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Ouray Silver Mines Inc. <br /> Technical Revision 10 August 14, 2018 <br /> • Aerobic wetlands <br /> Early (draft) results from the ongoing Treatability Study (Appendix B) indicates that all metal <br /> concentration standards can be met but testing for variable stressor conditions continues. The <br /> system will be built in the existing mine water and storm water ponds (Map 1), which will be <br /> referred to as Pond #1, Pond #2 and Pond 43 throughout the remainder of this text. <br /> 3.2 Groundwater Monitoring Well Installation <br /> In addition to water treatment, OSMI proposes a new well (GW-4)to monitor the pond for <br /> leakage and water quality impacts. This new well GW-4, along with existing Wells GW-IA, <br /> GW1-B, GW-2A, GW-213, GW-3R, and GW313 (Table 1), will be monitored quarterly for the <br /> groundwater parameter list as established in TR-09 (Table 2). Voluntary monitoring of Sneffels <br /> Creek locations on a quarterly basis will continue. <br /> 3.3 Diesel Tank Relocation <br /> Moving the Diesel tanks to the western edge of the Administrative buildings will allow for easier <br /> fueling access, in a lower traffic area, resulting in improved safety (Map 1). Additionally, the <br /> diesel location is next to the reagent building, and needs to be moved for safety reasons. <br /> 4 Physiochemical Characteristics <br /> Physical and chemical properties for each requested change are presented in this section. <br /> 4.1 Five Stage Passive Treatment System <br /> The following discussion of mill water treatment physiochemical characteristics is broken into <br /> three segments, describing the treatment process and changes in configuration for each of the <br /> three ponds. Each of the ponds will be expanded (Figures 1 and 2) and passive treatment related <br /> materials will be added (Figure 3) will be added, while maintaining freeboard (Figures 4-6) for <br /> storm events. The ponds and water conveyances associated with the passive treatment system <br /> will all be lined (a combination of membrane and clay liners)or contained in pipe. Composition <br /> of media to be placed in each pond has not yet been finalized but is expected to align with <br /> materials in the Treatability Study (Appendix B)that have successfully removed metals in pilot <br /> testing. As-built drawings will be submitted after construction. <br /> Pond#1 (also known as the Mine Water Pond) is the first pond encountered by mine water after <br /> it leaves the portal. The pond size will be increased, Collection Ditch 2 will be routed into Pond <br /> #I (the Mine Water Pond)to allow for the pond's expansion (Map 1, Figure 1). Outfall 001 A <br /> remains in place under Modification 4 of CDPS permit CO0000003. This pond is expected to <br /> contain settling and filtration/aerobic wetland components, final design of the bed media is <br /> pending completion of pilot tests. 2 feet of free board will be mainlined in Pond#1, as <br /> demonstrated by area capacity curves (Figure 4). Pond #1 will be lined, but an effort will be <br /> made to reuse the existing HDPE liner in combination with clay liners to create a pond that <br /> contributes to the natural environment with perimeter vegetation growth, as requested by the <br /> Army Corps of Engineers during 2017 inspection. <br /> Pond#2, which contains the current bioreactive pond, will be widened and deepened (Map 1, <br /> Figure 1). All existing media will be removed and either reused onsite or placed in the tailings <br /> 3 <br />