Opinion ID: 3039629
Heading Depth: 3
Heading Rank: 1

Heading: Longwall Mining and Bleeder

Text: Ventilation This case grows out of problems encountered while Cumberland was using a technique called “longwall mining” to extract coal from a mine in Greene County, Pennsylvania. Longwall mining involves the use of cutting machines to shear coal from one face of a large rectangular block, or 3 panel, of coal. In preparing to engage in longwall mining, a number of tunnels, sometimes called “entries,” are created in a coal seam, offsetting the block of coal to be mined. Some of these entries are “travelable,” meaning that people may safely move through them to access the mine. Mining equipment is installed directly adjacent to one of the walls of the block of coal, which wall, though it is in this instance one of the two of shorter width, becomes known as the “longwall face” and is the surface from which the coal is severed. In addition to the shearer that severs the coal from the longwall face, the mining equipment also includes conveyor belts to transport the coal. As the cutting head of the shearer moves back and forth across the longwall face, severed coal falls onto the first conveyor belt, which is positioned parallel to the face and transports the coal to a stage loader. The stage loader in turn feeds the coal onto another conveyor belt system for removal from the mine. The end of the longwall face towards which the first conveyor belt directs the severed coal for removal is called the “headgate,” and entries on that side of the panel are “headgate entries.” The opposite end is called the “tailgate,” and the entries there are “tailgate entries.” Longwall mining requires the use of hydraulic roof supports, or shields. These shields support the roof over the area being mined, advancing with the longwall face as the coal is removed. As the shields are moved, the unsupported roof material falls behind them to create what is called the “gob.” Though it has a nontechnical ring, the word “gob” is a term of art meaning “the space left by the extraction of a coal 4 seam into which waste is packed or the immediate roof caves.” (Respondent’s Brief at 8 n.6 (citing Am. Geological Inst., Dictionary of Mining, Mineral and Related Terms 239 (2d ed. 1997)).) In short, the term is used to describe the area behind the shields where coal has been extracted and the roof has been permitted to cave in. The gob is also sometimes referred to as the “worked-out area” or the “mined-out area.” Because methane gas, which is noxious and potentially explosive, is released during mining, a “bleeder system” or “bleeder ventilation system” is used to ventilate worked-out areas. “Bleeder entries” are integral to the bleeder system, serving as special air courses, or pathways, designed to remove methane from areas where mining has resulted in the extraction of a substantial portion of the coal.1 The bleeder system dilutes methane coming from the gob with fresh air coming through the bleeder entries. The entries may be connected to one another by “crosscuts,” which are small passageways usually driven at right angles to the entries. Air containing higher levels of methane exits the gob and enters the bleeder entries through connector entries that may contain 1 More technically, the bleeder entries are defined as “[p]anel entries driven on a perimeter of a block of coal being mined and maintained as exhaust airways to remove methane promptly from the working faces to prevent buildup of high concentrations either at the face or in the main intake airways.” (Respondent’s Brief at 6 n.4 (citing Am. Geological Inst., Dictionary of Mining, Mineral and Related Terms, 55 (2d ed. 1997)).) 5 adjustable ventilation control devices. The points at which air from the gob goes into the bleeder entries can be used for measuring methane concentrations and hence are called “bleeder evaluation points,” or “BEPs.”