COAL, one of the most important mineral has been valued for many purposes since 1880's and it has been used to generate electricity and utilized for multipurpose operations. The process of Coal mining has developed over the years and different methods have been evolved to extract the mineral which is available in different terrains across the world. The most economical method of extracting coal depends upon the depth and the quality of the coal seams. Coals are mined both from surface and underground.
Contour mining is associated with coal. This bed of coal is located at an elevation in a mountain range or any other hilly area. It is a method of strip or surface mining. It is also referred to as Bench mining. The coal is extracted from a mountainous area where it is not possible to extract the entire seam using mountain top removal mining. Only partial coal removal is done by this method of mining. Most of the time it can be noticed that this kind of mining happens in many locations on the same mountain. It is a method by which the overburden is removed from the coal seam following the contours around a mountain or any hilly area.
The process of mining begins with the construction of road to reach the coal seam located at the mountain top. The excavations of bench in the mountain are first done by placing the mining equipments and then preparing a store for other facilities. Drills are placed from the top of the mountain so as to drill out all the overburdens and to place the explosives in the holes. They are then systematically exploded and thereby the rocks are blasted and carried and shifted to into large haul trucks and finally moved to a fill area. These unused rocks will later be used to refill the mining area. It is then restored back to its original position, the mountainous core. When the rock covering the coal seam is removed the mining of the coal is done and it is crushed and made into the appropriate size .It is finally sent to a preparation plant where the non –coal materials are removed. As far as this method of mining is concerned, it looks into various aspects when the planning of the mine is done in the initial stage.The first step taken is to minimize the surface disturbance .Then efforts are taken to control the effects after the mining process like dust, vibration of the blast, water runoff, and many other causes that can bring negative effect to the environment. To extract more coal, augering method is used to bore holes into the outcrop of the coal seam. Later on, these holes are filled and the contour bench is retrieved according to the state and federal laws. Steps are also taken to plant shrubs and trees in the center of the surface to improve the wildlife habitat.
The limitations of this method of mining are both economical and technical .When the burden undertaken exceeds the coal obtained, the result would be a financial loss. The equipment available may not be able to increase a certain height of the wall, and then it is advisable to shift to augering method.
This method of mining is more prevalent in the steep Appalachian region of the United States. This method first makes a cut on the slope after they find that there is deposit of coal in that particular area. First the overburden is removed and then the coal. This process continues till the proportion of overburden to coal becomes uneconomical. When the resources are exhausted completely the process comes to an end. Coal resources and the operator resources contribute equally to the completion of this process.
The most important equipments which are required for this method of mining are backhoes, shovels, and bulldozers which are all earth moving equipments. These equipments are generally used for many construction activities. The people who are involved in this business can opt out and re enter according to the change in the market condition.
The amount of waste accumulated after this method of mining is comparatively very high to open pit mining. During the process of removal of overburdens some of the compaction is lost. Even after the replacement the volume again increases. The pits are also not large enough to hold this material. As a result the contour miners must find places to dispose this waste in another fill or disposal area.
Economical aspects have to be taken into consideration when the area for mining is fixed. It can be practiced only in areas where it is uneconomical to remove the overburden from the coal seams. The excavation of the coal starts by first removing the overburden and then recovering the coal seams. Excavation helps to understand the depth of the mountain.
In the nineteenth and early twentieth century the coal mines were not that deep. Almost everywhere there were surface mines .Surface coal mining in the early twentieth century included contour mining, which removed the top layer of soil to get a coal seam. But after World War II surface coal mining was enveloped by auger mining, which is a normal part of contour operations. Surface mining was referred to as strip mining or stripping or sometimes as surface mining itself. They often failed to differentiate these different methods of mining. Sometimes it was also called contour mining as it was the closest form of surface mining in Appalachia.
In West Virginia this method of mining was introduced in the 1916 and it was supported by steam technology. In Tennessee this method started slowly but the production like any other mountain states eventually shot up. After the recession period in 1956 we can see that the number of contour operations doubled. However, this method of mining could benefit the states only with mountain ranges. In places where accessibility is not very easy and where no other method of mining can be done, contour mining still prevails as one of the most important methods to excavate coal.