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r, 30 October 1998 AGE Project No. 95-0118 i' Page 4 of 6 • EPA method 8020 for volatile aromatics (benzene, toluene, ethyl benzene and xylenes: BTEX) and 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 July 1998 sampling event, the depth to ground water from the casing tops at the site ranged from 33.36 feet to 31.44 feet. The average relative ground water elevation has risen 'i approximately 3 feet. During this monitoring event the ground water flow was directed toward the north and northwest in the central portion of the site.The gradient measured from well MW-3 toward well MW-5 was 0.003 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 wells IAS-1 and IAS-2 contained TPH-g at concentrations of 350 parts per billion: ppb (reported as micrograms per liter), 490 ppb,700 ppb and 620 ppb,respectively. The same samples contained benzene at concentrations of 4.7 ppb, 6.1 ppb, 4.1 ppb and 3.8 ppb, respectively. Other BTEX compounds were detected at concentration as great as 160 ppb (xylene). MTBE was detected only in well MW-2 at a concentration of 11 ppb. The presence of MTBE was confirmed by EPA Method 8260 at 11 ppb. The water samples collected. from MW-4, MW-5 and -MW-6 did not contain detectable concentrations of TPH-g, BTEX compounds, other oxygenated compounds or VOCs. Analytical f results of ground water samples are summarized in Table 2 and Table 3. The laboratory report (MAI Lab ID 91816 to 91823), Quality Assurance and Quality Control (QA/QC) report and a chain-of-custody form are included as Appendix C. Advanced GeoEnvironmentat,Inc. i I