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HomeMy WebLinkAbout2.2_Stormwater Calculations10 yr Existing Conditions Proposed Conditions Basin Sizing CalculationsWeighted C Value (Pre-Dev) Weighted C Value (Pre-Dev)Duration Duration Intensity Q Runoff Release RequiredArea Area Area Areamin hr in/hr cfs Volume Volume Storage (ft2) (acres) (ft2) (acres)2 0.03 5.84 7.46 895 74 822 0.95 0.00 0.004 0.07 3.72 4.75 1141 147 9940.80 0.00 0.006 0.10 2.86 3.65 1315 221 10940.20 111333 2.56 0.51 0.20 0.00 0.00 8 0.13 2.37 3.03 1455 295 1160 0.10 0.00 0.00 0.10 0.00 0.00 10 0.17 2.05 2.62 1573 368 1204 111333 2.56 0.51 111333 2.56 1.28 12 0.20 1.82 2.33 1676 442 123414 0.23 1.65 2.11 1769 516 12530.200.5016 0.27 1.51 1.93 1854 589 126418 0.30 1.40 1.79 1932 663 1269Time To Concentration TcTime To Concentration Tc20 0.33 1.31 1.67 2004 737 1268Tc Overland Flow (Up to 300ft) Tc Overland Flow (Up to 300ft)22 0.37 1.23 1.57 2072 810 1262Tc = 1.87(1.1-CCf)D0.5)/S1/3 (City of Bozeman Design Standards) Tc = 1.87(1.1-CCf)D0.5)/S1/3 (City of Bozeman Design Standards)24 0.40 1.16 1.48 2137 884 125226 0.43 1.10 1.41 2197 958 1239C = Weighted C Factor 0.20 C = Weighted C Factor 0.50 28 0.47 1.05 1.34 2255 1032 1223Cf = Frequency Factor1.00Cf = Frequency Factor1.00 30 0.50 1.00 1.28 2310 1105 1205D = Length 240.00ftD = Length 180.00ft32 0.53 0.96 1.23 2363 1179 1184S = Slope % 1.50 % S = Slope % 1.50 %Runoff Treatment Volume (Initial 0.5")Tc = 22.78MinutesTc = 13.15MinutesRTV = (0.5*Aimp)/12S = (1000/CN) - 10Tc Shallow Concentrated Flow (After 300ft) Tc Shallow Concentrated Flow (After 300ft) Ia = 0.2*SV = KukSp0.5 (HEC 22 eqn 3-4) V = KukSp0.5 (HEC 22 eqn 3-4)CN= 90 (TR-55)Ku = Conversion Factor3.28English UnitsKu = Conversion Factor3.28English UnitsS= 1.1 ink = Intercept Coefiicient 0.21HEC 22 Table 3-3k = Intercept Coefiicient 0.21HEC 22 Table 3-3Ia = 0.2 inSp = Slope %1.00%Sp = Slope %1.00%0.5" - Ia=0.3 inV = 0.70ft/sV = 0.70ft/s73557 ft2D = 0.00ftD = 210.00ft1703 ft3Tc =0.00MinutesTc =5.01Minutes1703ft3Total Tc (Overland and Shallow Concentrated) Total Tc (Overland and Shallow Concentrated)Outlet Structure Q = CLH3/2 (City of Bozeman Design Standards)Tc = 22.78 Minutes Tc = 18.16 MinutesQ = Discharge 0.56 cfsRunoff Rate (Intensity @ Tc) Runoff Rate (Intensity @ Tc)C = Weir Coefficient 3.33i = 0.64x-0.65 (COB Design Standards, Fig. I-3, 10 yr) i = 0.64x-0.65 (COB Design Standards, Fig. I-3, 10 yr) H = Head 1 ftx = storm duration (hrs.) 0.38 hrs. x = storm duration (hrs.) 0.30 hrs.i = 1.20 in/hr i = 1.39 in/hrL = Weir Width 0.167 ftQ = CiAQ = 0.61cfsQ = CiAQ = 1.78cfsL = Weir Width 2.00 inchesImperviousOpen Land6590 Davis Development - City of Bozeman Site PlanBasin A Detention Facility VolumeDesign Storm Frequency =C C*Area1.28GravelCW =Land UseTotalsCW =Open LandLandscapingTotalsLand UseImpervious Area = Minimum Pond Size Required = Initial 0.5" Pond Volume Req. =C C*AreaLandscapingDense Residential 0.50 111333 2.56 10 yr Existing Conditions Proposed Conditions Basin Sizing CalculationsWeighted C Value (Pre-Dev) Weighted C Value (Pre-Dev)Duration Duration Intensity Q Runoff Release RequiredArea Area Area Areamin hr in/hr cfs Volume Volume Storage (ft2) (acres) (ft2) (acres)5 0.08 3.22 3.96 1188 165 10230.95 0.00 0.0010 0.17 2.05 2.52 1514 330 11840.80 0.00 0.0015 0.25 1.58 1.94 1745 495 12500.20 107173 2.46 0.49 0.20 0.00 0.00 20 0.33 1.31 1.61 1930 660 12700.10 0.00 0.00 0.10 0.00 0.00 25 0.42 1.13 1.39 2086 825 1262 107173 2.46 0.49 107173 2.46 1.23 30 0.50 1.00 1.24 2224 989 123435 0.58 0.91 1.12 2347 1154 11930.200.5040 0.67 0.83 1.02 2459 1319 114045 0.75 0.77 0.95 2563 1484 1079Time To Concentration TcTime To Concentration Tc50 0.83 0.72 0.89 2659 1649 1010Tc Overland Flow (Up to 300ft) Tc Overland Flow (Up to 300ft)55 0.92 0.68 0.83 2749 1814 935Tc = 1.87(1.1-CCf)D0.5)/S1/3 (City of Bozeman Design Standards) Tc = 1.87(1.1-CCf)D0.5)/S1/3 (City of Bozeman Design Standards)60 1.00 0.64 0.79 2834 1979 85570 1.17 0.58 0.71 2991 2309 683C = Weighted C Factor 0.20 C = Weighted C Factor 0.50 80 1.33 0.53 0.65 3135 2639 496Cf = Frequency Factor1.00Cf = Frequency Factor1.00 90 1.50 0.49 0.60 3266 2968 298 D = Length 300.00ftD = Length 300.00ft100 1.67 0.46 0.56 3389 3298 91S = Slope % 1.50 % S = Slope % 1.50 %Runoff Treatment Volume (Initial 0.5")Tc = 25.47MinutesTc = 16.98MinutesRTV = (0.5*Aimp)/12S = (1000/CN) - 10Tc Shallow Concentrated Flow (After 300ft) Tc Shallow Concentrated Flow (After 300ft) Ia = 0.2*SV = KukSp0.5 (HEC 22 eqn 3-4) V = KukSp0.5 (HEC 22 eqn 3-4)CN= 90 (TR-55)Ku = Conversion Factor3.28English UnitsKu = Conversion Factor3.28English UnitsS= 1.1 ink = Intercept Coefiicient 0.21HEC 22 Table 3-3k = Intercept Coefiicient 0.21HEC 22 Table 3-3Ia = 0.2 inSp = Slope %1.00%Sp = Slope %1.00%0.5" - Ia=0.3 inV = 0.70ft/sV = 0.70ft/s77469 ft2D = 0.00ftD = 63.00ft1793 ft3Tc =0.00MinutesTc =1.50Minutes1793ft3Total Tc (Overland and Shallow Concentrated) Total Tc (Overland and Shallow Concentrated)Outlet Structure Q = CLH3/2 (City of Bozeman Design Standards)Tc = 25.47 Minutes Tc = 18.48 MinutesQ = Discharge 0.56 cfsRunoff Rate (Intensity @ Tc) Runoff Rate (Intensity @ Tc)C = Weir Coefficient 3.33i = 0.64x-0.65 (COB Design Standards, Fig. I-3, 10 yr) i = 0.64x-0.65 (COB Design Standards, Fig. I-3, 10 yr) H = Head 1 ftx = storm duration (hrs.) 0.42 hrs. x = storm duration (hrs.) 0.31 hrs.i = 1.12 in/hr i = 1.38 in/hrL = Weir Width 0.167 ftQ = CiAQ = 0.55cfsQ = CiAQ = 1.69cfsL = Weir Width 2.00 inches2.46CW =CW =Impervious Area = Initial 0.5" Pond Volume Req. =Minimum Pond Size Required = Open Land Open LandLandscaping LandscapingCTotalsImperviousDense Residential 0.50 107173TotalsC*Area1.23Gravel6590 Davis Development - City of Bozeman Site PlanBasin B Detention Facility VolumeDesign Storm Frequency =Land UseC C*AreaLand Use 10 yr Existing Conditions Proposed Conditions Basin Sizing CalculationsWeighted C Value (Pre-Dev) Weighted C Value (Pre-Dev)Duration Duration Intensity Q Runoff Release RequiredArea Area Area Areamin hr in/hr cfs Volume Volume Storage (ft2) (acres) (ft2) (acres)5 0.08 3.22 3.38 1014 141 8730.95 0.00 0.0010 0.17 2.05 2.15 1292 282 10110.80 0.00 0.0015 0.25 1.58 1.65 1489 422 10670.20 91471 2.10 0.42 0.20 0.00 0.00 20 0.33 1.31 1.37 1647 563 10840.10 0.00 0.00 0.10 0.00 0.00 25 0.42 1.13 1.19 1781 704 1077 91471 2.10 0.42 91471 2.10 1.05 30 0.50 1.00 1.05 1898 845 105335 0.58 0.91 0.95 2003 985 10180.200.5040 0.67 0.83 0.87 2099 1126 97345 0.75 0.77 0.81 2187 1267 921Time To Concentration TcTime To Concentration Tc50 0.83 0.72 0.76 2270 1408 862Tc Overland Flow (Up to 300ft) Tc Overland Flow (Up to 300ft)55 0.92 0.68 0.71 2347 1548 798Tc = 1.87(1.1-CCf)D0.5)/S1/3 (City of Bozeman Design Standards) Tc = 1.87(1.1-CCf)D0.5)/S1/3 (City of Bozeman Design Standards)60 1.00 0.64 0.67 2419 1689 73070 1.17 0.58 0.61 2553 1971 583C = Weighted C Factor 0.20 C = Weighted C Factor 0.50 80 1.33 0.53 0.56 2675 2252 423Cf = Frequency Factor1.00Cf = Frequency Factor1.00 90 1.50 0.49 0.52 2788 2534 254 D = Length 300.00ftD = Length 300.00ft100 1.67 0.46 0.48 2893 2815 78S = Slope % 1.50 % S = Slope % 1.50 %Runoff Treatment Volume (Initial 0.5")Tc = 25.47MinutesTc = 16.98MinutesRTV = (0.5*Aimp)/12S = (1000/CN) - 10Tc Shallow Concentrated Flow (After 300ft) Tc Shallow Concentrated Flow (After 300ft) Ia = 0.2*SV = KukSp0.5 (HEC 22 eqn 3-4) V = KukSp0.5 (HEC 22 eqn 3-4)CN= 90 (TR-55)Ku = Conversion Factor3.28English UnitsKu = Conversion Factor3.28English UnitsS= 1.1 ink = Intercept Coefiicient 0.21HEC 22 Table 3-3k = Intercept Coefiicient 0.21HEC 22 Table 3-3Ia = 0.2 inSp = Slope %1.00%Sp = Slope %1.00%0.5" - Ia=0.3 inV = 0.70ft/sV = 0.70ft/s68097 ft2D = 0.00ftD = 63.00ft1576 ft3Tc =0.00MinutesTc =1.50Minutes1576ft3Total Tc (Overland and Shallow Concentrated) Total Tc (Overland and Shallow Concentrated)Outlet Structure Q = CLH3/2 (City of Bozeman Design Standards)Tc = 25.47 Minutes Tc = 18.48 MinutesQ = Discharge 0.56 cfsRunoff Rate (Intensity @ Tc) Runoff Rate (Intensity @ Tc)C = Weir Coefficient 3.33i = 0.64x-0.65 (COB Design Standards, Fig. I-3, 10 yr) i = 0.64x-0.65 (COB Design Standards, Fig. I-3, 10 yr) H = Head 1 ftx = storm duration (hrs.) 0.42 hrs. x = storm duration (hrs.) 0.31 hrs.i = 1.12 in/hr i = 1.38 in/hrL = Weir Width 0.167 ftQ = CiAQ = 0.47cfsQ = CiAQ = 1.44cfsL = Weir Width 2.00 inches2.10CW =CW =Impervious Area = Initial 0.5" Pond Volume Req. =Minimum Pond Size Required = Open Land Open LandLandscaping LandscapingCTotalsImperviousDense Residential 0.50 91471TotalsC*Area1.05Gravel6590 Davis Development - City of Bozeman Site PlanBasin C Detention Facility VolumeDesign Storm Frequency =Land UseC C*AreaLand Use