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r <br /> i <br /> r <br /> r9 November 1992 <br /> (GeoAudit CV 42E1-1.8) <br /> Page 5 of 6 <br /> r <br /> boring logs. No evidence of hydrocarbon contamination was detected <br /> r in boring 3 , or in samples at 5 and 10 feet in borings 1, 2 , and 4 . <br /> Samples at 15 feet in borings 1 and 4 emitted a very slight odor, <br /> and readings of 8 parts per million (ppm) and 10 ppm were obtained <br /> ron the PID. <br /> Samples from 20 to 40 feet emitted strong to very strong <br /> hydrocarbon odors in borings 1, 2 , and 4 , and OV readings of 100- <br /> 1500 ppm. Steam and vapors escaping from borings 1 and 4 also gave <br /> readings in excess of 1000 ppm. <br /> r Below 45 feet in B1, hydrocarbon odors and vapor levels decreased, <br /> and no odors or vapors were detected in samples from 60, 65, and 70 <br /> feet. The other borings were terminated above this depth. <br /> r6.2 Laboratory Results <br /> Of the 31 soil samples and I water sample that were collected, a <br /> total of 20 samples were analyzed. The samples were analyzed for <br /> total volatile petroleum hydrocarbons (TPH-gasoline) and purgeable <br /> r aromatic hydrocarbons (BTE&X) by GEOCHEM ENVIRONMENTAL' S state- <br /> certified on-site mobile laboratory. Samples from borings 2 , 3 , and <br /> 4 were also analyzed for semivolatile petroleum hydrocarbons (TPH- <br /> diesel) . The laboratory report and chain--of-custody are included as <br /> rAppendix C. <br /> The laboratory results confirm the field observations of <br /> r contamination, although total concentrations are considerably lower <br /> than the vapor readings obtained with the PID. The highest levels <br /> of contamination occur between 20 and 40 feet, generally within the <br /> r downward-coarsening sand bed (layer 2) . TPH-g concentrations <br /> decrease steadily downward within the underlying silt bed, <br /> decreasing to 0 mg/kg at 60 feet in boring 1. <br /> r Concentrations of 9 . 16 mg/L TPH--g and 495 µg/L benzene were <br /> detected in the water sample. Toluene, ethylbenzene, and xylene <br /> were also detected. However, because this sample was obtained by <br /> bailer through the augers, the sample may have been contaminated by <br /> contact with the augers during retrieval, and it is uncertain <br /> whether the detected concentrations represent true measurements of <br /> water contamination. <br /> According to GE©CHEM ENVIRONMENTAL, the sharpness of the gas <br /> chromatograph peaks implies that the gasoline is relatively fresh, <br /> non-degraded, and young. <br /> r <br />