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permit boundary and this ditch prevents any undisturbed runoff from entering the site. See Map C -2. <br />Sediment Pond #I is simply a sediment cleanout pond and will not be used for detention volume. <br />Sediment Pond #2 will handle the runoff from the majority of the gold mining area. Pond A will <br />handle runoff from the prep plant area as well as from the main gravel operation. Map C -4 shows the <br />drainage areas for the site in addition to all ditches, berms and ponds. <br />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 <br />its way south through previous sumps and be delivered to Pond 42. This area is approximately 78 <br />acres. When the active pit is further south, more runoff will enter the pit, which does not represent <br />the worst 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. <br />Due 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 />Alma Placer Mine 1/15 22 <br />