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Engineering Analytics,Inc. 1600 Specht Point Rd. Suite 209 Fort Collins,CO 80525 970.488.3111 www.EngAnalytics.com <br /> July 12, 2024 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: 2024 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) has conducted the 2024 annual dam safety <br /> inspection for the San Luis Tailings Dam. The inspection was conducted on May 16th by the <br /> Engineer of Record for the facility, Mark S. Abshire, P.E., in conformance with the Tailing Dam <br /> Safety Inspection and Reporting Program prepared by Miller Geotechnical Consultants, Inc. <br /> (MGC), dated March 12, 2013. Also present were Jonathan Gillen, PE (Newmont), yourself and <br /> Julio Madrid(BMRI), and Eric Miller(EA). <br /> EA's inspection included review of the 2023 TSF inspection report. An overall site plan of the <br /> San Luis TSF is presented on Figure 1. Specific inspection results are detailed on the Tailing Dam <br /> Inspection Form (Attachment 1), and findings are presented on Figure 2. Figures 3 and 4 present <br /> piezometer levels and underdrain flow measurements,respectively. Photographs taken during the <br /> inspection are included as Attachment 2. <br /> PREVIOUS FINDINGS <br /> The primary issues identified in the 2023 annual inspection included the potential for surface <br /> erosion in disturbed areas around the South Diversion Channel Drop Structure, and a blocked <br /> culvert at the lower end of the HDPE-lined runoff channel at the downstream toe. <br /> INSTRUMENTATION <br /> Piezometers: Standpipe piezometer readings from January 2022 to April 2024 are presented <br /> graphically on Figure 3. The piezometers all indicate dry conditions or minor amounts of water <br /> present at the bottom of the casings due to moisture condensation. This behavior is consistent with <br /> historic observations and indicates that the sub-drains are functioning,and low phreatic conditions <br /> are maintained within the dam embankment. No abnormalities are indicated in the measurements. <br /> Eight new vibrating wire piezometers (VWPs) were installed at various depths in three borings <br /> within the impoundment in April 2024 to monitor the phreatic conditions within the TSF (Figure <br /> 1). The initial readings following installation are included in Table 1 and Figure 3. Initial <br /> measurements show saturated conditions approximately 84 feet below the ground surface (bgs) at <br /> the upstream toe (VWP-1A), with the phreatic surface rising towards the pool to the east. <br />