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. and MW-2) were in the range of 0 9 mg/L to 2 17 mg/L During the third quarter 2004, higher DO levels in the range of 2 6 mg/L to 11 4 mg/L were observed in wells MW-7 and MW-9 (located approximately 10 feet from the infection point) The DO levels in the observation wells appear to be generally greater than the background monitoring wells, and is probably due to ozone infection DO levels in the observation wells are consistent with previous monitoring events Concentrations of COD and hetetrophic plate counts appear to correspond to changes in GRO concentrations for wells MW-4, MW-6, and MW-8 (Figures 11 through 16) COD and heterotrophic plate counts serve as secondary indicators to evaluate oxygen sinks and to evaluate whether biodegradation is occurring Given the COD and heterotrophic plate count variations observed at wells MW-4, MW-6, and MW-8, it appears that biological activity is probably occurring at the site Based on the field and laboratory data collected to date, the ozone injection system appears to be supplying ozone and oxygen to the subsurface as designed LIMITATIONS This report was prepared in general accordance with accepted standards of care that existed at the time this work was performed No other warranty, expressed or implied is made Conclusions and recommendations are based on field observations and data obtained from this work and previous investigations It should be recognized that definition and evaluation of geologic conditions is a difficult and inexact art Judgments leading to conclusions and recommendations are generally made with an incomplete knowledge of the subsurface conditions present More extensive studies may be performed to reduce uncertainties This report is solely for the use and information of our client unless otherwise noted ATTACHMENTS • • Table 1 Groundwater Elevation and Analytical Summary • Table 2 Groundwater Analytical Results for Oxygenates and Additional Compounds • Table 3 Monitoring Plan Summary • Table 4 Physical Parameter Summary • Table 5 Analytical Parameter Summary • Figure 1 Site Location Map • Figure 2 Site Plan • Figure 3 Groundwater Elevation Contour Map (Third Quarter 2004) • Figure 4 Groundwater Analytical Summary (Third Quarter 2004) • Figure 5 DO Variation With Time (MW-1, MW-2, MW-5, MW-7, and MW-9) • Figure 6 GRO, Benzene, MTBE Variation with Time at MW-4 • Figure 7 GRO, Benzene, MTBE Variation with Time at MW-5 • Figure 8 GRO, Benzene, MTBE Variation with Time at MW-6 • Figure 9 GRO, Benzene, MTBE Variation with Time at MW-7 • Figure 10 GRO, Benzene, MTBE Variation with Time at MW-8 • Figure 11 COD and GRO Variation with Time at well MW-4 • Figure 12 COD and GRO Variation with Time at well MW-6 • Figure 13 COD and GRO Variation with Time at well MW-8 • Figure 14 Heterotrophic Plate Count and GRO Variation with Time at well MW-4 • Figure 15 Heterotrophic Plate Count and GRO Variation with Time at well MW-6 • Figure 16 Heterotrophic Plate Count and GRO Variation with Time at well MW-8 • Appendix A Field Data Sheets • Appendix B Sampling and Analysis Procedures • Appendix C Certified Analytical Reports with Chain-of-Custody Documentation and EDF Verification P IBP-Arco for URS\5469\Quarterty\2004\Arco_5469_3Q04 doe 37'RArU5