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Geotechnical Stability Report —Kersey Mine May 24, 2024 <br /> Kersey, Colorado Page 5 <br /> 2H:1V (static) 1.2 1.5 <br /> 2H:1V (pseudo-static/seismic) 1.1 1.1 <br /> 3H:1V (static) 1.8 1.5 <br /> 3H:1V (pseudo-static/seismic) 1.5 1.1 <br /> 2.5H:1V (static) 1.5 1.5 <br /> 2.5H:1V (pseudo-static/seismic) 1.3 1.1 <br /> CONCLUSIONS <br /> The slope stability analysis indicates that a proposed 2H:1V slope do not result in acceptable <br /> FOS,and therefore, should not be constructed. Therefore, shallower slopes were evaluated and <br /> determined that the maximum recommended slope to achieve an acceptable FOS of 1.5 for static <br /> conditions and 1.1 for seismic conditions is 2.5H:1V. Model geometry, slip surface, and FOS for <br /> the evaluated scenarios are provided in Attachment C. It is also anticipated that the preferred <br /> 50-ft buffer as previously discussed would be appropriate as the slope failure surfaces appear to <br /> terminate near the crest of the slope and do not extend back. Although groundwater was not <br /> encountered in the boreholes at the time of the exploration, seepage that develops along the <br /> excavation sloped may develop localized shallow sloughing. This is not considered global <br /> instability and can be addressed during routine maintenance on a case-by-case basis. <br /> LIMITATIONS <br /> This letter report has been prepared for the Colorado Sand Company LLC for planning and <br /> permitting of the proposed surface mining activities at the project site located in Kersey, CO. <br /> Transfer of this report or included information is at the sole discretion of the Colorado Sand <br /> Company LLC. TRC's contractual relationship remains with the Colorado Sand Company LLC <br /> and limitations stated herein remain applicable regardless of end user. The opinions, conclusions, <br /> and recommendations presented in this memorandum have been formulated in accordance with <br /> accepted geotechnical engineering practices that exist in the area at the time this memorandum <br /> was written. No other warranty, expressed or implied, is made or should be inferred. <br /> The opinions, conclusions and recommendations contained in this memorandum are based upon <br /> limited information obtained from our investigation, which includes data from a limited number of <br /> widely separated discrete locations, visual observations from our site reconnaissance, and review <br /> of other geotechnical data provided to us, along with local experience and engineering judgment. <br /> An attempt has been made to provide for normal contingencies; however, the possibility remains <br /> that differing or unexpected conditions may be encountered during construction. If this should <br /> occur, or if additional or contradictory data are revealed in the future, TRC should be notified so <br /> that modifications to this memorandum can be made, if necessary. TRC is not responsible for <br /> any conclusions or opinions drawn from the data included herein, other than those specifically <br /> stated, nor are the recommendations presented in this memorandum intended for direct use as <br /> construction specifications. <br /> Tr�C <br />