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Cripple Creek & Victor Gold Mining Company Squaw Gulch Valley Leach Facility Design <br />minimum grade of 1 percent and will extend beneath the VLF area. Refer to Detail R <br />on Drawing A250. <br />The secondary underdrains will consist of a minimum 8 square -foot cross - sectional <br />area of underdrain fill wrapped in a 12- oz/yd nonwoven geotextile and will be covered <br />with a minimum of 6 inches of select structural fill, per Detail S on Drawing A250. The <br />tertiary underdrains will consist of a minimum 6 square foot cross - sectional area of <br />underdrain fill wrapped in a 12- oz/yd nonwoven geotextile and will be covered with a <br />minimum of 6 inches of select structural fill, per Detail U on Drawing A250. The <br />grades of the secondary and tertiary underdrains will vary to fit the final site grading <br />plan. <br />As part of the VLF design, calculations were conducted to size the flow capacity of the <br />underdrains under various hydraulic heads, and to confirm the flow capacity of existing <br />VLF underdrains under 800 feet of ore depth. These calculations are presented in <br />Appendix C.9. <br />4.7 Liner System <br />4.7.1 Ore Storage Area (OSA) <br />The OSA composite liner system includes a minimum 1- foot -thick low- permeability <br />SLF overlain by an 80 mil single -sided textured (textured side down) LLDPE <br />geomembrane, overlain by 2 feet of DCF. In areas where the final basin slope is <br />generally greater than 2.5H:1 V, an 80 -mil double sided textured LLDPE will be <br />substituted for the 80 -mil single -sided textured LLDPE. This is the same liner <br />configuration approved and used for the Cresson Project VLF. A textured LLDPE <br />geomembrane was selected as it provides higher soil /liner interface shear strength <br />than smooth LLDPE geomembrane. Discussions regarding the shear strengths used <br />in the stability analyses are presented in Section 5.1.2. <br />Laboratory testing on representative samples of the SLF from the clay borrow <br />indicates that the material will provide an acceptable permeability of 1x10T cm /s or <br />less when compacted to 95 percent of the standard Proctor maximum dry density at or <br />near the optimum moisture content. A series of liner load tests conducted by Golder <br />(2005) indicate that the liner systems within the VLF can withstand ore depths of <br />approximately 800 feet, or approximately 610 pounds per square inch (psi) assuming <br />an ore density of 110 pcf. These results are presented in Appendix B.2. <br />4.7.2 Squaw Gulch VLF Pregnant Solution Storage Area (PSSA) <br />The PSSA will be constructed as an internal pond within the VLF area. The PSSA will <br />be formed by constructing a containment embankment across the Squaw Gulch <br />drainage. The PSSA embankment will also serve as an embankment for the Highway <br />Project No.: 74201125G0 Page 21 <br />1 September 2011 <br />cameo <br />