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20 <br />• <br /> couldn't be strictly enforced; the new standards are law and <br /> can be enforced (13). <br /> BIOTIC STANDARDS <br /> Another approach to defining harmfulness is to say <br /> that not only should humans be able to drink the water, but <br /> fish should be able to swim in it. The biotic concentrations <br /> suggested by Wentz (8) are listed in Table III. This dramati- <br /> cally changes the maximum levels of some species. In parti- <br /> cular, Wentz (8) related how studies have shown that fish <br /> are much more susceptible to Cu and Zn dissolved in water <br /> than are humans. This is no doubt the reason why no trout <br /> are found in some streams in Colorado which are fit for <br />. drinking by humans. <br /> EFFLUENT STANDARDS <br /> The Environmental Protection Agency has to define concen- <br /> tration levels for water effluents even though the drinking <br /> water levels and the biological criteria are certain to <br /> change (1, 2). Obviously, a long term mining operation can- <br /> not function under a system which changes from year to year. <br /> Consequently, the EPA defined harmfulness in a quite different <br /> manner. The operations for treating effluents for each <br /> industry were examined for current practices and for what <br /> would be the best methods that could be economically achieved. <br /> The levels of concentration for species that result from the <br /> best current technology were designated as the current <br /> standards and they are enforced from July 1, 1977 to July 1, 1984.