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n . • 22 rune 1998 AGE-NC Project No 95-0135 Page 2 of 4 analyzed in accordance with EPA Method 5030/8015m for TPH-g, EPA method 502 for BTE&X, and EPA Method 8260 and/8260m for volatile organic compounds, MTBE, TBA, DIPE, ETBE and TAME 3.0. FINDINGS 3 1 GROUND WATER ELEVATION AND GRADIENT On 18 December 1997,the casing elevation of each new well was surveyed relative to the elevation of the City of Stockton Bench Mark number 28 (BM#28- 12 1 T) The ground water elevation in each well was calculated by subtracting the depth to ground water from the surveyed casing elevation (Table 1) Ground water was inferred to be flowing toward the southwest at a calculated gradient of 0 0071 foot/foot on 09 April 1998 The contoured ground water elevation data from the site is illustrated in Figure 3 -Relative Ground Water Elevation 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-g, toluene, ethylbenzene and xylenes were detected in all water samples Benzene was detected in all water samples except MW-3AB The highest concentrations of hydrocarbons were detected in well MW-1 located near the western edge of the property, north of the former dispenser at the site TPH-g was detected at a concentration of 23,000 parts per billion (ppb, reported as micrograms per liter)in the sample from well NIW-IA (the lower screened casing of well MW-1) Sample MW-1B, collected from the upper screened casing of the well, contained TPH-g at a concentration of 2,200 ppb Benzene was detected at concentrations of 3,500 ppb and 42 ppb in samples MW-IA and MW- IB, respectively This well was located in the area of maximum detected benzene concentrations at the site The maximum toluene concentration detected was 180 ppb, encountered in MW-IA The maximum ethylbenzene and total xylenes concentrations of 940 ppb and 340 ppb, respectively, were . encountered in sample MW-IA Adi anted Geo Eli%irojunental,iuc