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Ouray Silver Mines Inc. <br /> Technical Revision 10 August 14, 2018 <br /> 1 Introduction <br /> This Technical Revision JR) allows for one major and several minor changes to the Revenue- <br /> Virginius (Mine) 112d designated mining permit. The Mine operates under Division of <br /> Reclamation, Mining, and Safety (DRMS) Permit No. M2012-032 (Permit). Each of the changes <br /> is briefly summarized in the bullet points below. <br /> • Construction of a five-stage passive treatment system for Mine effluent with surface <br /> water discharge to Sneffels Creek. <br /> • Installation of a new monitoring well (GW-4) between Pond 3 and Sneffels Creek to <br /> facilitate monitoring of the new passive treatment system. <br /> • Move the diesel tanks from near the Mill Building to the western end of the <br /> Administrative buildings. <br /> This TR describes the reasoning, characteristics, construction, and reclamation measures <br /> associated with these proposed changes. Supporting information is presented under the <br /> following sections: background information (Section 2), project rationale (Section 3), <br /> physiochemical characteristics (Section 4), construction and implementation (Section 5), <br /> operation (Section 6), and reclamation (Section 7); subsequently presented herein. <br /> 2 Background Information <br /> The Mine, owned and operated by Ouray Silver Mines Inc. (OSMI), is an active silver mine <br /> located approximately 5 miles south west of Ouray Colorado along County Road 26 down <br /> gradient of Yankee Boy Basin in the Sneffels District. The area has a rich mining history that <br /> began with the staking of the Virginius in 1876. The Revenue Tunnel was built as a lower access <br /> point to the Virginius in 1893. The bulk of mining activity occurred from 1878 through 1912, <br /> with intermittent mining since. The current Mine is permitted with a no discharge mill facility, <br /> underground mill and crushing circuits. Background information relevant to each of the proposed <br /> changes is presented below. <br /> 2.1 Five Stage Passive Treatment System <br /> Historically the Mine water discharged directly to surface water. As previous owners worked to <br /> bring the mine back into modern operation, an industrial waste water discharge permit was <br /> required through the Colorado Discharge Permit System (CDPS) for the water leaving the portal. <br /> CDPS permit number CO0000003 allowing discharge to surface water at Outfall OOIA was <br /> granted on August 2013, and construction was completed in early 2015. A number of compliance <br /> advisories occurred, triggering a Toxicity Reduction Evaluation. Following substantial <br /> investigation, OSMI determined that passive treatment and groundwater infiltration would be the <br /> best long-term alternative for managing the mine water. Submission and approval of Technical <br /> Revision 8 to DRMS permit#M2012-032, with CDPHE Enforcement consultation, resulted in the <br /> construction of a passive treatment system during the summer of 2016. OSMI ceased discharge at <br /> Permit Outfall-001 A,on September 8,2016,and informed CDPHE and DRMS immediately. Flow <br /> was transferred from Outfall-001 A to the bioreactive treatment system with groundwater <br /> infiltration. <br /> 1 <br />