All of these contaminant sources will be addressed to 

 some degree in the feasibility study of the site. Remedial 

 actions designed for the major contaminant sources could have 

 far reaching positive effects on the quality of water in the 

 Clark Fork. Of primary concern is the Warm Springs Ponds 

 system, which is the pivotal point in the drainage. An 

 intensive study is now focused on that system and some action 

 alternatives should be defined by early 1989. 



The EPA has lead responsibility for the Butte Addition 

 portion of the site. In the fall of 1986, the EPA Emergency 

 Response Branch began investigations of mercury contamination 

 in the Walkerville area. A year later, it proposed a plan 

 for removals associated with lead and mercury contamination. 

 Removal actions were initiated in April 1988 and were com- 

 pleted in the fall of 1988. In the summer of 1987, EPA 

 conducted a soil screening study of Butte, Centerville, and 

 surrounding areas. The data report, submitted in June 1988, 

 is being utilized to plan RI/FS activities for the Butte 

 Addition. 



A key issue at the Butte Addition site is the mine 

 flooding that has occurred in the Berkeley Pit and the 

 underground mine workings since the Anaconda Minerals Company 

 ceased dewatering pumpage in 1982. The water level in the 

 pit has been rising at about 72 feet per year. Although the 

 rate of rise will probably decline as the pit fills, worst- 

 case projections suggest that the pit may be filled to 

 capacity by the end of the century if no remedial actions are 

 taken. There is concern that rising pit water may cause 

 encroachment of contaminated water into the alluvial aquifer, 

 and arsenic and other metals may migrate downgradient and 

 adversely affect Silver Bow Creek and the Clark Fork (Camp, 

 Dresser and McKee 1987, 1988a). Water levels in the Travona 

 mine shaft and other mine workings southwest of the Berkeley 

 Pit have also been rising since 1984, and there is concern 

 over the potential for discharge of contaminated ground water 

 to the alluvium and/or the ground surface (Camp, Dresser and 

 McKee 1988b). However, during the first quarter of 1988, the 

 rate of rise in the water level had decreased from two to 

 five feet per month to 1.5 feet per month. 



EPA has conducted several preliminary studies to 

 evaluate the entire mine system, including a Berkeley Pit 

 water balance study (Camp, Dresser and McKee 1987) , an 

 evaluation of flooding in the West Camp area mine workings 

 (Camp, Dresser and McKee 1988b) , and an analysis of the 

 aqueous geochemistry of Berkeley Pit water (Camp, Dresser and 

 McKee 1988a) . Additional work on the mine flooding issues 

 will be done during the RI/FS phase. 



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