2000-12-11_REVISION - M1977342 (3)

Home Browse Search

~ • III IIIIIIIIIIIII III © 9CLIMAX{ MOLYBDENUM t;UMI'ANY A Suhsitl~ery of Phelps OoEge Corporation December 7, 2000 Mr. Allen Sorenson Environmental Protection Specialist Colorado Division of Mmerals and Geology 1313 Sherman Street, Room 215 Denver, Colorado 80203 l.J' i}~ENREpsON ®PERA710N5 19302 County Roetl 3 Parshall, Coloraoo 80468 [3031 569-3221 Fax 197017250038 l~f~~f~9~lE® DEC 1 1 2QUD Division of Minerals and Geology RE: 2-Dam Decant Grouting and 3-Dam Seepwater Management, Henderson Mill, Technical Revision TR-09, Permit No. M-77-342 Dear Mr. Sorenson: This letter is to provide the Division of Mmerals and Geology (Division) with all necessary remaining information it needs to grant approval for the Henderson Mrll to begin using our new 3-Dam seepwater lines. Please Snd enclosed a copy of the 3-Dam seepwater lines pressure testing report from ACA, a certification from Mr. Mrchael Ley, Civil Engineer/Project Manager for the project, and an explanation below outlining the minor deviations that took place during construction from the submitted drawings. A complete set of project drawings will arrive shortly under separate cover. The original scope of work on this project called for the removal of approximately 1,700 cubic yards of tailing material from the base of 3-Dam. The bottoms of the north and south ponds would then be regraded, compacted, and receive 12" of clean cover soil. Due to the physical characteristics of this material and the difficulty it caused in handling, this plan was abandoned. Therefore, Items 1.3.2, 1.3.3, and 1.3.6 were eliminated from the original scope of work. Additions to the scope of work include importing sufficient native soil cover (12"-36") to cap and bridge the existing tailing material. This cover material will then be graded to drain to the collection channels. Tailings material will be removed only as necessary based on this revised scope of work. Approximately 1,200 cubic yards of river cobble (3"-12") will be screened to line the collection channels. Amoco 2019 geotextile fabric will be laid in all collection channels prior to being rip rapped. Large cobbles (12"-36") will be utilized where necessary to stabilize the sub-base sufficiently to allow for the lining of the channels and for capping of the pond areas. Finally, ballast material will be placed over the large cobbles where necessary to establish proper grade. Henderson requests that the Division grant a timely Snal approval to use this EPF to help avoid any freezing problems at the inlet structure. Please call if you have any questions or are in need of any further information. I can be reached at (303) 569-3221 ext. 2214.