Warm Springs and Opportunity Ponds 



Superfund investigations have documented degraded ground 

 water in the vicinity of the Warm Springs Ponds and the 

 Opportunity Ponds (MultiTech 1987b; Tetra Tech 1986b) . 



Ground water downgradient of the ponds systems is con- 

 taminated, frequently exceeding federal drinking water 

 standards for arsenic, fluoride, iron, and sulfate. This 

 contaminant plume extends at least one-half mile downstream 

 from the Warm Springs Ponds. However, no domestic wells are 

 in the vicinity of the contaminated ground water; therefore, 

 there is no apparent or immediate threat to public health. 

 No measurable effects of contaminated ground water inflow to 

 the Clark Fork were found during the RI study periods. 

 Ground water from both the Opportunity Ponds and the Warm 

 Springs Ponds areas were the main sources of contaminant 

 inflow to the Mill-Willow Bypass (MultiTech 1987a) . 



Warms Springs Ponds . Extensive Phase II Superfund work 

 for the Warm Springs Ponds system has been completed by CH2M 

 Hill. Ground water investigations included an electro- 

 magnetic survey in the area between the Mill-Willow Bypass 

 and the Warm Springs Ponds system and in the area below Pond 

 1, installation of 14 monitoring wells at key locations 

 within and adjacent to the area, ground water sampling, 

 ground water level monitoring, and aquifer testing. The 

 objectives were to better define the extent and severity of 

 ground water contamination near the ponds and to better 

 quantify hydraulic characteristics of the area ground water 

 system. A data report with the results of these Phase II 

 activities is expected to be released in early 1989. The 

 feasibility study for the ponds is -also expected to be 

 completed by early 1989. A number of corrective or control 

 options for the ponds will likely be considered, including 

 improved treatment practices at the existing system, 

 structural modifications, and others. 



Opportunity Ponds . A plume of ground water enriched in 

 sulfate exits the Opportunity Ponds area to the northeast. 

 Highest concentrations of trace elements measured by Tetra 

 Tech (1986b) were 24 parts per billion (ppb) arsenic, 37 ppb 

 copper, and 166 ppb zinc. At present, a ground water mound 

 exists over a large portion of the tailings ponds, and the 

 water table is above the base of the tailings in over 70 

 percent of the area. However, it is estimated that ground 

 water levels will approach equilibrium in approximately 30 

 years, and the steady-state water table should be about 15 

 feet below the base of the tailings in the center of the pond 

 system. As the ponds have been drying out, an oxidizing 



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