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n <br /> I. H. KLEINFELDER&ASSCCIA rES <br /> in the area of the old tank site than the contour lines indicate, but no <br /> borehole was drilled at this location because emphasis was placed on <br /> completely encircling the affected area with a minimum number of borings. <br /> In addition, the tank and surrounding soil were previously removed and the <br /> contours depict contamination remaining in other areas. <br /> The contours of total petroleum hydrocarbons at !1 feet below ground <br /> surface (Elate 27) are slightly anomalous. The map indicates that there <br /> are two small zones where the highest contaminant concentrations exist, <br /> separated by a zone of lower concentrations. From this data and the site <br /> ! geology and soil conditions, it appears that a northeasterly trending sand <br /> stringer exists at thin depth and contaminant migration may have been <br /> i , strongly influenced by "che depositional pattern and soil characteristics <br /> of this geological layer. <br /> Soil permeability tests were performed on six soil samples. The data from <br /> irl these test are shown on Table 5. The permeabilit£es are low (10-5 to <br /> iQ 7 cm/sec), indicating that hydrocarbons probably moved at a <br /> relatively ' slow rate and resultant contamination has occurred over an <br /> be extended period of time. These data also suggest that conditions for a <br /> vapor extraction technique to --educe the contaminant levels are not <br /> ideal. The permeabilities also would make it difficult to achieve proper <br /> nutrient distribution and maintain hydraulic control in the vadose zone <br /> fz a <br /> for application of an in-situ bioremediation system. <br /> f'a <br /> ka <br /> 4.' 38-87-43 8 <br />