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San Luis TSF David Carino <br /> 2021 Annual Dam Safety Inspection Battle Mountain Resources,Inc. <br /> conditions for monitoring and inspecting the drain system, and to prevent the attraction of animals <br /> to the area by pooling of leakage from the drain pipes. <br /> INSTRUMENTATION <br /> Piezometers: Piezometer readings from June 2020 to June 2021 are shown in Table 1, and <br /> readings from July 2019 through June 2021 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. Low phreatic conditions are maintained within the <br /> dam embankment. No abnormalities are indicated in the measurements. <br /> Table 1 San Luis TSF Piezometer Levels: June 2020 -June 2021 <br /> PIEZOMETER ID P6 P7 P8 P9 P10 PH P12 P13 P14 P15 <br /> TOTAL DEPTH(ft)" 72.46 92.50 97.51 72.30 58.30 41.80 41.71 41.34 41.24 41.10 <br /> 6/30/2020 72.46 92.29 96.68 71.89 57.56 41.38 41.68 41.04 41.24 40.86 <br /> 7/30/2020 72.46 92.29 96.69 71.88 57.55 41.39 41.68 41.03 41.24 40.86 <br /> 8/31/2020 72.46 92.29 96.69 71.89 57.57 41.39 41.68 41.04 41.24 40.87 <br /> 9/30/2020 72.46 1 92.29 96.67 1 71.89 57.58 41.39 41.68 1 41.04 41.24 40.86 <br /> 10/29/2020 72.46 92.29 96.68 71.89 57.59 41.39 41.68 41.04 41.24 40.85 <br /> 11/30/2020 72.46 92.30 96.65 71.90 57.60 41.39 41.68 41.02 41.24 40.86 <br /> 12/31/2020 72.46 92.29 96.65 71.90 57.61 41.40 41.68 41.00 41.24 40.87 <br /> 1/28/2021 72.46 92.30 96.65 71.90 57.62 41.41 41.66 40.99 41.24 40.86 <br /> 2/25/2021 72.46 92.29 96.62 71.90 57.63 41.41 41.67 41.00 41.24 40.86 <br /> 3/31/2021 72.46 92.28 96.61 71.91 57.61 41.40 41.67 41.02 41.24 40.86 <br /> 4/29/2021 1 72.46 92.28 96.63 71.91 57.62 41.40 41.66 41.02 41.24 40.85 <br /> 5/27/2021 72.46 92.28 96.60 71.91 57.61 41.40 41.66 41.02 41.24 40.86 <br /> 6/30/2021 72.46 92.27 96.59 71.91 57.61 41.40 41.67 41.03 41.24 40.86 <br /> *Piezometer total depths measured from top of casing <br /> Underdrain: Underdrain flow rates discharging to the seepage collection pond from June 2020 <br /> through June 2021 are shown in Table 2, and flow rates from 2016 to 2021 are presented <br /> graphically on Figure 4. Average underdrain flow measurements from 2019-21 (32.5 gpm) are <br /> slightly lower than from 2016-2021 (34.8 gpm). <br /> The underdrain pipes were jet-cleaned in 2014 in conjunction with the first camera inspection of <br /> the accessible downstream ends of the pipes. A second video inspection of the pipe ends was done <br /> without jet cleaning in 2018. The 2018 videos showed some accumulation of sediment and <br /> precipitates in the pipes compared to the 2014 videos, but the pipes were all still flowing (not <br /> clogged). Thus, the observed slight reduction in underdrain flow in recent years is likely due to <br /> ongoing severe regional drought. The pipes were jet-cleaned again on October 5, 2020, with no <br /> video inspection. It is recommended that jetting of the pipes and video inspections be conducted <br /> at least every 3 years unless a change in measured drainage flow rates warrants more frequent <br /> cleaning and inspection. <br /> 2 Engineering Analytics,Inc. <br />