2008-07-11_PERMIT FILE - M2007044 (7)

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Energy Fuels Resources Corp. January 11, 2008 Frank Filas, P.E. -2- 073-81745 E • PROPOSED LINER SYSTEM DESIGN Compacted ROM waste materials were originally intended for use as the liner for the Whirlwind Mine ore pad, as discussed above. Because DRMS is requiring construction of an engineered liner system, and due to the lack of readily-available low permeability soils for a compacted clay liner, the following liner system (from top to bottom) is being proposed by EFRC: • •A minimum of 1 foot of compacted ROM waste rock; • A 2.5-foot thick cushion material; • Geosynthetic clay liner (GCL) material; and • Compacted subgrade. A schematic of the proposed liner system is provided in Figure 2. To prevent damage to the liner system, such as a reduction in the cushion layer thickness from continued operation of equipment on the ore stockpile pad, EFRC intends to place a minimum of one foot of ROM materials above the cushion zone. The proposed cushion material shall be produced by crushing mine waste rock or imported materials. The thickness of the cushion material was designed for the maximum anticipated equipment load (i.e., Caterpillar Model 950H Loader) based on a maximum allowable stress at the liner of approximately 8 pounds per square inch (psi). The cushion material thickness calculation is provided as Appendix A. Compaction of the cushion material according to a method specification has been incorporated into the specifications as this will result in increased performance as a stress redistribution layer. Equipment loading is the critical design factor for the cushion material thickness as it will be applying dynamic stresses on the liner due to continuous movement over the liner system, with discrete loads being applied at the tires (or tracks). The geosynthetic clay liner (GCL) proposed for the Whirlwind Mine ore stockpile is Bentomat® DN manufactured by CETCO Lining Technologies, or an approved equivalent. Bentomat® DN is a reinforced needlepunched GCL with two lightweight nonwoven geotextiles encapsulating a layer of Volclay® sodium bentonite. The proposed GCL provides good overall liner system stability at the proposed ore stockpile base grades (i.e., less than 5 percent). Preliminary stability analyses were conducted to compare the use of reinforced versus nonreinforced GCL materials. Nonreinforced GCL, such as Claymax® manufactured by CETCO, provides insufficient stability under saturated conditions at the anticipated liner grades due to the low hydrated internal shear strength. Proposed details for anchoring of the GCL and placement of GCL adjacent to structures embedded in the subgrade are provided in Figure 2. Squeegee (i.e., approximately '/4" roadbase fine material) will be placed where needed between the GCL and subgrade to prevent rocks protruding from the subgrade from damaging the GCL. Proposed technical specifications for construction of the engineered liner system are included as Appendix B. Clearing and topsoil removal are not required for the Whirlwind ore stockpile pad, but these specifications will be retained for future use on other similar projects. I:\07\81745\0400\0repadlinerdes_ I I J..08\07381745-Orepadlinerdesign_I I Jan07.D. Golder Associates