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concerned that the polypropylene liner could breach under the weight of the impounded <br />water. The Division agrees that the felt layer under the liner is an important feature that <br />acts to protect the integrity of the liner, but the Division is concerned about the angularity <br />and size of the rock bedding. Please commit to incorporating a layer of "new" crushed <br />rock, of 1.0 inch - minus, immediately under the liner and felt. If necessary, please revise <br />the gradient of the leach field slopes to accommodate placement of the crushed rock. <br />The mine water pond will now have 6 to 8 inches of minus 1/4 inch crushed rock <br />underneath the polypropylene and geotextile liners to further protect from leaks in the <br />liner. Also, the leach field slopes have been lessened to 2H:1 V to allow for the <br />placement of to 8 inches of minus 1/4 inch crushed rock underneath the polypropylene <br />and geocomposite liners and well as 8 to 10 inches of minus 1/4 inch crushed rock <br />above the polypropylene liner. See Maps G -11 and G -12 as well as the narrative of <br />Appendix 12. <br />7. Please provide a description of both of the liner materials, such as whether they are <br />delivered as folded or rolled products, whether they will be custom - manufactured to <br />specific sizes. <br />The liner materials will be purchased from Colorado Lining. The products are delivered <br />in accordion -style folding. The lining will be partially sized at the factory to facilitate the <br />installation on -site. The lining will have to be welded together using heat fusion on site <br />to meet the necessary sizes and shapes. <br />8. Please also provide the site preparation and installation details, such as: how the <br />bedding surfaces will be checked for smoothness or protruding rocks, who will install the <br />liners, how the seams will be welded, and the methods of QA/QC to check for integrity. <br />The site preparation and installation have been described in detail in Appendix 12. <br />Colorado Lining International will be supplying the overseeing of the installation of the <br />liners. A certified welding technician trained by International Association of <br />Geosynthetics Installers will be on -site during the installation perform welds and ensure <br />proper installation. All manufacturers' installation procedures are enclosed in Appendix <br />14. Silver Star will follow these procedures for all installations. <br />9. The design of the lined leach field is such that the gathering pipes are "at the bottom" of <br />the lined leach field. The gathering pipes are to be wrapped in filter fabric and fully <br />bedded within a sand layer, to aid in trapping sediments before the water leaves the <br />leach field. Above the pipes and sand, there will be more than 20 vertical feet of <br />crushed rock emplaced. The Division is concerned about the method of placement of <br />the rock, protection of the gathering pipes and floor of the liner, and the sides of the liner. <br />Will the sand layer extend up the sides of the interior of the leach field to any height as <br />additional protection? During filling and the ongoing life of this leach field, is it possible <br />that rocks shifting could breach the liner? Please describe the steps in the site <br />preparation and installation. <br />The layering of the liners in the leach field has been re- designed to address puncturing <br />and strength. Two layers of geocomposite have been added. A gravel layer has also <br />been added on both sides of the geocomposite, which will greatly reduce any chance of <br />puncturing. The sand above and below the gathering pipes provide further protection for <br />the pipes. Also, the gravel layer will extend up the sides of the interior of the leach field. <br />