How does mine drainage occur?

Mine drainage is formed when pyrite (an iron sulfide) is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Some or all of this iron can precipitate to form the red, orange, or yellow sediments in the bottom of streams containing mine drainage. The acid runoff further dissolves heavy metals such as copper, lead, and mercury into groundwater or surface water. The rate and degree by which acid-mine drainage proceeds can be increased by the action of certain bacteria.

Problems associated with mine drainage include contaminated drinking water, disrupted growth and reproduction of aquatic plants and animals, and the corroding effects of the acid on parts of infrastructures such as bridges.

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July 26, 2018

PubTalk 7/2018— Extreme acid mine drainage at Iron Mountain California

Title: Iron Mountain, California: An Extreme Acid Mine Drainage Environment

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Image: Ross basin, upper Cement Creek in Watershed above North Fork Cement Creek
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March 26, 2015

PubTalk 3/2015 — The Environmental Legacy of California's Gold Rush

by Andrea Foster, USGS Research Geologist & Christopher Kim, Associate Professor, Chapman University

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Image: Dried Acid Mine Drainage Residuals
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Dried Acid Mine Drainage Residuals

Dried acid mine drainage residuals that are formed during treatment of the drainage.  The USGS has pioneered a new use for these residuals that are currently a disposal challenge, using them to filter phosphorus from agricultural and municipal wastewaters.

Attribution: Water Resources
June 22, 2009

Tracking Mercury from Ore to Organisms

Mercury Cycling and Bioaccumulation In a Mine-Dominated Ecosystem.

July 13, 2008

What is mine drainage and how does it occur?

Listen to hear the answer.

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December 31, 2007

Cement Creek, Colorado, Acid Mine Drainage Investigations Site

Cement Creek, Colorado, is a site of U.S. Geological Survey (USGS) investigations of the fate of acid mine drainage. USGS scientists are developing methods to characterize contaminated streams that can be used by water-resource managers to make better cleanup decisions.

Image: Sampling Acid Mine Drainage in Elk_County, PA
November 6, 2007

Sampling Acid Mine Drainage in Elk_County, PA

Sampling acid mine drainage residuals in Elk County, Pennsylvania.  The USGS has pioneered a new use for these residuals that are currently a disposal challenge, using them to filter phosphorus from agricultural and municipal wastewaters.

Attribution: Water Resources
Image: Acid Mine Drainage Discharge Appalachian Stream
November 17, 2005

Acid Mine Drainage Discharge Appalachian Stream

An acid mine drainage discharge forms a plume in a stream in the Appalachian region.

Attribution: Water Resources
Extremely acid mine drainage on a wall

The world's most acidic water is found in a mine in California

The most acidic waters ever measured are percolating through an underground mine at Iron Mountain, near the northern California town of Redding. Hot acid solutions, more concentrated than battery acid, are dripping from colorful mineral stalactites in the abandoned copper and zinc mine at Iron Mountain, in northern California. The pH of the drip water was -0.7. The beaker

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Lead Queen mine tunnel precipitate

Orange, iron-rich precipitate (ochre) from outflow of Lead Queen mine tunnel, after late September 2014 monsoon storm. Photo by Glen E. "Gooch" Goodwin, Photographer - used with permission.