Pennsylvania’s coal mining region includes most of the western half of the state plus four large areas in the eastern half.  Coal-bearing rocks originally covered much of the remainder of the state as well, but erosion has long since stripped them away, leaving older rocks exposed at the surface in these areas.  The bituminous and coke coal industries were responsible for the late nineteenth century industrial growth of western Pennsylvania, largely to support the iron and steel industry.  Pennsylvania accounts for approximately 6.5 percent of total U.S. coal production.

At present, two main methods are used to extract coal in Pennsylvania—underground mining and open-pit (i.e. strip) mining. The particular method employed depends on a number of factors, such as surface topography, nature of the coal seam, property ownership, and ultimately, the economics of each situation.  Underground mining is the oldest method and historically has produced by far the greatest tonnage. The coal is removed from a shaft excavated down from above. Until recently, most underground mines employed the room-and-pillar mining method in which large “rooms” of coal are excavated, and intervening “pillars” of coal are left to hold up the roof. The room-and pillar method recovers only slightly more than half of the coal present, as the rest must be left in pillars and is effectively lost.  In the mid-1980s, another system of underground mining—termed the longwall method—has been increasingly used. In longwall mining, a single block of coal, sometimes more than 1,000 feet wide and 10,000 feet long, is mined by equipment that continuously shears coal off the face of entire width of the block. All of the coal is removed and the mine roof is allowed to collapse behind in a carefully controlled manner. Where a coal bed is sufficiently thick and continuous, longwall mining is very efficient and can produce a large amount of coal in a short time. In open-pit mining (also called strip mining) the rocks overlying a coal seam are first broken up by blasting and then removed by large excavators, allowing removal of the exposed coal. Open-pit mining, though highly efficient—often able to recover virtually all of the coal at a site—is usually limited to those areas where the rock cover over the seam is less than 100 feet thick.

The economic benefits derived from the widespread use of coal have not come without serious cost to the environment. Acid drainage from coal-mining operations has caused extensive pollution of streams and loss of fish and other wildlife. Mining also results in disruption of groundwater resources, soil erosion, scarring of the land, and habitat loss and fragmentation, especially in open-pit mining. Abandoned piles of waste material left behind from coal mining and coal processing blight many areas and contribute to surface water and groundwater pollution.  Increasingly strict regulation of coal mining and processing has reduced harmful side effects, and remedial work has corrected some of the past damage. Still, many mining-related environmental problems will persist into the future.

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