2012-10-01_REVISION - M1977305 (16)

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Hydrologically, these isolated zones, if they were saturated, would be referred to as perched water bodies. There is no indication that a continuous groundwater pathway exists for the transport of uranium related constituents - either in the Brushy Basin or the upper sandstone units of the Salt Wash Member of the Morrison Formation. 8.5 Geochemistry of Uranium Deposits The next factor to consider for the potential mobilization of constituents associated with uranium deposits is the geochemistry of the uranium deposits. For Colorado Plateau deposits, the chief ore mineral is carnotite and it was initially believed by many to be a primary sedimentary mineral, precipitated during or shortly after the deposition of the enclosing sediments (Fischer, 1942). Carnotite is fully oxidized. The discovery of increasing amounts of uraninite in deeper deposits began to raise a valence problem. The possibility began to develop that uraninite is an early uranium mineral and that carnotite is an oxidation product - the result of weathering (Garrels and Christ (1965). Hostetler and Garrels (1962) used Eh -pH diagram to illustrate the conditions under which uranium might be transported in underground waters in the presence of vanadium. The diagrams show for conditions of groundwater with a pH greater than 2 and oxidizing conditions, carnotite is stable and the dominant mineral. Several other studies suggest that uranium minerals, especially minerals that contain vanadium, are relatively insoluble, including carnotite. 8.6 Mobilization of Uranium Related Constituents With an understanding of the site geology, hydrology, and geochemistry, a scenario of possible mobilization and transport of uranium and related constituents needs to be developed to design an effective monitoring strategy. Mining would disturb the uranium deposits by introducing oxygen into reduced mineralized zones. It is possible that changes in redox conditions could mobilize uranium - related constituents but the geochemistry indicates that only limited amounts could be mobilized due to the low solubility of these uranium minerals. The lack of groundwater in the area further prevents a viable pathway for the transport of these constituents. If groundwater was encountered in sufficient quantities to transport the uranium and related constituents (all hydrologic data suggests this is not the case), then groundwater in the upper Salt Wash sandstone would migrate down and dip toward the syncline between the Paradox and Uncompahgre uplifts. Kearl (2005) conducted transport modeling studies to estimate the transport of mineral constituents associated with uranium ore deposits near the town of Uravan (Appendix II). These studies assumed that the Entrada Sandstone was the upper most aquifer in the area. A conservative approach consistent with the Nuclear Regulatory Commission requirements for high -level nuclear waste sites was used to develop a worst -case scenario - not necessarily the most likely scenario. Even under the worst case conditions, the modeling predicted that after 1000 years, uranium related constituents migrated approximately 200 feet vertically at a concentration of 10 -6 (1 /1,000,000 of the source O'Connor Design Group Inc. U - 16