2012-10-01_REVISION - M1977311 (12)

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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 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 I). These studies assumed that the Entrada Sandstone was the upper most aquifer in the area - applicable at SR -13A mine site based on the area well data. 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 concentration) of the initial concentration in the pore water of the waste rock. The uranium plume is contained in the Salt Wash Member of the Morrison Formation. The plume does not enter the Entrada Sandstone. The Summerville Formation provides an additional buffer zone restricting potential contamination from entering the groundwater. The results of this analysis indicate that conditions are not conducive to the transport of uranium - related constituents to the environment. Geochemistry suggests that mobilization of these constituents is unlikely. There is no indication of a continuous groundwater system that could provide a pathway for these constituents to migrate from the mine into the environment. Transport modeling has shown that vertical migration from the upper Salt Wash sandstone to the upper -most aquifer in the area (Entrada Formation) is highly unlikely due to the lack of water, low permeability of the strata and the sorption of uranium - related constituents. 8.7 Proposed Groundwater Monitoring Plan If water is encountered during mining, then the water will be sampled and a chemical analysis performed. If levels of uranium related constituents are above established regulatory guidelines, then a well will be placed down gradient of the mining area that contains groundwater and monitored according to DRMS regulations. This approach will provide a better chance of encountering groundwater in a monitoring well rather than drilling a hole at a random location down gradient of the mine workings. The data gathered by Cotter Corporation supports this plan. O'Connor Design Group Inc. T - 16