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2019 Plan of Operations Modification American Gypsum Company, LLC <br /> 6.1 Commodity <br /> The primary commodity is gypsum. There is no secondary commodity. <br /> 6.2 Scope of Operation <br /> The proposed mining activities would consist of the following: <br /> ➢ Road construction (Drawings 06 and 16): <br /> ❑ Remove a portion of the Upper Pit 6900 Access Road (BLM, 2019; CO DRMS, 2019a) <br /> to accommodate the Upper Pit expanded footprint, including constructing an interior <br /> pit road to access lower benches of the Upper Pit; <br /> ❑ Construct a new section of road from approximate elevation 6946 feet amsl on the <br /> Upper Pit 6900 Access Road to an Upper Pit elevation of 6958 amsl feet. This would <br /> include demolishing the riprap collar on the 30-inch culvert inlet proposed as part of <br /> the Upper Pit 6900 Access Road (BLM, 2019; CO DRMS, 2019a), installing a new <br /> 230-foot long section of 30-inch culvert where the proposed road fill crosses an <br /> existing drainage to create a continuous 30-inch culvert.The riprap apron at the culvert <br /> outlet (BLM, 2019; CO DRMS, 2019a) would remain intact throughout the culvert's <br /> operational life; <br /> ❑ Construct a new road through the partially reclaimed northern section of the Upper Pit; <br /> ❑ Construct a new road across the existing intraburden storage area and on native <br /> ground to the East Pit. This would include constructing a new 130-foot long 24-inch <br /> diameter culvert, riprap collar (inlet), and riprap apron (outlet) where the road fill <br /> crosses an existing drainage. Drawing 10 shows culvert details; <br /> ❑ Abandon, regrade, and reclaim as much of the original haul road and Upper Pit 6900 <br /> Access Road (BLM, 2019; CO DRMS, 2019a) as possible throughout operations <br /> (although there will likely be a short period of time where all three roads would be in <br /> use at the same time); and <br /> ❑ Throughout road construction and operation, following Best Management Practices <br /> (BMPs)for fill slopes to stabilize surface soils and reduce erosion potential. BMPs may <br /> include revegetating or installing erosion protection measures (straw wattles, silt <br /> fence, hay bales). Appropriate erosion protection would be determined by conditions <br /> encountered during operations. <br /> ➢ Open pit mining activities (Drawings 06 through 09): <br /> ❑ Expand the Upper Pit by approximately 11.7 acres outside the approved boundary <br /> from the 2002 permit(BLM, 2002; CO DRMS, 2001). The maximum pit footprint would <br /> be excavated to a pit floor elevation of approximately 6760 feet amsl. If additional <br /> gypsum is present in the pit footprint and groundwater is not encountered (identified <br /> through additional drilling), interior benches would be constructed to bring the pit floor <br /> elevation to approximately 6560 feet amsl. Drilling permits(including drill hole plugging <br /> and reclamation) would be obtained prior to drilling and drill holes would be plugged <br /> Am Gypsum Poo Mod/SSD 20190909 September 2019 [211 <br />