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I. H. KLEINFELDER & ASSOCIATES <br /> contamination above 10 feet is from a small amount of contamination <br /> migrating laterally towards B-10, while the main body of contamination <br /> moved downward at B-8. <br /> Another possible mode for the higher contamination at B-10 between 5 and <br /> 10 feet could be by movement of the contamination as a gas from B-8 <br /> i <br /> (10-foot interval) to B-10 (7-foot interval) back to B-8 (3- to 5-foot <br /> interval) after the tanks were removed. Movement of the gas phase along a <br /> i <br /> more permeable pathway from B-8 at 10 feet to B-10 at 7 feet is suggested <br /> by the pattern of the iso-chem drawings (Figures 36 through 38). The <br /> i <br /> stratigraphic trap at 10 feet in B-8 (described above) would prevent i <br /> upward movement of the contamination, while strata containing less clay <br /> (more permeable) near 8-'10 could flaw for lateral and vertical migration <br /> r <br /> of the contamination in that direction. The strata at B-10 contains less <br /> clay than the strata at B-10 between 5 and 10 feet, thus making a more <br /> i <br /> permeable material and better pathway for movement of the contamination. <br /> The origin of the contamination around B-13 and B-15 appears not to be <br /> C related to the origin for the contamination around B-8 and B-10. The <br /> origin for the contamination at B-2 is likely to be related to the <br /> contamination at B-13 and B-15 for •_his discussion. <br /> An examination of the layout of the service station shows B-2, B-13, and <br /> B-15 to be located at or near the pump islands. A study of the depths at <br /> which contamination occurs in B-2 and B-13 (Table 2) indicates that a near <br /> surface source for the contamination probably did not originate between <br /> these two borings. While the contamination occurring in B-13 appears to <br /> be as close at 10 feet to the surface for some of the constituents, the <br /> i <br /> origin for a source at this point could be a product line which is usually <br /> 2 to 3 feet below the surface. The lack of contamination at the 3- to <br /> 10-foot interval in B-13 indicates that the leak did not occur at this <br /> position, or the contaminated material between 3 and 10 feet was removed <br /> and replaced with non-contaminated fill. A point source Closer to B-15 <br /> was probably the origin for the contamination observed at locations B-13 <br /> and B-15. Table 2 and Figures 6 through 38 show contamination at 8-15 <br /> occurring between 3 and 10 feet above that found in B-13 and B-2. <br /> y 53-87--443 24 <br />