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Soil erodibility factor, K: 24, As determined for topsoil type from <br />• SCS publications. <br />Control practice factor: .45, For rangeland with no appreciable <br />canopy, grass cover, 0~ ground cover <br />contacting surface. <br />Soil size distribution: Permit, a typical soil particle size <br />distribution for the permit area is used. <br />This is the same as was used in the <br />original permit. <br />Event: 10 year, 24 hour event, 1.6" rainfall per SCS publication. <br />The run-off from the model shows that typically, the current berm <br />around the topsoil pile is inadequate to contain the ten year <br />event. As the berm and the impoundment formed at the base of the <br />• pile by the berm are nearly level, any water accumulating in this <br />area would be stilled by the lack of grade. A porous rock or gravel <br />outlet structure constructed at the low point of the berm would <br />allow some additional retention and filtering. <br />Therefore to control the sediment from the topsoil piles the <br />following measure will be taken: <br />1. The berm will be breached at its low point to prevent an <br />impoundment from being formed, and a 5 foot porous rock outlet <br />structure will be constructed in the breach to provide some <br />retention and filtering as the flow works its way through the <br />outlet structure. The rock outlet structures will be inspected <br />periodically to ensure that they are in good repair and are not <br />clogged with sediment. The discharge of these structures will be <br />