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Offilmh GEM SERVICES <br /> Dawson Project—Tailings Characterization Page 24 <br /> i <br /> Source: AMEC(2016) <br /> Figure 7: Conceptual Closure Cover System <br /> Leachate is expected to be produced when precipitation events exceed the storage capacity of the <br /> soil and sand& gravel layers and precipitation infiltrates to the tailings surface. Precipitation <br /> events are the more pertinent than monthly precipitation values since evaporation from the soil <br /> layer will occur between precipitation events. <br /> Soils slated for reclamation use are described as gravelly sandy loam (Exhibit E, Section 2.5.1 in <br /> the main reclamation permit application document). Field capacity for such soils range from 12% <br /> to 24%(Brady, 1990). The resulting storage capacity for the soil layer is equivalent to 0.72"to <br /> 1.44" of precipitation. The maximum average daily precipitation is 0.087"(Western Regional <br /> Climate Center). Under typical conditions, no leachate is expected from the FTSF. <br /> The potential for leachate production during storm events was also examined. The storage <br /> capacity of the cover was compared to the design storm precipitation values used in the pre- <br /> feasibility design of the FTSF (Amec, 2016). Porosity for sand& gravel range from 16%to 32% <br /> (Domenico and Schwartz, 1990). The same porosity range was assumed for the erosion <br /> protection layer,based on the specification in Amec(2016). A comparison of storage capacity <br /> and 24-hour rainfall depths is presented in Table 11. <br /> DDS/dds Zephyr_Dawson_TailinBs_Cheractedzadon_Final Report,Feb.3,22,1:18 PM Feb 2022 <br />