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  <br />10  <br />  <br />  <br /> <br />6.4 Species Level Material Damage Assessment <br />On the two fields where a material damage assessment was warranted, a conservative species <br />level damage assessment was implemented. This entails conducting a material damage <br />assessment on the most salt sensitive species (alfalfa) as if it were the only species in the field <br />(Table 8). The resulting calculation is the same for both fields. In this species level <br />assessment, the field salinity threshold is lowered to the most sensitive species (alfalfa - 2.00 <br />dS/m). Based on the field salinity threshold, the effective field irrigation water quality threshold <br />is 1.34 dS/m. Finally, the percent yield decrease per unit increase is specific to alfalfa. <br />Therefore, the species level material damage assessment on the alfalfa in fields 11 and 6 <br />resulted in a yield reduction of 2.72% based on the life of mine average irrigation water from <br />Goodspring Creek (1.72 dS/m). This value is below the 3% threshold for significance <br />demonstrating that no material damage has occurred. <br /> <br />  <br />Table 7 Colowyo - Salinity Study - 2021 <br />Percent Yield Decrease Per Unit Increase in Conductivity of Irrigation Water <br />By Species <br />By Field <br />(weighted <br />average) <br />Medicago sativa Alfalfa 80% 7.14 <br />Bromus inermis Smooth Brome 10% 4.00 <br />Thinopyrum intermedium Intermediate Wheatgrass 5% 6.67 <br />5% 7.14 <br />Medicago sativa Alfalfa 90% 7.14 <br />Thinopyrum intermedium Intermediate Wheatgrass 10% 6.67 <br />Percent Yield Decrease Per Unit <br />Increase in Conductivity of <br />Irrigation WaterRelative <br />CompositionCommon NameDominant SpeciesField <br />SubpartField <br />6 7.10Proctor <br />Other Grasses and Forbs <br />Cox 11 6.80 <br />Table 8 Colowyo - Salinity Study - 2021 <br />Species Level Material Damage Assessment <br />Field <br />Number <br />Field Salinity <br />Threshold - <br />Electrical <br />Conductivity <br />(dS/m) <br />Field Irrigation <br />Water Quality <br />Threshold - <br />Conductance <br />(dS/m) <br />Irrigation Water <br />Quality - Lower <br />Goodsprin g Creek - <br />Lab Collected Life <br />of Mine Average <br />(dS/m) <br />Percent Yield <br />Decrease Per Unit <br />Increase in <br />Conductivity of <br />Irrigation Water <br />(%) <br />Yield <br />Reduction <br />(%) <br />11 2.00 1.34 1.72 7.14 2.72 <br />6 2.00 1.34 1.72 7.14 2.72