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31 October 2002 <br /> AGE-NC Project No 95-0184 <br />! Page 2 of 5 <br />' 2 2 COLLECTION OF GROUNDWATER SAMPLES <br /> Water samples were collected from each monitoring and vapor extraction well using new disposable <br />' bailers after allowing the wells to achieve a minimum 80%recovery of the pre-purge water volume <br /> Each water sample was transferred into laboratory-supplied 40-ml VOA vials containing 0 5 ml <br /> 18% hydrochloric acid as a sample preservative, the sample from MW-4 was also transferred into <br />' a i-liter amber bottle without preservative After collection, the samples were properly labeled, <br /> placed to a chilled container and transported under chain-of-custody to Cal Tech Environmental <br /> Laboratories (CTEL), a California Department of Health Services (DHS)-certified analytical <br />' laboratory for analysis The samples were analyzed for <br /> • Total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d) in <br />' accordance with EPA Method 8015m, <br /> • Benzene, toluene, ethylbenzene and total xylenes (BTEX) and methyl tertiary-butyl ether <br />' (MTBE) in accordance with EPA Method 8021, <br /> • The fuel oxygenates di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), MTBE, <br /> tertiary-amyl methyl ether (TAME), tertiary butanol (TBA), and other volatile organic <br /> compounds (VOCs) by GUMS (full-scan 8260) <br />' 3.0. FINDINGS <br />' Ground water elevation and flow direction were inferred from field data, hydrocarbon-impact to <br /> ground water was quantified by laboratory analysis of the ground water samples <br />' 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION <br /> The elevation of ground water in each well was calculated by subtracting the depth to groundwater <br /> from the surveyed casing elevations (Table 1) Depths to ground water ranged from 31 94 feet to <br /> 32 58 feet below the tops of the well casings'-however, ground water levels are as high as <br />' approximately 22 feet above the screened interval Ground water elevations at the site ranged from <br /> -19 29 feet inMW-3 to -19 75 feet in VW-5C relative to mean sea level , <br />' The ground water appears to flow generally northeast across much of the site at a gradient of <br /> approximately 0 0033 ft/ft(Figure 2),however, an apparent northeast finger in the northern quarter <br />' of the site forces the northeasterly flow more to the north and increases the gradient to approximately <br /> 0 023 ft/ft The finger also separates the flow pattern into a northwesterly flow direction (gradient <br /> Advanced GeoEnvironmental,Inc <br />