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Battle Mountain Resources, Inc. <br />P.O. Box 310 <br />San Luis, CO 81152-03 1 0 <br />February 17, 2017 <br />Mr. Wallace H. Erickson <br />State of Colorado <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />Re: Technical Revision for New South Diversion Ditch Drop Structure <br />San Luis Mine Project <br />Permit No. M-88-112 <br />Dear Mr. Erickson: <br />The purpose of this letter is to request a Technical Revision of the Reclamation Plan for Battle <br />Mountain Resources Inc.'s (BMRI) Permit No. M-88-112. This proposed Technical Revision is <br />for construction of a new drop structure on the south embankment of the tailings facility dam, <br />which will receive stormwater runoff intercepted by the South Diversion Ditch. This proposed <br />Technical Revision addresses recommendations of the Tailings Dam Safety Inspection and <br />Reporting Programs at BMRI's San Luis site. Enclosed please find an accompanying bank draft <br />in the amount of $1,006 to cover the administrative cost of this request. <br />HISTORY <br />In 2014, Battle Mountain Resources, Inc. provided the first annual San Luis Project Tailings <br />Dam Detailed Inspection Report (Detailed Inspection Report) (Miller Geotechnical Consultants, <br />Inc., February 2014). The Detailed Inspection Report concluded that the tailings facility dam is <br />in good condition, but included recommendations for improvements to the South Diversion <br />Ditch and the associated drop structure to minimize risks associated with stormwater <br />management during major flood events. In 2015, 2016 and 2017, Miller Geotechnical <br />Consultants, Inc. completed hydrologic and geotechnical studies, and prepared design drawings <br />and specifications for improvements to achieve the recommendations. The improvements <br />included replacement of the existing conduit drop structure with a larger reinforced concrete <br />drop structure at the south embankment, and increasing the capacity of the South Diversion <br />Ditch. <br />The South Diversion Ditch was designed to divert upland runoff from a 100 -year event around <br />the perimeter of the tailings facility impoundment and over the south abutment of the tailings <br />dam via a drop structure. Larger floods were intended, by design, to overtop the ditch and flow <br />into the tailings impoundment, which has adequate capacity to contain floods up to and including <br />the probable maximum flood (PMF) event. <br />