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CLIMAY MOLYBDENUM COMPANY <br />4.4) : Rheas Dame VAN Czmoan, <br />.April 11, 2000 <br />Mr_ Bruce Humphries <br />Colorado Division of Minerals and Geology <br />13I3 Sherman Street. Room 215 <br />Denver Colorado 80203 <br />RE: Technical Revision TR - 04 <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 scepwater <br />collection and pumpback system. <br />Neaderssi_LQ,peratigns <br />5mp•re - :.'eraoo 9: 438 <br />Mon.' .303:2' <br />ut or State I7C3: 569.: 22' <br />=as '2031569 ' 53C <br />Darn No. 3 is one of three tailing darns at the Henderson Mill Site. Eventually. Dam No. <br />2 will be covered with tailing and Dams No. 1 and No. 3 will form one darn as the <br />ultimate proposed crest elevation of 8900' is approached. Currently. Darn 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 Darn No. 2. Henderson plans to <br />resume tailing deposition at Dam No. 3 in 2 <br />Decant System <br />'13Se Dam No. 2 decant system, which is no longer in use, has been inundated by Darn `o. <br />3. Decant Tower 5N is located on the face of Darn No. 3. See Drawing 501 -583. <br />Seepage of about 10 gpm has been observed emanating from Decant Tower 5N and is <br />currently being collected and managed in the Dam No. 3 seepwater collection and <br />pumpback system. It appears 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 5N is unknown. However, the most likely <br />sources are either inflow into the decant system along the length of the decant line or <br />