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Cripple Creek & Victor Gold Mining Company May 15, 2007 <br />Mr. Kevin Riley -2- 073-2140 <br />Technical Evaluation of the Liner Barrier <br />The location of the proposed liner barrier was selected using the following criteria: <br />• The liner barrier will divert leach solution flow around the uncertified area to the <br />Phase IV PSSA; and <br />• The liner barrier will allow CC&V to place ore over portions of the certified <br />Phase IV liner located above the LOB in a geotechnically stable configuration. <br />The purpose of the liner barrier is to isolate the uncertified area by diverting the leach solution to the <br />Phase IV PSSA while preventing the flow path of solution from contacting the uncertified area. To <br />determine the extents of the uncertified liner area, the present topography was compared to the <br />as-built liner grades. For the purpose of this evaluation, all areas where the depth of the over liner <br />material is less than 20 feet and where mine haulage trucks can potentially traverse are considered <br />uncertified. As shown on Figure 1, the uncertified areas of liner are generally on the southeast and <br />northeast sides of the existing LOB. The proposed liner barrier runs southwest to northeast, following <br />a subtle ridge in the as-built liner topography. The liner grades in this area slope from the northeast to <br />the southwest. Any leach and meteoric solutions on the northwest side of the liner barrier will be <br />diverted around the uncertified liner area. Ore placement on the southeast side of the liner barrier will <br />not occur. Figure 1 shows the locations of the uncertified liner area, the proposed liner barrier, and <br />the existing LOB superimposed on current topography. <br />The liner barrier will consist of a strip of 80-mil thick LLDPE geomembrane extrusion welded to the <br />existing 80-mil LLDPE primary liner, which will then be installed to a minimum height of three feet. <br />As shown on Figure 1, the liner barrier will extend down the existing geomembrane lined 3(H):I(V) <br />slope from control point (CP) 1 to CP-2. In this area, the drain cover fill is approximately 2 feet thick <br />with the relevant design detail for this reach shown as Detail 1 on Figure 2. The liner barrier will then <br />be extended from the toe of the slope to CP-3, which is ten feet beyond the downgradient limits of <br />uncertified liner. Within this reach, the depth of overliner is still two feet but ore materials have been <br />placed up to a depth of 20 feet. For this reach, the relevant section is shown as Detail 2 on Figure 2. <br />A section along the liner barrier is provided as Figure 3. Between CP-2 and CP-3, a trench will need <br />excavated with minimum 2(H):1(V) for safety considerations. On the downgradient (southern) side <br />of the trench, the existing depth of ore materials may be excavated to reduce the height of the liner <br />barrier required, as long as the minimum height of the barrier is three vertical feet. Alternatively, the <br />liner barrier can be extended up the full height of the trench. <br />Per the VLF design criteria, the maximum allowable hydraulic head on the liner is 2 feet. The <br />existing solution collection system has been designed to provide for the maximum 2 feet of hydraulic <br />head for the operational and contingency design conditions. The liner barrier will therefore extend <br />3 vertical feet above the existing liner to provide an adequate barrier to solution flow. The liner <br />barrier design includes installation of an additional 4-inch diameter highway grade perforated <br />corrugated polyethylene (PCPE) tertiary drain pipe to a supplement to the existing Phase IV high <br />volume solution collection piping and drain cover fill system (drain system). This pipe will be <br />extended along the interior limits of the liner barrier to ensure that hydraulic head is maintained to a <br />minimum level adjacent to the liner barrier. The slope of the drain pipe is 40% between CP-1 and CP- <br />2 and 6.2% between CP-2 and CP-3. Assuming 75% flow capacity for the four inch diameter PCPE <br />pipe with a slope of 6% slope, the additional PCPE pipe will provide an additional 240-gpm of <br />conveyance to the drain system. As such, given that this drainage pipe. is exterior to the loaded ore <br />and supplements the existing drain system, the inclusion of the PCPE drainage pipe will keep the <br />I:\OT2110\O100V.WptI50LATIONBARR-ISMAYOTO)32110LRJFRLSOLBARRIDLISMAYOI.DOC Golder Associates