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1 <br />' primary liner system at the downstream end of the channel. The leak detention layer consists of <br />a layer of geogrid material. The primary liner system is a layer of 60 mil HOPE liner which ties <br />into the main embattlmtent and pond liner system in the same manner as the secondary liner <br />system. The collection channel liner system is anchored on both sides in standard anchor trenches <br />along the channel alignment. <br />' 3S South Diversion Charnel <br />The south diversion channel collects surface water from the major drainages in the area and routes <br />' the water around the south side of the tailingv facilities and into the natural drainage below the <br />collection pond. The total length of the channel is approximately 5000-ft. The majority of the <br />' channel was established in cut with the exception of the upper 900-ft of the channel, and the dike <br />across a drainage located above the lower impoundment. The depth of the channel varies from 5-ft <br />at the upper end of the alignment to 10-ft at the main embankment. The invert has a .025 percent <br />' gradient and has 2:1 side slopes. The channel is established just upslope of the ultimate limits of <br />the tailing impoundment, i.e., 8620-ft elevation. After passing the center line of the main <br />' embattlvttent the channel is routed into a 36 in diameter CMP pipe which drops ahe runoff water <br />approximately 50-ft in elevation into the south drainage just downstream of the main embankment. <br />A concrete acceleration chute and a concrete energy dissipation sttvnture were constructed at the <br />' upstream and downstream end of the 36-in pipe, respectively. After leaving the energy dissipation <br />structure the water flows in a channel established in the old drainage. As the cha~tnel approaches <br />' the gentle slopes in the bottom of the valley it is routed farther downstream around the collection <br />pond and into the natural drainage. <br />' Water sheds on the north side of the impoundment were accounted for in the water balance for the <br />impoundment and are expected to drain into the impoundment. No diversion facilities were <br />established on the north side of the impoundment. <br />4.0 SYNTHEl'IC LINER INSTALLATION <br />t Appro:mately 53 million square feet (sf) of synthetic materials were installed in the impoundment <br />facilities during the phase 1 construction. The bulk of the synthetic material was d0 mil very low <br />density polyethylene (VLDPE) liner, totaling approximately 4,716,698-sf of the liner installation. <br />' Sixty mil high density polyethylene (HOPE) liner was installed in areas which will have continued <br />exposure or potentially high hydraulic heads. These areas consisted mainly of the collention pond <br />t liners and ditch liners. Approximately 346,696-sf of 60 mil IIDPE liner was installed for the phase <br />1 facilities construction. Synthetic geogrid material was used to create the leak deflection medium <br />15 <br /> <br />