Author’s Note: A quarry is an open-pit mine that produces building materials and dimension stone, such as granite, quartzite, marble, slate, bluestone, limestone, or sandstone, etc.
Author’s Note: A common topographic alteration to the landscape in open pit mines is an engineered dam/dyke system known as a tailing pond/pit, which is used to store mining refuse/gangue produced by the separation of economically valuable materials from the uneconomic part of an ore. In a great many instances, the containment structures comprising these ponds are not meant to be permanent and may be constructed of compacted earth, forming what are embankment dams. In areas of seasonally high rainfall, those structures may experience greater volumes of water than was anticipated and fail, often catastrophically, flooding areas downstream with a slurry of mud-like materials and water, resulting in loss of life and property. Here's an example. The Mount Polley open pit copper/gold mine, covering 18,892 hectares or nearly 46,700 acres in south-central British Columbia is operated by Vancouver-based Imperial Metals. The mill processes 20,000 tons of rock per day. In early August, 2014, a tailings pond dam at the mine failed, releasing at least 10 million cubic meters of contaminated water and waste rock into a local creek, expanding its width from four feet to 150 feet before entering nearby Quesnel Lake and its connected waterways, which are important habitats for Chinook and Sockeye Salmon as well as Rainbow Trout and White Sturgeon. The pond contained tailings from the mining process and were contaminated with arsenic, cadmium, copper, lead, and mercury, among other toxins and heavy metals that are hazardous to life. Another very recent example is the Samarco iron ore mine in Minas Gerais, Brazil, a joint venture between the Anglo-Australian mining giant, BHP Billiton, and Brazil’s biggest iron ore miner, Vale SA, which failed in early November 2015, releasing 81 million cubic yards of mining waste, killing perhaps 20 people, destroying nearby villages housing more than 600 people, polluting drinking water over an enormous area, and adversely affecting the Rio Doce, which is one of Brazil's most important rivers, and the adjacent landscape for more than 300 miles downstream. Not to mention the issue that mining companies love to gloss over in their press releases meant to reassure the affected public: residues from the iron mining operations and the consequent flooding are toxic and may be very hazardous to human and animal health. According to Brazil’s environmental agency, IBAMA, 50 million metric tons of toxic sludge from the mine dam failure are, at the end of December 2015, spreading along 30 miles of coastal beaches between the states of Rio de Janeiro and Bahia, turning the pristine blue waters brown and sliming the beaches themselves. When tailings impoundments are abandoned, improperly remediated, and gradually dry up, the resulting dust, which can and often does consist of toxic materials rather than simple mud/dirt particulates, can cover the adjacent environment and nearby settlements, increasing risks to life and health, including respiratory, skin, gastrointestinal (from inadvertent ingestion) and other adverse effects that can include different types of cancer.
Soils: changes in characteristics through accelerated wind and water erosion, sharply increased acidity and salt content, development of nutrient deficiencies or imbalances, compaction, surface crustiness, or desiccation. Soils can be removed partially or entirely, altered, indurated, contaminated with toxins, or otherwise adversely affected by road building or mining construction to certain depths below the surface such that short-term and even mid-term recovery following reclamation is problematic. The fairly intense disturbance of soil surfaces by mining activities may make soils susceptible to water and wind erosion, thus contributing to sediment loading in local or regional stream systems that reduce water quality and aquatic habitat. Chemical particulates and metals from smelter emissions and airborne tailings can settle on soil surfaces near or some distance from mineral processing facilities, although typically contamination of soils decreases with distance from the contaminant source. In many cases, toxic substances have been deposited along roads leading from the mine and have adversely affected not only soils in residential areas but also the health of people and animals living in proximity to the roads.
Groundwater: adverse effects on quality and quantity especially with regard to dewatering activities, drawdown, and techniques used to control dust and other particulates as well as acid mine drainage that infiltrates the groundwater system and adversely affects the natural pH levels, causing cascading effects on flora and fauna when the groundwater and surface water systems interact. This topic is far more complex and critical than can be described in a few short paragraphs. Serious students of the topic must investigate the various sub-topics independently.
Chemical residues: especially those from acids, hazardous and toxic chemicals, explosives, and radionuclides. Tailings ponds may frequently be toxic due to the presence of unextracted sulfide minerals and acids in the tailings or gangue (commercially valueless material in which ore is found). Those hazardous residues may wind up contaminating surface streams or groundwater or both.
Author's Note: The Berkeley Pit in Butte, Montana, is an inactive open pit copper mine owned and managed by Atlantic Richfield and Montana Resources. The Pit is one mile long by half a mile wide with an approximate depth of 1,780 feet holding about 45 billion gallons of water that is highly acidic (sulfuric acid) and is contaminated by high concentrations of dissolved toxic heavy metals. The Berkeley Pit was designated as a federal Superfund site in 1983. This mine popped into the news in late November 2016 when several thousand migrating snow geese died when they landed in the Berkeley Pit’s toxic water. For more information on the Berkeley Pit, see: http://www.pitwatch.org/berkeley-pit-history/
Open pit/open cast miining techniques are also frequently used to produce precious and semi-precious metals, especially, copper, silver, and gold, in developed as well as developing nations. Examples include the Bingham Canyon Copper Mine (also known as the Kennecott Mine) southwest of Salt Lake City, Utah; Chile’s Chuquicamata Mine, the world’s largest open pit copper mine and the second deepest open-pit mine; and the Grasberg Mine in the province of Papua in Indonesia, the world’s largest gold mine and the second largest copper mine; according to the non-profit Earthworks, that mining operation dumps about 80 million tons of mining debris into the Ajkwa River system every year.