The Wasatch Formation and local Quaternary age deposits comprise all of the overburden lithologies at the mine site. The Wasatch consists of alternating, lenticular deposits of sandstones, siltstones, claystones, coal, and carbonaceous shales. Coal has been mined exclusively from the Wyodak-Anderson (WA) Seam. The remaining coal is 50-87 ft thick and 180 to 460 ft deep within the leased area. The WA seam is in the uppermost section of the Paleocene Fort Union Formation. The coal is thickest on the northwest side of the lease. There are two main geologic features at NARM. The first is a monocline that exists in a northwest to southeast trend over the middle portion of the mine. The lower 12-14 feet of the WA seam splits off as a hanger seam (Lower Wyodak-Anderson, or LWA) and has a steeply dipping gradient after it splits. The LWA seam is not mined because of poor quality and an increasingly high strip ratio. The mineable WA coal thickness averages 80 feet in the west and 60 feet east of the monocline. The second geologic feature is a ribbon split occuring in the southwest portion of the lease and trending northwest to the southeast. The WA splits into two nearly equally thick (30-35 ft) mineable seams: WA1 (upper split) and WA2 (lower split). The midburden between the WA1 and WA2 increases to a maximum of 120 ft thick. Structurally, the WA2 seam remains relatively flat, whereas the WA1 rides up over the parting and has a dipping structure. In conclusion, several thin ride ........

The relatively shallow and very thick coal seam at this deposit determines that the most efficient mining method is the surface striping method which utilizes a combination of processes, including truck and shovel, cast blasting and dozing, dragline, etc. As a result of the high volume of sales with a wide range of quality requirements, the mining operation consists of multiple open pits mainly in four mining areas: West, North, East, and NARM North.

Conventional and cast blasting methods are generally used to fracture and fragment overburden and coal. After the cast blast and before the dragline operation, the backhoes are utilized to remove the shot material in the highwall and scale the highwall back to competent material down to a dragline bench operating level. Dozers are used to push more blasted material into the previous pit where the coal has been removed and at the same time prepare the working bench for the dragline. The dragline typically mines cuts that are 220 feet wide and with a bench height of 140-220 feet. The dragline is typically positioned on the spoil side of the pit when removing this remaining overburden. This allows for much of the dragline's spoil material to be stacked further from the low wall crest to reduce the overall spoil bank slope angle (internal angle of friction) to approximately the natural angle of repose of the shot material and thus minimize the risk of spoil slope failures or loose material rolling into the pit area. Oth ........

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