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r 17 April 1996 ' AGE-NC Project No 95-0120 Page 6 of 7 ' ppb Toluene was detected from MW2 at a concentration of 0 72 ppb TPH-d, ethyl benzene, xylenes, and methyl-tertiary-butyl-ether were not detected in the samples collected in February 1996 The analytical results of the ground water samples are included in Table 2 The laboratory report and chain-of-custody are included in Appendix D 1 44 ANALYTICAL RESULTS OF SOIL SAMPLES ' A total of twelve soil samples were collected from three soil borings and submitted to AAL for analysis of hydrocarbon petroleum constituents TPH-g and TPH-d were,detected from B12 at 45 feet bsg at concentrations of 24 and 9 5 parts per million (ppm, reported as milligrams per kilogram), ' respectively TPH-g, TPH-d, ethyl-benzene, and xylene were detected from B 13 at 45 feet bsg at concentrations of 100, 32, 0 24, and 0 55 ppm, respectively TPH-g, TPH-d, toluene, ethyl-benzene, and xylene were detected from B14 at 40 feet bsg at concentrations of 340, 47, 0 18, 1 1, and 4 2 ' ppm, respectively TPH-d was also detected in B 14 at 35 and 50 feet bsg at a concentration of 1 1 ppm Benzene was not detected from any soil samples No other petroleum hydrocarbons were detected in soil samples analyzed Analytical results of the soil samples are summarized in Table 3 The laboratory report and chain of custody forms are included in Appendix E ' 5 0. CONCLUSIONS & RECOMMENDATIONS TPH-g was reported in monitoring wells MW 1 through MW3 during October 1995, and in MW3 during February 1996 Benzene, ethyl-benzene, and xylene were not detected during the October 1995 and February 1996 monitoring events Only a trace concentration of toluene was detected in ' MW2 during the February 1996 monitoring event No other petroleum hydrocarbons were detected during these monitoring events ' A mass-volume calculation of the remaining impacted soil at the site yields approximately 216 53 gallons of petroleum hydrocarbons Average concentrations of 120 mg/kg, 159 85 mg/kg, 39 85 mg/kg, 2 78 mg/kg, and 2 78 mg/kg were used to calculate the total volume of remaining ' hydrocarbons at 35 to 40 feet bsg, 40 to 45 feet, 45 to 50 feet, 50 to 55 feet, and 55 to 60 feet, respectively Hydrocarbon-impacted soil volume assumptions and calculations are included as Appendix F Based upon data collected during ground water monitoring, it appears that the ground water depth at the site is in excess of 70 feet bsg, it is unlikely that the small volume of hydrocarbons remaining ' in soil poses a significant threat to ground water As hydrocarbons commonly are held by adsorption to clay and silt, most of the hydrocarbons remaining in the soil are probably adhering to the fine soil particles and have little mobility 1