2022-02-09_PERMIT FILE - M2021046 (5)

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GEM sFERVtCES Dawson Project-Tailings Characterization Page 23 Table 10: Predicted Seepage Quality from FTSF during Operations Development Rock -fa ilin s FTSF Seepa a Background Groundwater Quality Reg.41 Total North Well Groundwater Conc. Amount Conc. Amount Amount Conc. Standard Average ge Percentile mg/L mg mg/L mg mg mg/L mg/L mg/L mg/L pH 7-9 Aluminum Dissolved 1.6 273 0.015 300 573 0.028 0.14 0.47 5 Antimony Dissolved 0.0015 0.25 0.0004 8.0 8.2 0.00041 Arsenic Dissolved 0.0051 0.86 0.0003 6.0 6.8 0.00034 <0.01 <0.01 0.01 Barium Dissolved 0.25 42 0.0235 469 512 0.025 Beryllium Dissolved 0 0 0 0 0 0 <0.005 <0.005 0.004 Bismuth Dissolved 0 0 0 0 0 0 Boron Dissolved 0.090 15 0 0 15 0.00075 0.13 0.22 0.75 Cadmium Dissolved 0 0 0.00007 1.4 1.4 6.9E-05 <0.005 <0.005 0.005 Calcium Dissolved 22 3659 26.4 527157 530816 26 61.1 1 70.2 Chromium Dissolved 0 0 0.0000 0 0 0 <0.01 <0.01 0.1 Cobalt Dissolved 0 0 0.0006 12 12 0.00060 <0.01 <0.01 0.05 Copper Dissolved 0.003 0.50 0.0018 36 36 0.0018 0.0042 0.017 0.2 Iron Dissolved 0.12 20 0 0 20 0.0010 0.054 0.24 0.1 Lead Dissolved 0.017 2.9 0 0 2.9 0.00014 <0.003 <0.003 0.05 Lithium Dissolved 0.013 2.1 0.0108 216 218 0.011 0.030 0.046 2.5 Magnesium Dissolved 2.5 413 4.07 81270 81683 4.1 22.5 25.3 Manganese Dissolved 0.012 2.0 0.0713 1424 1426 0.071 0.072 0.15 0.05 Mercury Dissolved 0 0 0 0 0 0 <0.0002 <0.0002 0.002 Molybdenum Dissolved 0.14 23 0.0783 1563 1587 0.079 Nickel Dissolved 0 0 0.0317 633 633 0.0314 0.0046 0.024 0.1 Phosphorus Dissolved 0.24 40 0.61 12181 12221 0.61 Potassium Dissolved 6.3 1052 16.7 333467 334519 17 5.5 6.5 Selenium Dissolved 0 0 0.005 100 100 0.0050 <0.005 <0.005 0.02 Silicon Dissolved 5.7 951 0.75 14976 15927 0.79 Silver Dissolved 0 0 0 0 0 0 Sodium Dissolved 8.6 1449 10.8 215655 217105 11 26.4 64.6 Strontium Dissolved 0.38 64 0.392 7827 7892 0.39 Sulphur Dissolved 1.8 302 15 295527 295829 15 Tellurium Dissolved 0 0 0 0 0 0 Thallium Dissolved 0 0 0 0 0 0 Thorium Dissolved 0 0 0 0 0 0 Tin Dissolved 0 0 0 0 0 0 Titanium Dissolved 0.0048 0.81 0.0013 26 27 0.0013 Tungsten Dissolved 0.0033 0.55 0 0 0.55 2.7E-05 Uranium Dissolved 0.02076 3.5 0.00023 4.6 8.1 0.00040 Vanadium Dissolved 0.006 1.0 0 0 1.0 5.0E-05 0.1 Zinc Dissolved 0.006 1.0 0.002 40 41 0.0020 0.085 0.17 2 Zirconium Dissolved 1 0.0009 0.15 1 0.0000 0 0.15 7.5E-06 Bold=Exceeds groundwater quality standard 4.2 Post-Closure Period The closure and reclamation plan for the FTSF includes a composite cover over the facility that will store and release precipitation. A schematic of the cover is shown in Figure 7. The surface of the FTSF will be graded to maintain a minimum 3%gradient on the top surface of the FTSF to ensure runoff and to minimize ponding on the tailings surface. The performance of this cover will determine if leachate is produced. AMEC (2016)states that the amount of leachate production during post-closure will be negligible. Preliminary calculations were done to better understand under which conditions leachate production may be possible. DDS/dds Zephyr_Damon Tailings_Characterizatlor Final_jteport,Feb.3,22,1:18 PM Feb 2022