Open-pit mining: Difference between revisions

Revision as of 09:08, 12 August 2023

Revision as of 05:47, 14 October 2023

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{{main|Land rehabilitation#mine rehabilitation}}

[[File:New_Antelope_Rochelle_Coal_Mine.png|thumb|alt=A reclaimed area next to an active mine is now grassy hills.|A loadout station and reclaimed land at the [[North Antelope Rochelle Mine|North Antelope Rochelle]] open-pit [[coal]] mine, in [[Coal mining in Wyoming|Wyoming]], [[United States]]]]

After mining ends at a ___location, the mine area may undergo [[land rehabilitation]]. Waste dumps are contoured to flatten them out, to further stabilize them. If the ore contains [[sulfides]] it is usually covered with a layer of [[clay]] to prevent ingress of [[rain]] and [[oxygen]] from the air, which can oxidize the sulfides to produce [[sulfuric acid]], a phenomenon known as [[acid mine drainage]].<ref>Walter Geller; Helmut Klapper; Wim Salomons (6 December 2012). Acidic Mining Lakes: Acid Mine Drainage, Limnology and Reclamation. Springer Science & Business Media. {{ISBN|978-3-642-71954-7}}.</ref> This is then generally covered with [[soil]], and vegetation is planted to help consolidate the material. Eventually this layer will erode, but it is generally hoped that the rate of leaching or acid will be slowed by the cover such that the environment can handle the load of acid and associated heavy metals.<ref>Vasudevan Rajaram; Subijoy Dutta; Krishna Parameswaran (30 June 2005). Sustainable Mining Practices: A Global Perspective. CRC Press. pp. 207–. {{ISBN|978-1-4398-3423-7}}.</ref> There are no long term studies on the success of these covers due to the relatively short time in which large-scale open-pit mining has existed. It may take hundreds to thousands of years for some waste dumps to become "acid neutral" and stop leaching to the environment. The dumps are usually fenced off to prevent [[livestock]] denuding them of vegetation. The open pit is then surrounded with a [[fence]], to prevent access, and it generally eventually fills up with [[ground water]]. In arid areas it may not fill due to deep groundwater levels.<ref>[http://www.dmp.wa.gov.au/documents/mine_rehab.pdf "MINE REHABILITATION"] ''Department of Mines and Petroleum'' (October 2006) accessed 19 December 2011</ref> Instead of returning the land to its former natural state, it may also be reused, converting it into recreational parks or even residential/mixed communities.<ref>[http://lev.archi/mines2cities "Mines2Cities"] {{webarchive |url=https://web.archive.org/web/20160919141717/http://lev.archi/mines2cities |date=2016-09-19}} ''The Mines2Cities Project'' (April 2016) accessed 19 April 2016</ref> In Germany, the world's largest producer of [[lignite]] (virtually all of which these days is mined open-pit), the former mines are usually converted to [[artificial lake]]s. To mitigate the problem of acid mine drainage mentioned above, flooding is often done with the water of nearby rivers instead of using groundwater alone. In some cases, [[calcium oxide]] or other basic chemicals have to be added to the water to neutralize the [[pH]]-value.

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{{panorama|image = Tarnobrzeg, zalew Machowski.jpg|caption = An open-pit sulfur mine at [[Tarnobrzeg]], Poland, undergoing land rehabilitation|height = 125|alt = An artificial wetland.}}