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.