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San Luis TSF David Carino <br /> 2024 Annual Dam Safety Inspection Battle Mountain Resources,Inc. <br /> Measurements further back into the impoundment (VWP's 2 A, B, C and 3 A, B, C) indicate <br /> perched phreatic conditions at various depths. <br /> Table 1 San Luis TSF VWP Levels: April 2024 <br /> PIEZOMETER ID VWP VVVP VWP VWP VWP VWP VWP VWP <br /> O1A O1B 02A 02B 02C 03A 03B 03C <br /> INSTALLED DEPTH(ft BGS) 84.0 95.0 64.0 78.0 95.0 44.0 70.0 95.0 <br /> 4/03/2024 85.0 88.1 53.0 60.1 65.3 40.2 45.1 44.7 <br /> Underdrain: Underdrain flow rates discharging to the seepage collection pond from April 2023 <br /> to April 2024 are shown in Table 2, and flow rates from 2016 to 2024 are presented graphically <br /> on Figure 4. Average underdrain flow measurements from April 2023 to April 2024 (26.7 gpm) <br /> are lower than from 2016-2024 (33.0 gpm), and are trending lower. <br /> The pipes were jet-cleaned in the Fall of 2023. The observed continuing reduction in underdrain <br /> flow rates in recent years is likely due to a combination of ongoing severe regional drought and <br /> natural drain-down of the TSF. It is recommended that jetting of the pipes and video inspections <br /> be conducted at least every 3 years unless a change in measured drainage flow rates warrants more <br /> frequent cleaning and inspection. <br /> Table 3 San Luis TSF Underdrain Flow Measurements: April 2023 -May 2024 <br /> Date Flow (gpm) <br /> 4/27/2023 31.0 <br /> 5/31/2023 29.5 <br /> 6/14/2023 29.5 <br /> 7/31/2023 25.0 <br /> 8/31/2023 25.0 <br /> 9/28/2023 26.0 <br /> 10/31/2023 26.0 <br /> 11/30/2023 26.0 <br /> 12/28/2023 25.5 <br /> 1/31/2024 25.5 <br /> 2/29/2024 25.5 <br /> 3/28/2024 26.0 <br /> 4/11/2024 26.5 <br /> 2024 INSPECTION FINDINGS <br /> The overall surficial conditions of the tailings dam at the time of the inspection were generally <br /> satisfactory, except for minor issues discussed in more detail below. <br /> South Diversion Ditch Drop Structure Erosion: The erosional rilling previously noted on the <br /> right (north side) of the drop structure has been repaired and the soil seeded. Vegetation is taking <br /> hold along the slope, which should facilitate erosion resistance. Frequent monitoring of this area <br /> should continue to ensure successful revegetation and erosion control. Erosional rilling along the <br /> 2 Engineering Analytics,Inc. <br />