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Engineering Analytics,Inc. 1600 Specht Point Rd. Suite 209 Fort Collins,CO 80525 970.488.3111 wwwIngAnalytics.com <br /> August 24, 2021 Project No. 2101.05.15 <br /> Mr. David Carino <br /> Battle Mountain Resources, Inc. <br /> P.O. Box 310 <br /> San Luis, CO 81152-0310 <br /> RE: 2021 Annual Dam Safety Inspection Report <br /> San Luis Tailings Dam <br /> CDRMS Permit No. M-1988-112 <br /> Dear Mr. Carino, <br /> At your request, Engineering Analytics, Inc. (EA) conducted the 2021 annual dam safety <br /> inspection for the San Luis Tailings Dam. The inspection was conducted on June 8 by Mark S. <br /> Abshire, P.E., in conformance with the Tailing Dam Safety Inspection and Reporting Program <br /> prepared by Miller Geotechnical Consultants, Inc. (MGC), dated March 12, 2013. Also present <br /> were Deb Miller, PE (MGC), yourself and Julio Madrid (BMRI). <br /> EA's inspection included review of the following historical project documents: <br /> • San Luis Project Tailing Dam Detailed Inspection Report(MGC, February 2014) <br /> • 2015 Annual Inspection Report(MGC, June 10, 2015) <br /> • 2016 Annual Inspection Report(MGC, July 6, 2016) <br /> • 2017 Annual Inspection Report (EA, August 18, 2017) <br /> • 2018 Annual Inspection Report (MGC, August 7, 2018) <br /> • 2019 Annual Inspection Report (MGC, July 3, 2019) <br /> • 2020 Annual Inspection Report(MGC, September 25, 2020). <br /> An overall site plan of the San Luis TSF is presented on Figure 1. Specific inspection results are <br /> detailed on the Tailing Dam Inspection Form(Attachment 1),and findings are presented on Figure <br /> 2. Figures 3 and 4 present piezometer levels and underdrain flow measurements, respectively. <br /> Photographs taken during the inspection are included as Attachment 2. <br /> PREVIOUS FINDINGS <br /> The primary issues identified in the 2020 annual inspection included minor surface erosion on the <br /> downstream dam slope, the potential for surface erosion in disturbed areas around the South <br /> Diversion Ditch Drop Structure (construction completed in 2019), and the ongoing need for <br /> maintenance around the underdrain outfall to reduce ponding of surface water in that area. <br /> Additionally,it was recommended that BMRI consider installing a concrete structure for collecting <br /> underdrain flows from the toe drains to facilitate maintenance in the toe drain area, improve <br /> Engineering Analytics,Inc. <br />