Loading...
HomeMy WebLinkAbout06_2.1_Stormwater Calculations Retention_04282021North 3rd Avenue Duplexes CMP Infiltration Sizing Page 1 of 1 4/28/2021 By Miguel Ley RETENTION CHAMBER Design Storm: 10-Year, 2 Hour (City of Bozeman) Basin Area (ac): 0.26 Post-Dev C (weighted): 0.59 Storm Duration (min)120.00 Weighted Runoff Co-efficent: Area Runoff (acres) Coefficient Calculations Impervious 0.16 0.90 0.14 Undisturbed 0.10 0.10 0.01 Totals 0.26 0.15 Cw =0.59 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: 0.59 0.59 0.59 0.59 0.59 Storm Intensity (in/hr): 0.24 0.41 0.50 0.63 0.12 Post-Dev Qp (cfs): 0.04 0.06 0.08 0.10 0.02 Pond Size: 10-Year, 2 Hour Storm 100 Year Storm (Includes Infiltration) Duration Time: 7200.00 sec V100YR/2HR : 704 cf V100YR/24HR : 1598 cf V10YR/2HR : 452 cf Infiltration Area: 276 sf Infiltration Area Area:276 sf Infiltation Rate: 2.6 in/hr Infiltation Rate: 2.6 in/hr Volume Infltrated : 120 cf Volume Infltrated : 1435 cf Max CMP Storage: 619 cf Max CMP Storage: 619 cf Max CMP Capacity 739 cf Max CMP Capacity 2054 cf *Values are from COB Design Standards Figure 2 - Rainfall Intensity Druation in Minutes Notes: 36" Perf. CMP with 24' x 11.5' footprint - 619 cf storage per contech 30% Void space used in CMP Storage