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i . 2 0 GROUNDWATER MONITORING, SAMPLING AND ANALYSIS On August 23, 2004, to comply with quarterly groundwater monitoring requirements and to monitor the plume of impacted groundwater, Ramage Environmental monitored and sampled the six on-site monitoring wells In addition, Ramage Environmental continued monthly free product removal from MW-1 21 Groundwater Monitoring Depth-to-groundwater was measured to within 0 01 foot in each of the wells using a water level indicator The depth to static groundwater across the site ranged from 48 11 feet bgs in MW-6 to 49 41 feet bgs in MW-1 The corresponding groundwater surface elevation ranged from a high of 29 30 feet below mean sea level (ms]) at MW-2 to a low of 30 20 feet below ms] at MW-1 The groundwater elevations at MW-1 and MW-2 do not appear to fit the regional trend, possibly due to the presence of free product Otherwise, the groundwater table surface appears as a plane dipping toward the east at a gradient of approximately 0 0022 foottfoot A groundwater surface contour map is included as Figure 4 The well construction details and groundwater monitoring data are summarized in Table 1 22 Groundwater Sampling and Analysis Following the groundwater level measurements, all six monitoring wells were purged and sampled The wells were purged using a pump and dedicated disposable tubing, until at least three well casing volumes were extracted, and/or after groundwater temperature, pH and electrical conductivity values had stabilized Following well purging and recharge, groundwater was sampled from the wells using dedicated disposable bailers and 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 of the groundwater samples for TPH-as-gasoline and BTEX by EPA Method 8020/8015M, and for methyl tertiary butyl ether (MTBE), di-isopropyl ether(DIPS), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), tertiary butanol (TBA), and 1,2-dichloroethane (1,2-DCA) by EPA Method 82606 5