Laserfiche WebLink
SM-18 Mine Report <br />GeoScience Services <br />Comparing the extent of uranium and selenium migration shown in Figures 2 and <br />3, 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 analytes such as aluminum, lead and zinc would behave <br />in a similar manner and pose no significant threat to the underlying groundwater <br />resources. This statement is based on the facts that uranium 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 zinc. Consequently, the <br />extent of migrations in the subsurface for these additional constituents of concern would <br />be significantly less than uranium. <br />6.0 Conclusions and Recommendations <br />Numerical modeling studies of the transport of constituents of concern from the <br />waste rock pile (or temporary ore storage piles) at the SM-18 mine indicate that the pile <br />poses no significant threat to underlying groundwater resources. The flow and transport <br />model incorporated several conservative assumptions regarding the hydraulic and <br />geochemical parameters. Most conservative was the assumption that the pore-water in <br />the waste pile contained constituents of concern concentrations that reflected SPLP test <br />conditions. Actual rainwater exhibits a higher pH value (less acidic than SPLP leaching <br />fluid) and would leach constituents of concem at lower concentrations. In addition, for <br />the 1000 year simulation, concentrations of constituents of concern in the waste-rock <br />pore water were maintained at initial concentrations. In reality, as constituents of <br />concern are leached from the waste rock, concentrations would steadily decline with <br />time. The net result is a model that over predicted the amount and availability of <br />constituents of concem for transport. <br />Even using such conservative assumptions, results of the modeling simulations <br />showed that no contamination reached the underlying groundwater system. For alt of the <br />analytes tested, none will migrate through the Salt Wash Member of the Morrison <br />12 <br />