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22 <br />• but the adjustment of the pH to above 6 is helped by the <br />addition of bases such as lime (Ca(OH2) or calcite (CaC03). <br />Consequently, limits don't have to be set for Fe, Mn, Cd <br />or Ag. If the pH of the water is between 6 and 9, and there <br />are low amounts of total suspended solids, these constituents <br />cannot be in the water at harmful levels. <br />The EPA set limits on mill effluents at the same time <br />as mine effluents (2). In this case, the task was more <br />difficult. In a mill, species such as cyanide or organic <br />complexing agents might be added to the water to achieve <br />the beneficiation of the ore. These constituents, which <br />do not occur naturally in water, are sometimes difficult to <br />remove from water and may retain the base metals in the <br />• solution. Thus, for the case of metal mills, the current <br />limitations are more specific and the 1984 limitations <br />dictate that there be zero discharge in many of the milling <br />categories (2). <br />For many people, the limitations are not bothersome, <br />but dealing with all the agencies which have some control <br />over the operation is frustrating. A good explanation of <br />how all the regulations operate and how the controls and <br />effluents are set for a particular operation is in an <br />article by Andrews (27). He goes through an actual example <br />case from start to finish to show how the EPA limitations <br />and the drinking water standards dictate how well the efflu- <br />ent from a mining or milling operation will have to be treated. <br />0