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However, the overall flow direction over trme has been generally consistent toward the south-southwest (away from the Channel) The ground water samples were analyzed for purgeable hydrocarbons and BTEX constituents as well as general water quality parameters Analyses during the earliest monitoring events also included organic and total lead and ethylene dibrormde Recent sampling events have also included fuel ' oxygenates and 1,2-dichloroethane (1,2-DCA) Tables 4 and 5 present a summary of the quarterly ground water sample results for Site #1 The highest concentrations of TPH and BTEX detected since the October 1993 excavation were in ground water samples collected at monitoring wells MW-4 and MW-5 However, over time, the results of quarterly ground water samples collected from monitoring wells MW-4 and MW-5 have shown a steady decline in the concentrations of TPH (as gasoline and/or gasoline) and BTEX in ground water The last samples collected (July 1999) were non-detect for TPH (gasoline and diesel), except for a 014 mg/L concentration of TPH as gasoline in MW-5 An unknown hydrocarbon mixture, which probably reflects degraded gasoline and/or diesel,was also detected at a low concentration (0 08 mg/L) at MW-5 in July 1999 TPH detections have been less than 1 mg/L at both locations ' since September 1997 Analyses were run in April 1998 and July 1999 for fuel oxygenates (methyl Cert-butyl ether, tert-amyl methyl ether,2-methyl-2-propanol, diisopropyl ether, and ethyl tert-butyl ether) As shown in Table 4, these fuel oxygenates were not detected in any of the wells at Site #1 Analyses were run for 1,2-DCA in July 1999, and the only detection was a low concentration of 0 00056 mg/L in MW-5 ' Between October 1996 and ,1998 l ri AP ground water samples les collected ' from the wells at Site #1 were analyzed for various water quality parameters (Table 5) and heterotrophic plate counts (for microbes) to evaluate the effectiveness of the natural attenuation process The increase ' in heterotrophic count in the samples collected from MW-4 and MW-5 when compared to baseline results indicates that the presence of the ORC socks was enhancing microbial activity As presented in Table 5, the ' general water quality parameter measurements confirm that the subsurface conditions changed from anaerobic to aerobic conditions, as evidenced by comparison of post-ORC to baseline (October 1996) conditions Furthermore, pre-ORC measurements of certain constituents can be used to calculate the biodegradation capacity of the subsurface ' environment As provided in Appendix B (December 1998 report excerpt), the calculations performed for Site #1 indicate that the biodegradation capacity is more than adequate to address the low levels ' ERM 12 CATELLUS/2996 10-10/13/99 5