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Mr. Joe Lamanna <br /> June 9, 2021 <br /> Page 6 <br /> TABLE 1 -SLOPE STABILITY RESULTS AND SETBACKS <br /> 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 0.091 hor Static/Quake <br /> Freshwater and Gas Line 30 1.9 1.3 1.5/1.3 <br /> Silt Ponds <br /> (northwest, most <br /> critical section <br /> Cell 2(south, Slurry Wall 30 1.6 1.3 1.5/1.3 <br /> most critical <br /> section <br /> Cell 3 (north, Slurry Wall 30 1.6 1.3 1.5/1.3 <br /> most critical <br /> section <br /> CONCLUSIONS <br /> The mining setback will be 30-feet from the high wall to the slung wall or nearest structure. Based on the Factors of <br /> Safety listed in the table above,the mine will not be a hazard to neighboring structures provided the structure and slurry <br /> 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 /> and others. Stability analyses were performed using typical strength parameters for the various strata in the critical <br /> sections. Should the mining plans change or subsurface conditions vary from those portrayed in this letter,we should be <br /> contacted in order to re-evaluate the potential affects on permanent man-made structures. Stability analyses were run at <br /> the structure in question and were not run on failure surfaces closer to the highwall. Note also that surcharge loads due <br /> to 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: Figure —Mine Plan showing boring locations and sections used. <br /> XSTABL Model Outputs: Sections 1, 2, and 3 <br />