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HYDROLOGIC DOCUMENTATION <br />SMALL AREA EXEMPTION <br />NORTHSAE <br />The north slope of the upper pad will be designated a Small Area Exemption. The area of the <br />North SAE is approximately 0. 12 acres. Rip rap will be placed along the entire North SAE to <br />protect the culvert inlet. <br />To estimate the effectiveness of a sediment control structure we typically use the RUSLE <br />equation to calculate the amount of sediment runoff. The following is the RUSLE equation. <br />WW Yw'i <br />Where: A = Average annual soil loss in ton per year per acre <br />R = Rainfall /runoff erosivity <br />K = Soil erodibility <br />LS = Hillslope length and steepness <br />C = Cover management <br />P = Support practice <br />For Rip Rap cover, the K factor is in essence equal to 0 therefore, the average annual soil loss is <br />equal to 0 and sediment erosion will essentially be eliminated. <br />TR -68 Revised April 2010 <br />