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2019 Plan of Operations Modification American Gypsum Company, LLC <br /> Mining activities proposed herein would not significantly impact equipment used or frequency of <br /> use. Trucks would continue to travel on the existing roads (and proposed roads) at a rate of <br /> approximately 80 to 100 trucks per day, typically 5 days per week. When not in use, trucks would <br /> be parked in existing parking areas near the existing Mine Office shown on Drawing 01. <br /> 6.8 Soil, Waste, and Mineable Material <br /> Based on field observations and previous permits, there is no true "topsoil" at the Mine. Intact <br /> (native)growth medium is sparse and consists mainly of weathered gypsum(gypsite)and residual <br /> volcanic ash. Previous permits and investigations reported depths of volcanic ash ranging in <br /> thickness from 3 inches to 2 feet (isolated pockets as deep as 2 feet are typically found in dry <br /> creek beds); this material would be salvaged along with other growth medium during East Pit <br /> clearing and grubbing activities and stockpiled with maximum side slopes of 2H:1V in the growth <br /> medium stockpile shown on Drawing 06 for future use as growth medium during reclamation <br /> activities. Where salvaged growth medium contains biological soil crust material, the stockpiled <br /> depth would be limited to a depth of 4 feet to promote continued algae,fungi, and lichen formation <br /> and assist in stabilizing the growth medium stockpile surface. If stockpiled growth medium is <br /> dormant more than 6 months, the stockpile will be revegetated using an approved seed mixture <br /> to stabilize surface material and inhibit weed growth. <br /> Overburden was estimated for the East Pit only. No overburden is expected to be encountered in <br /> the Upper Pit area, as the pit is being actively mined and overburden was removed in the early <br /> stages of mining. Non-economic material encountered during mining is classified as intraburden <br /> (waste). The East Pit was anticipated to have a similar gypsum-to-intraburden ratio as the <br /> operational Upper Pit, assuming 55% of the material encountered during mining (by weight) is <br /> usable gypsum. Where the proposed East Pit depth exceeds the operational Upper Pit depth, the <br /> gypsum-to-intraburden ratio was estimated assuming only 40% of the pit material (by weight) is <br /> usable gypsum. As the Upper Pit and East Pit are developed, American Gypsum would propose <br /> additional drilling to refine these estimates and may modify the overall pit depth or footprint if drill <br /> data or continued mining activities do not produce usable gypsum (Section 6.9). Material <br /> estimates are summarized in Table 6.3. The conceptual growth medium stockpile location is <br /> shown on Drawings 06 and 08. <br /> Am Gypsum Poo Mod ISSD 20190909 September 2019 [271 <br />