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GEM SERVICES <br /> Dawson Project—Tailings Characterization Page 25 <br /> Table 11: Comparison of Cover Storage Capacity and 24-hour Storm Values <br /> Cover Storage Capacity Storm Precipitation Values <br /> Layer Lower Limit Upper Limit Return Period 24-hour Rainfall <br /> (rainfall depth (rainfall depth Depth <br /> equiv.) equiv.) (inches) <br /> Soil 0.96 in. 1.92 in. 2-year 1.82 <br /> Sand&gravel 1.68 in. 3.36 in. 5-year 2.27 <br /> Erosion 3.84 in. 7.68 in. 10-year 2.72 <br /> Total storage 6.48 in. 12.96 in. 25-year 3.43 <br /> 50-year 4.05 <br /> 100-year 4.74 <br /> 500-year 6.63 <br /> 1,000-year 7.56 <br /> In comparing the cover storage capacity to potential storm precipitation events,the FTSF cover is <br /> expected to contain and drain precipitation from extreme storm events. It should be noted that the <br /> cover storage capacity calculations do not take into consideration that a portion of precipitation <br /> would report to surface runoff during more extreme events rather than infiltrate the cover. Nor do <br /> the calculations take into account the 3%slope of the cover that would enable the sand and gravel <br /> layer to drain during storm events. <br /> It is concluded that functionally there will be no leachate from the base of the FTSF after closure. <br /> DDS/dds Zephyr Dawsor_Tailings Characterization—FinaLReport,Feb.3,22,1:18 PM Feb 2022 <br />