LOCAL GEOLOGY The most prolific lignite-bearing stratum in the state is the Sentinel Butte Formation of the Fort Union Group. The most prominent characteristics of the Fort Union Group formations are the cyclical deposition and lateral persistence of the lithologic units, especially the lignite seams. The Sentinel Butte Formation is a continental deposit comprising interbedded calcareous clays, sandy clays, and lignite beds, with isolated lenses of fine-grained sands, silts, and rare limestones, ranging in color from light gray to dark brown and black. Except for the limestones and an upper sandstone unit, the sediments are essentially nonindurated. The claystone and sandstones are generally thinly bedded and not jointed. These sediments were deposited mainly in swamps or in the floodplains of very slow, meandering rivers. The Sentinel Butte Formation conformably overlies the Tongue River Formation (also known as the Bullion Creek Formation). The Golden Valley Formation, which is stratigraphically above the Sentinel Butte Formation elsewhere, is present near the permit boundary, but is gone in the permit area due to postdepositional erosion; therefore, the younger glacial deposits of the Coleharbor Group unconformably overlie the Sentinel Butte Formation in the study area. Outcrops of the Sentinel Butte Formation are sporadic; bedrock is largely masked by residual soils, slopewash, and/or glacial drift. Where the entire Sentinel Butte Formation is present, as in western Merc ........

The lignite at Coyote Creek Mine surface mining operation is recovered using dragline and conventional truck and shovel mining methods due to the proximity of the lignite to the surface and the physical characteristics of the deposit. Mining operations includes; suitable plant growth material (SPGM) removal, replacement and storage, overburden removal, lignite production, and spoil backfill and grading. In the development phase, drainage and water control were established, and then the required infrastructure consisting of power, mine office and maintenance facilities, lignite stockpile facilities, and roadways were established.

ANNUAL AND TOTAL LIGNITE PRODUCTION
The Coyote Creek Mine is designed to supply a maximum of 2.5 million tons but generally supplies approximately 1.7 to 2.0 million tons of lignite per year to the adjacent Coyote Station Power Plant through 2040. Actual production is dictated by customer utilization. Approximately 36 Mt of lignite is expected to be mined and sold from 2022 through 2040 bringing the projected 25-year LOM tonnage to approximately 46 Mt since the mine’s inception.

TYPE AND GENERAL MINING METHOD
The Coyote Creek Mine is a single lignite seam surface mining operation, which currently encompasses approximately 8,444 acres within the permitted areas.

Coyote use standard surface mining techniques to extract lignite. Suitable plant growth material (SPGM) will generally be removed by tractor-scrapers ........

- subscription is required.

- subscription is required.