Coal mined at the Trapper Mine is delivered by truck to the Craig Station at an average rate of approximately 2.3 mtpy (with a maximum rate of 2.6 mtpy). The coal is mined from seven coal seams of the Upper Williams Fork Formation: the “H,” “I,” “K,” “L,” “M,” “Q,” and “R” seams. Within the Project Area, the “R” seam is too deep for surface mining. Draglines were the primary earthmoving equipment used until October 8, 2006, when a 250-acre landslide occurred within the Project Area. Following the landslide, mining has been accomplished by a combination of dragline, dozer, and truck and loader operations, depending on the depth and material being mined.
The overburden, or rock that lies above the coal seams to be mined, is drilled and blasted to break up the rock to allow it to be moved using the mining equipment. Blasting is performed using an ammonium nitrate and fuel oil (ANFO) mixture. After overburden blasting is completed, the overburden removal begins. For the Project Area, overburden removal would occur primarily using trucks and loaders. The maximum coal depth for the Project Area would involve the initial use of trucks and loaders because the draglines cannot economically remove materials deeper than 200 feet. The overburden ranges in depth from 100 to 150 feet.
Following removal of overburden by the trucks and loaders, dozers scrape the remaining thin layer of overburden material to expose the uppermost coal seam. Coal is either ripped with a d ........
