2022-09-06_REPORT - C1982056 (3)

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Foidel Creek Mine C-82-056 2021 Annual Hydrology Report 1.0 INTRODUCTION The 2021 Annual Hydrology Report (AHR) presents hydrologic monitoring data collected during the 2021 water year (October 2020 — September 2021) at the Twentymile Coal, LLC's (TC's) Foidel Creek Mine. This AHR fulfills the reporting requirements under the Colorado State Division of Reclamation Mining and Safety (DRMS) Permit No. C-82-056. 2.0 SITE LOCATION AND BACKGROUND The TC Foidel Creek Mine is located approximately 20 miles southwest of Steamboat Springs, Colorado, at the south end of Twentymile Park (see Figure 1). The Foidel Creek Mne is an active underground coal mine, that encompasses roughly 15,200 acres in south Routt County. The total Life-Of-Mine permit area includes approximately 22,647 acres. The primary surface facilities, including sediment basins, coal refuse pile, coal wash plant, and loadout areas, cover about 800 acres. The mine's portals and surface facility areas are bordered on the south and southwest by strip mine spoils from the former Colorado Yampa Coal Company (CYCC). Other associated satellite TC support facilities, including borehole and ventilation pads, contribute approximately 150 acres. Surface coal mining has been conducted in the area since the 1960's. The Foidel Creek Mine is an underground longwall operation that was established in 1983. Longwall mining is a form of underground mining where a 1000-foot-long wall is mined in a single slice (typically 2-3 m thick). The block of coal being mined, known as the longwall "panel", may be on the order of 12,000 feet long. The gate road along one side of the wall is called the main gate, while the other side is called the tail gate. The end of the block that includes the longwall equipment is called the "face". Air is provided by ventilation fans and associated bleeder vent shafts from the surface. The advantage of longwall mining is that over 80 percent of the coal is recovered, compared with about 50 percent for the traditional pillar method. In addition, subsidence is immediate, allowing for better planning by the mining company. The Foidel Creek Mine portals are faced-up in the down dip high-wall of the former strip mine. The permit area lies within the Trout Creek watershed is drained to the east-northeast by Fish Creek, Foidel Creek, and Middle Creek. Foidel Creek is located adjacent to the TC Foidel Creek Mine surface facilities and receives treated effluent from a series of sediment ponds established at 1