Coal - Energy Policy Analysis: A Conceptual Framework - page 20

with rolling to steep terrain. It was once common to deposit the spoil on the downslope side of
the bench thus created, but this method of spoil disposal consumed much additional land and
created severe landslide and erosion problems. To alleviate these problems, a variety of methods
were devised to use freshly cut overburden to refill mined-out areas. These haul-back or lateral
movement methods generally consist of an initial cut with the spoil deposited downslope or at
some other site and spoil from the second cut refilling the first. A ridge of undisturbed natural
material fifteen to twenty feet wide is often intentionally left at the outer edge of the mined area.
This barrier adds stability to the reclaimed slope by preventing spoil from slumping or sliding
downhill (OSM 1987, 5).
When an operation reaches a predetermined stripping ratio (tons of overburden per tons of
coal), it is not profitable to continue contour mining. Depending on equipment available, it may
not be technically feasible to exceed a certain height of highwall. At this point, it may be possible
to produce more coal with the augering method, in which spiral drills bore tunnels into a highwall
from the bench roughly horizontally up to 200 feet into a seam to extract coal without removing
the overburden (Christman et al. 1980, 78).
Mountaintop Mining
Mountaintop mining combines area and contour strip mining methods. In areas with rolling or
steep terrain and a coal seam occurring near the top of a ridge or hill, the entire mountaintop is
removed in a series of parallel cuts. Overburden is deposited in nearby “valley fills,” in steep ter-
rain where there are limited disposal alternatives. This method usually leaves ridge and hill tops
as flattened plateaus (Christman et al. 1980, 79).
Spoil is placed at the head of a narrow, steep-sided valley or hollow. In preparation for filling
this area, vegetation and soil are removed and a rock drain constructed down the middle of the
area to be filled, where a natural drainage course previously existed. When the fill is completed,
this underdrain will form a continuous water runoff system from the upper end of the valley to the
lower end of the fill. Typical head-of-hollow fills are graded and terraced to create permanently
stable slopes (OSM 1987, 5). In the United States, mountaintop coal mining operations are con-
centrated in eastern Kentucky, southern West Virginia, western Virginia, and Tennessee (USEPA
2005). When the ratio of tons of overburden removed to tons of coal recovered exceeds an eco-
nomically defined limit, the mine operator has three alternatives: (1) if conditions are favorable,
continue mining the seam with underground methods; (2) continue mining with auger mining; or
(3) close down the mining operation.
Environmental Costs of Surface Mining
Surface mining of coal destroys the genetic soil profile, degrades air quality, eliminates existing
vegetation, displaces or destroys wildlife and habitat, alters current land uses, and to some extent
permanently changes the general topography of the area mined (Hamilton 2005; OSM 1979).
During mining, the land surface—often hundreds of acres—is dedicated to mining activities
until it can be reshaped and reclaimed.
Soils
The community of microorganisms and nutrient cycling processes are upset by movement, storage,
and redistribution of soil. Generally, soil disturbance and associated compaction result in condi-