Operations Mining Operations
We currently have eight regional business units, including two in Virginia, four in West Virginia, one in Pennsylvania and one in Kentucky. These business units include 11 preparation plants, each of which receive, blend, process and ship coal that is produced from one or more of our 65 active mines (some of which are operated by third parties under contracts with us). We use two mining methods, underground room and pillar and surface. Underground Room and Pillar Mining. Underground mines in the United States are typically operated using one of two different methods: room and pillar mining or longwall mining. In 2007, approximately 56% of our produced coal volume came from underground mining operations using the room and pillar method with continuous mining equipment. In room and pillar mining, rooms are cut into the coal bed leaving a series of pillars, or columns of coal, to help support the mine roof and control the flow of air. Continuous mining equipment is used to cut the coal from the mining face. Generally, openings are driven 20 feet wide and the pillars are generally rectangular in shape measuring 35-50 feet wide by 35-80 feet long. As mining advances, a grid-like pattern of entries and pillars is formed. Shuttle cars are used to transport coal to the conveyor belt for transport to the surface. When mining advances to the end of a panel, retreat mining may begin. In retreat mining, as much coal as is feasible is mined from the pillars that were created in advancing the panel, allowing the roof to cave. When retreat mining is completed to the mouth of the panel, the mined panel is abandoned. The room and pillar method is often used to mine smaller coal blocks or thin seams, and seam recovery ranges from 30% to 70%, with higher seam recovery rates applicable where retreat mining is combined with room and pillar mining. Productivity for continuous room and pillar mining in the United States averages approximately 3.5 tons per employee per hour, according to the U.S. Energy Information Administration (EIA). The other underground mining method commonly used in the United States is the longwall mining method, which we do not currently use at any of our mines. In longwall mining, a rotating drum is trammed mechanically across the face of coal, and a hydraulic system supports the roof of the mine while it advances through the coal. Chain conveyors then move the loosened coal to an underground mine conveyor system for delivery to the surface. Our Central Appalachian reserves often include non-contiguous seams of coal that can be extracted at a lower cost using continuous mining as opposed to the more capital intensive longwall method. Surface Mining. Surface mining is used when coal is found close to the surface. In 2007, approximately 44% of our produced coal volume came from surface mines. This method involves the removal of overburden (earth and rock covering the coal) with heavy earth moving equipment and explosives, loading out the coal, replacing the overburden and topsoil after the coal has been excavated and reestablishing vegetation and plant life and making other improvements that have local community and environmental benefit. Overburden is typically removed at our mines using large, rubber-tired diesel loaders. Seam recovery for surface mining is typically 90% or more. Productivity depends on equipment, geological composition and mining ratios and averages 4.8 tons per employee per hour in eastern regions of the United States, according to the EIA. |