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| STRIP MINING |
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- 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.
Contour mining allows for the extraction of coal from mountainous areas,
where it is not feasible to extract the entire seam, using mountain top
removal mining. Contour mining allows for the partial removal of the coal
seam at the elevation of the coal seam. Quite often, contour mining is
utilized in more than one location on the same mountain.
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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