U.S. DEPARTMENT OF THE INTERIORBUREAU OF LAND MANAGEMENT
|Rock Springs Field Office|
How is coal formed? Coal is a fossil fuel that consists predominantly of carbonized plant material. Millions of years ago, the Wyoming climate was humid and mild enough to support dense, rich forests; as evidenced by the abundant plant fossils found in the coal-bearing rocks of the area. Peat beds, composed of the dead plant material derived from these forests, formed in swamps adjacent to ancient rivers that once flowed across this part of Wyoming. Over time and exposure to both pressure and heat, the peat was compressed and altered to form coal beds.
Early coal mining: Coal was initially discovered in Wyoming in 1843 by the Fremont Expedition. Coal mining began in the Rock Springs area with the arrival of the railroad in the early 1860’s. Large amounts of coal were needed to power the steam engines. Underground mines were opened on the seam outcrops and drifted back into the hillside until the pressure from the overlying rock became too great to allow the entries to stay open safely. Early underground coal mining primarily used drilling, blasting, loading and hauling to remove the coal from the face. Most of these tasks were done manually as very little automation existed. Modern-day coal mining in the area now occurs both underground and on the surface with larger, more automated equipment.
Modern coal mining: Modern underground mine workings are developed methodically using room-and-pillar and longwall panel layouts. The coal is sheared from the face with either longwall shearers or continuous miners and then loaded onto conveyor belts that haul it to the surface.
Current surface coal mining techniques use a near concurrent cycle of material removal and backfill. A pit is opened by removing the topsoil, which is either used to reclaim other mined- out areas or stockpiled for later use. Then, the overburden material overlying the coal is removed and carried around behind the pit and is placed in an area where the coal has previously been recovered. The exposed coal is loosened by blasting and then removed by large power shovels scrapers, or front-end loaders and loaded into large dump trucks. These haul trucks take the coal to a centrally located load-out area where it is blended and loaded onto a conveyor belt which takes it to a stockpile, unit train, or a power plant. As the pit progresses, the backfilled areas are regraded to approximate original surface contours. Topsoil is replaced and subsequently the area is seeded with indigenous plants.
Where is coal mined in southwestern Wyoming? Presently, coal deposits in the Rock Springs vicinity are being mined from the northeastern flank of the Rock Springs Uplift located in Sweetwater County, Wyoming. Two different operators are recovering coal from the Almond, Fort Union and Lance Formations; one operation is surface, the other is underground and surface. Coal mining also occurs near Kemmerer in Lincoln County, Wyoming. This deposit is composed of multiple coal seams in the Adaville Formation that dip steeply to the west. Due to this unique geologic setting, the operator has developed Wyoming's deepest open-pit coal mine.
Statistics: The BLM Rock Springs Office oversees management of approximately 42,000 acres of federal coal leases held by the four different operators. These operators are Bridger Coal Company and Black Butte Coal Company, both located to the east of Rock Springs, and P&M located near Kemmerer and Arch Coal, Inc., east of Hanna, WY. Annual combined output for these mine operations in 2006 exceeded 13.9 million tons of coal, produced by a labor force numbering 864 people.