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Mr.Lucas J. West <br /> October 7,2025 <br /> Page 2 <br /> Table 2-Monthly Piezometer Elevations <br /> Monitoring Well Obs t Piezometer Depth Depth to Water Depth of Water <br /> Identification ervation Dae ft ft ft <br /> P6 9/30/2025 72.46 DRY N/A <br /> P7 9/30/2025 92.50 DRY N/A <br /> P8 9/30/2025 97.51 96.71 0.80 <br /> P9 9/30/2025 72.30 71.96 0.34 <br /> 1110 9/30/2025 58.30 57.48 0.82 <br /> I'll 9/30/2025 41.80 41.42 0.38 <br /> P 12 9/30/2025 41.71 41.66 0.05 <br /> 1113 9/30/2025 41.34 41.02 0.32 <br /> P 14 9/30/2025 41.24 DRY N/A <br /> P15 9/30/2025 41.10 40.85 0.25 <br /> The leak detection system at the LTF Collection Pond was inspected September 30, 2025, and 910 gallons were <br /> evacuated from the leak detection system and pumped to the LTF. The LTF underdrain system was visually inspected <br /> September 30,2025,and the flow rate was measured to be approximately 26 gallons per minute(gpm). <br /> West Pit Waste Water Treatment Plant <br /> During the month of September 2025, the West Pit Waste Water Treatment Plant (WWTP) was operated <br /> intermittently(3 to 4 days per week)under Colorado Department of Public Health and Environment(CDPHE)CDPS <br /> Permit No. C00045675 for discharge into the Rito Seco alluvial aquifer. During the month, 6,748,700 gallons <br /> (20.71 acre-feet)of treated water was discharged to the Rito Seco and 1,030,100 gallons(3.16 acre-feet)of water was <br /> transferred from the West Pit to the Lined Tailing Facility (LTF). Additionally, no water was reinfiltrated into the <br /> West Pit in September. <br /> BMRI performed the monthly visual seepage expression inspections on September 30, 2025, in the historic seepage <br /> area identified in Figure 2 of the permit. No seepage expressions were observed in the historic seepage area. <br /> BMRI measured the monthly West Pit backfill, alluvial and monitoring wells as required under the QA/QC Plan. <br /> Measurements obtained for the monthly wells are shown in Table 3. <br /> Table 3-Monthly and Quarterly Groundwater Depth to Water <br /> Monitoring Well Identification Observation Date Depth to Water <br /> ft <br /> BF-4 9/30/2025 24.85 <br /> BF-511 9/30/2025 30.78 <br /> BF-6 9/30/2025 30.90 <br /> M-6 9/30/2025 DRY <br /> M-7 9/30/2025 DRY <br /> M-8 9/30/2025 DRY <br /> M-9 9/30/2025 141.04 <br /> M-10 9/30/2025 23.99 <br /> M-11 R 9/30/2025 37.68 <br /> M-12 9/30/2025 174.18 <br /> M-13R 9/30/2025 125.57 <br /> M-14 9/30/2025 130.4 <br /> M-16 9/30/2025 21.64 <br /> M-17 9/30/2025 30.05 <br />