Surface coal mining in the Appalachian coalfield states of Kentucky, Tennessee, Virginia, and West Virginia is conducted by a variety of mining methods and in different topographic settings. "Mountaintop mining" considers all types of surface coal mining (mountaintop removal, contour, area, etc.) in the steep terrain of the central Appalachian coalfields.
Typical reclamation of a mountaintop coal mine site.
Mountaintop coal mining is a surface mining practice involving the:
- (1) removal of mountaintops to expose coal seams, and
- (2) disposing of the associated mining overburden in adjacent valleys, "valley fills".
Removal of overburden and interburden (rock above and between coal seams, respectively) during mountaintop mining operations results in generation of excess spoil, because the broken rock will not all fit back into the mining pit. The excess spoil must be placed in disposal sites adjacent to the mining pits in order to allow for efficient and economical coal extraction.
Typical locations for excess spoil disposal sites are valleys, also known as heads-of-hollows or uppermost (headwater) stream reaches. The usual method of disposing of this excess spoil is to place it in engineered earthen and rock structures known as excess spoil disposal areas or colloquially known as head-of-hollow fills, hollow fills or valley fills.