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l <br /> 07 April 1999 <br /> AGE-NC Project No 96-0235 <br />' Page 2 of 5 <br />' 2 2 COLLECTION OF GROUND WATER SAMPLES <br /> Water samples were collected from each well using new disposable plastic bailers Each water <br />' sample was transferred into 40-m1 VOA vials containing 0 S iiil 18% hydrochloric acid as a sample <br /> preservative and into 1-liter amber bottles without preservative After collection, the samples were <br /> properly labeled, placed in a chilled container and transported under chain-of-custody to Alpha <br />' Analytical Laboratories, Inc (AAL), a State of California Department of Health Services (DHS)- <br /> certified analytical laboratory Each sample was analyzed for <br />' • Total Petroleum hydrocarbons quantified as, gasoline (TPH-g) and diesel (TPH-d) in <br /> accordance„with EPA Methods 5030/8015m; <br />' • Volatile aromatics(benzene,toluene,ethylbenzene and xylenes,BTEX)with methyl tertiary- <br /> butyl ether (MTBE) in accordance with EPA Method 602/8020, and <br /> • Oxygenated compounds (Diisopropyl ether [RIPE], ethyl tertiary-butyl ether [ETBE], <br />' MTBE,tertiary-amyl methyl ether [TAME] and tertiary butanol [TBA]) in accordance with <br /> EPA Method 8260B <br /> 30. FINDINGS <br />' The casing elevationof each well was previously surveyed relative to a City of Stockton bench mark <br />' Ground water elevations were determined by subtracting the measured depths-to-water from the <br /> casing elevations (Table 1) Ground water flow direction was determined by contouring the water <br /> elevations on a scaled site plan(Figure 3) <br /> i <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 ground water <br /> from the surveyed casing elevations Depths-to-ground water ranged from 16 30 feet to 17 77 feet - <br />' below the tops of the well casings Ground water elevations at the site ranged from -9 80 feet in <br /> MW-6A to -11 31 feet mean sea level (MSL) in MW-2, an average rise of elevation of 0 37 feet <br /> 1 To infer ground water flow direction, the ground water elevation data was divided into two sets <br /> based on the'well screen intervals Ground water was between 23 and 28 feet above the screened <br />' intervals in monitoring wells MWA, MW-2, MW-3, MW-6B and MW-8B, comprising the lower <br /> data set Ground water was within the screened intervals for monitoring wells MW-4, MW-5, MW- <br /> 6A, MW-7 and MW-8A Figure 3 Illustrates the ground water elevations based on the two data sets <br /> Advanced GeoEnvironmental,Inc <br /> 1 <br />