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TABLEI Runoff Curve Nu mbers for Seneca II Mine Vegetation Hydrologic H drolo is Soil Grou Cover Type Cover Condition B C D RECLAIMED AREA Herbaceous; seeded rases and contoured 50-80% fair to ood 69 78 83 UNDISTURBED AREA 30-70% fair 48 57 63 Oalc-Aspen; mixed brush-aspen 70-100% ood 30 51 48 30-70% fair 51 63 70 Sagebrush-Grass; upland sagebrush 70-100% ood 35 47 55 30-70% fait 69 79 84 Pasture or Range; grassland used fox grazing 70-100% ood 61 74 80 Herbaceous; range (grass, foxbs, low-growing 30-70% fair 71 81 89 brash 70-100% ood 62 74 85 DISTURBED AREA Paved w/ o en ditches; includin xi ht-of-wa 89 92 93 Gravel Roads; includin ri ht-of-wa 85 89 91 Dirt Roads; indudin ri ht-of-wa 82 87 89 Newl Graded Areas ox Baxe Ground 86 91 94 Notes: This table is presented in the approved Seneca II Mine Permit Application Package as Table 7- 6-1. Ada red from Urban H drolo or Small lY/aterrhed, Technical Release No. S5, SCS, 1986. • Hydxograph response: East Results of [he SEDCAD demonstration axe presented in Attachment A, S$DCFID4 Demonstration. 3.0 CHANNEL DESIGN The channel utility sub-routine contained within SEDCAD4 was used to design Channel PL-1. The design methodology is based on the limiting permissible velocity. If the actual design velocity is Less than the permissible velocity, the channel is stable. SCC evaluated three types of channel design for the Old Wolf Creek area: • vegetated channel • riprap channel • vegetated channel with a turf reinforcement mat Chamzel sections with shallow slopes or low flows were evaluated as a vegetated channel. Once the channel sections were too steep or higher peak flows exceeded the limiting velocity threshold, then either vegetated channels with turf reinforcement matting (TRM) or rock riprap were evaluated as channel lining material to assure channel stability. Old \r/olf Creek Area Remediation Plan 3 Revised 06/07