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Earth Engincering Consultants,LLC <br /> EEC Project No. 1172053 <br /> ,tune 28,2022 <br /> Page 2 <br /> Response: In our opinion, a minimum setback of 100 feet of the mining boundary from the <br /> permit boundary near Ken Pratte Boulevard right-of-way would maintain an acceptable <br /> factor of safety of at least 1.5 as indicated for static slope stability for Critical Structures <br /> (based on the conditions described in our February 7 Report, including maximum mining <br /> depths of 25 feet below ground surface). 'Phis assumes a relatively flat backslope and no <br /> stockpile or other surcharges at the ground surface between the mining and permit <br /> boundaries. Note the minimum factors of safety and definitions of Non-Critical Structures <br /> and Critical Structures, are based on Colorado Division of Reclamation,Mining and Safety, <br /> Proposed Slope Stability/Geotechnical Analvsis Policy for The Mined Land Reclamation <br /> Board, dated May 16, 2018; that specification should be reviewed for completeness. If the <br /> factors of safety required vary from those specifications, this report should be reviewed by <br /> EEC and revised as necessary. <br /> We trust the information provided in this letter provides the necessary information you <br /> requested; however, if additional information is needed, or if we can be of further service to you <br /> in any other way,please do not hesitate to contact us. <br /> Very truly yours, <br /> Earth Engineering Consultants,LLC <br /> v <br /> m <br /> 'r gyp" <br /> Ethan P. Wiechert,P.E. <br /> Senior Project Engineer <br />