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23 Chapter Two: Mining Coal

As coal is cut from one strip, the overburden is cleared ahead of it, and then put into the dug-out area behind it, known as backfill. About two- thirds of US surface mines use this method. Open pit mining uses similar machines to dig coal from a huge hole or pit, which gets wider and deeper until the coal runs out. Contour mining follows the coal seam along the contour or slope of a hillside. Again overburden is removed, the coal excavated, and the overburden and leftovers, or spoil, from the second cut fills the first one. This style is typical of rolling hills with exposed coal seams, as in the Appalachian Mountains. Less common methods are pit mines, augers, and dredging (see sidebar). Another more recent method is mountaintop removal (MTR), or mountaintop mining (MTM). If there are coal seams in

Rarer Forms of Surface Mining • Pit mines have narrow holes or pits dug into steeply dipping coal seams. • Auger mining uses an auger—a huge drill-type device like a massive corkscrew, perhaps 7 feet (2 meters) wide. It churns into the seam and carries the coal out. • In dredging , coal or other minerals are scooped up by a crane with a large bucket, which sits on a floating ship or barge.

the lower levels of a hill or mountain, the soil and rocks above—perhaps 1,000 feet (almost 300 meters) high—are “sliced off ” by diggers and excavators, as overburden. The exposed coal is then dug out. In some areas, the overburden is dumped into nearby valleys or hollows. The result is that the whole landscape is flattened. The overburden may also be replaced in an effort to remake a hill or mountain, lower than the original, as an attempt at “rehabilitation.” This mining method has caused huge controversy, as explained later. Underground (Deep) Mining Several types of mine are used to get at coal seems deep underground. In a drift mine, the tunnel goes straight into a hillside. In a slope mine, the tunnel angles down to follow a sloping coal seam. In a shaft mine , vertical tunnels or “shafts” go straight down. Usually there are two or more shafts, for workers and machines to go in, for