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06 October 1997 A - GE-NC Project No 95 0105 ' Page 2 of 4 2 2 COLLECTION OF GROUND WATER SAMPLES Water samples were collected from each well using a new disposable plastic bailer Each water sample was transferred into two 40-m1 VOA vials containing 0 5 ml of 18% hydrochloric acid as a sample preservative and into one 1-liter amber bottle After collection, the samples were properly labeled, placed in a chilled container and transported under chain-of-custody to McCampbell Analytical, Inc , (MAI) Each sample was analyzed for total petroleum hydrocarbons quantified as gasoline and as diesel (TPH-g and TPH-d) in accordance with EPA Methods 5030/8015-Modified, and for volatile aromatic compounds (benzene, toluene, ethylbenzene and total xylenes BTE&X) with methyl tertiary-butyl ether (MTBE) in accordance with EPA Methods 5030/8020 or 602 As MTBE was detected in one sample, the three samples were analyzed by EPA Method 624 or 8240/624 by GC/MS to analyze the detection of MTBE, and by EPA Method 8260 for oxygenated volatile organics by GC/MS ' 30 FINDINGS 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION The elevation of ground water in each well was calculated by subtracting the ground water depth ' from the surveyed casing elevation(Table 1) The casing elevation of each well had been previously surveyed relative to a City of Tracy bench mark ' Ground water elevations at the site ranged from 2129 feet in MW-6 to 22 28 feet in MW-4 Between December 1996 and August 1997, ground water elevation decreased an average of 0 93 feet at the ' site The ground water flow direction for August 1997, is complex, but is, roughly similar to the regional ground water flow direction toward the north A trough of lower elevation ground water cuts diagonally, noitheast/southwest across the property, roughly perpendicular to the ground water ' flow direction The ground water flow direction is depicted in Figure 3 - Relative Ground Water Elevation Contour Map 3 2 PETROLEUM HYDROCARBON-IMPACTED GROUND WATER ' None of the analytes of interest were detected in the ground water samples collected from MW-5 and MW-6, all the analytes of interest were detected in the ground water sample collected from MW-4 TPH-g and TPH-d were detected in monitoring well MW-4, at concentrations of 31,000 parts per billion (ppb, reported as micrograms per liter) and 18,000 ppb, respectively Benzene, toluene, . ethylbenzene and xylenes were detected in well MW-4 at concentrations of 120 ppb, 1,100 ppb, 1,300 ppb and 4,000 ppb,respectively by EPA Method 8020 MTBE was also detected in the sample