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Henderson Mill — Permit No. M-1977-342 <br /> Technical Revision No. 32 <br /> 3 Dam Buttress— Phase II <br /> The 3 Dam Buttress—Phase II Project was approved as Technical Revision No. 32 to Mill Permit No. <br /> M-1977-342 on July 20, 2020. The project is located at Climax Molybdenum Company's Henderson <br /> Mill in Grand County. Phase II of the project included two additions to the Phase I south toe <br /> buttress on Original 3 Dam, plus additions to the Phase I multi-tiered buttress on Stepback 3 Dam. <br /> The buttress was constructed from tailings material borrowed from 1 Dam by removing an interim <br /> non-instrumentation bench. The completed crest elevations for the three Phase II buttress areas <br /> are El. 8825 ft for the main part of the south toe buttress; El. 8780 ft for the brow berm to the south <br /> toe buttress; and El. 8825 ft, 8837 ft and 8842 ft for the multi-tiered stepback buttress. Overall <br /> constructed slopes range from 3:1 horizontal to 4:1 horizontal. <br /> Henderson Mill completed construction over the 2020 season (July to October 2020). The project <br /> was designed by AECOM. Modifications to the initial design have been reflected in the construction <br /> record drawings signed and dated February 9, 2021. <br /> AECOM provided full-time construction oversight of the buttress placement and instrument <br /> installation activities for Phase II with construction by Henderson Mill. The project was completed in <br /> general conformance with the approved design as submitted to the Division of Reclamation, Mining, <br /> and Safety. The statement is based in part on information provided by others. <br /> o�p0 REG. .. j l <br /> Lisa R. Yenne, P.E �, . OEyF.•y <br /> O gN, Y•,c^ <br /> AECOM _3 z Date: August 11, 2021 <br /> Colorado PE No. 35847 ��F ..,....•����4� <br /> ssiONAL E� <br />