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H 20 July 1998 AGE-NC Protect No 98-0448 ' Page 2 of 4 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 EPA-approved 40-m1 VOA vials containing 0 5 ml 18% hydrochloric a , ' acrd as a preservative for the samples Care was taken to ensure that visible air bubbles were not present in the VOAs 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 EPA Methods i • 8015M for total petroleum hydrocarbons quantified as gasoline (TPH-g), • 8020 for volatile aromatics (benzene, toluene, ethyl benzene and xylene BTE&X) with methyl-tertiary butyl ether (MTBE), and • 8260 for tertiary butanol (TBA), di-isopropyl ether(DIPE),ethyl tert butyl ether(ETBE)and tert amyl methyl ether (TAME), and to confirm and quantify MTBE if detected by EPA Method 8020 3.0. FINDINGS 31 RELATIVE GROUND WATER ELEVATION AND GRADIENT The depth to ground water in monitoring wells MW- through MW-3 was measured at 15 66 to p � g g 16 52 feet below the tops of the well casings Between April 1997 and June 1998, ground water elevation increased an average 4 80 feet at the site The ground water elevation data for MW-1 though MW-3 during June's ground water monitoring event is,depicted in Figure 3 During the June 1998 monitoring event, the ground water surface was between 3 53 and,4 34 feet above the screened intervals in monitoring wells MW-I through MW-3 Therefore, the wells are I "drowned", and may not yield samples fully representative of ground water conditions near the top of the saturated zone, where fuel hydrocarbons would be expected to have the greatest impact In June 1998,the gradient was calculated to be 0 006 ft/ft,or approximately 31 feet per mile(Figure 3) Based upon ground water momtonng data collected in June 1998, ground water was inferred to be flowing toward the southeast However, due to the low gradient at the site, slight variations in Advanced GeoEnvironmental,Inc ' i