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10 September 1996 <br /> AGE-NC Project No. 95-0106 <br /> Page 6 of 8 <br /> 4.0. FINDINGS <br /> 4.1. STRATIGRAPHY <br /> Tan and gray, silty clay was encountered from the surface to depths of approximately six feet bsg, <br /> in each probing. Gray, silty clay was encountered between five and ten feet bsg during the <br /> installation of the ground water monitoring wells. Coarse sand was distributed below the clay, from <br /> ten to twenty-five feet bsg in monitoring wells MW-1,MW-3 and MW-4. Silty clay was encountered <br /> throughout the sampled interval of MW-2. <br /> Based upon soil samples submitted for geotechnical analysis, the upper clay layer appears to have <br /> a lower permeability than the saturated, fine sand encountered below approximately 10 feet bsg. <br /> Ground water is present in the sand, however it appears that the clay immediately above restricts the <br /> vertical migration of ground water. A stratigraphic cross section of the soils at the site, including the <br /> area of unsaturated impacted soil, is depicted in Figure 4- Stratigraphic Cross Section. <br />. 4.2. LABORATORY RESULTS OF PROBING SOIL SAMPLES <br /> TPH-g was detected in three of seven soil samples analyzed, at concentrations as high as 200,000 <br /> mg/kg(milligrams per kilogram or parts per million: ppm). Concentrations of BTE&X were detected <br /> in the same three samples at concentrations as high as 93 ppm (xylenes, P1-6), the maximum <br /> benzene concentration was 2.3 ppm. Analytical results of soil samples are summarized on Table 1. <br /> The laboratory report (MAI Laboratory ID 59841 through 59847) and chain-of-custody are in <br /> Appendix E. <br /> 4.3. LABORATORY RESULTS OF PROBING GROUND WATER SAMPLES <br /> TPH-g was detected in four of five grab water samples at concentrations as high as 210,000 ,ug/l <br /> (micrograms per liter or parts per billion: ppb). BTE&X were also detected in four of five grab <br /> ground water samples at concentrations up to 35,000 ppb (toluene, P6), the maximum benzene <br /> concentration was 12,000 ppb (P6). Analytical results of grab water samples are included in Table <br /> I. The laboratory report (MAI Laboratory ID 59836 through 59840) and chain-of-custody are <br /> presented in Appendix E. <br /> 4.4. LABORATORY RESULTS OF MONITORING WELL SOIL SAMPLES <br />. TPH-g,benzene,toluene, ethyl benzene and xylenes were detected in one soil sample analyzed from <br />