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Privileged and Confidential-Attorney Client Communication Geosyntec <br /> 1 . I 11 ODT (' 110N <br /> 1.1 Overview <br /> Ouray Silver Mines Inc. (OSMI) is in the process of designing and constructing a new <br /> passive hybrid water treatment system for the Revenue Silver Mine (Mine) to treat <br /> water pumped from the Mine portal prior to discharge to Sneffels Creek. The portal <br /> water is currently collected from various underground locations and is being transported <br /> via pipeline to a settling pond, after which the water can be either discharged to Sneffels <br /> Creek or discharged into an infiltration bioreactor system. The portal water contains <br /> mining-related water quality constituents that are above regulatory discharge <br /> requirements for the Mine. The new passive hybrid water treatment approach has been <br /> selected due to the remote location of the Mine and the system will be designed to <br /> achieve regulatory compliance during the long-term operation of the Mine. <br /> Geosyntec Consultants (Geosyntec) prepared this Treatability Study Work Plan (Work <br /> Plan)on behalf of OSMI in support of development of the new passive hybrid treatment <br /> system. The new treatment system is intended to achieve compliance with surface water <br /> discharge limits identified in the Colorado Department of Public Health and <br /> Environment (CDPHE) Colorado Discharge Permit System (CDPS) Permit No. CO- <br /> 0000003, Permit Modification 3. The objectives of this Work Plan are to evaluate <br /> alternatives for the treatment system, identify a preliminary conceptual design, and <br /> establish a bench- and pilot-scale treatability testing approach. <br /> 1.2 Mine Background <br /> The silver-producing Mine is located near Ouray, Colorado and is characterized by cold <br /> temperatures and highly variable seasonal flows, which are important considerations for <br /> passive treatment system design and operation. Passive treatment is a practical option <br /> for this site because it is remote, there is land to build the treatment system on, prior <br /> piloting at the Mine indicated biological treatment is a viable approach for metals <br /> reduction, numerous case studies have demonstrated that it is generally a viable <br /> technology for mine water treatment(Ness, Janin, & Stewart, 2014), and it will visually <br /> blend in with the high alpine environment, further supporting tourist use of the area. <br /> Table 1 lists specific design considerations regarding the Mine. <br /> Treatabilay Study Work Plan I February 8,2019 <br />