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07 January 1998 AGE-NC Project No 95-0130 Page 4 of 5 reported from VW-3A at a concentration of 4,400 ppb,while the lowest concentration was reported from MW-3 at 28 ppb TBA was detected from MW-3 and MW-5 at concentrations of 42 ppb and 140 ppb,respectively TAME, DIPE and ETBE were not aetected in the laboratory analysts of any Iground water samples The analytical results for grouted water samples are summarized In Table 2 - Analytical Results of Ground Water Samples The laboratory reports (Castle Analytical Laboratory Reference No 1268 and McCampbell Analytical Inc Lab I D 81300 to 81307)and chain-of-custody forms are included in Appendix B I4.0. DISCUSSION AND CONCLUSIONS IBased upon data collected from the site AGE finds • Monitoring well elevation survey data collected at the site on 18 December 1997 indicates ' a recalculated ground water flow direction towards the northeast for ground water monitoring events performed in January, March, June and September 1997 This varies from to the previous monitoring well survey data which had indicated a ground water flow direction towards the southeast • The ground water surface elevation at the site continues to remain above the slotted screened intervals in wells MW-1 through MW-5, and VW-IC Therefore, samples collected from these wells may not be representative of actual surface ground water dissolved petroleum hydrocarbon concentrations • Concentrations of benzene detected in samples collected from wells MW-2, MW-3, VW-I C, VW-2A and VW-3A were above the State of California Maximum Contaminant Level (MCL) for drinking water of 1 0 ppb The approximate distribution of dissolved benzene in wells with appropriate screen intervals (MW-5, VW-1, VW-2 and VW-3) is depicted in Figure 4 Well screen intervals are listed in Table 1 • Concentrations of toluene were above the MCL of 150 ppb in wells VW-I C, VW-2A and VW-3A, concentrations of ethylbenzene were above its MCL of 700 ppb in wells VW-IC, VW-2A and VW-3A, concentrations of xylenes were above the MCL of 1,750 ppb in wells VW-IC, VW-2A and VW-3A • MTBE was detected in samples collected from wells MW-3, VW-I C, VW-2A and VW-3A I The detection of MTBE suggests that at least a portion of the release may have occurred within the last 20 years • TBA was reported above the laboratory detection limits from wells MW-3 and MW-5 ITherefore, it appears that TBA could be present at other well locations at the site but may not been detected due to raised detection limits Advanced GeoEnvironmental,Inc I