Laserfiche WebLink
• In some Instances, mining will cause the drainage area to change during the life of the <br />sedimentation structu [e. When the pit moves into the watershed, runoff is intercepted <br />by the pit. In these cases, a conservative procedure was used; the structure was <br />analyzed for the largest anticipated disturbed drainage area that will contribute runoff <br />to the structure. It was estimated that this condrtion will occur if all of the proposed <br />mining area is disturbed and the area is in different phases of mining and reclamation. <br />In addition, the structure was conservatively designed to include adequate capacity for <br />sediment storage and to treat [he runoff from a 10-year, 24-hour precipitation evens. <br />Finally, the design censerv atively assumed the pond is 100 percent full [o the emergency <br />spillway during the 25-year, ?4-hour and 100-year, .4-hour press pr tau on events and <br />provides for maintenance of adequate freeboard to prevent ovettopptny of the embankment. <br />SCS Curve Number and "k." Factor The cu [ve numbers are based on information presented in <br />Attachment 13-1. The "k" factors were de[ermrned w[th th=_ aid of [he USDA-ARS's revised <br />USLE software package and are shown in Attachment 13-1. The curve numbers and "k" <br />factors were assigned the sam<_ values as those used Eor Pond 010. <br />TABLE 13-4A-2 <br />CIJ Calculations for <br />Fond 011 As-BUrlt <br />Vegetation Hyd [o logic <br />Cover T}~e Soil Group CN Area IACI <br />Spoil 6 91 33.36 <br />Undistrubed B 56 107.91 <br />• 13-4A-3 Revised 1?/12/57 <br />