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iii iiiiiiiiiiiuiii • • <br />/- ,, ~ CLIMA)3 MOLYBDENUM COMPANY Henderson operations <br />a s~os~arery of aneios ooage m~mng [omoanv PO Box 6B <br />~~ Empire. Co4oratlo 00438 <br />Metro (3031 271-0107 <br />Ouc of State [3031 569-3221 <br />Fax [3031569-0930 <br />~~~~~~~® <br />APR 122000 <br />April 11, 2000 ~~ <br />Division of Minerals & Geolol~yy ~ ~ COQ <br />Mr. Bruce Humphries $S75 • C~ <br />Colorado Division of Minerals and Geology ~D~ ~ ~D (fin, „~.a 3~~ <br />1313 Sherman Street, Room 215 t~-~" <br />Denver Colorado 80203 <br />RE: Technical Revision TR-08 <br />Change to Environmental Protection Facility <br />Dear Mr. Humphries: <br />The Henderson Mine is planning to change portions of an existing Environmental <br />Protection Facility (EPF). These changes will be to the decant system for Dams No. 2 <br />and 3 (hereafter referred to as No. 2 decant system) and the Dam No. 3 seepwater <br />collection and pumpback system. <br />Dam No. 3 is one of three tailing dams at the Henderson Mill Site. Eventually, Dam No. <br />2 will be covered with tailing and Dams No. t and No. 3 will form one dam as the <br />ultimate proposed crest elevation of 8900' is approached. Currently, Dam No. 1 crest <br />elevation is an elevation of approximately 8810 and Dam No.3 crest elevation is <br />approximately 8828. <br />Dam No. 3 is not currently being used for tailing deposition and is hydraulically <br />separated from tailing deposition at Dam No. 1 by Dam No. 2. Henderson plans to <br />resume tailing deposition at Dam No. 3 in 2002. <br />Decant System <br />The Dam No. 2 decant system, which is no longer in use, has been inundated by Dam No. <br />3. Decant Tower SN is located on the face of Dam No. 3. See Drawing 501-583. <br />Seepage of about ] 0 gpm has been observed emanating from Decant Tower SN and is <br />currently being collected and managed in the Dam No. 3 seepwater collection and <br />pumpback system. It appeazs that the hydrostatic level of the decant system is <br />sufficiently high to have caused the flow to reverse in the decant system. The source of <br />the water emanating from Decant Tower SN is unknown. However, the most likely <br />sources are either inflow into the decant system along the length of the decant line or <br />