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ditches, and culverts, A copy of the computer program's input and output file information <br />has been included in each sedimentation pond design report. <br />The input includes precipitation amount (inches), watershed area (acres), time of <br />concentration (hours), ruttoff curve ~ number (CN), representative particle-site <br />distributions of the soil types in the watershed, sedi mentology ihf ormetion, and spillway <br />information, etc. <br />The precipitation amounts for the Yoest Mine for the design storm durations vere obtained <br />from the NDAA Precipitation Frequency Atlas Pr ecioitation - Freguenc Atlas of the Western <br />States Volume ll[ - Colorado, 1973, end 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 uat er emanating from snow cover as snowmelt in a limited <br />period of time. <br />Thp runoff curve number (CN) is a factor relating the amount of rainfall to the amount of <br />runoff for a given area. Thp soil erodibility factor ("k" factor) is a Factor of a soils <br />suscepti biliiy to erosion and infiltration capacity- These factors are dependent upon the <br />infiltration characteristics of the soil types and the type and amount of vegetatioh. <br />cables 13.1 end 13-2 list the values of CN and "k" for different soils types at the Yoast <br />Mihe. <br />The CN and "k" factor for each of the ponds is determined as a weighted average. The <br />undisturbed area curve number and "k" factor inf ormetion is based on the vegetation and <br />soils information found within Tabs 9 end 10, resppctivel y, of the Yoast Mina permit, <br />The sediment storage is calculated using the Revised Universal Soil loss Equation <br />contained within 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 <br />design report. <br /> All sediment ponds are designed and located to capture surface runoff from upstream <br /> disturbance areas antl to comply with all applicable State and Federal regulations. <br />Designs for the folLOwing sedimentation ponds are provided in this tab: <br />7 Revised 05/23/95 <br />