Abstract. More and more often, in treating waters associated with mining projects, it is not acid rock drainage that is the focus of concern. Consequently, we have coined a new phrase "mining influenced waters" to include all the types of water that can be encountered. These waters can be divided into four categories. For acid rock drainage (ARD) the primary treatment problem is the elimination of mineral acidity in the form of soluble iron and aluminum. For mineral processing waters, the water is usually basic and the primary treatment problem is usually the elimination of cyanide, arsenic and selenium. For marginal waters, the water is circum-neutral but contains contaminants slightly above aquatic standards. For these waters, the treatment problem is often reducing small concentrations of contaminants in high flows of water. Finally, for residual waters, the primary treatment problem is the removal of high levels of total dissolved solids. For residual waters, there are few treatment options and these waters are becoming a serious environmental problem in some mining operations.