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r 05 April 1999 P AGE Project No. 95-0118 Page 2 of 4 in Pacheco, California, a State of California Department of Health Services (DHS)-certified laboratory. Each sample was analyzed in accordance with the following: • EPA Method 8015 Modified for total petroleum hydrocarbons quantified as gasoline (TPH- g) and • EPA Method 8020 for volatile aromatics (benzene, toluene, ethyl benzene and xylenes: BTEX), methyl tertiary butyl ether(MTBE). 3.0. FINDINGS 3.1. RELATIVE GROUND WATER ELEVATION AND GRADIENT The relative ground water elevation in each well was calculated by subtracting the ground water depth from the surveyed casing elevations. The depth to ground water and the relative ground water elevations are summarized in Table 1.During the January 1999 sampling event,the depth to ground r3 water from the casing tops at the site ranged from 33.12 feet to 31.49 feet. The average relative ground water elevation has remained the same over the quarter. During this monitoring event the ground water flow was directed toward the northwest in the central portion of the site. The gradient measured from well MW-3 toward well MW-5 was 0.00044 feet/feet. Relative ground water elevation contours are illustrated in Figure 3. 3.2. ANALYTICAL RESULTS OF GROUND WATER SAMPLES Water samples from monitoring wells MW-2,MW-3 and air-sparging well IAS-2 contained TPH-g at concentrations of 640 micrograms per liter (E.cg/l), 320 yg/l and 100 ug/l, respectively. The samples from MW-2 and MW-3 contained benzene at concentrations of 16 k1g1l and 7.9 jzg/l, respectively. Other BTEX compounds were detected at concentrations as great as 56µg/1 (xylene). MTBE was detected only in well MW-2 at a concentration of 9.5 ygll. The water samples collected from MW-1, MW-4, MW-5 and MW-6 did not contain detectable concentrations of TPH-g or BTEX compounds. Analytical results of ground water samples are summarized in Table 2 and Table 3. Advanced GeoEnvironmenfail,Inc.