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Date October 04,2004 Quarter- 3`d Quarter,2004 DISCUSSION: Gasoline range organics (GRO), benzene, toluene, ethylbenzene, total xylenes (BTEX), methyl tert-butyl ether (MtBE), and 1,2-DCA were detected above laboratory reporting limits in groundwater samples collected from site wells this quarter GRO and BTEX concentrations in MW-1,MW-4,MW-5,and MW-7 increased but remain within historical ranges 1,2-DCA was not detected above laboratory reporting limits in MW-1B for the first time since August 2002 Ethylbenzene and total xylenes concentrations in MW-2 and benzene, ethylbenzene, and total xylenes concentrations in MW-3 increased this quarter In MW-6, GRO, toluene, ethylbenzene, and total xylenes concentrations increased relative to the previous sampling event 1,2-DCA concentrations increased in MW-8 but, as discussed in the previous section, the results may be biased high In MW-8C, MtBE was not detected above laboratory reporting limits for the first time since December 2001 Groundwater elevations across the site decreased relative to the previous quarter The inferred direction of groundwater flow across the site ranged from the northeast to the southeast at an average hydraulic gradient that ranged from 0 001 to 0 005 ft/ft This report is based on data, site conditions, and other information that are generally applicable as of the date of the report,and the conclusions and recommendations herein are therefore applicable only to that time frame TABLES Table 1 Groundwater Elevation and Analytical Data Table 2 Fuel Oxygenates Analytical Data . Table 3 Groundwater Gradient Data FIGURES Figure 1 Groundwater EIevation Contours Figure 2 Groundwater Analytical Summary APPENDICES Appendix A Field and Laboratory Procedures Appendix B Laboratory Analytical Reports,Cham-of-Custody Documentation, and Field Data Sheets Appendix C GeoTracker Upload Confirmation i K%WP—eWJ5 BP ARCO\0216MQuanerW004\3 QTR 04\2168 cWMR 3QO4 d�c Page 2