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How does mine drainage occur?
USGS Mine Drainage Activities
As settlers traveled west and mined the American landscape, thousands of new mines were created over the centuries and then abandoned. Now, these long forgotten remnants of a bygone area still haunt us, as their operations left behind materials and rock exposures that can be easily eroded and carried downstream. The USGS helps track the sources of acidic mine drainage and helps land managers develop better mitigation strategies.
BACKGROUND
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Mine drainage refers to any surface water or groundwater that drains from an active or abandoned mining operation. Mine drainage can be high-quality similar to natural waters or contaminated by leftover materials. Polluted mine drainage can be extremely acidic and is often laden with high concentrations of toxic, heavy metals. In general, the more acidic the water, the more likely it is to be harmful to living organisms.
Mine drainage forms from a chemical reaction between water and rocks containing sulfur-bearing minerals. The resulting waters become rich in sulfuric acid and dissolved iron. As the iron settles out of the water, it can form red, orange, or yellow sediments in the bottom of streams. The acidic runoff further dissolves heavy metals such as copper, lead, 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.
THE CHEMISTRY OF MINE DRAINAGE
Because the chemistry of water samples can rapidly change if removed from the mine, many mine drainage measurements are made in the field. The first measurement typically looks at acidity, which is reported as pH. A neutral pH has a value of 7. Any sample that reads below a pH of 7 is characterized as being acidic. Anything greater than 7 is described as being basic. The more acidic the water is, the better it is at eroding mining slag, rocks, and other materials. The water then transports the contaminated mine materials to nearby rivers before eventually depositing the materials downstream. Some mine drainage has been seen to have pH in the 2.5-4 range1.
Another water-quality parameter that is useful for characterizing water quality of acid mine drainage is specific conductance. Conductance is a measurement of the electrical conductivity in a water sample and is a indicator of what's dissolved in a liquid. It is also very inexpensive to measure, unlike testing for metals and other pollutants. Different substances will affect the conductance of water, allowing scientists to use changes in conductance as an indicator of changes of whatever is in the water - in this case the amount of contaminants coming from the mine.
Media
Sources/Usage: Public Domain. View Media Details
RELATED USGS RESEARCH
- USGS Mine Drainage Activities
- Contamination associated with active and abandoned hard-rock mining
- USGS Central Mineral Resources team
ADDITIONAL RESOURCES
U.S. Environmental Protection Agency
Examples of research USGS conducts on mine drainage.
Emerging Geoenvironmental Issues Related to Proposed Mining in the Lake Superior Region
We are studying environmental issues related to mining, and potential mining, in the Great Lakes region, continuing the study of characterizing baseline geochemistry of several watersheds in Minnesota and Michigan, examining the potential for aquatic toxicity from metals, and examining the acid-neutralizing and acid-generating potentials of mine waste, and the environmental, and possible human...
Gold King Mine release (2015): USGS water-quality data and activities
On August 5, 2015, U.S. EPA was conducting an investigation of the Gold King Mine near Silverton, Colorado. While excavating as part of the investigation, water began leaking from the mine tunnel, and about three million gallons of water and sediment were released into Cement Creek, a tributary of the Animas River. The USGS provided pre- and post-release water-quality and streamflow data from...
Chemical Modeling of Acid Waters Questa Baseline and Pre-Mining Ground-Water Quality Investigation, Red River Valley Basin, New Mexico
The US Geological Survey and the New Mexico Environment Department entered into a Joint Powers Agreement as of April 30, 2001 to execute an investigation of baseline and pre-mining ground-water quality in the Red River Basin, New Mexico. The main objective is to infer the pre-mining ground-water quality at the Questa Molycorp mine site. This study was formulated because New Mexico law states that...
The USGS produces many types of multimedia products. Use the links below to browse our offerings of photographs, podcasts, other related multimedia related mine drainage.
Below are frequently asked questions associated with mine drainage.
How does mine drainage occur?
Mine drainage is surface water or groundwater that drains from an active or abandoned mine. In some cases, pyrite (an iron sulfide mineral) 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...
How can I find U.S. Bureau of Mines publications?
After 85 years of service, the U.S. Bureau of Mines (USBM) closed in 1996. Certain functions, such as the collection, analysis, and dissemination of minerals information, have been returned to the U.S. Geological Survey (USGS). For information on former USBM programs or publications, please see the following sources: The National Technical Reports Library (part of the National Technical...
As settlers traveled west and mined the American landscape, thousands of new mines were created over the centuries and then abandoned. Now, these long forgotten remnants of a bygone area still haunt us, as their operations left behind materials and rock exposures that can be easily eroded and carried downstream. The USGS helps track the sources of acidic mine drainage and helps land managers develop better mitigation strategies.
BACKGROUND
Media
Sources/Usage: Public Domain. View Media Details
Mine drainage refers to any surface water or groundwater that drains from an active or abandoned mining operation. Mine drainage can be high-quality similar to natural waters or contaminated by leftover materials. Polluted mine drainage can be extremely acidic and is often laden with high concentrations of toxic, heavy metals. In general, the more acidic the water, the more likely it is to be harmful to living organisms.
Mine drainage forms from a chemical reaction between water and rocks containing sulfur-bearing minerals. The resulting waters become rich in sulfuric acid and dissolved iron. As the iron settles out of the water, it can form red, orange, or yellow sediments in the bottom of streams. The acidic runoff further dissolves heavy metals such as copper, lead, 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.
THE CHEMISTRY OF MINE DRAINAGE
Because the chemistry of water samples can rapidly change if removed from the mine, many mine drainage measurements are made in the field. The first measurement typically looks at acidity, which is reported as pH. A neutral pH has a value of 7. Any sample that reads below a pH of 7 is characterized as being acidic. Anything greater than 7 is described as being basic. The more acidic the water is, the better it is at eroding mining slag, rocks, and other materials. The water then transports the contaminated mine materials to nearby rivers before eventually depositing the materials downstream. Some mine drainage has been seen to have pH in the 2.5-4 range1.
Another water-quality parameter that is useful for characterizing water quality of acid mine drainage is specific conductance. Conductance is a measurement of the electrical conductivity in a water sample and is a indicator of what's dissolved in a liquid. It is also very inexpensive to measure, unlike testing for metals and other pollutants. Different substances will affect the conductance of water, allowing scientists to use changes in conductance as an indicator of changes of whatever is in the water - in this case the amount of contaminants coming from the mine.
Media
Sources/Usage: Public Domain. View Media Details
RELATED USGS RESEARCH
- USGS Mine Drainage Activities
- Contamination associated with active and abandoned hard-rock mining
- USGS Central Mineral Resources team
ADDITIONAL RESOURCES
U.S. Environmental Protection Agency
Examples of research USGS conducts on mine drainage.
Emerging Geoenvironmental Issues Related to Proposed Mining in the Lake Superior Region
We are studying environmental issues related to mining, and potential mining, in the Great Lakes region, continuing the study of characterizing baseline geochemistry of several watersheds in Minnesota and Michigan, examining the potential for aquatic toxicity from metals, and examining the acid-neutralizing and acid-generating potentials of mine waste, and the environmental, and possible human...
Gold King Mine release (2015): USGS water-quality data and activities
On August 5, 2015, U.S. EPA was conducting an investigation of the Gold King Mine near Silverton, Colorado. While excavating as part of the investigation, water began leaking from the mine tunnel, and about three million gallons of water and sediment were released into Cement Creek, a tributary of the Animas River. The USGS provided pre- and post-release water-quality and streamflow data from...
Chemical Modeling of Acid Waters Questa Baseline and Pre-Mining Ground-Water Quality Investigation, Red River Valley Basin, New Mexico
The US Geological Survey and the New Mexico Environment Department entered into a Joint Powers Agreement as of April 30, 2001 to execute an investigation of baseline and pre-mining ground-water quality in the Red River Basin, New Mexico. The main objective is to infer the pre-mining ground-water quality at the Questa Molycorp mine site. This study was formulated because New Mexico law states that...
The USGS produces many types of multimedia products. Use the links below to browse our offerings of photographs, podcasts, other related multimedia related mine drainage.
What is mine drainage and how does it occur?
Listen to hear the answer.
Below are frequently asked questions associated with mine drainage.
How does mine drainage occur?
Mine drainage is surface water or groundwater that drains from an active or abandoned mine. In some cases, pyrite (an iron sulfide mineral) 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...
How can I find U.S. Bureau of Mines publications?
After 85 years of service, the U.S. Bureau of Mines (USBM) closed in 1996. Certain functions, such as the collection, analysis, and dissemination of minerals information, have been returned to the U.S. Geological Survey (USGS). For information on former USBM programs or publications, please see the following sources: The National Technical Reports Library (part of the National Technical...