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The Leadville Mill 4.3.4 GEOSYNTHETIC CLAY LINER M 1990 -057 EXHIBIT C — MILL PLAN Page 4 -13 A Bentomat® DN geosynthetic day liner, or equivalent, will be placed on the interior slopes and impoundment bottom. The geosynthetic clay liner is installed concurrent with the leak detection drainage net system and the 45mi1 polypropylene geomembrane liner. Geosynthetic clay liner specifications are presented in Appendix 4 -1.1, Geosynthetic Clay Liner. 4.3.5 LEAK DETECTION SYSTEM Concurrent with the installation of the geosynthetic clay liner, a seepage leak detection system will be placed between the geosynthetic clay layer and the synthetic liner with the collection system located in the northwest corner of the impoundment, and the impoundment bottom sloping at 0.5% to the northwest. Figure 4 -8 shows additional details on the leak collection system and sump. The leak detection system is concurrently installed between the top layer of the 1x10 -6 cm /s (or Tess) geosynthetic clay liner and the 45mi1 polypropylene geomembrane liner. The leak detection system is a composite drainage product, produced by thermally laminating a 6oz /yd nonwoven geotextile to both sides of a polyethylene drainage net, capable of intercepting liquid within the leak detection zone and conveying the liquid to a collection sump for storage. The leak detection drainage net system is shown on Figure 4 -8 and 4 -9. The volume of the collection system is limited to the sump and is approximately 90 gallons. The sump is accessed through a 4in PVC pipe to the top of the impoundment. Collected leachate will be returned to the TSF and then recycled to the mill through the impoundment decant pump(s). The leak detection system requires a manual inspection of the sump through the 4in PVC pipe. If leachate is detected (indicating a leak in the 45mi1 polypropylene), the level will be monitored, a small pump will be installed in the PVC pipe and the Division notified of fluids from the leak detection system. If groundwater is detected (indicating a leak in the geosynthetic day liner), the level will be monitored, a small pump will be installed in the PVC pipe, the groundwater pumped to the impoundment and the Division notified of fluids from the leak detection system. Leak detection drainage net system specifications are presented in Appendix 4 -1.2, Leak Detection. Version 1.0 April2013