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Colorado Water Science Center

Effects of Metal-mine drainage on Water Quality in selected areas of Colorado, 1972-73

Colorado Water Resources Circular 25

By Robert E. Moran and Dennis A. Wentz


Colorado is a child of mining. In the past, towns such as Cripple Creek, Leadville, Creede, and many others were the lifeblood of the economy. While metal mining is still economically important to Colorado, another legacy of this past activity is attracting increasing attention—the detrimental effects of drainage from abandoned and active mines and tailings piles (waste rock piles) on streams. Concern with metal-mine drainage is due to the acid resulting from oxidation of pyritic material. The acid itself can be harmful to aquatic organisms, and can make the water unusable for various recreational and industrial needs. Just as importantly, however, the acid dissolves metals from ores and tailings piles and releases them into the streams. Many of the metals are toxic to aquatic organisms, humans, and livestock; and, like excess acidity, the metals can make streams unusable for some types of recreation and industry.

In July 1971, a study of the effects of both metal- and coal-mine drainage on surface-water quality in Colorado was undertaken by the U.S. Geological Survey in cooperation with the Colorado Water Pollution Control Commission. Based on the reconnaissance phase of this project (Wentz, 1974), 17 areas judged to be adversely affected by metal-mine drainage were chosen for further study. One additional area was included because it is the only place found in Colorado that potentially could be affected by coal-mine drainage. The present report summarizes the intensive study of these areas; it is the second product of the mine-drainage study. The first report was published as Colorado Water Resources Circular 21.

CWR Circular 25

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