The Black Thunder mining complex currently consists of four active pit areas and two active loadout facilities.
The pits are typically 200 to 230 feet wide, with pit lengths ranging from 4,310 feet to 16,906 feet in the LOM Plan. The typical pit configuration is an initial truck/shovel pass for prestrip, since the draglines cannot handle the total depth of overburden. In some areas, coal (Wyodak Rider seams) is encountered in the prestrip and where quality is acceptable, it is mined. Most of the overburden is blasted, although there are some unconsolidated areas where blasting is not required.
The mining method at the Black Thunder Mine is surface mining utilizing draglines and truck/shovel mining equipment. The Black Thunder Mine is mining the Upper and Main splits of the Wyodak Seam and parting interval within the seam utilizing draglines, shovels, front-end loaders, trucks, dozers, or scrapers in three long pits.
The Black Thunder Mine currently operates a fleet of four draglines and nine shovels for overburden removal and four shovels for coal removal from three pits. The shovels develop a series of benches that range from 50 to 100 feet to prepare a bench for the draglines. A fleet of seven diesel-powered drills create 12-1/4-inch boreholes at a 60 degree angle for cast-blasting the overburden 150 feet above the coal. The draglines remove the overburden above the coal from a bench created by the dozers, after the cast-blast. After the ove ........