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4 . CONCLUSIONS AND RECOMMENDATIONS <br /> Based on this investigation, the following is concluded: <br /> 1 . Hydrocarbon contamination is present in ground water <br /> underlying this site. <br /> 2 . No immediate threat to existing or potential ground-water <br /> supplies appears to exist. <br /> 3 . No apparent threat exists to any future construction on <br /> the site. Because there is no significant contamination <br /> of unsaturated soil, excavation would not be an effective <br /> remedial action, and therefore any construction should <br /> not interfere with future investigations or cleanup. <br /> 4 . For the following reasons, no clear on-site source of <br /> this contamination is apparent: <br /> a. Ground-water contamination levels increase towards <br /> the north and northwest, and the highest <br /> ►. concentrations are not in the vicinity of the former <br /> EXXON tank and piping locations. <br /> b. The chemical gradient (as indicated by the benzene- <br /> to-xylenes/ethylbenzene ratios illustrated in Figure <br /> 14 ) indicates a source located to the north or west <br /> of the site. <br /> C. No significant soil hydrocarbon contamination was <br /> found. This is indicative of no on-site free product <br /> gasoline. <br /> d. The minor soil vapor hydrocarbon contamination <br /> observed has no correlation with ground-water <br /> L <br /> 35 <br />