Phase I studies, specific geographic areas were selected for 

 a more detailed Phase II study, conducted from December 19^5, 

 to January 1986. 



Ground water contamination sources identified during tha 

 Superfund investigations of Silver Bow Creek are summarized 

 in Table 3-26. Contaminants are likely entering the surface 

 and ground water via several mechanisms, including: 

 infiltration of water through tailings, upward movement of 

 metallic salts to the surface via capillary action and 

 entrainment by surface runoff, and direct erosion and 

 entrainment of streamside tailings (MultiTech 1987a) . 



MultiTech (1987a) concluded that ground water in the 

 Silver Bow Creek study area is a severely degraded resource 

 that may pose hazards to human health, aquatic life, and the 

 environment. Present and future use of the ground water 

 resource in upper Silver Bow Creek would be limited. 



Samples from several monitoring wells in the study area 

 exceeded federal drinking water standards for a number of 

 metals and other trace elements. Several domestic wells 

 showed exceedences of secondary drinking water standards. 



Butte Mine Flooding . When the Anaconda Minerals Company 

 ceased operations in Butte in 1982 and stopped pumping water 

 out of the Kelley Shaft, the water level in the shafts rose 

 to the level of the Berkeley Pit bottom within one year. The 

 water level in the pit is now rising at a rate of about 72 

 feet per year. Water levels have also risen in various min© 

 workings in the Butte area. Water samples from the Berkeley 

 Pit and the Kelley Shaft have been collected by the MBMG and 

 Camp, Dresser and McKee. Laboratory analyses for selected 

 parameters are provided in Table 3-27. Values for arsenic, 

 cadmium, copper, and zinc are very high, and there is concern 

 that contaminated water from the pit and mine workings may 

 eventually discharge to the alluvial aquifer and further 

 impair an already degraded ground water system. Because of 

 strong hydrologic connection between the ground water and 

 surface water in some areas. Silver Bow Creek and ultimately 

 the Clark Fork could also be adversely affected. If the pit 

 or shaft water were to intrude into the alluvium, there could 

 be multiple violations of federal and state water standards. 



Although EPA has conducted preliminary studies to 

 address the mine flooding issue (Camp, Dresser and McKee 

 1987, 1988a, b) , additional work is ongoing to refine 

 predictions and to develop strategies to deal with potential 

 problems. 



3-106 



