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GEM sr-RvicEs <br /> Dawson Project—Tailings Characterization Page 21 <br /> 4 FTSF Seepage Quality <br /> 4.1 Operational Period <br /> The seepage from the FTSF will comprise of filtrate introduced to the facility with the tailings <br /> and infiltration water that contacts the tailings and the support buttresses(development rock). <br /> The metal release data presented in Section 3 above were combined with the seepage estimates <br /> presented in Amec Foster Wheeler(2016)to derive a seepage quality estimate for the facility. <br /> An empirical, mass balance approach was used to derive the seepage quality estimate. The <br /> following data was used in the estimate: <br /> • Filtrate quality presented in Table 9 representing solute contribution from tailings <br /> • The SFE data presented in Table 8 representing solute contribution from development rock <br /> • Seepage volume of 259,548 ft3/yr(Amec Foster Wheeler, 2016) <br /> • Development rock(support buttress)volume of 1,881 cu.yd. (4,200 short tons) in FTSF <br /> (Amec Foster Wheeler,2016) <br /> • Tailings amount of 500,000 short tons in FTST(Amec Foster Wheeler, 2016) <br /> The amount of each element contributed by development rock and tailings was combined in <br /> proportion to the tonnage of each material expected in the FTSF. Given the significantly larger <br /> volume of tailings compared to development rock in the FTSF, it is expected that tailings will <br /> dominate overall seepage quality. <br /> The concentration of element i in seepage was calculated as follows: <br /> yn mg DRY+mg tails <br /> seepage cone ( g�L) = FTSF seepage volume (L) <br /> Where <br /> mg DR, = conc.DR((m"g/L) ton DR* (ton oa+on tails* FTSF seepage volume (L)) <br /> mg tails, = conc.tails((mg1L) ton tails <br /> * * FTSF seepage volume (L) <br /> ton DR + ton tails <br /> And <br /> DR=development rock(supporting buttress) <br /> Tails=tailings <br /> DDStdds Zephyr DawsorlTailings_Characterization_FinaLR®port,Feb.3,22,i l8 PM Feb 2022 <br />