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States Volume III - Colorado, 1973, and are listed below: <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 <br /> runoff for a given area. The soil erodibility factor ("k" factor) is a factor of a soils <br /> susceptibility to erosion and infiltration capacity. These factors are dependent upon the <br /> infiltration characteristics of the soil types and the type and amount of vegetation. <br /> Tables 13-1 and 13-2 list the values of CN and "k" for different soils types at the Nucla <br /> 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 <br /> Mine Permit. <br /> The sediment storage is calculated using the Modified Universal Soil Loss Equation <br /> contained within the SEDIMOT II computer program. The spillways are designed using the <br /> spillway routing subroutine program in the SEDIMOT II computer program and applicable <br /> engineering procedures as described in the text of each sedimentation pond's design <br /> 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 <br /> provided in this tab: <br /> I.D. Name Location Design (Tab 13) Approval Date <br /> Sedimentation Structure 001 Nucla Attachment B 1986 <br /> Sedimentation Structure 002 Nucla Attachment C 1987 <br /> Sedimentation Structure 004 Nucla Attachment D 1987 <br /> Sedimentation Structure 005 Nucla Attachment E 1987 <br /> Sedimentation Structure 006 Nucla Attachment F 1986 <br /> Sedimentation Structure 007 Nucla East Attachment G Submitted 4/88 <br /> 13-7 Revised 04/11/88 <br />