After Barack Obama became president, permits became more difficult to obtain as mountaintop removal polarized public and political opinion regarding opposition or support. The West Virginia Department of Mines first reported production figures for surface mining in 1938, when the northern counties of Preston, Brooke, and Hancock produced about 200,000 tons of coal using that technique. Initial mining operations could begin with relatively small capital investments and produce large amounts of coal with few men and machines. The term dimension stone encompasses certain stone products used for architectural purposes such as granite countertops, marble flooring, and monuments, among a few others. The goal in the mining of these products is to remove large slabs that can be cut and machined to exacting architectural applications. Unlike open pit mining in which benching is required to prevent failure of the sides or pit slopes, the high strength and competency of the rock mass in quarries is such that vertical walls of 1000’ or more can be excavated.
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- As a result, these seams can exist at multiple locations within rock and with varying thicknesses.
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This is a method to recover additional coal from under the highwall of a contour mine, when the ultimate stripping ratio has been achieved in open cast operations. It is sometimes referred to as secondary mining because it is done after the open cast mine has reached an economic limit. Because surface mining requires the removal of the existing vegetation along with underlying topsoil, deforestation becomes an inevitable impact of all surface mining ventures.
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The procedure then lasts along the contour of the mountain up until the coal resources, or the operator’s resources, are fatigued. When the operator gets to the last cut, the only spoil left to fill this cut is the overburden from the https://xcritical.solutions/ original or box cut. Further detailed consideration of surface mining disturbance is given by Grim and Hill (1974). Terraced subsidence resulting from the working of seams that show 27–45° dipping and where the land surface slopes.
In a relatively new technique that originated in 1970s to early 1980s, explosives are used to move or throw the overburden into the previous pit in a process called cast blasting. The difference in the quantity of explosives required to fragment rock in place versus fragment and cast or throw the rock across the active pit and into the previous pit is cost-effective. Many surface strip mines use explosives to move overburden in addition to the primary swing equipment (dragline or continuous excavator), displacing up to 35% of the overburden by cast blasting. When cast blasting is used, the dragline may excavate from the spoil side of the pit, sitting on the leveled, blasted overburden. Strip mining, removal of soil and rock (overburden) above a layer or seam (particularly coal), followed by the removal of the exposed mineral. 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.
They found an early ally when West Virginia’s young secretary of state, Jay Rockefeller, announced in 1970 that he would work for the abolition of the practice. Rockefeller lost the 1972 gubernatorial election against Arch A. Moore, partly because of his stand on surface mining. Later, Rockefeller toned down his opposition and was elected governor twice, in 1976 and 1980, and then U.S. senator. Another problem for orphan lands in hilly terrain is the ecological island left when hills are completely enclosed by high headwalls. This is not unlike the ecological islands created in the southwestern United States from climate changes and vertical zonation of vegetation.
The Cons of Strip Mining
If caprock is encountered, expensive and time-consuming blasting is required, a frequent occurrence in the United States. Economic analysis then determines the area and depth of profitable overburden removal. Finally, contracts must be negotiated with landowners; strip mines commonly end abruptly at property lines.
Strip mining is only a temporary use of land, so it is imperative to restore the land as soon as mining is over to save the land. For instance, in Montana, U.S.A. reforestation plans had a success rate of only percent, while in some areas in Colorado only 10 percent of planted oak aspen saplings survived. However, as the box cut spoil may be at some distance from the last cut, the operator normally finds it more inexpensive not xcritical scammers to tow the box cut spoil to the last cut. Area mining is the system most regularly applied in the flat or mildly rolling countryside of the Midwest and Western United States. Bowl or cirque-type subsidence caused by the working of medium or thick seams dipping up to 27°. The handling of mine runoff and overburden fills must follow strict pollution regulations to avoid criminal fines and irreversible harm to local environments.
In many cases, mining businesses will resume coal mining via different methods, such as auger, to reach a deeper ore body after contour mining endeavors cease. Keleberda and Dan’ko (1975) studied the Dneprov spoil heap that resulted from the strip mining of the Chasov Yar refractory clays (Donetsk region). This spoil heap was recultivated with sweetclover (Melilotus volgicus) as a green manure plant. Invertase activity of the cm layer was also higher in the sweetclover plots than in the controls (Keleberda, 1976), and proteinase activity also increased in the top layer of the sweetclover plots (Keleberda, 1977). The primary planning mechanism used in strip mining is the range diagram, which is a cross-sectional plan of the shape of the pit in various stages of mining. The range diagram allows the dragline or continuous excavator equipment characteristics of dig depth, reach, and physical size to be placed on the geologic dimensions of depth to seams (overburden), and depth between seams (interburden).
⛏️ Understanding the Strip Mining Process
This strip mining method produces a terraced effect along the shape of the hill or mountain. These mining operations remove top layers of soil and rock, approaching mineral deposits through the surface rather than from underground. Other types of mining methods include mountaintop removal, dredging and highwall mining (an adapted form of auger mining done from the surface). Mining operations that treat or leach ores and/or store acid chemicals for the extraction of metals can generate large volumes of acidic metal-containing wastewaters and/or leachates.
Given the fact that most impacts from area mining are retained onsite, and that orphan lands possess great potential for recreation , especially fishing and hiking, at least some should be left undisturbed. This technique is used for near-surface, relatively flat sedimentary mineral deposits. How deeply the mining can occur is essentially determined by the combination of technological capabilities and the economics involved. The latter includes the xcritical value of the mineral, contractual arrangements with the landowner, and mining costs, including reclamation . Strip mining is used for mining phosphate fertilizer in Florida, North Carolina, and Idaho, and for obtaining gypsum (mainly for wallboard) in western states.
Cultural Eutrophication; Causes, Effects and Solutions
Terraced excavations usually 10–30 m deep with deposit dipped xcritical at 8°; some internal storage of overburden (Fig. 2.1C).
Coal Mining, Design and Methods of
One method to maximize pit recovery is to minimize drill and blast damage to the top of the coal. Drill and blast damage is reduced by stopping the drill holes from touching the coal seam or by placing nonexplosive material in each drill hole, called stemming. Pit recovery is also maximized by matching the pit width with the characteristics of the machinery used to extract the coal.
Effects of Mining on Surface Water
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Strip Mining Is Faster
Most other mining techniques require the digging of tunnels, which adds additional time to the process. Strip mining does not rely on the digging of tunnels and since the route to the surface is much shorter, this also cuts down on the amount of time spent. Retrieving minerals and transporting them is much simpler when using strip mining methods. The examples of decimated land in Appalachia have motivated calls for prevention, or at least major efforts at reclamation. Strip mining for coal comprises well over half of the land that is strip-mined, which totaled less that 0.3% of land in the United States between 1930 and 1990. This is far less land than the amount lost to agriculture and urbanization.