Coal Mining's Water Pollution: A Hidden Crisis

Coal mining has a significantly negative impact on water bodies, including rivers, streams, lakes, and drinking water supplies. The process of extracting coal often involves clearing forests, removing vegetation, and using explosives to blast away mountains, which can cause sedimentation, erosion, and the destruction of wildlife habitats. The exposed rocks and minerals can react with air and water to form sulfuric acid, leading to acid mine drainage, which contaminates nearby water sources with heavy metals and toxins. Additionally, the storage and disposal of coal waste and coal ash can result in leaks and spills, further polluting waterways and posing risks to human health and the environment. These issues highlight the importance of transitioning to renewable energy sources and implementing more sustainable mining practices to mitigate the harmful effects of coal mining on water.

Acid mine drainage

AMD is often the result of sub-surface mining, which often progresses below the water table. As such, water must be constantly pumped out of the mine to prevent flooding. When a mine is abandoned, the pumping ceases, and water floods the mine, creating the conditions for AMD to occur. The oxidation of metal sulfides (often pyrite, or iron sulfide) within the surrounding rock and overburden generates acidity. Colonies of bacteria and archaea, called extremophiles, accelerate the decomposition of metal ions, though the reactions can also occur without them.

AMD can also be released anywhere on the mine where sulfides are exposed to air and water, including waste rock piles, tailings, open pits, underground tunnels, and leach pads. The liquid that drains from coal stocks, coal handling facilities, coal washeries, and coal waste tips can be highly acidic and is treated as acid rock drainage. These have a detrimental impact on the streams' aquatic environments, with many impacted streams having a pH of 4 or lower—similar to battery acid.

The effects of AMD on the environment are severe. A literature review on AMD concluded that "no hard rock surface mines exist today that can demonstrate that acid mine drainage can be stopped once it occurs on a large scale." The economic burden of treating polluted water can be significant, especially if a company files for bankruptcy or refuses to cover the costs.

Heavy metal contamination

Coal mining has a significant impact on water bodies in the vicinity of the mines. One of the ways in which coal mining pollutes water is through heavy metal contamination.

Another way heavy metal contamination occurs is through acid mine drainage, a natural process in which sulphuric acid is produced when sulphides in rocks are exposed to air and water. This acid runoff further dissolves heavy metals such as copper, lead, and mercury into groundwater or surface water. This process can be accelerated by the action of certain bacteria and can last for hundreds or even thousands of years. The acid mine drainage can change the pH of nearby streams to the same level as vinegar, making the water virtually unusable and killing aquatic life.

The heavy metals in coal ash, which is produced by coal-fired power plants, can also escape into nearby waterways and contaminate drinking water. Coal ash has been linked to an increased risk of cancer, heart damage, reproductive problems, and neurological disorders. In 2014, 39,000 tons of coal ash spilled into North Carolina's Dan River.

The impact of heavy metal contamination from coal mining on wildlife has been observed in Central Appalachian streams, where scientists found a 32% decline in the number of species present and a 53% decline in the total number of invertebrates, fish, and salamanders compared to streams unaffected by mining operations. In regions of British Columbia and Montana affected by coal mining, fish with deformities such as missing gills, misshapen skulls, and crooked spines have been recorded.

Mountaintop removal

The Environmental Protection Agency (EPA) has found that contaminated valley fills created by mountaintop removal have altered the composition of nine out of ten streams in mining areas since 1992. These streams have been found to have less than half as many fish species and about a third as many fish as non-impacted streams. Other studies have found adverse impacts on birds, insects, and even bacteria. The conductivity of these streams—a proxy for pollution—frequently measures more than six times the level that the EPA has identified as the limit for preserving their health.

The water contamination from mountaintop removal has also been linked to negative health impacts on people living in nearby communities. Research by Indiana University's Michael Hendryx has shown that mountaintop removal is leading to increases in cardiovascular disease, lung cancer, pulmonary disease, and birth defects in Appalachia. Hendryx's research also found that mountaintop removal contaminates billions of gallons of water across the region with cleaning chemicals, proprietary formulas, and noncombustible materials removed from the coal, including heavy metals like arsenic and mercury.

In the United States, mountaintop removal is allowed by section 515(c)(1) of the Surface Mining Control and Reclamation Act of 1977 (SMCRA). While mountaintop removal sites are normally restored after mining operations are complete, reclaimed soils have higher bulk density, lower organic content, low water-infiltration rates, and low nutrient content. Additionally, reclamation efforts have traditionally focused on stabilizing rock formations and controlling erosion, rather than on the reforestation of the affected area, which is necessary for restoring wildlife habitats.

Coal washing and waste storage

Coal washing is the process of using water and chemicals to remove impurities from mined coal before it is burned. The resulting mixture of water and impurities is known as coal slurry or sludge, which contains many toxic substances and heavy metals, including arsenic, lead, and mercury. This slurry must then be stored, often in coal ash ponds, landfills, or abandoned mines.

The storage of coal slurry is a significant source of water pollution. Often, it is stored in improvised ponds that can leak, spill, or fail, contaminating nearby rivers and streams. For example, in 2000, a coal slurry impoundment in Kentucky leaked, releasing over 300,000,000 gallons of sludge into nearby rivers and streams, an amount 30 times larger than the Exxon-Valdez oil spill.

Coal ash ponds are another common storage method for coal slurry. Over time, the toxic substances in the ash can escape into nearby waterways, contaminating drinking water sources. Coal ash contains concentrated amounts of toxic elements, including arsenic, lead, and mercury, which have been linked to an increased risk of cancer, heart conditions, reproductive issues, and neurological disorders. In 2014, 39,000 tons of coal ash spilled into North Carolina's Dan River, and in 2008, over 5 million cubic yards of coal ash were released into Tennessee's Emory River, causing one of the largest environmental disasters in US history.

The disposal of coal waste into abandoned mines has also been linked to water pollution. As rain filters through the toxic ash pits, it leaches out toxic metals, which are then carried by gravity into the soil and local water sources. All landfills eventually leak, and this can contaminate drinking water supplies.

The burning of coal can also contribute to water pollution. "Once-through" coal plants pump water directly from a source, heat it, and then discharge it. This waste water is typically hotter than the receiving water, creating "thermal pollution" that can negatively impact aquatic life.

Impact on wildlife

Coal mining has a profound impact on wildlife, with far-reaching consequences that can be felt long after mining activities have ceased. The environmental impacts of coal mining extend beyond greenhouse gas emissions, causing devastation to landscapes and waterways.

One of the most destructive forms of coal mining is mountaintop removal, which is commonly practised in the Appalachian region, particularly in the east. This process involves clearing the land, including vegetation, and then using explosives to blast away the mountaintops to access coal seams. The resulting debris is dumped into the valleys below, forming "valley fills". This practice has buried more than 2,000 miles of headwater streams, causing irreversible losses to wildlife habitats and clean water sources. It also alters the composition of nearby streams, leading to water quality degradation that can persist for decades.

The process of coal mining often involves clearing forests and stripping away the earth, leaving behind barren land incapable of supporting wildlife. Excessive logging and removal of vegetation contribute to erosion, as precipitation washes away loose topsoil into nearby waterways. This sedimentation further degrades water quality and harms aquatic life.

The water used to wash coal before burning, known as coal slurry or sludge, often contains chemicals and impurities. Improper storage of this slurry in improvised ponds can lead to leaks and spills, contaminating rivers and streams with toxic substances. Coal ash, a byproduct of burning coal, is another source of pollution. It contains high levels of toxic elements such as arsenic, lead, and mercury, which can escape into nearby waterways and contaminate drinking water.

The impact of coal mining on wildlife is evident in the decline of species diversity and the deformation of aquatic organisms. Studies have shown a significant decrease in the number of species present in streams affected by coal mining, with a particularly notable decline in invertebrates, fish, and salamanders. Selenium pollution in water from coal mining has been linked to the decline and deformation of sensitive fish populations, as well as deformities in birds. These pollutants can accumulate in organisms as they move up the food chain, leading to severe consequences for higher-level predators, including humans.

The release of heavy metals, such as arsenic, lead, and copper, during coal mining and processing further exacerbates the problem. These metals contaminate waterways and pose risks to both aquatic life and humans who depend on these water sources. The acidic water produced during coal mining, known as acid mine drainage, can alter the pH levels of nearby streams, making them inhospitable to aquatic life.

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