The overburden from the initial cut may be used to fill in the final cut, and the top part of the headwall is sometimes cut down to grade into the spoil. The spoil banks are leveled and the topsoil replaced; fertilization and replanting, usually with grasses or trees for erosion control, and subsequent monitoring of revegetation efforts, complete the process. In large operations, the leveling and replanting coincide with mining, which is ideal since this rapidly rebuilds the vegetation cover.
- The top of each bench is equivalent to a working level, and access to different levels is gained through a system of xcriticals.
- The general repair rate (the percentage of reclaimed land to the total destroyed land) of mine wasteland was merely about 10–12 percent.
- In these regions, revegetation and further efforts, such as land reclamation, result from local environmentalist actions.
- A gift from the Mesozoic to the Industrial Age, source of London’s pea soup fogs and of violent labor strikes before the New Deal, coal can feel anachronistic in the twenty-first century.
The toxic water could contaminate groundwater, streams, soil, plants, animals, and human beings. Statistics show that strip mining accounts for about 40% of the world’s coal mining, while open pit mines make up 80% of total coal production. Both mountaintop removal and climate change, the iconic crisis of the age, are geological, changes in chemistry and physical structure of the Earth. Both tell us that we are no longer just scratching the surface, but instead working in our changes very deep, where they will not come out soon.
Environmental Effects of Strip Mining
Chinese coal demand has gone from rapid growth a few years ago, which drove up the value of coal companies, to outright decline. Twice, in 1999 and 2002, federal district courts in West Virginia found that valley fills violated legal duties to protect streams. In 2001 and 2003, the federal appeals court in Richmond, Virginia, reversed those decisions, allowing valley fills to go forward. As a pit is deepened, more and more waste rock must be stripped away in order to uncover the ore. Eventually there comes a point where the revenue from the exposed ore is less than the costs involved in its recovery.
The most common pre-mining landform was a slope with a pitch of 28 degrees, about as steep as the upper segments of the cables of the Brooklyn Bridge. Today, the most common is a plain with a slope of 2 degrees, that is, level but uneven. Across the entire study region, mining has filled a steep landscape with pockets of nearly flat ground. Open-pit mining often (but not always) results in a large hole, or pit, being formed in the process of extracting a mineral. In strip mining a long, narrow strip of mineral is uncovered by a dragline, large shovel, or similar type of excavator.
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This mining technique involves the removal of layers of soil, rock, and vegetation to access buried resources. While strip mining has played a significant role in meeting the world’s demand for minerals and energy resources, it is also a practice that raises complex environmental, social, and economic concerns. It involves the removal of the overlying rock and soil layers in horizontal strips to access the mineral deposits below. The mining process starts at the edge of the deposit and moves inward in successive strips until the entire deposit is mined. One of the primary environmental impacts of open-pit mining is the destruction of natural habitats. The creation of the open pit can also alter the topography and drainage patterns of the area, leading to soil erosion and water pollution.
Consequently, most contour miners need to get rid of their extra spoil in another “valley fill” or disposal zone. The FIA report found the largest decline in production in Appalachia, and predicted that coal mining there would fall a further 8 percent over 2016. On February 22, xcritical scam the Rhodium Group, a consultancy, reported that the combined market value of the largest four American mining companies had fallen from a 2011 peak of $34 billion to just $150 million. Two of the four, Arch Coal and Alpha Natural Resources, filed for bankruptcy last year.
The waste rock and soil are then placed in the lower strips to create a stable base for the next strip. In the past, strip-mined mineral deposits that became exhausted or uneconomical to mine often were simply abandoned. The result was a barren sawtooth, lunarlike landscape of spoil piles hostile to natural vegetation and generally unsuitable for any immediate land use. Such spoil areas are now routinely reclaimed and permanent vegetation reestablished as an integral part of surface-mining operations.
Topsoil Removal
After the mineral has been removed, an adjacent strip is uncovered and its overlying waste material deposited in the excavation of the first strip. Since strip mining is primarily applied to thin, flat deposits of coal, it is not discussed here (see coal mining). In hilly terrain, only a few cuts are all that is usually profitable because the depth of overburden increases rapidly into the hillside. Since the worst complications as a result of strip mining occur on hillsides, the environmental price for a limited amount of coal is very high.
After removing the coal from the initial cut, the operator makes a second, parallel cut. The operator positions the overburden from the second cut into the ditch formed by the original cut and grades and compresses the spoil. After the removal of vegetation and top layer of soil, area mining commences with a preliminary rectangular cut (called the box cut). Area mines dig huge rectangular pits, cultivated in a succession of parallel strips or cuts which can range several hundred yards in width and more than a mile in length. Strip mining is only applicable when the ore body to be dug is somewhat close to the surface.
Because of their high mobility, very large-capacity wheel loaders (front-end loaders) are also used in open-pit mines. 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. However, in agriculturally rich areas like Illinois and Indiana there is a growing concern over the onetime disruption of land for mineral extraction, compared to the long term use for food production. In the US, between the years 1930 and 2000, coal mining transformed around 2.4 million hectares [5.9 million acres] of natural landscape, bulk of it formerly forest.
This initial, or drop, cut is then progressively widened to form the new pit bottom. Miners make cuts along these seamed slopes, getting at any thin coal seams along the surface. This strip mining https://xcritical.solutions/ method produces a terraced effect along the shape of the hill or mountain. This method evolves from auger mining, but it does not include the removal of overburden to expose the coal seam.
An air compressor on the drilling machine forces air down the centre of the drill string so that the cuttings are removed. In smaller pits holes are often drilled by pneumatic or hydraulic percussion machines. The land disturbance necessary for most strip mining techniques results in devastating changes to natural landscapes.
Open-pit mining is a type of strip mining that involves the excavation of a large, open pit in the ground. This method is commonly used for mining minerals such as copper, gold, and silver. The mining process involves the removal of the overlying rock and soil layers to access the mineral deposits below.