2012-02-28_REVISION - M1980244 (65)

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Cripple Creek & Victor Gold Mining Company Squaw Gulch Valley Leach Facility Design 67 realignment, as discussed in Section 4.4. The PSSA layout and details are presented on Drawings A300 through A320. The liner system for the PSSA will consist of the following: • Outside of the PSSA sump, the liner system will consist of 12 inches of SLF overlain by a 100 -mil textured (single -sided with textured side down) LLDPE bottom geomembrane overlain by 3 feet of LVSCF overlain by a 100 -mil smooth LLDPE top geomembrane overlain by 2 feet of DCF. A textured LLDPE geomembrane was selected for the bottom liner as it provided for higher interface shear strength than smooth LLDPE geomembrane. • Inside of the PSSA sump, the liner system will consist of 12 inches of SLF overlain by a 100 -mil textured (single -sided with textured side down) LLDPE bottom geomembrane overlain by 3 feet of LVSCF overlain by a 100 -mil smooth LLDPE top geomembrane overlain by 5 feet of DCF. A textured LLDPE geomembrane was selected for the bottom liner as it provided for higher interface shear strength than smooth LLDPE geomembrane. 4.8 Leak Detection System (LDS) A leak detection system (LDS), comprised of a geomembrane -lined 1- foot -by -1 -foot deep trench, will be installed along alignments identified in Drawings A205 and A210 for Phase 1 and Phase 2, respectively, beneath the SLF component of the composite liner. The LDS trenches will be lined with 40 -mil smooth LLDPE geomembrane on the bottom and one side, as with previous VLF designs. A 12 oz/yd nonwoven geotextile will then be placed in the LDS trench and wrapped around a 3 -inch diameter perforated corrugated polythylene pipe and 3/4 -inch minus leak detection fill. The trenches will be excavated on a typical grade of 1 percent toward a sump located at the edge of the VLF. Typical details for the LDS are illustrated in A260. 4.9 Low Volume Solution Collection System (LVSCS) As a part of the PSSA design, a LVSCS is being installed between the upper 100 -mil LLDPE geomembrane and the lower 100 -mil LLDPE geomembrane. The LVSCS consists of a 3 -foot layer of LVSCF, which is 1 -inch minus screened material (refer to the specifications contained in Appendix H). Solution that enters the LVSCS is returned to the VLF process circuit via pumps lowered inside two of the three riser pipes (one spare riser pipe) which extend into the LVSCS sump (located under the PSSA sump). The riser pipes design consists of three 18 inch - diameter high density polyethylene (HDPE) pipes, which are connected together to create a manifold within the LVCSC sump. The manifold and lower 12 feet of the riser pipes are perforated to allow solution flow into the pipes. Details of the LVSCS sump and riser pipes are included in Drawings A420 and A430. A small building constructed at the ground Project No.: 74201125G0 Page 22 1 September 2011 amec0