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` 10 May 2002 AGE-NC Project No 96-0229 ' Page 2 of 5 ' 2 2 GROUND WATER SAMPLING Following well purging, ground water levels from each well achieved a minimum of 80 percent recharge prior to sample collection except for MW-1,which was purged"dry" Ground water samples were collected from the purged wells utilizing new, disposable polyethylene bailers and 40-m1 EPA- approved VOA vials containing 0 5 mi 18% hydrochloric acid as a sample 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 for • Total petroleum hydrocarbons quantified as gasoline (TPH-g)by EPA Method 5030/8015M, • Benzene, toluene, ethyl benzene and xylene (BTEX) and methyl-tertiary butyl ether (MTBE) lie by EPA Method 8020, and 4 1,2-dichloroethane (1,2-DCA), ethylene dibromlde (EDB), tertiary butanol (TBA), di- isopropyl ether (DIPE), ethyl tert butyl ether (ETBE), tert amyl methyl ether (TAME) and MTBE by EPA Method 8260 3.0. FINDINGS Ground water elevation, flow direction and gradient were determined from field data collected on 31 December 2001, the contaminant impact to ground water was quantified from the laboratory data I 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT During the 31 December 2001 monitoring event, depths to ground water in wells MW-1 through MW-IOB were measured between 29 24 and 30 81 feet below the tops of the well casings, ground water elevations were calculated to be between 18 43 feet and 20 22 feet below mean sea level (MSL) Ground water elevation at the site decreased an average 0 12 feet between the September 2001 and the December 2001 ground water monitoring events, generally, decreasing ground water -elevations were observed at the site-between March and D_ec_ember 2_001 (Table 2) The ground water _ • elevation data for MW-1 through MW-1013 during the December 2001 ground water monitoring event is depicted and contoured in Figure 3 Advanced CcoEnvironmental,Inc I