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4. IL1 August 1999 _ AGE-NC Project No. 95=0.109 Page'6 of 10 sample collected from a depth'of 45 bsg.in' probing P22. TPH-g.was detected at concentrations as high as 2,000 ppm in 12 of the 25 remaining samples analyzed. Benzene was,detected-in six of the 26 samples analyzed at concentrations as high as 6.8 ppm. Toluene, ethylbenzerie and xylenes were :detected.'at concentrations as high as 120 ppm, 49,ppm and-690 ppm;'respectively. Petroleum hydrocarbons were not detected in 12 of the 26 soil samples analyzedfrom the site. MTBE was not detected in the 26 soil'samples analyzed. ' -Significant decreases in hydrocarbons concentrations were observed in 23 of the 26 samples,relative ; to samples .previously collected nearby. The greatest decreases were observed 'in the lighter. ' components (benzene and toluene)while heavier,components showed smaller decreases (xylenes). Analytical results of soil samples are summarized on Table 2 and compared with data from previous borings-`advanced-near the current boring locations: The•laboratory report(MAI Sainple,Nos."03.295- " 03320) and chain-of-custody forms are included'in Appendix B. Low concentrations of biodegrading microorganisms were detected. Nutrients, except moisture, appear to be present at acceptable concentrations. The laboratory report for physicochemical properties and'bioenumeration (A. Keith Kaufman, March 11,'1999) is-included in Appendix.B. 3:3. EXTENT OF HYDROCARBON-IMPACTED SOIL ' ' Two major.areas of-impacted soil have been identified at the site (Figure 6a). The northern and more extensive "area is located east of MW-14, corresponding-to,the former dispenser island location; at depths of 25 to 50 feet.bsg. The second, shallower area of impacted soil is slightly north of VW-1,- 'Corresponding,to the former location of the product USTs, at depths of 15 to 25 feet. The estimated extent of impacted soil is illustraied,on'Figii s 5a.through 8b,�10, 1 1, '13, 14,:16 and l 7. 34. ]MASS BALANCE`OF,,HYDROCARBONS IN SOIL Approximately 3,550 gallons of gasoline are.,estimated to ha"ve been present in soil-beneath the site . in' October 1993, impacting a=total'of 12,200 cubic yards of soil.'Approximately 315 gallons of gasoline are'estimated to remain beneath.the site in'February 1999, in3pacting 2,150 cubic 'yards. Approximately 90 per,cent-of hydrocarbons'in soil at the'site-have been remediated as of February _ 1999 ; Approximately 42 per cent of-the remaining hydrocarbons in soil are located in the section east of ; MW-14'at,a depth-between 27 and,38'feet b'sg (Figure 7b, areas 11 and J2). Approximately 47 per, ' cent of the remaining hydrocarbons are located east;of MW-14 below a depth of 38 feet bsg(Figure • 8b, areas NI ,and N2): Adi-anced CeoEnvironmental,Inc.