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14 October 1997 AGE-NC Project No. 95-0106 Page 2 of 4 were transferred into 40-m1 EPA-approved vials containing 0.5 ml 18% hydrochloric acid as a preservative. The samples were transported in a chilled container, under chain of custody, to McCampbell Analytical Inc. (MAI) a state-certified analytical laboratory located in Pacheco, California. The samples were analyzed in accordance with EPA Method 5030/8015m for total petroleum hydrocarbons quantified as gas (TPH-g), and in accordance with EPA method 602 for volatile organic compounds (benzene,toluene, ethylbenzene and xylenes (BTE&X) and for methyl- tert-butyl ether (MTBE). As MTBE was detected in one sample, the samples were re-analyzed in accordance with EPA Method 8260 to confirm the presence of MTBE and to check for other oxygenated volatile organic compounds. 3.0. FINDINGS 3.1. GROUND WATER ELEVATION AND GRADIENT The ground water elevation in each well was calculated by subtracting the depth to ground water from the surveyed casing elevations (Table 1). Ground waterradient on 05 September 1997 was calculated to be an average of 0.0078ft/ft or 0.40 g p g variably directed toward the northwest to northeast. 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 The highest concentrations of hydrocarbons were detected in wells MW-4, located down-gradient (north)of the former UST excavation, and in MW-1 located near the former UST excavation. TPH-g was detected at concentrations as high as 1,200 parts per billion (ppb, reported as micrograms per liter) in MW-4. The maximum concentrations detected of the BTE&X compounds detected by EPA Method 8020 were as follows: benzene - 80 ppb, toluene - 13 ppb, ethylbenzene - 62 ppb, and xylenes - 94 ppb, respectively. All were encountered in MW-4. Neither TPH-g nor BTE&X were detected in the ground water samples from monitoring wells MW- 2, MW-3, MW-5, MW-6 (upper) or MW-6 (lower). MTBE was detected in only in the sample collected from MW-4 at a concentration of I I ppb. Confirmatory analysis by EPA Method 8260 did not detect MTBE, but did detect vinyl acetate at 1.6 ppb in MW-I and at 9.8 ppb in MW-4.Additionally,the EPA Method 8260 detected 4.4 ppb 1,2- Advanced GeoEnvironmental,Inc.