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GEM SERVICES <br /> Dawson Project—Tailings Characterization Page 22 <br /> The estimated seepage quality thus derived was then compared to the groundwater quality <br /> standard and the baseline groundwater quality to ascertain its suitability for discharge. <br /> In deriving the seepage quality estimate, a number of assumptions were made: <br /> 1. All infiltration water contacting the tailings will acquire the quality of the filtrate. <br /> 2. If the element concentration is different between altered and unaltered filtrate,the higher <br /> concentration was used. <br /> 3. The element concentration in the development rock SFE tests represents an ongoing <br /> release rate. This is a conservative assumption since an SFE result represents the total <br /> amount of soluble metal available for release,not the rate at which it is released. <br /> 4. The largest element concentration in the five development rock SFE results was used. <br /> 5. Leaching of development rock in the FTSF will occur at a 1:1 water to solid ratio. The <br /> 3:1 ratio at which the SFE test is conducted is too dilute to represent development rock <br /> leachate. SFE results were re-calculated to produce higher element concentrations. <br /> 6. No elements precipitate out of solution. This is a conservative approach. <br /> 7. The ratio of tailings volume to development rock volume is similar to the ratio of tailings <br /> footprint area to buttress footprint area. <br /> The estimated FTSF seepage quality is presented in Table 10. As expected,the predicted seepage <br /> quality is very similar to tailings filtrate. The predicted seepage quality meets the groundwater <br /> quality standard,with the exception for manganese. However,the predicted manganese <br /> concentration(0.071 mg/L) is less than the background groundwater concentration(0.072 mg/L <br /> average; 0.15 mg/L 95'percentile). The groundwater quality standard is 0.05 mg/L. <br /> Based on the above analysis, it is expected that FTSF seepage will not require treatment prior to <br /> discharge. The FTSF seepage quality is suitable for discharge via the sedimentation/stormwater <br /> detention pond. <br /> The predicted seepage quality presented herein would be reflective of short term and operating <br /> conditions when fresh tailings are added on a continual basis. <br /> DDSldds Zephyr Dawson Tailings_Characterfzation_FInaLReport,Feb.3,22,1:1 B PM Feb 2022 <br />