The contour mining method is typically used in the mountainous terrain of the Eastern U.S., where coal seams are exposed in outcrops on hillsides and mountainsides. First, a cut is made in the hillside above a coal seam and the coal is further exposed as the overburden is removed.
The mine is then enlarged by successive cuts that follow the coal seam around the side of the hill. The mining extends into the hill to the point where the overburden is too thick to make further exposure of the coal economic. Auger mining often is used at this stage to maximize coal recovery.
The contour mining operation in the illustration is removing multiple seams of coal. Reclamation has been completed in the foreground. Active mining is proceeding around the hill in the middle foreground. A sedimentation pond for this operation was constructed adjacent to a natural drainage swale just below the mining area. As the reclamation is completed, such ponds become unnecessary and usually are removed and the entire site reclaimed and planted.
After the area has been cleared and blasted, the spoil in the active mining area is loaded by front-end loaders into trucks and taken to the previously mined area, where it is spread. As coal is uncovered, it is loaded and trucked to a coal preparation plant. Smaller pieces of equipment are generally used in contour mining than in area mining because of the restricted working area.
As can be seen in the right foreground of the cross section, a temporary highwall is left in the hill at each level of mining after the overburden and coal have been removed, because the mining operation has cut into the hill. One of the principal reclamation requirements for contour mining is that highwalls must be covered after mining is completed. Spoil is trucked from a working cut, dumped on the mined-out area, spread with bulldozers until it covers the highwall, and compacted as necessary to ensure stability of the reclaimed hillside.
As can also be seen in the cross section, a ridge of undisturbed natural material 15 to 20 feet wide is intentionally left at the outer edge of the mined area. This barrier adds to the stability of the reclaimed slope by preventing the spoil from slumping or sliding downhill.
Following backfilling and grading of the spoil with bulldozers, the topsoil is spread and a seedbed is prepared. In steep slope conditions, such as in the middle foreground of the illustration, a slope disk may be used to prepare the topsoil for seeding without having to drive equipment on the steep slope. Hydroseeding may be used to aid in establishing vegetation and preventing soil erosion on steep terrain. This truck-mounted equipment makes it possible to seed the steeply sloping ground from the base or top of the reclaimed slope without disturbing the graded topsoil.
In the completed reclamation area shown in the center foreground of the illustration, seedling trees and shrubs were hand planted to enhance the wildlife habitat, stabilize the site, and provide a long-term economic return from the reclaimed land.