Tailings Disposal Areas 



There are two major tailings disposal areas in or near 

 the floodplain in the headwaters of the Clark Fork. The 

 Colorado Tailings southwest of Butte cover about 30 acres 

 within the floodplain of Silver Bow Creek (Duaime et al. 

 1987) . The Anaconda and Opportunity tailings ponds east of 

 Anaconda cover approximately 4,000 acres (Tetra Tech 1987). 

 These areas and the Old Works and Warm Springs Ponds are 

 discussed below. 



Colorado Tailings 



The Colorado Tailings lie between the Butte Sewage 

 Treatment Plant on the east and the Ranchland Packing Company 

 on the west. The site is bounded by Silver Bow Creek on the 

 north, east, and west and the Burlington Northern Railroad 

 grade on the south (Figure 3-2) . The tailings are the waste 

 product of the smelter and concentrator of the Colorado and 

 Montana Smelter Company, which began operation in 1879. 

 Eventually, the facility was bought by the Anaconda Company, 

 and the smelter and concentrator were demolished between 1905 

 and 1907 (Duaime et al. 1987). 



Tailings were disposed of in a marshy area adjacent to 

 Silver Bow Creek, north of the facility. The earliest 

 tailings were quite coarse but became finer as mill tech- 

 nology improved. The tailings average about five to six feet 

 in depth and overlie an organic-rich peat layer that is 

 discontinuous, particularly near the edges of the tailings 

 deposit. Approximately 15 to 30 feet of alluvium underlie 

 this layer (Duaime et al. 1987). 



Heavy metals and arsenic concentrations (in parts per 

 million [ppm]) in the Colorado Tailings and underlying layers 

 are summarized in Table 3-6. Typical values for uncon- 

 taminated natural soils are provided for comparative 

 purposes. The enrichment in the peat layer relative to the 

 overlying tailings and the underlying alluvium indicates that 

 the peat layer is concentrating metals that have leached down 

 through the tailings. The Colorado Tailings are of par- 

 ticular concern because of documented ground water and 

 surface water degradation in the vicinity. These problems 

 are discussed later in this chapter. 



A variety of reclamation alternatives for the Colorado 

 Tailings have been discussed, including: amendment of the 

 existing surface, tailings removal and revegetation, covering 

 the tailings with soil and revegetation, application of a 

 rock mulch, relocation of Silver Bow Creek to the southern 



3-32 



