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Technical Revision 90-06 <br />• ~ The slope length gradient factor selected was a conservative estimate reflecting <br />the most adverse erosion conditions as determined by a series of slope/length <br />measurements for the contributing drainage area and the SCS "Slope-effect" <br />chart was then utilized. <br />~ Crop management factors "C" were determined for each drainage sub-area, <br />utilizing data from the SCS or National Cooperative Highway Research program. <br />A weighted average crop management factor for the entire drainage area was <br />calculated on the basis of "C" factors and relative acreages for drainage sub- <br />areas. <br />~ Since neither disturbed nor undisturbed areas will be utilized as cropland, and <br />erosion control practice factor "p" of 1.0 was utilized in all calculations as <br />recommended by the SCS Handbook No. 537. <br />• The soil loss calculated by using the "Universal Soil Loss Equation" was then multiplied by a <br />sediment delivery ratio based upon the acreage contained in the drainage area, the three year <br />sediment storage design criteria, and the drainage area acreage, to determine the three year <br />sediment yield for the contributing drainage area. <br />POND DESIGN <br />Impoundment Design <br />The sedimentation control structures have been designed to minimize surface disturbance, <br />effect compliance with applicable state and federal regulations, provide effective sediment <br />control, facilitate operation and maintenance, and ensure long-term structural stability. <br />Ponds have been sized to contain a three year accumulation of sediment and the runoff <br />volume from a 10-year, 24-hour design storm event for the contributing drainage areas. A <br />. primary outlet structure and emergency spillway have been incorporated in the pond designs. <br />TR 90-06 Exhibit 3 - 9 Revised 1 1 /16/90 <br />