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15 June 2004 AGE-NC Project No. 95-0167 Page 2 of 4 2.2. COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES Prior to collection of ground water samples,the depth to ground water was measured in each purged well to ensure that a minimum of 80% of the initial well volume had recharged. Then a water sample was collected from each purged well using the dedicated disposable plastic bailer. Each water sample was transferred into three 40-ml volatile organic analysis (VOA) vials containing 0.5 ml 18%hydrochloric acid as a sample preservative.After collection,the samples were properly labeled,placed in a chilled container and transported under chain-of-custody to Cal Tech Environmental Laboratories (CTEL), a California Department of Health Services (DHS)-certified laboratory, and were analyzed for: • Total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with EPA Method 8015 Modified; • Benzene, toluene, ethylbenzene and total xylenes (BTEX) and the fuel additives methyl- tertiary butyl ether (MTBE), di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether(TAME),tertiarybutyl alcohol(TBA), 1,2-dibromoethane(EDB) and 1,2-dichloroethane (1,2-DCA) in accordance with EPA Method 8260B. 3.0. FINDINGS Ground water flow direction, elevation, and gradient were determined from data collected in the field.The hydrocarbon impact to ground water was quantified by the laboratory data obtained from the ground water samples. 3.1. GROUND WATER ELEVATION AND GRADIENT For the August 2003 sampling event, depths to ground water ranged from 16.04 feet to 16.85 feet below the tops of the well casings.Ground water elevations at the site ranged from 6.43 feet(MW-5) to 7.76 feet (MW-2)below mean sea level (MSL). Ground water was within the screened interval of MW-1 through MW-6 and had an average elevation decrease of 0.60 feet since the last monitoring event. The ground water flow direction was determined by plotting and contouring the ground water elevation data. The water table at the time of the December 2003 monitoring event was modeled to be a west-northwest-plunging trough. Net flow of ground water at the site was determined to be to the west-northwest under an average gradient of 0.009 feet/feet. Figure 3 illustrates the contoured ground water elevations as measured in December 2003. `.. Advanced GeoEnvironmental,Inc.