Surface Mining

Surface mining of coal is an alternative to underground mining and is practiced as strip mining, the most common form, and auger mining. Some coal is also produced through dredging and culm bank (i.e., anthracite waste piles) recovery; however, these quantities are relatively small compared to underground, strip, and auger mining. The quantities of coal produced in 2002 by the various methods, as reported by MSHA, are listed in Table 3-2 [14]. Note that the production totals reported by MSHA and those of the National Mining Association/Energy Information Administration (see Figure 2-10) differ slightly.

Strip mining is favored when the overburden (the overlying rock strata) is typically 200 feet or less in thickness but can be economical with overburden thickness up to 600 feet [15]. Another factor that is considered when determining the economics of strip mining is the stripping ratio, which is the ratio of overburden thickness to coal seam thickness. Typically, the maximum stripping ratio that is economical is 20 to 1 [4]. The two general methods of strip mining are area mining and contour mining. In area mining, a trench is dug, the overburden is piled to one side, and the coal is removed. As mining progresses, the overburden from the new trench is dumped into the first trench. In contour mining, which is used when coal lies beneath hilly terrain or outcrops on a hillside, the overburden is removed and dumped on the downhill side of the mining operation [3].

Auger mining can be used for coal outcrops on a hillside or in strip mines where the stripping ratio has become too high to be economical for strip mining [4]. In auger mining, an auger drills it way into the face of the coal seam, and the coal is removed via conveyor and loaded directly onto a truck.

Many adverse environmental impacts could potentially result from area surface mining of coal if no reclamation practices are used. Such measures are used with varying degrees of effectiveness in the United States [1]. Air quality can be affected in several ways. Fugitive dust from coal

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