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Home My WebLink About09_StormwaterPre-DevelopmentCalcs_07082021North 3rd Avenue Duplexes CMP Infiltration Sizing Page 1 of 1 7/8/2021 By Miguel Ley PRE-DEVELOPMENT CONDITIONS Design Storm: 10-Year, 2 Hour (City of Bozeman) Basin Area (ac): 0.26 Pre-Dev C (weighted): 0.20 Storm Duration (min)120.00 Weighted Runoff Co-efficent: Area Runoff (acres) Coefficient Calculations Impervious 0.00 0.90 0.00 Undisturbed 0.26 0.10 0.03 Totals 0.26 0.03 Cw =0.10 Runoff Rate (Rational Method): Storm Event (yr): 2-yr, 2-hr 10-yr, 2-hr 25-yr, 2-hr 100-yr, 2-hr 100-yr, 24-hr *Storm Coeff. A: 0.36 0.64 0.78 1.01 1.01 *Storm Coeff. B:0.60 0.65 0.64 0.67 0.67 Composite C: 0.20 0.20 0.20 0.20 0.20 Storm Intensity (in/hr): 0.24 0.41 0.50 0.63 0.12 Pre-Dev Qp (cfs): 0.01 0.02 0.03 0.03 0.01 Pre-Dev V (cubic feet): 89 153 187 238 45 Pre-Development Runoff: 10-Year, 2 Hour Storm Duration Time: 7200.00 sec V10YR/2HR : 153 cf *Values are from COB Design Standards Figure 2 - Rainfall Intensity Druation in Minutes