Laserfiche WebLink
Cripple Creek & Victor Gold Mining Company May 15, 2007 <br />Mr. Kevin Riley -3- 073-2140 <br />level of hydraulic head to at or near the top of the drain pipe. The PCPE drain pipe will be extended <br />to a minimum 10 feet downgradient (west) of the downgradient limits of the uncertified liner limits as <br />shown on Figure 1. <br />In accordance with the Phase IV design criteria, the required static factor of safety against global <br />stability failure of the heap is 1.3. Because the addition of the liner barrier will alter the ore stacking <br />plans, stability analyses were conducted to determine the ore loading considerations required to <br />maintain stability in the vicinity of the liner barrier. The results of the analysis are documented in <br />Attachment 1 and summarized below: <br />• As a result of the downgradient dip of the liner system in the area where the new <br />ore will be loaded, the first lift will be placed starting at the lowermost toe limits <br />(to buttress subsequent ore placement). <br />• The first lift will be limited to 30 feet in height with the lowermost slope reduced <br />from angle of repose to 2:1 (H:V). The commitment to reduce the angle of <br />repose slope to approximately 2:1 (H:V) is limited to 50 feet on either side of the <br />drainage low point, as this will provide a buttress for the upgradient placed ore. <br />• Each subsequent lift will be placed at angle of repose (approximately 38 degrees) <br />and no higher than 50 feet. <br />• Overall composite slopes will be benched between lifts to provide a composite <br />2.2:1 (H:V) slope or shallower. <br />• Ore placement will proceed from lower elevations upwards. <br />• The ore will be loaded such that the ore slope is perpendicular to the as-built liner <br />grades. This generally means that the toe of the ore slope is parallel to the liner <br />barrier. Ore will not be placed where it is un-buttressed in the direction of the <br />ore slope. <br />CONSTRUCTION CONSIDERATIONS <br />It is anticipated that the DCF material excavated to expose the existing liner will be re-used to <br />construct the berm and as liner cover fill over the liner barrier. In accordance with the Phase IV <br />minimum DCF specifications, the minimum thickness of DCF fill will be 2 feet. To make-up the <br />material deficit of DCF, additional DCF will need to be imported using low ground pressure <br />construction equipment with a maximum 8.7 psi ground pressure. In accordance with the Phase IV <br />design requirements, the thickness of the DCF can be increased to accommodate larger equipment as <br />long as the pressure at the liner interface does not exceed 8.7 psi, as approved by the certifying <br />engineer. <br />The barrier extends up a 3:1 (H:V) slope, thereby prohibiting large haulage equipment to access this <br />area. It is expected that a low ground pressure dozer, bobcat, or similar sized piece of equipment will <br />be utilized for the majority of the work. It will also be necessary for portions of the work to be <br />completed by hand. For example, extreme care will be used when removing the last few inches of <br />liner cover fill so that the existing liner is not damaged. <br />I:\OT21<0\OIOOWMQtISOLATIONBARR-15MAYOM7321JOLpJERLSOLBARR0415MAY07- Golder Associates