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JD-8 Mine Report <br />Geoscience Services <br />dilution factor of 106--far exceeding the requirement of SOx required by the Colorado <br />Division of Minerai and Geoiogy for groundwater. Since selenium is contained in the <br />upper portions of the Salt Wash and does not reach the groundwater, there is substantial <br />protection of the groundwater resowces in the azea. <br />Comparing the extent of uranium and selenium migration shown in Figwes 3 and <br />4, illustrates the effects of sorption. Selenium exhibits a Kd value for sandstone four <br />times higher than uranium resulting in greater sorption and the subsequent retardation of <br />the selenium plume. The other analyzes such as aluminum, lead and arsenic would <br />behave in a similar manner and pose no significant threat to the underlying groundwater <br />resources. This statement is based on the facts that wanium exhibits the highest degree <br />of mobility in the subsurface and a concentration an order a magnitude higher than any <br />values for waste rock or ore measured for aluminum, lead, or arsenic. Consequently, the <br />I~ extent of migrations in the subsurface for these additional constituents of concern would <br />~ be significantly less than wanium. <br />~ 6.0 Conclusions and Recommendations <br /> <br /> <br /> Numerical modeling studies of the transport of constituents of concem from the <br />• waste rock pile (or temporary ore storage piles) at the SM-18 mine and applied to the JD- <br /> 8 mine indicate that the pile poses no significant threat to underlying groundwater <br /> resources. The flow and transport mode] incorporated several conservative assumptions <br /> regarding the hydraulic and geochemical parameters. Most conservative was the <br />~ assumption that the pore-water in the waste pile contained contaminant concentrations <br /> <br /> that reflected SPLP test conditions. Actual rainwater exhibits a higher pH value (less <br />• acidic than SPLP leaching fluid) and would leach constituents of concern at lower <br />~ concentrations. In addition, for the 1000 year simulation, concentrations of constituents <br />~ of concern in the waste-rock pore water were maintained at initial concentrations. In <br /> reality, as constituents of concern are leached from the waste rock, concentrations would <br />~ steadily decline with time. The net result is a model that over predicted the amount and <br /> <br /> availability of constituents of concern for transport. <br /> <br /> 12 <br /> <br /> <br />