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6.0 DISCUSSION 6. 1 VICINITY OF SEWER LINE AND FORMER USTs Borings B-7 and B-8 were drilled in the vicinity of the sewer line and former UST locations. Only minor concentrations of TPH were detected in sample B-7 @ 51 . No TPH were detected in soil samples collected from boring B-8. The only VOCs detected were toluene at concentrations ranging from 0 . 011 to 0. 017 ppm and xylenes at 0 . 019 ppm. The total lead concentrations varied from 6 . 63 to 11. 4 ppm. The carbon chain breakdown for the hydrocarbons contained in soil sample B-7 @ 5 ' indicate a hydrocarbon range from C11 to C20 with the maximum being C17-C18 (see Table 2) . 6. 2 VICINITY OF FUEL ISLANDS Borings B-9 and B-10 were drilled in the vicinity of the fuel islands on the east and west sides of PL-7 . Elevated concentrations of TPH (1, 200 to 3 , 490 ppm) were detected from samples B-9 @ 15 ' through B-9 @ 301 . TRPH were determined only in sample B-9 @ 20 ' at 563 ppm. No benzene was detected in any of the samples tested. Elevated concentrations of toluene, xylenes and ethylbenzene were also detected in those samples 9 which had elevated TPH concentrations (see Table 1) . The total lead concentrations varied from 5. 72 to 13 . 4 ppm. No soluble lead was detected in the sample (B-10 @ 101 ) which contained the highest total lead concentration. The carbon chain breakdown for the hydrocarbons present in sample B-9 @ 20 ' indicate a hydrocarbon range from C8 to C18, with the maximum occurring in the C9-C10 range. The C8 concentration is only 106 ppm which will rule out gasoline as the contaminant. However, the peak concentration does not correspond to that of the diesel fuel, and the concentrations of light hydrocarbons exceed that of diesel. The information obtained from simulated distillation and analyses of the gas chromatograph for sample B-9 @ 30 ' agree with those discussed above, and the chromatograph indicates that the contaminant corresponds to heavy naphtha (see Tables 2 and 3 and Appendix C) . Naphthas are derived from both petroleum and coal tar. r Petroleum naphthas are composed principally of aliphatic hydrocarbons and are termed "close-cut" fractions. "Medium- range" and "Wide-range" fractions are made up of 40 to 80% aliphatic hydrocarbons, 25 to 50% naphtenic hydrocarbons, 0 to 10% benzene, and 0 to 20% other aromatic hydrocarbons. Coal tar naphtha is a mixture of aromatic hydrocarbons, principally toluene, xylenes, and cumene. Benzene, however, is present in I _ appreciable amounts in those coal tar naphthas with low boiling _ !- points. Rubber solvent naphtha boils at 750 to 110° C, and coal tar naphtha at 1600 to 220° C. Naphthas are used as organic Pro]ect No. 1232 -7- ENVIRONMENTAL AUDIT,INC®