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Mr. Mark Johnson <br /> June 17, 2019 <br /> Page 3 <br /> Bedrock <br /> Bedrock below the alluvium is sandy claystone, siltstone, and sandstone that is commonly interbedded and weathered in <br /> the top foot. Sandstone and siltstone are typically stronger than claystone. Claystone is generally a weak bedrock. <br /> Because of the common sandstone and siltstones and the interbedded nature of the bedrock,we modeled the bedrock <br /> as sandy claystone. For the sandy claystone bedrock both weathered and unweathered strength conditions were <br /> considered. Based on the borings at the site,the weathered bedrock was modeled with less cohesion and a slightly <br /> lower friction angle. <br /> Dry Unit Moist Unit Saturated Unit <br /> Weight(pco Weight(pco Weight(pco Cohesion C'psf Friction Angle�'° <br /> Unweathered= Unweathered= Unweathered= <br /> 124 134 0 Unweathered=29 <br /> 116 Weathered= 120 Weathered <br /> ea he ed Weathered=50 Weathered=26 <br /> STABILITY ANALYSES RESULTS <br /> The factor of safety shown below is the minimum factor of safety of the conditions listed above. <br /> TABLE 1 -SLOPE STABILITY RESULTS AND SETBACKS <br /> Condition Location Critical Structure Static Factor Seismic Factor of DRMS Draft FOS <br /> Structure Setback From of Safety at Safety at Requirement <br /> Mine Limit(ft) Structure Structure(0.085g Static/Seismic <br /> horizontal <br /> Center of Cell 2 Overhead 23 2.4 1.5 1.5/1.3 <br /> Full Reservoir Powerline <br /> Center of Cell 2 Overhead <br /> 2 Empty Power Line 23 2.1 1'6 1.5/1.3 <br /> Reservoir <br /> CONCLUSIONS <br /> The power line at Cell 2 is stable based on the most current DRMS requirements because the operator mines at a 3:1 <br /> (h:v)slope. <br /> In addition, Civil resources reviewed the mine plan and found that no structures encroach within 55 feet of the planned <br /> mine limits and will be stable based on previous analyses and the conditions under the current permit.. <br />