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~I <br />I <br />~J <br />r 1 <br />Table 2.05.3(4)(d)-8 <br />CMP SIZING CALCULATION <br />CMP LOCATED NEAR THE SEDIMENT POND <br />The computer program Storm (ver. 6.21) was used to develop the following peak <br />flow determination for sizing the culvert located near the sediment pond. See <br />drawing 2.05.3(4)-2(a) for the location of the culvert. <br />The curve numbers are derived from the SCS Handbook, Procedures for Determining <br />Peak Flows in Colorado, Table 2-2d - Run-off curve numbers for arid and semiarid <br />rangelands. The cover type was chosen as sagebrush with grass underetory in fair <br />condition, (306 to 708 ground cover). The 1992 vegetation survey determined that <br />the ground cover of perennial vegetation was 34.96. <br />The drainage areas presented below are the same ae those presented on table <br />2.05.3(4)(d)-4 except the acreage from drainage sub-area 2 was deleted from the <br />went area because flow from sub-area 2 will not flow though the culvert. <br />Tha storm event for the 30 year 24 hour storm was developed from figure S-7 in <br />the SCS handbook. <br />Project Title = RCM Culvert Sizing Calculation <br />WATERSHED HYDROGRAPH <br />Inflow into structure #1 <br />Structure type: Null <br />-- Watershed data for watershed #1 - No. 1 East Area <br />Curve number = 74.0 <br />Area - 9.5 acres <br />Hydraulic length 1860.0 feet <br />Elevation change = 200.0 feet <br />Concentration time = 0.16 hours <br />Concentration time type SCS Upland Curves <br />Unit hydrograph type = Disturbed <br />-- Watershed data for watershed #2 - No. 2 East Area <br />Curve number = 74.0 <br />Area = 15.4 acres <br />Hydraulic length 1610.0 feet <br />Elevation change = 200.0 feet <br />Concentration time = 0.13 hours <br />Concentration time type SCS Upland Curves <br />Unit hydrograph type = Disturbed <br />-- Watershed data for watershed #3 - West Area <br />Curve number = 74.0 <br />Area = 6.9 acres (18.56 - 11.63) <br />Hydraulic length = 1260.0 feat <br />Elevation change = 200.0 feet <br />Concentration time = 0.1 hours <br />Concentration time type = SCS Upland Curves <br />Unit hydrograph type = Disturbed <br />-- Total Area <br />-- Storm Data <br />Total precipitation <br />Storm type <br />Peak discharge <br />Discharge volume <br />= 31.8 acres <br />= 2.0 inches <br />= SCS Type 2 storm, 24 hour storm <br />= 9.52 cfs Use 24" Diameter Culvert <br />= 0.93 acre feet <br />• New 6/07/93 <br />