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been computerized by various individuals and agencies. SEDIMOT II was developed by Research <br />Specialist Bruce N. Wilson, Professor Billy J. Barfield, and Assistant Professor Ian D. Moore at the • <br />Department of Agricultural Engineering, University of Kentucky, Lexington, Kentucky. SEDCAD+ is an <br />enhanced PC version of the SEDIMOT li computer program (see Attachment 13-11. This program is <br />used to estimate runoff peak flow and volume which are necessary for the design of sediment ponds, <br />ditches, and culverts. A copy of the computer program's input and output file information has been <br />included in each sedimentation pond design report. <br />The input includes precipitation amount )inches), watershed area )acres), time of concentration Ihoursl, <br />runoff curve number ICNI, representative particle-size distributions of the soil types in the watershed, <br />sedimentology information, and spillway information, etc. <br />The precipitation amounts for the Seneca II-W Mine for the design storm durations were obtained from <br />the NOAA Precipitation Frequency Atlas Precipitation -Frequency Atlas of the Western States Volume <br />111 -Colorado, 1973, and are listed below: <br />10-year, 24-hour- 1.70 inches* <br />25-year, 24-hour- 2.10 inches <br />100-year, 24-hour 2.50 inches <br />*These amounts also include water emanating from snow cover as snowmelt in a limited period of <br />time. <br />The runoff curve number ICNI is a factor relating the amount of rainfall to the amount of runoff fora <br />given area. The soil erodibility factor 1"k" factor) is a factor of a soils susceptibility to erosion and <br />infiltration capacity. These factors are dependent upon the infiltration characteristics of the soil types <br />and the type and amount of vegetation. Tables 13-1 and 13-2 list the values of CN and "k" for <br />different soils types at the Seneca II-W Mine. <br />The CN and "k" factor for each of the ponds is determined as a weighted average. The undisturbed <br />area curve number and "k" factor information is based on the vegetation and soils information found <br />within Tabs 9 and 10, respectively, of the Seneca II-W Mine Permit. <br />The sediment storage is calculated using the Revised Universal Soil Loss Equation or the Modified <br />Universal Soil Equation contained within the SEDCAD+ computer program. The spillways are <br />designed using the spillway routing subroutine program in the SEDCAD+ computer program and <br />applicable engineering procedures as described in the text of each sedimentation pond design report. <br />All sediment ponds are designed and located to capture surface runoff from upstream disturbance areas <br />and to comply with all applicable State and Federal regulations. <br />Design and as-built reports, when applicable, for the following sedimentation ponds are provided in this • <br />tab: <br />TR-50 6 Revised 11/04 <br />