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Surface mining, including strip mining, open-pit mining and mountaintop removal mining, is a broad category of mining in which soil and rock overlying the mineral deposit (the overburden) are removed, in contrast to underground mining, in which the overlying rock is left in place, and the mineral is removed through shafts or tunnels.
Surface mining began in the mid-16th century [ dubious ] and is practiced throughout the world in the mining of many different minerals, although the majority of surface coal mining occurs in North America. In North America, surface mining gained popularity throughout the 20th century, and surface mines now produce most of the coal mined in the United States.
In most forms of surface mining, heavy equipment, such as earthmovers, first remove the overburden. Next, large machines, such as dragline excavators or bucket-wheel excavators, extract the mineral.
The pros of surface mining are that it has a lower financial cost and is a lot safer than underground mining because all mining operations take place above the surface. The cons are the hazards it presents to human health and the environment. Humans face a variety of health risks caused by mining such as different cardiovascular diseases, food, and water contamination. Habitat destruction, alongside air, noise, and water pollution, are all significant negative environmental impacts caused by the side effects of surface mining.
There are five main types of surface mining as detailed below.
Strip mining is the practice of mining a seam of mineral, by first removing a long strip of overlying soil and rock (the overburden); this activity is also referred to as overburden removal. It is most commonly used to mine coal and lignite (brown coal). Strip mining is only practical when the ore body to be excavated is relatively near the surface and/or is mostly horizontal.This type of mining uses some of the largest machines on earth, including bucket-wheel excavators which can move as much as 12,000 cubic metres of earth per hour.
There are two forms of strip mining. The more common method is area stripping, which is used on fairly flat terrain, to extract deposits over a large area. As each long strip is excavated, the overburden is placed in the excavation produced by the previous strip.
Contour mining involves removing the overburden above the mineral seam near an outcrop in hilly terrain, where the mineral outcrop usually follows the contour of the land. Contour stripping is often followed by auger mining into the hillside, to remove more of the mineral. This method commonly leaves behind terraces in mountainsides.
Open-pit mining refers to a method of extracting rock or minerals from the earth through their removal from an open pit or borrow. It is best suited for accessing mostly vertical deposits of minerals. Although open-pit mining is sometimes mistakenly referred to as "strip mining", the two methods are different (see above).
Mountaintop removal mining (MTR) is a form of coal mining that mines coal seams beneath mountaintops by first removing the mountaintop overlying the coal seam. Explosives are used to break up the overburden (rock layers above the seam), which is then removed. The overburden is then dumped by haul trucks into fills in nearby hollows or valleys. MTR involves the mass restructuring of earth in order to reach coal seams as deep as 400 feet (120 m) below the surface. Mountaintop removal replaces the original steep landscape with a much flatter topography. Economic development attempts on reclaimed mine sites include prisons such the Big Sandy Federal Penitentiary in Martin County, Kentucky, small-town airports, golf courses such as Twisted Gun in Mingo County, West Virginia and Stonecrest Golf Course in Floyd County, Kentucky, as well as industrial scrubber sludge disposal sites, solid waste landfills, trailer parks, explosive manufacturers, and storage rental lockers.
This method has been increasingly used in recent years in the Appalachian coal fields of West Virginia, Kentucky, Virginia, and Tennessee in the United States. The profound changes in topography and disturbance of pre-existing ecosystems have made mountaintop removal highly controversial.
Advocates of mountaintop removal point out that once the areas are reclaimed as mandated by law, the technique provides premium flat land suitable for many uses in a region where flat land is rare. They also maintain that the new growth on reclaimed mountaintop mined areas is better able to support populations of game animals.
Critics[ who? ] contend that mountaintop removal is a disastrous practice that benefits a small number of corporations at the expense of local communities and the environment. A U.S. Environmental Protection Agency (EPA) environmental impact statement finds that streams near valley fills sometimes may contain higher levels of minerals in the water and decreased aquatic biodiversity. The statement also estimates that 724 miles (1,165 km) of Appalachian streams were buried by valley fills from 1985 to 2001.
Blasting at a mountaintop removal mine expels dust and fly-rock into the air, which can then disturb or settle onto private property nearby. This dust may contain sulfur compounds, which some claim corrode structures and tombstones and is a health hazard.
Although MTR sites are required to be reclaimed after mining is complete, reclamation has traditionally focused on stabilizing rock and controlling erosion, but not always on reforesting the area.Quick-growing, non-native grasses, planted to quickly provide vegetation on a site, compete with tree seedlings, and trees have difficulty establishing root systems in compacted backfill. Consequently, biodiversity suffers in a region of the United States with numerous endemic species. Erosion also increases, which can intensify flooding. In the eastern United States, the Appalachian Regional Reforestation Initiative works to promote the use of trees in mining reclamation.
Dredging is a method for mining below the water table. It is mostly associated with gold mining. Small dredges often use suction to bring the mined material up from the bottom of a water body. Historical large-scale dredging operations often used a floating dredge; a barge-like vessel that scoops material up through a conveyor belt on the bow, filters out the desired component on board, and returns the unwanted material to the water via another conveyor belt on the stern. In gravel-filled river valleys with shallow water tables, a floating dredge can work its way through the loose sediment in a pond of its own making.
This section needs additional citations for verification .(January 2016)
Highwall mining is another form of mining sometimes conducted to recover additional coal adjacent to a surface-mined area. The method evolved from auger mining but does not meet the definition of surface mining since it does not involve the removal of overburden to expose the coal seam. 19.72 feet (6.01 m). Then, the PTM automatically inserts a 19.72-foot-long (6.01 m) rectangular pushbeam (screw-conveyor segment) into the center section of the machine between the Powerhead and the cutterhead. The pushbeam system can penetrate nearly 1,200 feet (370 m) (proven in 2015 till today)[ citation needed ] into the coal seam. One patented highwall mining system uses augers enclosed inside the pushbeam that prevent the mined coal from being contaminated by rock debris during the conveyance process. Using a video imaging and/or a gamma-ray sensor and/or other geo-radar systems like a coal-rock interface detection sensor (CID), the operator can see ahead projection of the seam-rock interface and guide the continuous miner's progress. Highwall mining can produce thousands of tons of coal in contour-strip operations with narrow benches, previously mined areas, trench mine applications, and steep-dip seams by utilizing a controlled water-inflow pump system and/or a gas (inert) venting system.CERB final report No. 2014-004 "Highwall Mining: Design Methodology, Safety, and Suitability" by Yi Luo characterizes it as a "relatively new semi-surface and semi-underground coal mining method that evolved from auger mining". In highwall mining, the coal seam is penetrated by a continuous miner propelled by a hydraulic pushbeam transfer mechanism (PTM). A typical cycle includes sumping (launch-pushing forward) and shearing (raising and lowering the cutterhead boom to cut the entire height of the coal seam). As the coal recovery cycle continues, the cutterhead is progressively launched into the coal seam for
Recovery with tunneling shape of drives used by highwall miners is much better than round augering holes, but the mapping of areas that have been developed by a highwall miner are not mapped as rigorously as deep mined areas. Very little soil is displaced in contrast with mountaintop removal; however, it is comparatively more expensive to own and operate a highwall miner.
Mapping of the outcrop, as well as core hole data and samples taken during the bench-making process, are taken into account to best project the panels that the highwall miner will cut. Obstacles that could be potentially damaged by subsidence and the natural contour of the highwall mine are taken into account, and a surveyor points the highwall miner in a line (theoretical survey plot-line) mostly perpendicular to the highwall. parallel lines represent the drive cut into the mountain (up to 1,200 feet (370 m) deep (2015 records),[ citation needed ] without heading or corrective steering actuation on a navigation azimuth during mining results in missing a portion of the coal seam and is a potential danger of cutting in pillars from previous mined drives due to horizontal drift (roll) of the pushbeam-cuttermodule string. Recently[ when? ] highwall miners have penetrated more than 1,200 feet (370 m) (2015 ongoing records[ citation needed ] into the coal seam, and today's models are capable of going farther, with the support of gyro navigation and not limited anymore by the amount of cable stored on the machine. The maximum depth would be determined by the stress of further penetration and associated specific-power draw (torsion and tension in screw transporters string), but today's optimized screw-transporters conveying embodiments (called pushbeams) with visual product development and discrete element modeling (DEM) using flow simulation behavior software shows smart-drive extended penetrations are possible, even so under steep inclined angles from horizontal to more than 30 degree downhole. In case of significant steep mining the new mining method phrase should be "directional mining" (commonly used technologies as valuable synergy directional drilling and directional mining are categorized in "surface to in-seam" (SIS) techniques), dry or wet, dewatering is developed or cutting and dredging through screw transporters are proactive in developing a roadmap of the leading global highwall mining engineering company.[ clarification needed ]
Historically, moving materials out of surface mines was accomplished through manual labor, horse-drawn vehicles, and/or mining railways.
Current practices tend to use haul trucks on haul roads designed into the features of the mine.
This section needs expansion. You can help by adding to it. (March 2021)
To properly clean and restore a once operational surface mine requires a large sum of money and extensive remediation plans.Some mining companies do not have the funds to properly clean up, therefore the environment is negatively affected. Federal governments have emplace multiple laws and regulations which mining companies have to strictly follow. In the United States, the Surface Mining Control and Reclamation Act of 1977 mandates reclamation of surface coal mines. Reclamation for non-coal mines is regulated by state and local laws, which may vary widely. The National Environmental Policy Act (NEPA), Resource Conservation and Recovery Act (RCRA), Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and many more laws deal with the subject of surface mining. In some cases, even with proper legislation in place for surface mining some negative human health and environmental impacts remain.
Health studies have been conducted on humans that work or live near surface mines and have found many negative health effects.One particular effect on human health is particulate matter, such as particles of dust, metals, acid, and soil suspended in the air can be inhaled and lead to serious repercussions. Once inhaled, they may decrease lung function, lung capacity, cardiovascular desires may arise and worse case, cancer. Large exposed surface areas like strip, open-pit, mountaintop removal, and highwall mines contribute to extensive air pollution and suspended particulate matter. Miners that work in surface mines are at high direct risk for health complications, whereas local communities experience different effects. People who live near a surface mine can experience health effects such as cardiovascular problems, water contamination where metals or acid leach into the groundwater and contaminate agriculture. Western Virginia has large surface mining productions such as mountaintop removal, which can lead to the contamination of water that communities at the base of the Appalachian mountains use.
Governments such as the Canadian government have specific legislation to keep the miners, communities, and the environment safe. In Canada, the Environmental Code of Practice for Metal Mines (ECPMM), Metal Mining Effluent Regulations (MMER), the Canadian Environmental Assessment Act, and many other laws and regulations have been implemented to help protect the health of the people.
Surface mining can have a number of effects on the local environment, ranging from the negative to the positive. The negative effects involve soil, water, air, and noise pollution as well as landscape alteration and various other negatives.The flip side is the positive ramification; with new technology and proper management, it has become easier to properly treat the local water supply and restore the local ecology which helps rebuild the environment.
Each type of surface mining has its own environmental impact, as laid out below.
Strip mining - Once operations have ended, the tailings are placed back into the hole and covered up to make the site resemble the landscape before the mining operation. Topsoil may be placed over the tailing along with planting trees and other vegetation. Another reclamation method involves filling in the hole with water to create an artificial lake. Large tailing piles left behind may contain heavy metals which can leach out acids such as lead and copper and enter into water systems.
Open-pit mining - One of the world's largest types of mine and the size of these operations leave behind massive landscape scars, destruction to environmental habitats, and substantial clean-up cost.An open-pit mine can yield an enormous quantity of waste rock, sinkholes can form down the road, flooding and similar negative impacts as strip mining.
Mountaintop removal mining - Involves the removal of whole mountaintops, the waste rock of which is used to flatten out the surrounding land by infilling rivers and valleys. This is very destructive as it physically permanently alters the landscape and the associated ecosystem. Throughout the Appalachians in states such as Kentucky and Virginia, mountaintop removal is a common mining method where whole forests are cleared and the area becomes vulnerable to possible landslides, with restoration sometimes being too difficult/costly.
Dredging - A form of surface mining where the environmental impacts are primarily found underwater. The method of extracting material from the seafloor or any water body leads to the harmful risk of marine life. Overall, the effect are far less compared to the other mining methods. The influx of sediment can bury flora and fauna, change water levels and can alter the oxygen content.Water and noise pollution is a concern that must be monitored because marine life is very sensitive and vulnerable to drastic and harmful changes within their ecosystem.
Highwall mining - Has a lower environmental impact than mountaintop removal because of the smaller external surface area present but there is still negative side effects.Air and noise pollution from blasting are common environmental effects along with the large tailing piles, which can leach into waterways and numerous ecosystems.
Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. These deposits form a mineralized commodity that is of economic interest to the miner.
A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their environmental impact.
Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production. In the United Kingdom and South Africa, a coal mine and its structures are a colliery, a coal mine is called a 'pit', and the above-ground structures are a 'pit head'. In Australia, "colliery" generally refers to an underground coal mine.
Open-pit mining, also known as mega-mining, open-cast or open cut mining, is a surface mining technique of extracting rock or minerals from the earth by their removal from an open-air pit, sometimes known as a borrow.
Tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are distinct from overburden, which is the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed.
Mining in the engineering discipline is the extraction of minerals from underneath, above or on the ground. Mining engineering is associated with many other disciplines, such as mineral processing, exploration, excavation, geology, and metallurgy, geotechnical engineering and surveying. A mining engineer may manage any phase of mining operations, from exploration and discovery of the mineral resources, through feasibility study, mine design, development of plans, production and operations to mine closure.
In mining, overburden is the material that lies above an area that lends itself to economical exploitation, such as the rock, soil, and ecosystem that lies above a coal seam or ore body. Overburden is distinct from tailings, the material that remains after economically valuable components have been extracted from the generally finely milled ore. Overburden is removed during surface mining, but is typically not contaminated with toxic components. Overburden may also be used to restore an exhausted mining site during reclamation.
Mountaintop removal mining (MTR), also known as mountaintop mining (MTM), is a form of surface mining at the summit or summit ridge of a mountain. Coal seams are extracted from a mountain by removing the land, or overburden, above the seams. This process is considered to be safer compared to underground mining because the coal seams are accessed from above instead of underground. In the United States, this method of coal mining is conducted in the Appalachian Mountains in the eastern United States. Explosives are used to remove up to 400 vertical feet of mountain to expose underlying coal seams. Excess rock and soil is dumped into nearby valleys, in what are called "holler fills" or "valley fills".
Drift mining is either the mining of an ore deposit by underground methods, or the working of coal seams accessed by adits driven into the surface outcrop of the coal bed. A drift mine is an underground mine in which the entry or access is above water level and generally on the slope of a hill, driven horizontally into the ore seam. Random House dictionary says the origin of the term "drift mine" is an Americanism, circa 1885–1890.
A spoil tip is a pile built of accumulated spoil – waste material removed during mining. These waste materials are typically composed of shale, as well as smaller quantities of carboniferous sandstone and various other residues. Spoil tips are not formed of slag, but in some areas, such as England and Wales, they are referred to as slag heaps. In Scotland the word bing is used.
The Office of Surface Mining Reclamation and Enforcement (OSMRE) is a branch of the United States Department of the Interior. It is the federal agency entrusted with the implementation and enforcement of the Surface Mining Control and Reclamation Act of 1977 (SMCRA), which attached a per-ton fee to all extracted coal in order to fund an interest-accruing trust to be used for reclamation of abandoned mine lands, as well as established a set environmental standards that mines must follow while operating, and achieve when reclaiming mined land, in order to minimize environmental impact. OSMRE has about 500 employees, who work in either the national office in Washington, DC, or of the many regional and field offices.
The health and environmental impact of the coal industry includes issues such as land use, waste management, water and air pollution, caused by the coal mining, processing and the use of its products. In addition to atmospheric pollution, coal burning produces hundreds of millions of tons of solid waste products annually, including fly ash, bottom ash, and flue-gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals. Coal is the largest contributor to the human-made increase of carbon dioxide in Earth's atmosphere.
The following outline is provided as an overview of and topical guide to mining:
Environmental effects of mining can occur at local, regional, and global scales through direct and indirect mining practices. The effects can result in erosion, sinkholes, loss of biodiversity, or the contamination of soil, groundwater, and surface water by the chemicals emitted from mining processes. These processes also affect the atmosphere from the emissions of carbon which have an effect on the quality of human health and biodiversity. Some mining methods may have such significant environmental and public health effects that mining companies in some countries are required to follow strict environmental and rehabilitation codes to ensure that the mined area returns to its original state.
Mining in the United States has been active since the beginning of colonial times, but became a major industry in the 19th century with a number of new mineral discoveries causing a series of mining rushes. In 2015, the value of coal, metals, and industrial minerals mined in the United States was US $109.6 billion. 158,000 workers were directly employed by the mining industry.
Coal was discovered in Kentucky in 1750. Since the first commercial coal mine opened in 1820 coal has gained both economic importance and controversy regarding its environmental consequences. As of 2010 there were 442 operating coal mines in the state, and as of 2017 there were fewer than 4,000 underground coalminers.
The Last Mountain is a feature-length documentary film directed by Bill Haney and produced by Haney, Clara Bingham and Eric Grunebaum. The film premiered at the 2011 Sundance Film Festival and went into general release on June 3, 2011. The film explores the consequences of mining and burning coal, with a particular focus on the use of a method for coal strip-mining in Appalachia commonly known as mountaintop removal mining.
The Hobet 21 Coal Mine in West Virginia was operational between 1974 and 2015. Straddling the border of Boone County and Lincoln County in the Appalachian Mountains, the Hobet 21 mine was one of the largest mountaintop-removal coal mining operations in West Virginia. Originally owned by Fil Nutter, the mine used both underground mining and strip mining techniques, and later even more intensive surface mining using a dragline. Increasing productivity and profitability encouraged workers to successfully strike for their health plan in 1993, which resulted in unusually thorough coverage for mine workers at this time. The Hobet mine was incorporated into Arch Coal in 1997, along with several other mines, following booming coal demand. The mine was sold two more times: to Magnum Coal in 2005 and to Patriot Coal in 2008. Patriot Coal subsequently went bankrupt in 2015, and the Hobet site was passed into a Virginia-based conservation firm who continued to mine the land while reclaiming and planting trees to offset carbon emissions for other companies.
Environmental justice and coal mining in Appalachia is the study of environmental justice – the interdisciplinary body of social science literature studying theories of the environment and justice; environmental laws, policies, and their implementations and enforcement; development and sustainability; and political ecology – in relation to coal mining in Appalachia.
Environmental issues in Appalachia, a cultural region in the Eastern United States, include long term and ongoing environmental impact from human activity, and specific incidents of environmental harm such as environmental disasters related to mining. A mountainous area with significant coal deposits, many environmental issues in the region are related to coal and gas extraction. Some extraction practices, particularly surface mining, have met significant resistance locally and at times have received international attention.
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