The Contour or Bench method of surface or strip mining is usually associated with coal, where a seam or multiple seams are located at a certain elevation or elevations through a mountain or hill.
The process of contour mining begins with constructing roads to access the coal seam elevation and the top or the mountain. A bench is excavated in the mountain at the coal seam elevation, allowing for room for the mining equipment and facilities. From the top of the mountain, drills are used to drill the overburden and place explosives in the holes. They are systematically detonated, blasting the rock where it can be loaded using shovels and loaders, into large haul trucks, and transported to a fill area. Much of the rock will later be used to backfill the mined area, restoring it to a mountainous contour.
Once the overburden (rock covering the coal seam) is removed, the coal is mined, in the same method. The coal is then crushed and sized and usually sent to a process or preparation plant to remove non-coal material.
In the design and planning of the mine, surface disturbance is usually minimized, and great efforts are expended to control the effects of mining, such as dust, blast vibrations, water runoff, so as to not impact the environment in a negative way.
When the coal is depleated by contour mining, Augers are usually used to bore holes into the outcrop of the coal seam to extract more coal. Then the holes are filled, the contour bench is reclaimed in accordance with applicable state and federal laws.
In Fig. 1, the original mountain contour is shown, with the coal seam and the overburden and coal to be removed.
In Fig. 2, the bench is shown after the overburden and coal seam has been mined.
In Fig. 3, the post mining mountain is shown, with the backfilled and planted hillside in place.
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