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, 10 March 2000 AGE-NC Project No 96-0235 Page 2 of 4 ' 2 2 COLLECTION OF GROUND WATER-SAMPLES, r Water samples were collected from each purged well using new disposable plastic bailers Each ' water sample was transferred into 40-m1 VOA vials containing 0 5 ml 18% hydrochloric acid 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 chain-of-custody to -� McCampbell Analytical, Inc (MAI), a State of California Department of Health Services (DHS)- certified analytical laboratory, and were analyzed for ' Notal petroleum hydrocarbons quantified as gasoline (TPH-g) and as diesel (TPH-d) in , accordance with EPA Methods 5030 and 8015m, Volatile aromatic hydrocarbons benzene, toluene, ethylbenzene and total xylenes (BTEX) ' with methyl tertiary-butyl ether(MTBE) in accordance with EPA Method 6021$020, and for h • Fuel oxygenates di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), MTBE, ' tertiary-amyl methyl ether (TAME) and tertiary butanol (TBA) in accordance with EPA Method 8260 Modified lieA 3.0. FINDINGS IGround water elevation and flow direction were calculated from field data, hydrocarbon-impact to ground water was inferred from 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 k ' The casing elevation of each well was previously surveyed relative to a City of Stockton bench mark 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 97 feet to r ' 19 12 feet below the'tops of the well casings Ground water elevations at the site ranged from -10 94 feet in MW-4 to -12 69 feet mean sea level (MSL) in MW-2 Ground water elevation increased 0 94 , ' feet in MW-6B, ground water elevation,increased an average of 0 20 feet in the remaining wells To infer ground water flow direction, the ground water elevation data was divided into two sets I based on the well screen intervals Ground water was between 20 9 and 23 0 feet above the screened intervals in monitoring wells MW-1, MW-2, MW-6B, MW-8B and MW-9, comprising the deeper water data set Ground water was within the screened intervals for monitoring wells MW-4, MW-5, c Advanced GeoEnvironmental,Inc i , s