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3-10 <br />tions, a significant drop for sample points 25, 26 and 27. If tailings pond <br />seepage is effectively being stopped by the slurry wall, a decrease in ground <br />water cyanide concentration in downstream areas as observed would be expect— <br />ed. Such a decrease result from dilution with fresh ground water, which would <br />take some length of time to occur in this situation. Larger quantities of <br />fresh ground water would normally flow through the area, but with the slurry <br />wall in place, such recharge is very limited. Improvement of ground water <br />quality in areas downstream from the slurry wall appears to be taking place. <br />Based on observations of changes in surface water flow and ground water <br />levels, the slurry wall cutoff appears to be doing an effective job of <br />stopping tailings pond seepage from passing downstream through the alluvium at <br />weathered rock below the alluvium. However, an accurate assessment of its <br />performance will require monitoring ground water quality, pump—back rates, and <br />ground water levels over a longer period of time (many more months). <br />Nonetheless, significant improvement in downstream conditions has already been <br />observed and the cutoff appears to be functioning well for its intended <br />purpose of Intercepting near surface flows. <br />