GeoEnvironmental,Inc <br /> I <br />