Mountaintop removal (MTR) is a method of surface mining predominantly used in the Appalachian Mountains to access deep, thin seams of coal. This technique involves radically altering the topography of a ridge or peak by removing the earth and rock, known as overburden, that lies above the target coal layers. The process uses sequential, large-scale mechanical actions and explosives to efficiently expose and extract the subterranean resource.
Site Preparation and Overburden Drilling
The MTR process begins with clearing the mining site to prepare for the massive earth-moving operation. All timber and vegetation are removed from the designated mine pit and waste disposal areas. Following the clearing, any available topsoil is stripped from the surface and stored separately for use during the reclamation phase.
Geotechnical specialists plan the controlled destruction of the mountain above the coal seam. This involves drilling a precise grid of deep holes, known as blast holes, into the rock and subsoil overburden. The number and depth of these boreholes are calculated to ensure effective fragmentation of the rock layers during the subsequent blast.
These blast holes, which can extend hundreds of feet into the mountain, contain the explosives that will shatter the dense rock. The drilling phase guides the removal of sometimes 400 to 800 vertical feet of mountain elevation. This preparatory work determines the volume of fragmented material, or “spoil,” that must be handled later.
The Blasting Phase
The core action of mountaintop removal is the use of high-volume explosives to fracture and loosen the immense quantity of overburden. Once the blast holes are drilled, they are charged with explosive material, typically Ammonium Nitrate and Fuel Oil (ANFO). ANFO is an inexpensive industrial explosive ideal for large-scale rock blasting.
The precise timing and sequencing of the detonation are controlled to maximize fragmentation while minimizing ground vibration. The resulting explosion shatters the solid rock into loose debris, exposing the coal seams hundreds of feet below the original surface.
A single detonation event displaces hundreds of tons of rock and soil. The blast is designed to break the rock and move the majority of the overburden off the exposed coal seam. This resulting material, called spoil, must be cleared away before the coal can be accessed.
The blasting phase is repeated incrementally as the mining operation advances across the mountain, gradually exposing successive coal seams. Each blast is engineered to create a manageable volume of fragmented rock for heavy machinery to move.
Coal Seam Recovery
Once the overburden has been blasted and pushed aside, the coal seams are exposed and ready for extraction. This recovery phase utilizes specialized, enormous earth-moving equipment. Power shovels, front-end loaders, and massive draglines are the primary tools employed to scoop the coal directly from the exposed seam.
Draglines are effective for this task, as their large buckets move immense quantities of material in a single pass. These machines scrape the coal layer by layer, working through multiple seams. The coal, mixed with small amounts of residual rock fragments, is loaded into large haul trucks.
These specialized trucks transport the raw coal away from the mine pit to a nearby processing facility, often called a preparation plant. At the preparation plant, the coal undergoes cleaning to separate it from remaining rock, ash, and other impurities. This process prepares the coal for shipment to power plants.
The MTR method allows for a high percentage of the coal in the seam to be recovered. The recovered coal is then ready for distribution via rail or truck to domestic and international markets.
Managing Waste Rock and Initial Reclamation
The extraction sequence concludes with managing the vast quantities of waste rock, or spoil, generated by the blasting phase. This material must be permanently disposed of because its volume far exceeds the capacity of the original mine pit.
The primary disposal method involves creating “valley fills,” where the excess spoil is systematically dumped into adjacent valleys and stream beds. These fills can be hundreds of feet deep and extend for miles, permanently burying headwater streams and altering the local watershed. The placement of the spoil is a planned engineering process designed to stabilize the material into a permanent, man-made landform.
Following coal recovery, the mining company is required by law to begin the initial reclamation process. This involves grading the remaining disturbed area to create a gentler slope than the original mountain. The stored topsoil is then spread over the regraded surface, and the area is typically seeded with grasses and non-native vegetation to prevent erosion and stabilize the new landscape.