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E22 June 1998 • AGE-NC Project No 95-0173 Page 2 of 5 2 2 GROUND WATER SAMPLING The ground water levels in the monitoring wells achieved a minimum of 80 percent recharge prior to sample collection Ground water samples were collected utilizing disposable polyethylene bailers and new nylon rope Sufficient ground water sample was collected from each well to fill three 40-m1 EPA-approved VOA vials containing 0 5 ml 18%hydrochloric acid as a presen ative for the samples and one liter amber bottle Care was taken to ensure that visible air bubbles were not present in the VOA vials after filling and capping Ground water sample containers were labeled with the well designation, date, time, and sampler's Initials 23 LABORATORY ANALYSIS OF GROUND WATER SAMPLES Each ground water sample was logged on a chain-of-custody form, placed In a chilled container and transported to a California state-certified laboratory for analysis in accordance with the following EPA method 8015M for total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d, respectively) EPA method 8020 for volatile aromatics (benzene, toluene, ethyl benzene and xylene BTE&X) with methyl-tertiary butyl ether (MTBE) • EPA method 8260 for volatile organic compounds (including oxygenates) tThe laboratory reports (Castle Analytical Laboratory Lab No 1532, McCampbell Analytical Inc Lab I D 88097 to 88100) and chain-of-custody forms are presented in Appendix B 3 0. FINDINGS 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT Measured depths to ground water in the monitoring wells ranged from 26 03 feet to 28 33 feet below the tops of the well casings Between October 1997 and April 1998, ground water elevation increased an average 6 10 feet at the site Duringthe April 1998 round water monitoring event, the gradient was calculated to be 0 0035 Rift, p g g or approximately 19 feet per mile (Figure 3) Ground water monitoring data collected in the area of the monitoring wells suggests that the ground water flow direction was generally toward the east- southeast The ground water elevation data for the monitoring wells during the April 1998 ground Advanced GeoEnrironmenial,Inc