Laserfiche WebLink
The primary underdrains will consist of a minimum 15 square -foot cross sectional area of <br />underdrain fill with a 4 -inch perforated, corrugated polyethylene pipe ( "PCPE ") wrapped <br />in a nonwoven geotextile and covered with a minimum of 6 inches of select structural fill. <br />The primary underdrain will be placed at a minimum grade of 1 percent and will extend <br />beneath the SGVLF area. <br />The secondary underdrains will consist of a minimum of 8 square -foot cross - sectional <br />area of underdrain fill wrapped in a nonwoven geotextile and will be covered with a <br />minimum of 6 inches of select structural fill. Similarly, the tertiary underdrains will <br />consist of a minimum of 6 square -foot cross - sectional area of underdrain wrapped in a <br />nonwoven geotextile and covered with a minimum of 6 inches of select structural fill. <br />The grades of the secondary and tertiary underdrains will vary to fit the final site grading <br />plan. <br />As part of the SGVLF design, calculations were conducted to size the flow capacity of <br />the underdrains under various hydraulic heads to confirm the flow capacities. Detailed <br />designs and flow calculations are presented in Appendix 9, Volume V. <br />7.2.1.2 Ore Storage Area Liner System <br />The ore storage area will be constructed with the composite liner system as previously <br />approved and certified for the AGVLF. The liner system consists of a minimum one -foot <br />thick SLF with a maximum permeability of 1x10 -6 cm/sec placed on a prepared surface <br />and overlain by an 80 -mil single -sided textured (texture side down) LLDPE <br />geomembrane. The geomembrane will be overlain by a pipe drain system and a <br />minimum of two feet of DCF prior to placement of the ore. The pipe drain system, called <br />the high volume solution collection system ( "HVSCS "), consists of a network of pipes <br />laid in a dendritic pattern to maintain a permeable layer leading to the PSSA. The <br />HVSCS is discussed in Section 7.2.4 below. <br />The SLF will come from one of two clay borrow areas (or clay stockpiles); one of the <br />borrow areas is located within the ECOSA footprint and the other located within the <br />SGVLF footprint as shown on Drawing C -4 in Exhibit C, Volume I. Laboratory testing <br />on representative samples of the SLF from the clay borrow areas indicates that the <br />material will provide an acceptable permeability of 1 x10 cm/sec or less when <br />compacted to 95 percent of the standard Proctor maximum dry density at or near the <br />optimum moisture content. <br />Cripple Creek & Victor Gold Mining Company <br />Cresson Project Mine Life Extension 2 <br />7 -4 <br />