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2019 Plan of Operations Modification American Gypsum Company, LLC <br /> outcroppings with a thin gypsite crust that grades thorough weathered gypsum to solid gypsum <br /> rock. Experience has shown that these gypsite crusts vary in thickness from 3 inches to 2 feet. <br /> The gypsite crusts generally contain some silty-clayey material due to the weathering of inter- <br /> bedded clastic sediments. <br /> In summary, the surface in the area can mainly be described as gypsum and weathered gypsum <br /> (gypsite) outcroppings with intermingled basins of volcanic ash. The gypsum outcroppings <br /> predominate in the area as evidenced by the lack of vegetation in areas other than the <br /> intermingled volcanic ash basins. <br /> Drawing 05 shows the soils map from the NRCS soil resource report for the site (NRCS, 2016), <br /> along with aerial imagery. <br /> There are no known cave resources in the proposed disturbance area. Should any caves be <br /> discovered in the process of developing the Upper Pit expansion, East Pit, or associated roads, <br /> American Gypsum would notify the BLM. <br /> 3.4 Cultural Resources <br /> A Class III cultural resources survey was conducted in 2001 on 157 acres for Mine features <br /> proposed at that time. No previously-recorded sites or isolated finds were noted. The Mine area <br /> was expected to have low potential for cultural resources due to steep slopes and location <br /> between the `Flat Tops' Wilderness Pinyon-Juniper woodlands and the Eagle River Valley. <br /> A cultural resources survey was conducted during the summer of 2018 in the proposed Upper Pit <br /> expansion area. A second cultural resources survey was conducted in the summer of 2019 to <br /> cover gaps in previous surveys near the existing sediment control ponds previously approved by <br /> CO DRMS as TR-06 and TR-07 (CO DRMS, 2003; CO DRMS, 2006). Other areas of proposed <br /> disturbance have been covered by previous surveys conducted between 1989 and 2017. <br /> According to the surveys, the steep landscape is not conducive to archaeological preservation. <br /> No sites have been documented in the area. <br /> 3.5 Paleontology <br /> The main geologic formation in the Mine area, Eagle Valley Evaporite, is not included on the <br /> BLM's list of formations in the CRVFO Planning Area with paleontological resources(BLM, 2015). <br /> Included on the list is Basalt of Bimodal Suite (Tbb), which is listed as having a moderate to <br /> unknown, or high potential to yield fossils. No paleontological resources have been uncovered to <br /> date during mining operations. <br /> 3.6 Vegetation <br /> According to the BLM CRVFO Record of Decision and Approved Resource Management Plan <br /> (BLM, 2015), the BLM lands near the Mine are comprised of pinyon-juniper woodlands and <br /> sagebrush shrublands. Previous permit documents note that vegetation cover in undisturbed <br /> areas of the Mine consists mainly of sagebrush and greasewood. Vegetation is sparse on steeper <br /> slopes; some areas include solid gypsum rock outcroppings. Like the existing mining area, the <br /> Am Gypsum Poo Mod ISSD 20190909 September 2019 [141 <br />