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i 30 December 1997 AGE-NC Project No 97-0343 ' Page 5 of 6 ' trimethylbenzene, and xylenes were detected in B1-15, 133-15, 135-15 and BS-30 at concentrations as high as 62 ppm (reported in micrograms per kilograms, converted here to ppm), 350 ppm, 38 ppm, 120 ppm, 680 ppm, 520 ppm, 160 ppm, and 1,700 ppm, respectively In general, the highest concentrations were encountered in sample 135-30,followed by BI-30 and BI-15 Sec-butyl benzene and tert-butyl benzene were detected in B 1-15 at concentrations of 9,700 ppb and 17,000 ppb, respectively Ethylene dibromide and methyl butyl ketone were detected in 133-15 at concentrations ' of 8 0 and 7 1 ppb, respectively Samples BI-50 and BI-60 contained 1,2-dichloroethane at concentrations of 13 ppb and 9 2 ppb, respectively The results of analysis by EPA Method 8260 are shown in Table 2 The areal distribution of selected volatile organic compounds are shown in Figure 6 Table 3 shows a comparison of concentrations of toluene, ethylbenzene and total xylenes as determined by EPA Methods 8020 and 8260 None of the thirteen samples analyzed for oxygenating volatile organic compounds by EPA Method 8260-M contained detectable concentrations of these chemical compounds Tables 1 and 2 contain the analytical data for all compounds detected in the soil samples analyzed The laboratory report (MAI sample Nos 81051 through 81071), QA/QC report and chain of custody forms are included in Appendix B 40 CONCLUSIONS The unauthorized release of petroleum hydrocarbons from the UST system at the subject site has impacted soil from 10 feet bsg to as deep as 60 feet bsg,however,the zone of significantly impacted soil does not appear to extend below 40 feet bsg Only trace concentrations of a few hydrocarbon compounds were detected in samples collected and analyzed from between 40 feet bsg and 60 feet big Overall,the most intensely impacted soil lies at 30 feet bsg In borings B 1 and B5, and between 10 feet to 15 feet bsg in the area of boring B3 For many of the analytes, sample B5-30 was more impacted than sample B1-30, however, 135-15 was less impacted than B1-15 The higher concentrations in B3 and B5 compared to B 1 at 15 feet bsg and 30 feet bsg,respectively,may be due to the greater adhesion of organic compounds to finer-grained soil in B3 and B5 The hydrocarbon distribution suggests that B 1 and B2 were closer to the point of the hydrocarbon release,and that the hydrocarbons migrated northward and downward Sail in the area of borings B2 and B4 has not been impacted,providing a maximum horizontal extent of hydrocarbon-impacted soil towards the south and east The extent of hydrocarbon-impacted soil towards the north and west has not been delineated by data currently available Impacted soil may extend under the structure on the subject site Advanced GeoEnve ron men 1.91,Inc