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2019 Plan of Operations Modification American Gypsum Company, LLC <br /> 6.0 MINING PLAN <br /> The proposed Modification would be a continuation of current mining operations. According to <br /> existing permits, the existing Upper Pit will be mined within the approved boundary of the 2002 <br /> permit(BLM, 2002; CO DRMS, 2001), to an estimated Upper Pit floor elevation of 6900 feet amsl. <br /> The existing Mine Office would remain in its current location north of the Lower Pit, along with the <br /> existing equipment laydown yards and parking lots (shown on Drawing 01). <br /> The Upper Pit footprint would be expanded to a pit floor elevation of 6760 feet amsl, with 1 H:1 V <br /> pit face slopes and 10-foot wide flat benches constructed every 40 vertical feet of development. <br /> To accommodate the lower pit extents, a portion of the Upper Pit 6900 Access Road (BLM, 2019; <br /> CO DRMS, 2019a)would be mined out and the road alignment would be modified by constructing <br /> a new road northeast of the Upper Pit 6900 Access Road. Once the Upper Pit floor reaches an <br /> elevation of 6760 feet amsl, the pit configuration would be modified to increase the pit depth <br /> without impacting the overall footprint. This would create interior benches to an ultimate pit floor <br /> elevation of 6560 feet amsl as shown on Drawings 06 and 07. <br /> Before the Upper Pit is exhausted, American Gypsum plans to develop a new area to the east of <br /> the Upper Pit (East Pit). Approximately 1.19 million cubic yards (2.1 million tons) of overburden <br /> would be removed from the East Pit area prior to reaching usable gypsum and used as <br /> construction material for the East Pit Access Road. This estimate is based on previous drill data <br /> and experience at the Lower Pit and Upper Pit. Existing site roads would be used to access the <br /> East Pit during initial overburden removal while the main East Pit Access Road is being <br /> constructed.The East Pit Access Road would be constructed through a partial ly-backfilled section <br /> of the Upper Pit to connect the East Pit to the modified Upper Pit 6900 Access Road (BLM, 2019; <br /> CO DRMS, 2019a).As the East Pit progresses to its ultimate planned elevation of 6900 feet amsl, <br /> the East Pit Access Road within the East Pit footprint would be mined out to maintain the same <br /> elevation as the pit floor(Drawing 08). <br /> Mining methods are anticipated to remain the same throughout the Upper Pit and East Pit <br /> development, as described in Section 6.10.1. Stormwater controls are discussed further in <br /> Section 8.0. Intraburden removed during Upper Pit mining activities would be used as backfill <br /> material for progressive reclamation activities in the Upper Pit. Overburden and intraburden <br /> removed from the East Pit area would be used to construct the East Pit Access Road and as <br /> backfill material for progressive reclamation activities in the Upper Pit and East Pit. Reclamation <br /> activities are discussed further in Section 7.0. <br /> Production capacity from the Mine is estimated to continue at a nominal rate of 500,000 tons of <br /> gypsum shipped to the wallboard plant per year, with a maximum of 600,000 tpy. This mining rate <br /> results in approximately 80 to 100 trucks per day traveling from the Mine to the wallboard plant. <br /> Am Gypsum Poo Mod ISSD 20190909 September 2019 [201 <br />