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or stockpiled in the designated stockpile areas for later reclamation. The stockpiles will have a mini- <br />mum of 2.SH:1 V sideslopes and will be seeded with a temporary mix designated as Mix A in the <br />reclamation plan. As of April, 2003, approximately 2500 cy of silt has already been stockpiled from <br />recent gravel operations in Fines Pile #4. <br />Willits Ponds #2 and #3 will overflow into Pond A, which should always contain relatively clean <br />water. This pond is hydrologicaly sealed and will be used for recirculating water during drought peri- <br />ods when sufficient water is not available from the River or the Columbia Ditch. <br />Willits Pond #4 will handle all surface runoff from the plant azea and stockpile area. This is approxi- <br />mately 7 acres in size. The calculations to demonstrate that this pond is adequate to contain the 100 <br />yeaz 24 hour event aze shown below: <br />Design Volume Calculations <br />Willits Pond #4 <br />Area (acres) 7.0 <br />Design Event 100 yr. storm <br />Design Precipitation 2.8 Calculated S <br />Average CN 67 4.92537313433 <br />Description Gravel Topsoil Piles <br />Calculated Runoff Volume (Q) 0.4886955832 <br />Calculated Runoff Volume (acre-ft.) 0.28507242353 <br />Ponding Percentage 5 <br />Actual Runoff Volume (acre/ft.) 0.27081880236 <br />A CN of 67 is assigned to the gravel since it is neazly void of fines and almost all runoff penetrates <br />into the ground. This pond has a surface azea of 0.11 acres therefore, its required depth is 2.45 feet. It <br />will be dug 3.0 feet deep urith 2H:1 V sideslopes. <br />Alma Placer 7/03 27 <br />