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I , i t II F r M I i . 20 December 2001 AGE-NC Project No 96-0235 ' T P*'2 of 5 , 1 2 2 COLLECTION OF GROUND WATER SAMPLES I Water samples were collected-from each purged well using new disposable plastic,bailers Each , M ' water sample was transferred into 40-m1 VOA vials containing 0 5 ml 18% hydrochloric acrd as a sample preservative and into 1-liter amber bottles without preservative After collection,the samples were properly labeled, placed in a chilled container and transported under cham-of-custody to ' McCampbell Analytical, Inc (MAI), a State of California Department'of Health Services (DHS)- certified analytical laboratory, and were analyzed for ' • Total petroleum hydrocarbons quantified as gasoline (TPH-g) and as diesel (TPH-d) m y accordance with EPA Methods 5030/8015 and`3550/8015, respectively, ' • Benzene, toluene, ethylbenzene and total xylenes (BTEX) and the oxygenated ether methyl tertiary-butyl ether (MTBE) in accordance with EPA Method 602/8020, and for • Fuel oxygenates - di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), MTBE, ' tertiary-amyl methyl ether (TAME), tertiary butanol (TBA), methanol, ethanol, ethylene dibromide (EDB) and 1,2-dichloroethane(1,2-DCA) in accordance with EPA Method 8260 ' Modified 3.0. FINDINGS Ground water elevation and flow direction were inferred from field data, hydrocarbon--impact to groundwater was quantified by laboratory,analysis of the ground water samples Field observations, results of laboratory analysis of ground water samples and a discussion of data collected during field work follows 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION I L a 4 s l f I I -The casing elevation of each well was previously surveyed relative to a City of Stockton benchmark - The elevation of ground water in each well was calculated by subtracting the depth,to ground water from the surveyed casing elevations (Table 1) Depths to ground water ranged from 16 91 feet to 19 79 feet below the'tops of the well casings Ground water elevations at the site ranged from 1120 feet in MW-5 to 13 33 feet below mean sea level(MSL) in MW-2 The average groundwater elevation decreased approximately 0 64 feet in the wells To infer ground water flow direction, the ground water elevation data was divided into two sets based on the well screen intervals Ground water was between 20 21 and 22 30 feet above the screened intervals in monitoring wells MW-1, MW-2, MW-613, MW-8B, MW-9, MW-11B, Advanced GeoEnviromriental,Inc u