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This report evaluates the geologic conditions of the subject properties and possible geologic <br />hazards. All determinations and evaluations in this report are based on Natural Resource <br />Conservation Service mapping of the properties in question, CGS geologic mapping of the area, <br />and site-specific geologic analysis. <br />1. Baseline Conditions <br />1_1 Regional Geology <br />The Rincon Materials operations lies in the eastern portion of the White River Plateau, Colorado <br />which is part of a large topographical high that extends from New Mexico through Colorado. <br />The regional geology) is complex, with periods of uplift, compressional and tensional tectonics, <br />and volcanism. These tectonically active periods are interspersed with long periods of <br />quiescence, typified by deposition of many thousands of feet of sedimentary rocks. Recent <br />erosion by rivers, glaciers, and other mechanical means has resulted in the deposition of thick <br />deposits of unconsolidated clastic materials. These types of clastic deposits will be mined by <br />Rincon Materials. <br />Beginning about 1790 Ma (million years ago), continental crust was formed as a series of arcs <br />and interarc basins that were accreted to an Archean craton as oceanic crust was subducted <br />beneath continental crust which pushed each subsequent arc and associated basin onto the craton. <br />Plutons consisting of granodiorite, granite, and quartz monzonite intruded and cut the crustal <br />rocks during a period of 1780 — 1074 Ma. A period of tectonic quiescence and inland seas <br />resulted in the deposition of large packages of shelf -type sedimentary rocks during the early <br />Paleozoic. These clastic sedimentary rocks included shales, mudstones, and sandstones <br />comprised of clasts eroded from topographical highs composed of the igneous and metamorphic <br />rocks emplaced during the Proterozoic. <br />In Early Pennsylvanian time, approximately 320 Ma, uplift of the northwest to north —northwest <br />trending Ancestral Rockies resulted in the erosion of much of the shelf sedimentary rocks <br />deposited during the early Paleozoic. Accumulations of these eroded sediments in flanking <br />basins resulted in the deposition of up to 20,000 feet of clastic sedimentary rocks. These include <br />the Belden Formation, a shale which was deposited above the Leadville Limestone and which <br />acts as a confining layer in areas where the Leadville Limestone is an aquifer. Also formed <br />during this time were locally thick evaporite deposits in structurally controlled sub -basins <br />including the predominantly gypsum Eagle Valley Formation. The Laramide Orogeny occurred <br />from 70 — 40 Ma and, in the Colorado area, was a period of crustal contraction, uplift, faulting, <br />and igneous activity that initiated the formation of the modern Rocky Mountains. <br />Neogene intrusive centers and volcanism including the Dotsero Volcanic Center formed and <br />deposited igneous rocks such as basalts overlying the inclined sedimentary bedding of the Grand <br />Hogback monocline. Geomorphic formation of canyons, for example the Glenwood Canyon, <br />resulted in the exposure of Proterozoic basement rocks as rivers incised through areas of regional <br />uplift. Circulation of groundwater undersaturated in calcite led to the formation of large collapse <br />features as evaporite deposits such as the Eagle Valley Formation, were dissolved and <br />transported via saline solutions. <br />Finally, Quaternary deposits of alluvium, landslides, and glacial deposits were emplaced upon <br />the previous deposited lithologies. Resultant erosional processes, including fluvial and mass <br />Rincon Materials - Geology Greg 1. kki and Ass Uto, PLIA <br />February 2020 2 <br />