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Mr. Drew Damaniano <br /> December 30, 2021 <br /> Page 5 <br /> TABLE 1 -SLOPE STABILITY RESULTS AND SETBACKS <br /> Section Location Critical Structure Static Factor of Seismic Factor of DRMS Draft FOS <br /> Structure Setback From Safety at Safety at Structure Requirement <br /> Mine Limit ft Structure 0.082 horizontal Static/Quake <br /> 1 Unlined Cell to Gas Line 40 1.75 1.32 1.511.3 <br /> be wet mined <br /> 50', 2h:1 v <br /> 2 Lined Cells Dry Gas Line 40 1.60 1.32 1.511.3 <br /> Mined (50', <br /> 1.5h:1 v <br /> 3 Lined Cells Dry Slurry 73 1.67 1.37 1.511.3 <br /> Mined (85', Wall/Gas <br /> 1.5h:1v)) Line <br /> CONCLUSIONS <br /> Based on the Factors of Safety listed in the table above,the mine will not be a hazard to neighboring structures provided <br /> the structure and slurry wall offsets, as well as the perimeter mine slopes,follow the mine plan. <br /> LIMITATIONS <br /> Our review is based on regional geologic mapping, present mining plans, and in part borehole data by Civil Resources. <br /> Stability analyses were performed using typical strength parameters for the various strata in the critical sections. Should <br /> the mining plans change or subsurface conditions vary from those portrayed in this letter,we should be contacted in <br /> order to re-evaluate the potential affects on permanent man-made structures. Stability analyses were run at the <br /> structure in question and were not run on failure surfaces closer to the highwall. Note also that surcharge loads due to <br /> temporary material stockpiles and overburden berms were not considered in the analysis. <br /> Please call with any questions or comments. <br /> Sincerely, <br /> Civil Resources, LLC <br /> Gary Linden, P.G. <br /> Senior Engineering Geologist <br /> Attachments: <br /> U.S.G.S. Uniform Hazard Tool Earthquake Acceleration <br /> XSTABL Model Outputs: Sections 1, 2, and 3 <br /> J:\Brannan\Gilcrest Geology\Stability Analysis\Stability analysis report-Sec 20.doc <br />