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US~lli~4 ii9:^a FAS gill A85 1JaJ ENFIRiit_il\, IBC. --- REST ELR fm iiiiJ~005 <br />Table 1.0 Peak Runoff Calculation Parameters <br />Paza~neter Value Source <br />Gribble Gulch Wntershed Area 1115 Acs es (.1.74 sq. miles) USGS Topographic Quad Map, <br />LPG 1Vatershed Area 1003 Acres (1.57 sq. miles) Somerset, Colo., <br />Subwatershed for North Face N3852.5-W 10722.5/7.5, 1964. <br />Light Use Road 80 Acres photorevised 1978 <br />Gribble Gulclt Drainage Reach 12?00 feet USGS Topogrepluc Quad Mep, <br />Lone Pine Gulch Reach 13,150 feet So~uerset, Colo. <br />10-yearl24-hour Type II 1.6 inches Figure S-7, SCS Peak Flows in <br />Precipitation CG., 1980 <br />Hydrologic Soil Group Group C -Silty Loam Existing Conditions <br />Vegetation Cover Oak~Aspen Forest-Range, 607•, Existing Conditions <br /> coverage <br />AMC II SCS Runoff Curve 53 => rounded up to 60 Figure S-3, SCS Peak Flows in <br />Number CO., 1930; <br /> also Figure 9.5, Chspter 9, <br /> NEH Section 4, Hydrology; <br /> also curve number used Cor <br /> "Baseli~te H}•drology/Geology <br /> Repm't, Mt. Gunnison Coal <br /> Project, Phase 11, Near <br /> Somerset, Co", Woodward <br /> Clyde Consultants, July, 1978 <br />' RunofT for Inches of Rninfnll, 0.01 inches per inch of t'ni nfall Curve 60, SCS Peak Flaws in <br />10-yr/24-ftt' Type II Event CO., 1980 <br />Peak Discharge, Steep Slope Gribble Gulch Watershed = 300 Figure S-L4, SCS Peak Flows <br />Type II Storm Cor Western csflinch of runoff in CO., 1980 <br />Colorado LPG Watershed = 300 cfs/inch <br /> runoff <br /> North Face of Access Road <br /> Subwatershed = 60 csC/inclt of <br /> runatF <br />Estimated Peak Runoll <br />Gribble Gulch 300'0.01=3.0 => round to 6 cfs <br />Lonn Pine Gulch 300.0.01=3.0 => round to 6 cfs <br />North Face Light Use Road 60'0.01=0.6 => round to 1 cfs <br />