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12102 02 TUE 09 16 FAX 19259469968 ERMWEST WC Z008 <br /> Mr Harlin Knoll <br /> 15 June 1999 <br /> Page 7 <br /> Toluene and xylenes were detected in soil above industrial Preliminary <br /> Remediation Goals (PRGs) and benzene, toluene and xylenes were <br /> detected in ground water above California Maximum Contaminant <br /> Limits (MCL) The concentrations of TPH-g and BTF-X in both soil and <br /> ground water decrease both horizontally and vertically moving away <br /> from the vicinity of the former UST Fuel oxygenates were only detected <br /> above laboratory detection limits in soil and ground water collected from <br /> B-6 <br /> Figure 4 represents a cross section drawn laterally through the suspected <br /> source area from B-7 to MW-2(cross section A-A', shown on Figure 2) <br /> and displays the concentrations of TPH-g detected in soil at various <br /> intervals As can be seen by this figure,the highest concentration of <br /> TPH-g(17,p00 mg/kg)was detected below the former UST (B-2) and <br /> decreases by at least one order of magnitude within 10 feet, moving both <br /> laterally (B-5) and vertically (B-2) away from the source BTEX <br /> concentrations in soil are not displayed on this cross section, however, <br /> the concentration of BTEX compounds parallel the pattern and <br /> distribution of TPH-g displayed on Figure 4 As shown in Table 2, BTEX <br /> concentrations dunini.sh by a nunimum of one order of magnitude <br /> moving laterally (B-5) and vertically (B-2) away from the former UST <br /> Fuel oxygenates were detected in the sample collected from boring 13-6 <br /> only <br /> Figure 5 represents a cross section drawn longitudinally through the <br /> suspected source area from boring MW-1 to MW-3 (cross section B-B', <br /> shown on Figure 2) with concentrations of benzene detected in ground <br /> water Benzene was detected at a maximum concentration of 2,300 <br /> micrograms per liter (µg/l) in boring B-5 and at a concentration of 38 <br /> µg/11n boring B-6, approximately 15 feet downgradient These <br /> detections were collected from temporary ground water sampling points <br /> from a one-tinge sampling event Benzene was not detected in ground <br /> water samples collected upgradient (MW-1), cross-gradient (MW-2) or <br /> downgradient(MW-3) of the former UST MW-1, MW-2, and MW-3 are <br /> permanent monitoring wells installed to accurately monitor ground <br /> water at the site <br /> As can be seen on Figure 5, benzene concentrations decrease significantly <br /> moving a short distance away from the source area(from B-5 to B-6) and <br /> decrease to non-detect levels in MW-3, approximately 50 feet <br /> downgradient TPH-g concentrations in ground water are not displayed, <br /> however, the concentration of TPH-g in ground water parallels the <br />