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<br /> <br /> <br /> <br /> <br />Introduction <br /> <br />The following report presents the results of a slope stability analysis for a proposed open <br />cut gravel extraction operations at the Raptor Materials, LLC (Raptor) Pit 125 operations <br />located near Platteville, Colorado. This analysis was performed at the request of Raptor. <br />This report is being submitted in partial fulfillment of an OMLR 112 Mine Permit <br />Application. <br />Background Information <br /> <br />The proposed gravel quarry is located in portions of section 29, Township 3 North, Range 67 <br />West of the 6th principal meridian. The surrounding land use consists of agricultural, rural <br />residential and natural gas and oil gathering operations. The proposed mine occupies an <br />estimated 197 acres. The water table at the site is located in unconsolidated alluvial deposits <br />with the depth to water varying between seven and 28 feet below ground surface. Soil <br />conditions generally consist of varying thicknesses of top soil underlain by sand and gravel <br />deposits, which in turn are underlain by claystone and sandstone bedrock. Over the entire <br />area the average saturated thickness of the sand and gravel deposits (prior to mining) is <br />estimated at about 35 feet. It is our understanding that the sand and gravel will be dewatered <br />during aggregate extraction. The site location is presented on Figure 1. <br />Previous Investigations <br />Raptor conducted a sand and gravel study in August 2023. The study consisted of drilling six <br />soil borings from ground surface to bedrock to determine the potential aggregate mass <br />within the proposed mine boundary. Selected sand and gravel samples were obtained for <br />direct shear testing. The depth to bedrock over the site varied between 23 and 50 feet below <br />ground surface. The geotechnical laboratory report is presented as Attachment A. Soil boring <br />logs are presented in Attachment B. <br /> <br />Overview of Stability Analyses <br />Soil strength testing for the sand and gravel deposits was performed as part of the Raptor <br />study. Density testing was not performed on field samples and unit weights used by the <br />Division of Reclamation and Mining Safety were used for bedrock and overburden clay. Unit <br />weight values reported by Engineering Analytics, Inc., of Fort Collins, CO for were used for the <br />sand and gravel deposits. <br />