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r . 2 0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS On August 19, 2004, to comply with quarterly groundwater monitoring requirements, and to monitor the plume of impacted groundwater, Ramage Environmental monitored and sampled the three wells 21 Groundwater Monitoring Depth-to-groundwater was monitored to within 0 01-foot using a water level indicator The static depth to the groundwater table, as measured in the three monitoring wells, ranged from 16 61 feet below grade in MW-1 to 28 77 feet below street grade in MW-3 The groundwater surface elevation in the three wells ranged from a high of 16 47 feet below mean sea level (msl) at MW-1 to a low of 17 21 feet below msl at MW-3 The resulting groundwater surface appears as a regular plane dipping to the northeast at a gradient of approximately 0 0086 foot/foot A groundwater surface contour map is included as Figure 4, and the groundwater monitoring data are summar¢ed in Table 3, and the sample information field sheets are included in Appendix A r 22 Groundwater Sampling and Analysis Following groundwater level measurements, the wells were purged and sampled The wells were purged with a pump and dedicated disposable tubing until at least three well casing volumes had been removed and/or after groundwater temperature, pH and electrical conductivity values had stabilized Groundwater was sampled from the wells using disposable polyethylene bailers and r laboratory-supplied containers Each sample container was transported in an iced cooler with chain-of-custody documentation to Excelchem Environmental Labs (Excelchem), a state of California certified hazardous waste testing laboratory (Certification #2119) Excelchem analyzed each groundwater sample for TPH-as-gasoline and benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA Method 8020/8015M, and for MTBE, di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), tertiary butanol (TBA), and 1,2-dichloroethane (1,2-DCA) by EPA Method 82608 All three wells contained detectable concentrations of MTBE The highest concentrations of gasoline compounds were detected in the sample collected from MWA 5,700 micrograms per liter (µg/l) of TPH-as-gasoline, 420 µg/l of benzene, 570 µg/l of ethylbenzene, 1,200 µg/l of xylenes, and 7 7 µg/l of MTBE MTBE was detected in MW-2 at 1 7 p,g/l and in MW-3 at 5 9 gg/l ' The groundwater sample analytical results are summarized in Table 2, the distribution of gasoline in groundwater is shown on Figure 5, and the laboratory reports are included in Appendix B 6 r r