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S C <br />SMITH WILLIAMS CONSULTANTS, INC. <br />PSSA, and the base of the LVSCF is sloped to drain to the LVSCS sump. Solution collected in <br />the LVSCS sump has been designed to be pumped back to the VLF via two pumps installed in <br />18-inch-diameter high-density polyethylene (HDPE) riser pipes. A third riser has been included <br />in the LVSCS to provided additional capacity, should it be needed. A shed will enclose the <br />LVSCS riser pipes and associated instrumentation, electrical, and piping components (provided <br />by others). <br />4.9 High Volume Solution Collection System (HVSCS) <br />The purpose of the HVSCS is to provide a means to collect and route process solutions from the <br />ore storage area to the PSSA. The HVSCS for Phase 5 VLF has been designed to consist of <br />24 inches of free draining DCF, which is supplemented with a solution collection piping system <br />placed directly over the upper geomembrane liner at the base of the DCF. <br />Within the Phase 5 VLF area, the primary solution collection pipes will consist of three 26-inch <br />DR 11 perforated HDPE pipes located along the bottom of the Phase 5 VLF PSSA. These pipes <br />are sized to provide 6,000 gallons per minute (gpm) each under gravity flow conditions. <br />Secondary solution collection pipes, which will vary in size from 8- to 15-inch-diameter PCPE <br />(ADS N-12, or equivalent) pipe, will direct solution collected from 4-inch-diameter highway <br />grade PCPE tertiary pipes that are on 90-foot typical centers into the primary solution collection <br />pipes. Detailed calculations supporting the pipe spacing and pipe sizing are presented in <br />Appendix. C. The general layout of the primary, secondary, and tertiary solution collection pipes <br />are shown on Drawing A400. Solution collection pipe details are shown on Drawing A410. <br />The HVSCS pipes were sized and will be located to maximize solution recovery while <br />accounting for acceptable pipe deformation under 590 feet of ore.depth. All of the piping - <br />calculations assume "arching" will occur. within the DCF, thereby maintaining open solution <br />flow space. The 4-inch-diameter PCPE pipe spacing of 90 feet was based on minimizing the <br />hydraulic head on the liner system in the ore storage area to no more than 2 feet, with zero slope <br />on the foundation (a conservative assumption). The secondary pipe sizes were based on full <br />flowing conditions assuming a pipe collapse configuration. <br />The primary solution collection pipes were sized as heavy=walled-HDPE to allow pipe deflection <br />without collapse. Studies of flexible pipes under high loads conducted by Watkins (1990) <br />indicate that flexible pipes, like HDPE, in granular "arching" materials will remain open as long <br />as the ring deflection does not exceed the vertical strain of the bedding materials and does not <br />exceed 20 percent (Lupo, 2001). After the vertical strain of the pipes reach 20 percent, the pipe <br />section will deform into a "binocular" shape, but will still convey flow. Calculations presented <br />S:\PROJECTS\1125 CCBV PHASE 5 VLF1H2 - DESIGNWREQUA VLFlVLF PHASE 5 FINAL REPORT V2.DOC 26 <br />