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amec <br />October 30, 2008 <br />Mr. Mark Vanoni <br />Senior Environmental Coordinator <br />Cripple Creek & Victor Gold Mining Company <br />Post Office Box 191 <br />Victor, Colorado 80860 <br />Re: Phase IVB/C Berm Raise <br />Dear Mark: <br />Project 84201125D0 <br />AMEC Earth and Environmental, Inc. (AMEC) has prepared this letter report presenting the details and <br />supporting engineering evaluations for the Phase IVB/C perimeter berm raise. The purpose of the berm <br />raise is to provide a positive capillary break between the Valley Leach Facility (VLF) and the perimeter <br />berm, and to augment solution collection for the VLF. <br />The berm raise extends along the northwestern edge of the Phase IVB/C VLF. A detailed plan and <br />section for the berm raise is presented in Drawings 1 and 2, attached. It is important to note that the <br />berm raise is not intended for additional ore storage or solution storage, rather it is to be used to provide a <br />positive hydraulic (capillary) between the VLF and the perimeter berm. <br />The berm raise was designed to account for the following conditions within the VLF: <br />¦ Maximum potential leach solution flow (up to 0.008 gpm/ft2, which is twice the nominal <br />application rate) <br />¦ Inflow from the 100-year/24-hour storm event <br />¦ A minimum of 30% additional capacity for dry freeboard. <br />The raise will consist of placing Select Structural Fill (SSF) on top of the existing perimeter berm. The <br />berm raise height is a nominal 2 feet above the existing berm. A geomembrane liner flap will be extrusion <br />welded onto the existing liner system and over the SSF to form the berm raise geometry shown in the <br />drawings. This geometry provides sufficient capacity to fully contain the maximum leaching rate and the <br />100-year/24-hour storm event, occurring simultaneously, with more than 1.5 feet of dry freeboard. Note <br />that since this berm is not to be used for ore or solution storage, there is no requirement for placing Soil <br />Liner Fill (SLF) beneath the geomembrane liner. <br />In addition to the berm raise, two 6-inch PCPE pipes are to be installed along the interior side of the berm <br />to augment solution collection and routing. The details of the PCPE pipe installation are shown in <br />Drawing 2. One 6-inch PCPE has sufficient capacity to fully pass the maximum leaching rate and the <br />100-year/24-hour storm event; however, a second pipe is included to provide a minimum factor of safety <br />of two for the piping system. <br />The design presented in Drawings 1 and 2 provides two redundant systems: (1) pipe flow and (2) open <br />channel flow. Each system is designed to fully pass the maximum leaching rate and design storm event. <br />Supporting calculations for the berm raise sizing and solution collection piping are attached to this letter <br />report. <br />AMEC Earth & Environmental, Inc. <br />304 Inverness Way South. Suite 490 <br />Englewood, Colorado 80112 <br />Tel: (303) 433-0262 <br />Fax: (303) 433-0362 www.amec.com <br />SAprojects\t 125d cc&v adr & slf geotech design\h4 - other reports\benn raise letter.doc