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M- 1977 -417 EPP <br />Appendix U -2 <br />Ore Stockpile Liner Design <br />The Sego Mine Project is proposed to include a 0.1 -acre ore stockpile pad. The ore materials <br />anticipated for temporary storage at the Sego Mine are non -acid generating, with ore derived from <br />the Salt Wash Unit of the Morrison Formation. The ore stockpile will be constructed near the mine <br />portal and will be accessed via loaders and trucks on a consistent basis. One or more stockpiles <br />will be placed on the pad to a maximum height of 20 feet. The proposed location of the ore stockpile <br />pad is illustrated in Figure 2. The ore stockpile pad will be surrounded by berms on all sides to <br />provide drainage isolation. <br />PROPOSED LINER SYSTEM DESIGN <br />The proposed Sego Mine liner is patterned after the design submitted by Energy Fuels Resources <br />Corporation for the Whirlwind Mine (M- 2007 -044). Much of the following is excerpted from that <br />application as designed by Golder Associates (used by permission of Energy Fuels). Any references <br />to figures or appendices in the following text of this Appendix U -2 refer to this Appendix only, and <br />not to the Figures referenced elsewhere in Exhibit U. The following liner system (from top to bottom) <br />is being proposed. <br />• A minimum of 1 foot of compacted Run- Of -Mine (ROM) waste rock; <br />• A 2.5 -foot thick cushion material; <br />• Geosynthetic clay liner (GCL) material; and <br />• Compacted subgrade. <br />A schematic of the proposed liner system is Figure 2. <br />To prevent damage to the liner system, such as a reduction in the cushion layer thickness from <br />continued operation of equipment on the ore stockpile pad, a minimum of one foot of ROM materials <br />will be placed above the cushion zone. <br />The proposed cushion material shall be produced by crushing mine waste rock or imported materials. <br />The thickness of the cushion material was designed for the maximum anticipated equipment load (i.e., <br />Caterpillar Model 950H Loader) based on a maximum allowable stress at the liner of approximately <br />8 pounds per square inch (psi). The cushion material thickness calculation is provided as Appendix <br />A of the Golder report. Compaction of the cushion material according to a method specification has <br />been incorporated into the specifications as this will result in increased performance as a stress <br />redistribution layer. Equipment loading is the critical design factor for the cushion material thickness as <br />it will be applying dynamic stresses on the liner due to continuous movement over the liner system, <br />with discrete loads being applied at the tires (or tracks). <br />The geosynthetic clay liner (GCL) proposed for the Sego Mine ore stockpile is Bentomat® DN <br />manufactured by CETCO Lining Technologies, or an approved equivalent. Bentomat® DN is a <br />reinforced needlepunched GCL with two lightweight nonwoven geotextiles encapsulating a layer of <br />Volclay sodium bentonite. The proposed GCL provides good overall liner system stability at the <br />proposed ore stockpile base grades (i.e., less than 5 percent). Preliminary stability analyses were <br />conducted to compare the use of reinforced versus nonreinforced GCL materials. Nonreinforced <br />GCL, such as Claymax® manufactured by CETCO, provides insufficient stability under saturated <br />conditions at the anticipated liner grades due to the low hydrated internal shear strength. Proposed <br />11 <br />