2025-11-14_PERMIT FILE - M2025056 (32)

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JD-8 Mine-Drainage Design Plan 13 ADTable 11. Drainage Basin Areas - Planned Final Topography Area Area Zone (ft2) (acres) Type Reclaimed Waste Rock 223,707 5.14 Disturbed area 1 50,280 1.15 Non-contact area(undisturbed) 4 73,550 1.69 Non-contact area(undisturbed) 4.2 10-year 24-hour Runoff and Retention for Post-Mining Condition The calculated total runoff entering the operational and post mining retention Pond 3 from the 10-year 24- hour storm is shown in Table 12 and calculated at 12,785 ft3. Table 12. Calculated 10-year 24-hour Runoff based on Planned Final Topography Soil Type/ Curve Rainfall Runoff Runoff AREA Hydrologic Group/ Conditi AREA Number P Retention q Q Cover Description on (acres) CN (inches) S (inches) (ft3) Reclaimed Bodot/Ustic Torriorthents Waste Rock Group C Poor 5.14 85 1.80 1.76 0.65 12,165 Sagebrush with grass understory Bodot/Ustic Torriorthents 1 Group C Fair 1.15 63 1.80 5.87 0.06 251 Sagebrush with grass understory Bodot/Ustic Torriorthents 410 4 Group C Fair 1.69 63 1.80 5.87 0.06 369 Sagebrush with grass understory Total: 12,785 ft3 The preliminary location and dimensions for Retention Pond 3 are shown in Figure 3 and Table 13. The proposed volume of 13,130 ft3 (at 2.5 ft. deep) using the available 9,656 ft2 footprint shown with 5H:IV side slopes and a 3.5 ft total depth will retain runoff from the 10-year 24-hour event with a 1.0 ft freeboard. The freeboard will be reduced to 0.5 ft during the 100-year 24-hour event. Table 13. Planned Dimensions for the Operational and Post-Mining Storm Water Retention Structure (Pond 3) Area of Storm Water Pond 9,656 ft2 Area of Floor(5H:1V slopes) 3,375 ft2 Perimeter of Floor 300.6 ft Total Depth 3.5 ft Volume(2.5 ft. deep) 13,130 ft3 0.301 acre-ft 98,210 Gallons Freeboard(10-year 24-hour) 1.0 ft Freeboard(100-year 24-hour) 0.5 ft 4.3 100-year 24-hour Routing Capacity • The storage and routing capacity of Pond 3 in the operational and post-mining conditions were evaluated using the NRCS Graphical Peak Discharge Method. Calculation parameters for the 100-year 24-hour 4122A.120702 Whetstone Associates