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Mountaintop removal mining (MTR), also known as mountaintop mining (MTM), is a form of surface mining that involves the mining of 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 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 (120 m) 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."〔(Appeals Court Upholds Mountaintop Removal Mining )〕〔U.S. Environmental Protection Agency, "Mountaintop Mining/Valley Fills in Appalachia: Final Programmatic Environmental Impact Statement," issued 2005 June 25, available at (http://www.epa.gov/region03/mtntop/index.htm ) (accessed 2006 August 20).〕〔(Mountaintop Mining and Valley Fills in Appalachia (MTM/VF) - Programmatic Environmental Impact Statement )〕 Less expensive to execute and requiring fewer employees, mountaintop removal mining began in Appalachia in the 1970s as an extension of conventional strip mining techniques. It is primarily occurring in Kentucky, West Virginia, Virginia, and Tennessee. The practice of mountaintop removal mining has been controversial. The coal industry cites economic benefits and asserts that mountaintop removal is safer than underground mining. Published scientific studies have found that mountaintop mining has serious environmental impacts that mitigation practices cannot successfully address. A high potential for human health impacts has also been reported. 〔http://www.crmw.net/files/Hendryx_mortality_from_heart_respiratory_and_kidney_disease_2009.pdf〕 ==Overview== Mountaintop removal mining (MTR), also known as mountaintop mining (MTM), is a form of surface mining that involves the topographical alteration and/or removal of a summit, hill, or ridge to access buried coal seams. The MTR process involves the removal of coal seams by first fully removing the overburden laying atop them, exposing the seams from above. This method differs from more traditional underground mining, where typically a narrow shaft is dug which allows miners to collect seams using various underground methods, while leaving the vast majority of the overburden undisturbed. The overburden from MTR is either placed back on the ridge, attempting to reflect the approximate original contour of the mountain,〔(【引用サイトリンク】title=Abstract )〕 and/or it is moved into neighboring valleys.〔 Excess rock and soil containing mining byproducts are disposed into nearby valleys, in what are called "holler fills" or "valley fills."〔(Appeals Court Upholds Mountaintop Removal Mining )〕〔(Mountaintop Mining and Valley Fills in Appalachia (MTM/VF) - Programmatic Environmental Impact Statement )〕 MTR in the United States is most often associated with the extraction of coal in the Appalachian Mountains, where the United States Environmental Protection Agency (EPA) estimates that of Appalachian forests will be cleared for MTR sites by the year 2012. Sites range from Ohio to Virginia.〔Copeland (2004) pp.39〕 It occurs most commonly in West Virginia and Eastern Kentucky, the top two coal-producing states in Appalachia, with each state using approximately 1,000 tonnes of explosives per day for surface mining.〔(【引用サイトリンク】 title=U.S. Geological Survey report on consumption of explosives )〕 At current rates, MTR in the U.S. will mine over 1.4 million acres (5,700 km²) by 2010,〔(【引用サイトリンク】 title=Frequently Asked Questions about Mountaintop Removal )〕 an amount of land area that exceeds that of the state of Delaware. Mountaintop removal has been practiced since the 1960s.〔 Increased demand for coal in the United States, sparked by the 1973 and 1979 petroleum crises, created incentives for a more economical form of coal mining than the traditional underground mining methods involving hundreds of workers, triggering the first widespread use of MTR. Its prevalence expanded further in the 1990s to retrieve relatively low-sulfur coal, a cleaner-burning form, which became desirable as a result of amendments to the U.S. Clean Air Act that tightened emissions limits on high-sulfur coal processing. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mountaintop removal mining」の詳細全文を読む スポンサード リンク
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