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The precipitation amounts for the Nucla Mine for the design storm durations were obtained from <br />the NOAA Precipitation Frequency Atlas Precipitation -Frequency A iac of tha W .ctern Sat -~ <br />Volume III -Colorado, 1973, and are listed below: <br />• <br />10-year, 24-hour - 1.60 inches <br />25-year, 24-hour - 1.80 inches <br />100-year, 24-hour - 2.40 inches <br />The runoff curve number (CN) is a factor relating the amount of rainfall to the amount of runoff <br />for a given area. The soil erodibility factor ("k" factor) is a factor of a soils susceptibility to <br />erosion and infiltration capacity. These factors are dependent upon the infiltration characteristics <br />of the soil types and the type and amount of vegetation. Tables 13-1 and 13-2 list the values of <br />CN and "k" for different soils types at the Nucla Mine. <br />The curve number (CN) and 'k° factor for each of the ponds is determined as a weighted <br />average. The undisturbed area curve number and °k" factor information is based on the <br />vegetation and soils information found within Tabs 8 and 9, respectively, of the Nucla Mine <br />Permit. <br />The sediment storage is calculated using the Modified Universal Soil Loss Equation contained <br />within the SEDIMOT II computer program. The spillways are designed using the spillway routing <br />subroutine program in the SEDIMOT II computer program and applicable engineering procedures <br />• as described in the text of each sedimentation pond's design report. <br />All sediment ponds are designed and located to capture surface runoff from upstream <br />disturbance areas 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 <br />in this table: <br />I.D. NAME DESIGN <br />(TAB 13) APPROVAL <br />DATE REVISED <br />DESIGN <br />(TAB 13) APPROVAL <br />DATE <br />POND 001 ATTACHMENT B 1986 N/A <br />POND 002 ATTACHMENT C 1987 ATTACH. C1 1992 <br />POND 004 ATTACHMENT D 1987 ATTACH. D1 1992 <br />POND 005 ATTACHMENT E 1987 ATTACH. E1 1992 <br />POND 006 ATTACHMENT F 1986 ATTACH. F7 1992 <br />• <br />13-7 <br />