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iii iiiiiiiiuiu iii <br /> <br />~'' RESPONSE TO COMMENTS CONCERNING <br />Doc Date:12/1112001 <br />• <br />NOV C-85-081 (SEDIMENTATION PONDS), SENECA Il M1NE <br />In her letter dated January 14, 1986, Anne Baldrige of the Mined Lond Reclamation <br />Division (MLRD) responded to Vern Pfannenstiel's (Peabody Coal Copmony) letter dated <br />November S, 1985 regarding NOV C~5-081. As stated in the second to last paragraph of <br />her letter, "The information presented in your response letter (I I /I 5/85) should be cor- <br />rected or verified as per my comments and submitted for insertion to the permit." The <br />following narrative presents additional information and corrections per comments I <br />through 4 of Anne Baldrige's letter and should fully satisfy abatement of NOV C-85-081. <br />COMMENT I <br />As we have discussed, the Wadge Impoundment is of sufficient size to hold the 10 yr-24 <br />hr storm and 170.6 ac-ft of sediment. Peabody presented calculations for an..annval <br />sedimentation rote of 10.2 ac-ft/yr but did not explain how this number was reached. <br />Some explanation should be presented. Using 10.2 ac-ft/year, since pond construction <br />available storage has been depleted by 54.4 ac-ft. The remaining storage will be <br />depleted in 11.4 years. While this is a few years away, I strongly recommend Peabody <br />re-evaluate their sediment yield calculations for this area to show that these figures are <br />conservative. This will eliminate the need for pond surveys in the future to show that <br />cleanout is or is not necessary. This can be done as part of The 5 year permit renewal. <br />RESPONSE: <br />Calculated annual sediment rate was determined using the USLE (Universal Soil Loss <br />Equation). The calculations are explained as follows: <br />USLE = A = (R)(K)(LS)(C)(P) <br />R ='30 (See Figure 5.3, Barfield, Warner and Haan, 1981, A lied H drolo and <br />Sedimentolo for Disturbed Areas, Dept. of Agricultural ngineering, <lahoma <br />tote nrv., ti water, a oma . <br />K = 0.21 <br />LS = 10 <br />C = 0.12 <br />P=1 <br />A = (30)(0.21)(10)(0.12)(1) = 7.56 tons/ac-yr <br />(7.56 tons/ac-yr)(2382 acres) = 18,008 tons/yr <br />~ • <br />1 <br />