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S I17 April 2001 i AGE-NC Project No 99-0624 ' Page 2 of 4 22 COLLECTION AND,ANALYSIS OF GROUNDWATER SAMPLES ' Water samples were collected from each monitoring well using new disposable bailers after allowing ' the wells to achieve a minimum 80% recovery of the pre-purge water volume The samples were , transferred Into laboratory-supplied 40-m1 EPA-approved VOA vials containing 0 5 ml 18% hydrochloric acid as a sample preservative The sample vials were then labeled with the monitoring I well designation,date,time of sampling and the sampler's initials The samples were transported in a chilled container under chain of custody to McCampbell Analytical, Inc (MAI), a California Department of Health Services(DHS)-certified analytical laboratory for analysis The samples were ' analyzed for + Total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with EPA ' Method 5030/8015 Modified, • Volatile aromatic compounds - benzene, toluene, ethylbenzene, and total xylenes (BTEX) ' and methyl tertiary butyl ether(MTBE) in accordance with EPA Method 8020, and • Fuel oxygenates - tertiary butanol (TBA), di-Isopropyl ether (D1PE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and MTBE in accordance with EPA Method lie 8260M ' 30. FINDINGS The ground water elevation in each well was determined by subtracting the measured depths-to- water from the surveyed casing elevations and are presented in Table 1 Ground water flow direction was determined by contouring the ground water elevations on a scaled site plan (Figure 2) I Hydrocarbon-Impact and MTBE-impact to ground water were assessed from laboratory analysis of the ground water samples ' 3 1 GROUND WATER ELEVATION AND GRADIENT IDepths to ground water ranged from 50 29 feet to 51 39 feet below the tops of the well casings Ground water elevations at the site ranged from 11 89 feet (MW-4) to 12 09 feet (MW-1) below mean sea level The top of the saturated zone occurred,within the screened intervals*of all the monitoring wells _ ' The ground water flow direction was determined by contouring the ground water elevation data The ground water underlying the site was Inferred to have an average gradient of 0 002 ft/ft, the flow . direction varied radially from a more southwesterly direction at the western half of the site to a more IAdvanced GeoEnvironmentaI,Inc i