| 21. | By 1912, surface mining was conducted with steam shovels designed for coal mining.
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| 22. | From 1928 until the 1960s it was planted on surface mine spoils in Indiana.
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| 23. | Surface mining disrupts virtually all aesthetic elements of the landscape.
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| 24. | Sediment contamination of surface water is common with surface mining.
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| 25. | MinePro is a primary sales channel for surface mining equipment.
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| 26. | Limited deep mining resumed under contractors and contract surface mining continued into the 1990s.
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| 27. | Globally, about 40 percent of coal production involves surface mining.
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| 28. | Downstream from the gorges, a large surface mine producing cement from a limestone deposit.
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| 29. | A representative example of the period are Puzzlewood's surface mines.
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| 30. | About two-thirds of Appalachia's coal is produced by surface mining.
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