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1. RESPONSE: RESPONSES TO QUESTIONS TR 15 (8/11/88) Attachment "A" is CMLRD's policy for monitoring sediment level in sediment ponds. The original USLE handbook was published over 20 years ago based on work of Wischmeier and Smith. The original USLE method was primarily applicable to midwest agricultural areas with slope lengths less than 400 feet and slopes flatter than 9 percent. In the last several years, the USDA and SCS have taken a lead role in revising the USLE factors in order to obtain more realistic results for other geographic regions. As a result of McCool, Foster, Renard and others work (see Attachment "B"), the factors for the USLE have been revised. Enclosed is Rena rd's 1981 paper, "Principles of Soil Erosion Control: Rangeland" which discusses the current work being performed by USDA-ARS to revise the USLE method. Also enclosed is D.K. McCool's revised LS equation based on his work entitled, "Revised Slope Steepness Factor for the Universal Soil Loss Equation" (see • Attachment "C"). Based on these papers and personal communications by Peabody's staff with Renard and Foster in 1988, Peabody used the revised USLE factors to compute the soil loss per acre and sediment yield to each pond. Based on previous work discussed in Appendix 7-6, a sediment delivery ratio of 60 percent and a sediment density of 80 pounds per cubic foot was assumed. Based on the predicted sediment loss and sediment delivery ratio, the sediment yield or predicted sediment which might be transported to the ponding area has been calculated utilizing the following equations: Sediment Loss Tons/Acre/Year = (R)(K)(LS)(C)(P) Sediment Loss (A) Tons/Year = (A)Tons/Ac/Yr x (Area) Ac Sediment Yield (Tons/Yr) = Sediment Loss (Tons/Yr x Sediment Delivery Ratio Fur each pond's watershed, revised USLE factors were determined for each type of surface condition. The total sediment yield was calculated as follows: •