The Water Contamination Hazards of Mining

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Gold King Mine. Photo Credit: La Plata County

By Nick Law, Staff Writer and Editor for Save The Water™ | October 14, 2015

On August 5, 2015, 3 million tons of toxic sludge leaked into the Animas River in Colorado, giving its waters a bright yellow hue. According to most news sources, the leak was caused by a team of workers employed by the Environmental Protection Agency (Heck). The Gold King Mine has been leaking fluids into its surrounding area since its shuttering in 1923. This has resulted in the formation of dozens of toxic wells in its immediate vicinity. In order to contain this environmental disaster, work crews from the EPA have been attempting to “slurp out the worst pools of sludge and dispose of them properly” (Dokoupil). However, while they were working near Silverton, some of their heavy equipment “disturbed an earthen wall that secured the liquid, releasing an up to 80-mile ribbon of pollution downstream” (Dokoupil). The contaminated water contains high levels of heavy metals, “including lead and arsenic” (Heck), and water tests a few days later after the spill indicated that levels of arsenic and lead were respectively at “300 and 3,500 times the normal levels” (Dokoupil).

The EPA has since owned up to causing the incident and made several statements promising prompt rectification measures and the establishment of new oversights that would prevent another similar spill (Dokoupil). However, the incident compromised the livelihood of many farmers situated along the Animas River and its tributaries. The city of Durango was also affected because it draws a significant amount of its water supply from the Animas River, and much of its tourist trade depends on “water-based recreation” (Morgan). Fortunately, human casualties are non-existent, and current reports indicate that so far, park agents and biologists working for La Plata County have found no significant amounts of dead fish or animals in or beside the polluted water bodies. This means that the polluted water poses little danger to fish or other wildlife (Johnson). However, the long term consequences of this incident remain to be seen.

The Animas River. Photo Credit: EPA

Despite the fact that the adverse health effects of exposure to heavy metal contaminants are very well known, heavy metals are still very much in use today throughout the world. One of the major pollutants spilled into the Animas River was arsenic, a metalloid that occurs naturally in rock, soil, water, and air; its inorganic form is present in groundwater used for drinking in several countries all over the world while its organic compound is primarily found in fish (Järup). It can also come into contact with humans through pesticides, wood preservatives, and contaminated food and water. Moreover, contaminated “soils such as mine-tailings… [are another] potential source of arsenic exposure” (Järup). Inorganic arsenic is extremely toxic, and “intake of large quantities leads to gastrointestinal symptoms, severe disturbances of the cardiovascular and central nervous systems, and eventually death. In survivors, bone marrow depression, haemolysis, hepatomegaly, melanosis, polyneuropathy and encephalotopathy may be observed” (Järup). Individuals exposed to arsenic through drinking water face “excess risk of mortality from lung, bladder, and kidney cancer” (Järup).

The other major pollutant, lead, is another common metal used frequently in many modern day products, most notably lead emissions from the burning of petrol. Individuals might also be exposed to lead when working in mines, smelters, or battery plants. All of these places give off high levels of lead emissions that suffuse their surrounding area, causing airborne lead to “be deposited on soil and water, thus reaching humans via the food chain” (Järup). Acute lead poisoning causes headaches, irritability, abdominal pain, and various nervous system-related symptoms; children in particular are more drastically affected by lead poisoning, suffering from behavioral disturbances, learning, and concentration difficulties on top of all the aforementioned symptoms. Long-term exposure to lead can result in disastrous consequences, such as permanently diminished mental faculties in adults and stunted growth in children (Järup).

Figure 3: Evaporation Pond. Photo Credit: Doc Searls

Since exposure to heavy metal contaminants can result in such adverse effects to human health, it is imperative that mines manage their waste water with the utmost scrupulousness. Most mining operations recognize this and develop “water management plans to minimize the potential for water contamination… and to prevent the release of polluted water into the environment” ( Some mines use water control techniques, such as diverting surface and drainage water from the mine site, recycling water used for processing ore, using evaporation ponds for contaminated water, and installing liners and covers on waste rock and ore piles to prevent them from coming into contact with groundwater (

Other mines take their measures one step further by treating the contaminated water produced by their operations with technologies that can be categorized as either active or passive. In active water treatment, acidic mine waters are treated with alkaline compounds such lime, limestone, or caustic soda. The elevation of the pH levels causes dissolved metals to precipitate and sink to the bottom of the sedimentation ponds that hold this water. These sediments can then be subsequently removed. Other technologies such as ion exchangers, membrane filters, and reverse osmosis might also be used to achieve a similar effect (

In contrast, passive water treatment relies on “natural physical, chemical, and biological processes that remove water… [contaminants] without additional physical or chemical inputs… [Some] of these processes include bacteria-controlled metal precipitation, contaminate uptake by plants, and filtration through soil and sediments” ( Mines that employ such approaches towards water treatment rely on constructed wetlands in which contaminated water is filtered and purified by natural mechanisms before being allowed to rejoin other water bodies. However, passive water treatment requires constant, challenging water monitoring and can be ineffective when dealing with highly acidic water.

The work crews assigned to the area around the Gold King Mine were trying to control the contaminated water with a variety of the aforementioned methods, most ostensibly through the use of evaporation ponds and combinations of active and passive water treatment processes in a bid to induce metal precipitation. Despite their efforts, all it took was a sudden accident and error of judgment on their part to cause massive quantities of lead and arsenic to flow into the Animas River.

Although the effects of the spill have so far been relatively minor, the long-term consequences are as yet unknown. Mining is an essential aspect of the global economy, so calls to curtail or reduce mining operations are unreasonable and unproductive. However, mines could definitely benefit from improved sustainable water management technologies directed at the prevention of any contamination issues. Save the Water is a non-profit organization focused on the development of water science. Any contributions you can make to our research and development endeavors will help us to prevent an incident like the Animas River spill from ever occurring again.

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