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HomeMy WebLinkAboutWS CAT, Stormwater Plan , Sheet (5) V1Page 3 221182 Appendix B: Stormwater Calculations Project: Client: Designer: Location: Date & Time: Flow, Q = CIA (cfs) Pre-Developed Runoff Coefficient, Cpre = 0.00 Developed Runoff Coefficient, Cw = 0.74 Storm Event = 100 year Total Area, A = 0.97 acres Time of Concentration, tc = 5 min Infiltration Area, Ai = 1,625 sqft Available Facility Volume, Va = 3900 cuft Infiltration Rate, Ir = 1 in/hour = 0.0014 ft/min Infiltrated Flow Rate, Qi = Ai x Ir = 2.3 cfm Offsite Historical Discharge Rate, Qd = Cpre x I x A (see table below) Maximum Flow, Qpeak = Cw x I x A - Qd (see table below) Pond Volume, V = Qpeak x t - Qi x (t + tc) - (Qd x t) (see table below) Sedimentation Increase Factor, fv = 1.15 Required Facility Volume, Vr = V x fv (see table below) Time to infiltrate, ti = (Vr / Qi) / 60 I V Vr hours minutes in/hr cfs cfm cfs cfm cf cf 0.08 5 4.38 0.00 0.0 3.14 188.6 921 1,059 0.17 10 3.16 0.00 0.0 2.27 136.1 1,327 1,526 0.25 15 2.57 0.00 0.0 1.84 110.7 1,615 1,857 0.33 20 2.17 0.00 0.0 1.56 93.5 1,813 2,085 0.50 30 1.73 0.00 0.0 1.24 74.5 2,156 2,480 0.67 40 1.47 0.00 0.0 1.06 63.3 2,431 2,795 0.83 50 1.24 0.00 0.0 0.89 53.4 2,546 2,928 1 60 1.06 0.00 0.0 0.76 45.7 2,592 2,981 2 120 0.61 0.00 0.0 0.44 26.3 2,870 3,301 3 180 0.45 0.00 0.0 0.32 19.4 3,071 3,532 4 240 0.36 0.00 0.0 0.26 15.5 3,168 3,643 5 300 0.30 0.00 0.0 0.22 12.9 3,188 3,666 6 360 0.26 0.00 0.0 0.19 11.2 3,207 3,688 8 480 0.21 0.00 0.0 0.15 9.0 3,247 3,734 <<<<< 10 600 0.17 0.00 0.0 0.12 7.3 3,027 3,482 12 720 0.15 0.00 0.0 0.11 6.5 3,015 3,467 18 1080 0.11 0.00 0.0 0.08 4.7 2,668 3,068 24 1440 0.08 0.00 0.0 0.06 3.6 1,886 2,169 Maximum Required Pond Volume, Vr = 3,734 cf < 3900 cf, VOLUME OK! Storm Duration Resulting in Max Volume = 8 hours Approximate Time to Infiltrate, ti = 27.6 hours = 1.1 days Truck Shop Parking Lot Expansion Western States CAT Centanni 131 S.W. 5TH Avenue, Suite A, Meridian, Idaho 83642 Meridian, ID Phone: 208.288.1992 - Fax: 208.288.1999 12/21/2021 10:57 IDF CURVE ZONE A - STORM WATER INFILTRATION FACILITY Duration, t Qd Qpeak 12/27/21 A-2021-0223