The economically mineable coal in the reserve occurs in the Sentinel Butte Formation, and is overlain by the Coleharbor Formation. The Coleharbor Formation unconformably overlies the Sentinel Butte Formation. It includes all of the unconsolidated sediments resulting from deposition during glacial and interglacial periods. Lithologic types include gravel, sand silt, clay and till. The modified glacial channels are in-filled with gravels, sands, silts and clays overlain by till. The coarser gravel and sand beds are generally limited to near the bottom of the channel fill. The general stratigraphic sequence in the upland portions of the reserve area consists of till, silty sands and clayey silts. [2019, F10K, p. 12, 13]

The mineable coal bed is known as the Upper Beulah bed and is contained within the Sentinel Butte Formation of the Fort Union Group. The Upper Beulah bed ranges generally from 10 to 12 feet in thickness, with a weighted average thickness of approximately 11 feet throughout the permit area. The overburden directly above the Upper Beulah bed ranges in thickness from 15 feet along a portion of the cropline to more than 150 feet. [April-2020, EA, p. 19]

Typical surface mining techniques to extract coal occur in a sequence of seven events:
• suitable plant growth material (SPGM) removal and stockpiling;
• overburden removal;
• coal removal;
• overburden replacement;
• final grading;
• SPGM replacement; and
• revegetation.

Overburden removal includes the removal of any material between the SPGM and the targeted coal bed. Overburden removal is accomplished with the use of draglines, hydraulic truck-shovel fleets, tractor-scrapers, or other auxiliary equipment.

Coal processing equipment consisting of primary and secondary crushing with a rated capacity of 2,000 tons/hour.

The coal processing facility (primary and secondary crushing equipment) and conveyor are located adjacent to the stockpile within the permit boundary. A dozer feeds coal from the unprocessed coal storage pile to an apron feeder, which feeds the primary crusher at the coal processing facility. The coal is then crushed to a prescribed size and transported on a covered conveyor to Coyote Station.