2008-01-16_PERMIT FILE - C1994082A (2)

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C • • TR-36 Yoast Mine Pond 12A Design HYDROLOGIC INPUT PARAMETERS SEDCAD 4 Channel YPM-1-1 Watershed ID -Structure 1 - SWS1 Watershed Area: 54.2 Curve Number: HYDROLOGIC CURVE AREA WATERSHED TYPE VEGETATION COVER SOIL GROUP NUMBER (acres) Reclaimed Fair (30% - 70%) B 71 50.3 Reclaimed Topsoiled, no vegetation B 86 0.8 Aspen/Mountain Shrub Good (>70%) C 41 2.4 Sagebrush Good (>70%) C 47 0.7 Total 54.2 CURVE NUMBER 70 Approved Yoast Mine curve numbers are presented in Appendix 13-12, Postmining Drainage and Sediment Control ,Table 13-12.1. Values were adapted from Urban Hydrology for Small Watersheds, Technical Release No. 55, Soil Conservation Service, 1986. SEDCAD 4 Channel YPM-1-1 Watershed ID -Structure 1 - SWS1 Watershed Area: 54.2 Sedimentology: k Factor and Control Factor HYDROLOGIC CONTROL AREA WATERSHED TYPE VEGETATION COVER SOIL GROUP k FACTOR FACTOR (acres) Reclaimed Fair (30% - 70%) B 0.16 0.043 50.3 Reclaimed Topsoiled, no vegetation B 0.16 1.0 0.8 Aspen/Mountain Brush Good (>70%) C 0.37 0.042 2.4 Sagebrush Good (>70%) C 0.19 0.042 0.7 Total 54.2 0.17 0.057 Undisturbed vegetation information taken from Exhibit 10-1, Premining Vegetation Map. Hydrologic soil group values based on soil types which were taken from Exhibit 9-1, Soils Type and Soils Salvage Map.. Disturbed area vegetation information (Reclaimed: vegetated, fair [30% - 70%]; or, topsoiled, no vegetation) taken from 2006 Annual Reclamation Chronological Seeding Map (Yoast Mine 2006 Annual Reclamation Report). Field observations as of June 2007 indicate areas seeded in 2006 display good stand establishment and growth. Approved Yoast Mine "k" Factor and Control Factor values are presented in Appendix 13-12, Postmining Drainage and Sediment Control ,Tables 13-12.2 and 13-12.3, respectively. 13-12.1-63 Revised 08/07