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justify any additional benefit to understanding the groundwater flow system or protecting <br />the environment. Conventional groundwater monitoring programs are intended for <br />aquifers where groundwater transport rates justify several wells to provide adequate <br />information on subsurface conditions. Under any reasonable definition of a groundwater <br />aquifer, the Salt Wash does not meet water quality or quantity requirements. The <br />conservative estimates on groundwater transport rates of a few hundredths of a foot per <br />year clearly indicate that the transport of constituents of concern in the Salt Wash <br />sandstones is not a viable mechanism that could impact the surrounding environment. <br />8.5 Geochemistry of Uranium Deposits <br />The next factor to consider for the potential mobilization of constituents associated with <br />uranium deposits is the geochemistry of the uranium deposits. For Colorado Plateau <br />deposits, the chief ore mineral is carnotite and it was initially believed by many to be a <br />primary sedimentary mineral, precipitated during or shortly after the deposition of the <br />enclosing sediments (Fischer, 1942). Carnotite is fully oxidized. The discovery of <br />increasing amounts of uraninite in deeper deposits began to raise a valence problem. The <br />possibility began to develop that uraninite is an early uranium mineral and that carnotite <br />is an oxidation product — the result of weathering ( Garrels and Christ, 1965). <br />Hostetler and Garrels (1962) used Eh -pH diagram to illustrate the conditions under which <br />uranium might be transported in underground waters in the presence of vanadium. The <br />diagrams shows that for conditions of groundwater with a pH greater than 2 and <br />oxidizing conditions, carnotite is stable and the dominant mineral. Several other studies <br />suggest that uranium minerals, especially minerals that contain vanadium, are relatively <br />insoluble including carnotite. <br />8.6 Mobilization of Uranium Related Constituents <br />With an understanding of the site geology, hydrology, and geochemistry, a scenario of <br />possible mobilization and transport of uranium and related constituents needs to be <br />developed to design an effective monitoring strategy. Mining would disturb the uranium <br />deposits by introducing oxygen into reduced mineralized zones. It is possible that <br />changes in redox conditions could mobilize uranium related constituents but the <br />geochemistry indicates that only limited amounts could be mobilized due to the low <br />solubility of these uranium minerals. <br />Another factor is the mechanical dissolution of uranium related constituents by mining <br />activities. Groundwater seeps entering the mine flow large distances across the mine <br />floor before being collected at sumps. Ore or waste rock, either naturally occurring in the <br />mine or spilled during mining operations, is exposed along the mine floors and the <br />collection ditches where flowing water dissolves minerals. Table 3 provided sampling <br />data for several sumps located at the base of the mine decline and various working areas <br />within the mine. Comparing uranium values from the sumps with groundwater data from <br />the monitoring well presented in Table 4 shows values that are equal to or as high as 5 <br />times greater. Selenium values in the mine can be less than or as much as twice the <br />O'Connor Design Group Inc. U - 18 <br />