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The worst case for runoff into Pond #2 is when the operation has recently crossed the previous access <br />road and has begun moving south. Although some runoff will be trapped in the pit, most will make its <br />way south through previous sumps and be delivered to Pond #2. This area is approximately 78 acres. <br />When the active pit is further south, more runoff will enter the pit, which does not represent the worst <br />case. Part of the area is previously disturbed and very gravelly. The CN for undisturbed <br />areas is 74 and disturbed gravel is 70. The approximate average for the entire disturbed area is 72. Due <br />to a number of depressions present in the basin, a ponding percent of 20% has been assigned. <br />The design calculations for Pond #2 are shown below. <br />Design Volume Calculations <br />Sediment Pond #2 <br />Area (acres) <br />72.6 <br />Design Event <br />100 yr. storm <br />Design Precipitation <br />2.8 <br />Calculated S <br />Average CN <br />72 <br />3.88888888889 <br />Description <br />Porous Gravel Topsoil <br />Piles <br />Calculated Runoff Volume (Q) <br />0.6918128655 <br />Calculated Runoff Volume (acre -ft.) <br />4.18546783626 <br />Ponding Percentage <br />20 <br />Actual Runoff Volume (acre/ft.) <br />3.34837426901 <br />As shown on Map C-2, Pond #2 is 1.15 acres in surface area, therefore, its required depth is 2.9 feet to <br />hold 3.34 acre feet. It will be constructed to 3.3 feet deep and 211:1V sideslopes. All other ponds will <br />use similar slopes. <br />Runoff from the initial gold mining area and the prep plant area will be directed to Pond 4. Although <br />Pond 4 generally contains water, it is never allowed to be within 3 feet of the top of the dam. There- fore, <br />storage volume is available for storm runoff. <br />Alma Place Mine 01/15 20 <br />