Seven tailings pond systems in the Coeur d'Alene Mining District, Idaho, were studied to identify the discharge of heavy metal ions into regional water resources. Two major categories of tailings ponds were studied: ponds receiving only concentrator effluents and ponds receiving wastes from concentrators, processing plant and smelters, and acid mine drainage. Analytical results indicate that tailings ponds using peripheral discharge and constructed in a series were effective in reducing suspended solids, ph, and dissolved metal ions. Tailings ponds receiving several types of industrial wastes were not satisfactorily removing deleterious metals from their pond discharges. Peripheral discharge of milling wastes also encourages tailings pond stability.