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' 29 January 1999 • AGE-NC Project No 98-0448 ' Page 2 of 5 ' 2 2 GROUND WATER SAMPLING Following purging, ground water levels in monitoring wells MW-2 through MW-7 achieved a ' minimum of 80 percent recharge prior to sample collection, ground water levels to monitoring well MW-I only achieved 75 percent recharge prior to sample collection Ground water samples were collected from the purged wells utilizing new, disposable polyethylene bailers and three 40-m1 EPA- approved VOA vials containing 0 5 ml 18% hydrochloric acid as a preservative Care was taken to ensure that visible air bubbles were not present In the vials after filling and capping Ground water ' sample containers were labeled with the well designation, date, time, and sampler's initials ' 2 3 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 Department of Health Services (DHS)-certified laboratory for analysis in accordance with ' • EPA Method 8015M for total petroleum hydrocarbons quantified as gasoline (TPH-g), • EPA Method 8020 for volatile aromatics (benzene, toluene, ethyl benzene and xylene ' BTEX) with methyl-tertiary butyl ether (MTBE), and • EPA Method 8260 for tertiary butanol (TBA), dl-isopropyl ether (D1PE), ethyl tert butyl ether (ETBE), tert amyl methyl ether(TAME) and MTBE I ' 30. FINDINGS From the field data, AGE was able to determine the ground water flow direction and gradient ' Laboratory analysis detected petroleum hydrocarbons in five of seven ground water samples, oxygenated fuel additives were detected In two of seven ground water samples 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT ' The depths to ground water from wells MW-1 through MW-7 were measured between 17 16 and 20 06 feet below the top of well casings Between August 1998 and December 1998, ground water elevation decreased an average 1 11 feet at the site Ground water elevation measured from MW-4A . (screened 8 to 33 feet bsg) was measured 1 57 feet above ground water elevation measured at MW- 4B (screened 45 to 50 feet bsg), due to anomalous measurements at MW-4, the ground water Advanced GcoEnN iron mental,Inc