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i <br /> 2 0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS <br /> 1 On <br /> September 21, 2005, to comply with quarterly groundwater monitoring requirements and to <br /> 1 monitor the plume of impacted groundwater, Ramage Environmental monitored and sampled the <br /> seven on-site monitoring wells In addition, Ramage Environmental continued monthly free <br /> product removal 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 /> indicator The depth to static groundwater across the site ranged from 45 85 feet bgs in MW-7 to <br /> 48 36 feet bgs in MW-1 The corresponding groundwater surface elevation ranged from a high of <br /> 27 80 feet below mean sea level (msl) at MW-7 to a low of 29 15 feet below msl at MW-1 The <br /> groundwater table surface appears as a plane dipping toward the east-southeast at a gradient of <br /> approximately 0 0024 foot/foot A groundwater surface depression at MW-1 does not fit within the <br /> regional trend A groundwater surface contour map is included as Figure 4 The well construction <br /> details and groundwater monitoring data are summarized in Table 1 <br />'. 2.2 Groundwater Sampling and Analysis <br /> Following the groundwater level measurements, all wells except MW-1 were purged and sampled <br />' Due to the presence of a free product layer 0 05-foot thick, MW-1 was not sampled The wells <br /> 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 /> P Y <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 8021 B18015M, and for methyl tertiary butyl ether <br /> (MTBE), di-isopropyl ether(DIPE), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether <br /> (TAME), and tertiary butanol (TBA) by EPA Method 8260B <br /> 1 5 <br /> • <br />