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2 0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS <br /> On .tune 9, 2004, to comply with quarterly groundwater monitoring requirements and to monitor <br /> the plume of impacted groundwater, Ramage Environmental monitored and sampled the six on- <br /> site monitoring wells In addition, Ramage Environmental continued monthly free product removal <br /> from MW-1 <br /> 21 Groundwater Monitoring <br /> Depth-to-groundwater was measured to within 0 01 foot in each of the wells using a water level <br /> g 9 <br /> indicator A free product sheen was observed in MW-1 <br /> The depth to static groundwater across the site ranged from 46 90 feet bgs in MW-6 to 47 94 feet <br /> bgs in MW-1 The corresponding groundwater surface elevation ranged from a high of 28 00 feet <br /> below mean sea level (msl) at MW-2 to a low of 28 80 feet below msl at MW-4 The groundwater <br /> elevations at MW-1 and MW-2 do not appear to fit the regional trend, possibly due to the <br /> presence of free product Otherwise, the groundwater table surface appears as a regular plane <br /> dipping toward the east at a gradient of approximately 0 0020 foot/foot A groundwater surface <br /> contour map is included as Figure 4 The well construction details and groundwater monitoring <br /> data are summarized in Table 1 <br /> 22 Groundwater Sampling and Analysis <br /> Fallowing the groundwater level measurements, MW-2, MW-3, MW-4, MW-5 and MW-6 were <br /> purged and sampled Due to the presence of a free product sheen, MW-1 was not sampled The <br /> wells were purged using a pump and dedicated disposable tubing, until at least three well casing <br /> volumes were extracted, and/or after groundwater temperature, pH and electrical conductivity <br /> values had stabilized Following well purging and recharge, groundwater was sampled from the <br /> wells using dedicated disposable bailers and laboratory-supplied containers <br /> Each sample container was transported in an iced cooler with chain-of-custody documentation to <br /> Excelchem Environmental Labs (Excelchem), a state of California certified hazardous waste <br /> testing laboratory (Certification #2119) Excelchem analyzed each of the groundwater samples <br /> for TPH-as-gasoline and BTEX by EPA Method 8020/8015M, and for methyl tertiary butyl ether <br /> (MTBE), di-isopropyl ether(DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether <br /> (TAME), tertiary butanol (TBA), and 1,2-dichloroethane (1,2-DCA) by EPA Method 8260B <br /> • 5 <br />