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Climax Molybdenum COLORADO OPERATIONS <br />Henderson Mine and Mill <br />H P.O. Box 68 <br />A Freeport- McMoRan Company Empire, CO 80438 <br />Phone (303) 569 -3221 <br />Fax (303) 569 -2830 <br />August 28, 2014 <br />Sent Via Email and Certified Mail: 7006 2150 0001 8831 9964 <br />Mr. Peter Hays <br />Environmental Protection Specialist <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />Re: Climax Molybdenum Company, Henderson Mill, Permit No. M- 1977 -342 <br />Proposed Technical Revision No. 24, Tailing Delivery Line Drop Tower 13 & 14 <br />Removal <br />Dear Mr. Hays, <br />Climax Molybdenum Company (CMC) is hereby submitting this request for a new Technical <br />Revision (TR -24) for the Tailing Delivery Line (TDL) Drop Tower 13 & 14 removal and <br />replacement of a 2,500 foot section of 36 -inch reinforced concrete pipe (RCP) with 42 -inch <br />HDPE pipe. <br />In the fall of 2013 a section of the RCP on the TDL was replaced with HDPE. When the RCP <br />was removed it revealed a groove in the invert of the pipe that compromised the reinforcing bar <br />of the RCP and reduced the pressure capacity of the existing RCP. Knowing that pressure <br />changes are likely through this section in the future, Henderson has decided to replace the <br />remaining RCP that will experience pressure along the TDL. The purpose of this project is to <br />provide a safe and cost effective means of reestablishing the structural integrity of the TDL. <br />The proposed design will involve placing Wide Flange Section Beams adjacent to the existing <br />bar joists. The load will then be transferred from the existing joists to the new beam structure. <br />The lower 2,500 feet of existing RCP will be replaced with sections of 42 -inch HDPE. The <br />existing drop towers 13, 14, 15 and 16 will be removed in the process. Activities required to <br />complete this project will include hydro- excavation, temporary shoring, concrete formwork and <br />placement, steel shop drawing preparation, steel component fabrication and delivery, structural <br />steel erection, concrete and steel demolition, HDPE fusing and HDPE placement. The removal of <br />Drop Tower's 15 and 16 is outlined in Technical Revision No. 22 submitted on March 26, 2014. <br />As shown in the included drawing (attachment 1), this project will involve the removal of Drop <br />Tower's 13 and 14 and the 2,500 feet of RCP that will be replaced with HDPE beginni ,at Drop <br />Tower 12. As was the case with the removal of droptower 17, periodic removal of the eii xi <br />dissipating drop towers will occur, so long as TDL pressures can be appropriately managed. v <br />✓/+F J- RPT <br />,/ YUa V�61C&I,GrL <br />