The Project Area lies within a region that is deformed by several major folds, indicating that various seams have folded over and split. The Project Area occurs on the southern and northern limbs of the generally southeast-trending asymmetrical Collom Syncline and extends east toward the north-northeast-trending Elkhorn Syncline (KEC 2005, USGS 2008). The complex structures seen in the Project Area are overlain by younger sedimentary sequences that reflect upward-diminishing deformation. Periodic movements along the ancestral Axial Fault located north of the Danforth Hills coal field are believed to have been the source of the major deformation seen presently in the Project Area. The latest movement along the fault was during the Laramide Uplift, a Tertiary orogenic event (35-70 million years ago), which led to the uplift of the modern Rocky Mountains. This episode of uplift was a compressional event that eventually formed faults and major folds, such as the Collom and Elkhorn Synclines, and the prominent Axial Basin Anticline, the axis of which occurs in the basin north of the Project Area (BLM 2006).

The coal seams in the Project Area are contained within the Upper Cretaceous Williams Fork Formation of the Mesaverde Group (BLM 2006, USGS 2008). The Mesaverde Group generally consists of a thinly to thickly interbedded succession of shale, siltstone, and sandstone that was deposited largely in a terrestrial environment. The Mesaverde Group is categorized into two f ........

At Colowyo mine, mining is carried out utilizing truck/shovel, dragline and highwall mining techniques.

Colowyo commenced surface mining in 1977 and has mined from four distinct pits during the life of the existing operation. The East Pit was the first pit opened and where mining concluded in 2006. Mining commenced in the Section 16 Pit in 1992 and continued until 2002. Mining in the Section 16 Pit was a single seam operation, whereas, the other pits at Colowyo have required the mining of multiple seams. Reclamation on a majority of the Section 16 Pit occurred from 1993 to 1998. The remaining acres of the Section 16 Pit that have not been reclaimed are supporting ongoing mining activities, and they will be reclaimed with the South Taylor Pit. Mining began in the West Pit in 1994 and mining was concluded in 2014. Currently, the West Pit is in various stages of reclamation. In 2008, Colowyo opened the South Taylor Pit and this pit is the current mining location.

Collom pit (Little Collom X and Collom Lite Pits) project is an expansion of the existing Colowyo Coal Mine.
As current mining operations in the South Taylor pit are being completed and land is being reclaimed, Colowyo Coal is continuing to develop and actively mine the Collom pit at the Colowyo Mine to access coal reserves for future production. Coal production from the Collom pit began in July 2019. Coal seams that would be mined via truck/shovel, dragline, and highwall miner techniques. < ........

Historically and currently, coal is mined from the pits and hauled to a primary crusher. Once it is sized at the primary crusher it is then hauled along the existing haul road to the north northeast approximately 3.9 miles (6.3 km) to the Gossard Loadout. Once coal arrives at the Gossard Loadout it is sized accordingly again, and then loaded on a train for shipment.