2008-01-15_PERMIT FILE - M2007044 (2)

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d. Whirlwind Bulkhead The Whirlwind Decline was carefully evaluated to find a competent sandstone that is located below the entrance point of the water in the decline but before the start of the mineralized zone of the Salt Wash Formation, where the uranium ore is found. This evaluation was performed by Dick White, certified geologist for Energy Fuels. A competent sandstone zone was found in anon-mineralized area at the very top of the Salt Wash Formation. This proposed seal location is shown on Figure F 1 and Map C2 included in Attachments E and C, respectively. As is seen in Figure F1, the estimated vertical distance from the seal location to the water entrance point is 23 feet. Figure F2 of Attachment E shows a conceptual layout of the 1.6-foot thick bulkhead, including forms, timber, piping, and the surrounding rock. The sandstone was sampled and laboratory tests were conducted for compressive strength and hydraulic conductivity. These test results are presented in Attachment B. The compressive strength was found to be 8,490 pounds per square inch (psi). This is about twice the compressive strength of cured, high-quality concrete and more than adequate for the seal installation. The hydraulic conductivity was found to be 2.5 x 10"3 m/d (equivalent to 2.9 x 10"6 cm/s). Although not completely impermeable, it is within the range of an aquiclude. The plan for the seal is to employ low pressure grouting of the surrounding sandstone to ensure that water does not bypass the seal. Mr. White also prepared an analysis of the sandstone beds of the Brushy Basin zone based on his experience with drilling on Beaver Mesa and other similar areas within the Colorado Plateau. His analysis, cross-sections and conclusions are presented in Attachment A. He concludes that the expected water level above the seal would be no more than 15 vertical feet above the water entrance point. Because the seal will be located about 23 vertical feet below the entrance point, the total estimated head on the seal will be no more than 38 feet. Using the Einarson and Abel (1990) template, this would result in a theoretical seal concrete thickness of 0.40 feet Because a seal of this thickness would be difficult to adequately anchor in the surrounding sandstone, Energy Fuels commits to using a seal thickness of 1.6 feet. This seal would be capable of handling 147 feet of head, which is very conservative for this site-specific application. Cost estimation for this seal as well as the Packrat contingency seal (see Attachment H) are based on the As-built Report for the Terry Tunnel Bulkhead. The Terry Tunnel Bulkhead was installed at the Sunnyside Mine in Silverton, CO and the DRMS considers this design to be satisfactory. A revised bond estimate for the Whirlwind seal in included as Attachment I. The seal estimates provided in both Attachments H and I take into account the following differences between the Terry Tunnel Bulkhead and the proposed bulkheads for the Whirlwind Mine. • Labor costs have increased over time. A list of the current labor costs for Energy Fuels is presented in Attachment I. l~netg.- l.'uels l~esc~~icee5 C;t;~r~C~ruttit~I1 =1~ l~nion I3cn~lee-a~•d, Suite fit~(7 19 1~~~1:e~~ ot~ci. C`C) ~£? 1 ~ ~ 1'hc~~~e; 3~~-<)`7~-2 ~1 ~(}