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20 <br />couldn't be strictly enforced; the new standards are law and <br />• can be enforced (13). <br />BIOTIC STANDARDS <br /> <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. <br />