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Engineering Analytics,Inc. 1600 Specht Point Rd. Suite 209 Fort Collins,CO 80525 970.488,3111 bvww.EngAnalytics.com <br /> i N <br /> July 14, 2023 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: 2023 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 2023 annual dam safety <br /> inspection for the San Luis Tailings Dam. The inspection was conducted on June 14 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 Jonathan Gillen, PE (Newmont), yourself and Julio Madrid(BMRI). <br /> EA's inspection included review of the 2022 TSF inspection report (August 5, 2022). An overall <br /> site plan of the San Luis TSF is presented on Figure 1. Specific inspection results are detailed on <br /> the Tailing Dam Inspection Form(Attachment 1), and findings are presented on Figure 2. Figures <br /> 3 and 4 present piezometer levels and underdrain flow measurements, respectively. Photographs <br /> taken during the inspection are included as Attachment 2. <br /> PREVIOUS FINDINGS <br /> The primary issues identified in the 2022 annual inspection included the potential for surface <br /> erosion in disturbed areas around the South Diversion Ditch Drop Structure (construction <br /> completed in 2019), and a blocked culvert at the lower end of the HDPE-lined runoff channel at <br /> the downstream toe. <br /> INSTRUMENTATION <br /> Piezometers: Piezometer readings from April 2022 through May 2023 are shown in Table 1, and <br /> readings from January 2021 through May 2023 are presented graphically on Figure 3. The <br /> piezometers all indicate dry conditions or minor amounts of water present at the bottom of the <br /> casings due to moisture condensation. This behavior is consistent with historic observations and <br /> indicates that the sub-drains are functioning, and low phreatic conditions are maintained within <br /> the dam embankment. No abnormalities are indicated in the measurements. <br />