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� f until these parameters stabilized Samples were collected from the wells using dedicated bailers The groundwater samples were decanted from the bailers into 40-m1 volatile organic analysis (VOA) vials, preserved with hydrochloric acid and sealed without headspace All of the samples were labeled and stored on ice for transport to Kiff Analytical, LLC of Davis, California (ELAP #2236) under appropriate chain-of-custody documentation Well sampling field logs are presented in Appendix A The site drinking water well was sampled through a sampling port and was purged prior to sampling Well sampling purge water was disposed of through the on-site activated carbon treatment system 4 . 0 GROUNDWATER SAMPLE ANALYSIS The groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPH-G), benzene, toluene, ethylbenzene, a n d total xylenes (collectively known as BTEX), and methyl-t-butyl-ether (MTBE) by EPA Method 8015M/8020 and total petroleum hydrocarbons as diesel (TPH-D) by EPA Method 3510/8015 The analytical results for this . and previous sampling periods are presented in Tables Two and Three The certified analytical report and chain-of-custody documentation are included as Appendix B 5.0 CONCLUSIONS Free-floating hydrocarbons were present on the groundwater surface in monitoiing wells MW-5, MW-6, and piezometer P-4 The product thickness in MW-5 was 001-feet as measured with an oil/water interface probe The product was bailed and did not appear to re--enter MW-5 a n d the well was sampled Monitoring well MW-5 has historically contained free-product Monitoring well MW-6 and piezometer P-4 have contained product since it was discovered during the previous quarterly sampling period in June Isoconcentration contour maps for TPH-G, benzene, and MTBE in the shallow water-bearing zone are presented as Figures 5 through 7, respectively The benzene concentration detected in groundwater samples collected from monitoring wells MW-5 and MW-13 exceeded the California . Department of Health Services (DHS) maximum contaminant level (MCL) for drinking water The toluene and total xylene concentrations in Frank's One Stop Quarterly Report — October 2001 Sampling -3-