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The Leadville Mill <br />4.3.6 POLYPROPYLENE LINER <br />M 1990 -057 <br />EXHIBIT C — MILL PLAN <br />Page 4 -14 <br />Concurrent with the installation of the seepage /leak detection system, a synthetic <br />pond liner of 45mi1 polypropylene geomembrane, or equivalent, will be installed as <br />shown in Figure 4 -9. The hydrostatic head on the geomembrane liner will be Tess <br />than 2ft. UMC will continuously decant the water for reuse in the mill to minimize <br />makeup water requirements. Typically, tailings will be laid down in a bench, or <br />splay within the impoundment and a barge mounted decant sump pump(s) located <br />at the lowest level will pump the water back to the mill. This pump(s) will be <br />pressure sensor activated (or float switch activated). UMC is incorporating a <br />standard liner keying system. Typically this is a trench 2ft wide, approximately 3ft <br />or more from edge of the inside slope, 2ft deep. The liner is rolled down the trench <br />wall, across the trench floor, and then the trench is backfilled and compacted to the <br />specified embankment compaction standards. Details are presented in Figure 4 -9. <br />Geomembrane liner specifications are presented in Appendix 4 -1.3, Geomembrane <br />Liner. <br />4.3.7 INITIAL TSF LINER STABILIZATION <br />The impoundment liner will initially be held in place with water (ballast) hauled into <br />the site from the local construction water metering station. Next, the approximately <br />1,000st of historic tailings stored on the temporary storage pad will be moved to the <br />edge of the TSF by front -end loader, and washed down the slope of the TSF with <br />water from the TSF. <br />UMC has committed to CDRMS to initiate removal of the existing onsite ore <br />stockpiles within 60days following start-up. The material is currently stockpiled on <br />the west side of the mill entrance road, at the "Y" for the lower access (south) road. <br />With this in mind, the mill operation will use this material as initial feedstock to <br />further secure the liner. Historic tailings, the existing ore stockpiles, water, or onsite <br />soils will also be used in ballast pipes or sand bags to stabilize the liner on the TSF <br />embankment slopes. <br />4.3.8 QA/QC <br />The Quality Assurance /Quality Control (QAQC) Plan for the TSF is as follows. <br />Version 1.0 April2013 <br />