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JD-8 Mine - Drainage Design Plan 8 <br />• 3.1 Runoff Areas <br />Flow directions and runoff areas during mine operations will resemble the current condition. Water will be <br />routed westward across the site and southward off the face of the waste rock pile. However, the waste rock <br />pile will be expanded to encompass the area currently occupied by the existing constructed catchment and <br />planned expansion/construction of the western catchment (near the topsoil stockpile). When these <br />stormwater retention facilities are removed and replaced by waste rock, the pre-existing road will be <br />realigned between the property boundary and the toe of the waste rock pile. A drainage ditch will be <br />constructed to store and convey water to a proposed new stormwater retention pond located west of the <br />planned final waste rock pile (Figure 3). <br />The proposed retention pond will receive water from the mine as well as runoff from the non-contributing <br />area NC-D (shown in Table 1 and Figure 1). The calculated total runoff entering the catchment from the <br />10-year 24-hour and 100-year 24-hour storms is shown in Table 8. Total runoff from the 10-year 24-hour <br />storm is calculated at 12,870 W (0.30 acre-ft, 96,300 gallons). <br />Table & Calculated Runoff from the 10-year 24-hour and 100-year 24-hour Storms based <br />on Planned Final Topography <br /> Soil Type / Hydrologic AREA Curve Rainfall Retention Runoff Runoff <br />AREA Group/ Cover Description Condition (acres) Number P S Q Q <br />W <br /> CN (inches) (inches) ( <br />) <br />100-Year 24-Hour Storm <br /> Bodot / Ustic Torriorthents <br />Reclaimed Waste Group C Poor 5.14 85 2.60 1.76 1.26 23,484 <br />Rock Sagebrush with grass <br /> understory <br /> Bodot / Ustic Torriorthents <br />NC-D Group C Fair 3.10 63 2.60 5.87 0.28 3,133 <br /> Sagebrush with grass <br />Bodot / Ustic Torriorthents <br />3 Group C 0.15 63 2.60 5.87 0.28 147 <br />Sagebrush with grass <br />understory <br />10-Year 24-Hour Storm <br />Bodot / Ustic Torriorthents <br />Reclaimed Waste Group C Poor 5.14 85 1.80 1.76 0.65 12,165 <br />Rock Sagebrush with grass <br />Bodot / Ustic Torriorthents <br />NC-D Group C Fair 3.10 63 1.80 5.87 0.06 677 <br />Sagebrush with grass <br />understory <br />Bodot / Ustic Torriorthents <br />3 Group C 0.15 63 1.80 5.87 0.06 32 <br />Sagebrush with grass <br />understory <br />• <br />4122A.110601 Whetstone Associates