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hydrostatic head on the geomembrane liner will be less than two feet. UMC will continuously decant the <br />water for reuse in the mill to minimize makeup water requirements. Typically, tailings will be laid down <br />in a bench, or splay within the impoundment and a barge mounted decant sump pump(s) located at the <br />lowest level will pump the water back to the mill. This pump(s) will be pressure sensor activated (or float <br />switch activated). UMC is incorporating a standard liner keying system. Typically this is a trench 2ft <br />wide, approximately 3 feet or more from edge of the inside slope, 2 feet deep. The liner is rolled down <br />the trench wall, across the trench floor, and then the trench is backfilled and compacted to the specified <br />embankment compaction standards. Details are presented in Exhibit TSF -06. <br />Geomembrane liner specifications are presented in Figure C -6, 45 -mil Polypropylene Liner. <br />Initial TSF Liner Stabilization <br />UMC has committed to the Division to initiate removal of the existing onsite ore stockpiles within 60days <br />following startup. The material is currently stockpiled on the west side of the mill entrance road, at the <br />"Y" for the lower access (south) road. This material is angular and of varying size, but predominately - <br />1 in with a large fine proportion. <br />The impoundment liner bottom will initially be held in place with water hauled onto the site from the <br />local construction water metering station. Additionally, the impoundment liner will be held in place with <br />material from the ore stockpiles discussed in the ORE STOCKPILES section. The material may be <br />placed in sand bags and placed on the liner, and the existing on -site stockpiles may also be initial feed <br />stock for mill startup with the tailings reporting to the tailings facility. These stockpiles are on -site and <br />have been covered with visqueen since 2009. <br />The slopes of the impoundment will not receive direct placement of material. Ballast tubes from the top <br />of the embankment to the bottom of the impoundment, typically constructed from 6in PVC tubes or <br />geotextile socks and filled with material or water, will hold the liner down following installation until the <br />tailings cover the exposed liner. These ballast tubes will be held in place from the top by keying into the <br />anchor trench and extend to the impoundment bottom. The ballast tubes will not prevent lift, but will <br />minimize lift. <br />M1990 -057 May 14, 2013 <br />