irrigation season for lands that would have been supplied 

 from tributary flow. Water availability considerations 

 further pared the number of acres of irrigable lands in the 

 upper Clark Fork to about 8,400. 



MINING 



A number of companies have recently submitted plans to 

 DSL to mine gold, silver, and copper in various tributaries 

 of the Clark Fork. These proposed projects must be closely 

 scrutinized to ensure that environmental degradation is 

 minimized and that water quality is not further impaired. 

 Some of the larger operations propose to utilize a cyanide 

 heap leach process to recover gold from the ore deposit. In 

 this process, crushed ore is placed on a leach pad and 

 sprayed with a dilute cyanide solution to dissolve the gold 

 and silver values in the ore. This solution percolates down 

 through the ore and collects on the pad liner. The gold-and- 

 silver-bearing solution is pumped to a process plant for 

 removal of the gold and silver. The solution is then pumped 

 back onto the ore pile, and the process is repeated until 

 recovery of metals from the ore falls below acceptable 

 economic levels (Sunshine Mining Company 1988) . Because the 

 cyanide heap leach process has the potential to cause 

 environmental problems, new mine plans proposing to use it 

 will be reviewed very closely. Comprehensive water monitor- 

 ing programs for leach pad facilities will be necessary to 

 ensure protection of the water resources. 



New mines proposed in the Clark Fork Basin are discussed 

 briefly in the following sections. More detailed information 

 can be obtained through the DSL, the agency responsible for 

 administering the state's hard rock mining rules and 

 regulations. 



New Butte Mining. Inc. 



In October 1987, Butte Mining Pic (London) purchased 

 two major mining claim blocks on the Butte Hill from Montana 

 Mining Properties, Inc. New Butte Mining, Inc. (NBMI) , was 

 formed as the operating company for Butte Mining Pic and will 

 actively mine these two claim blocks and a third that was 

 purchased later. NBMI plans to develop new and old under- 

 ground workings along multiple vein systems in the Butte Hill 

 for silver, lead, zinc, and gold. Extensive surface and 

 subsurface exploration activities have begun to verify 

 grades, tonnages, and metallurgical processing data. 



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