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HomeMy WebLinkAbout10_Engineering Report Appendix AAppendix A – Flow Rates, Pond Sizing, and Spread Calculations 0.90 0.50 0.20 Note: Coefficients obtained from CoB Design Standards Table I-1 BASIN A Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.23 0.90 0.21 Dense Residential 0.00 0.50 0.00 Open Land 0.50 0.20 0.10 Phase 3 Norton 2.35 0.36 0.85 Phase 5 Norton 1.61 0.40 0.64 Totals 4.69 1.80 Cw =0.38 BASIN B Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 1.20 0.90 1.08 Dense Residential 1.75 0.50 0.88 Medium Residential 0.56 0.35 0.20 Open Land 0.87 0.20 0.17 Totals 4.38 2.33 Cw =0.53 BASIN C Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.33 0.90 0.30 Dense Residential 0.37 0.50 0.18 Open Land 0.12 0.20 0.02 Totals 0.82 0.51 Cw =0.62 BASIN D Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.80 0.90 0.72 Dense Residential 2.05 0.50 1.02 Open Land 0.64 0.20 0.13 Totals 3.48 1.87 Cw =0.54 MAJOR SUBDIVISION Weighted Runoff Coefficients URBAN + FARM PHASE 1 Asphalt/Concrete Dense Residential Open Land L:\203430\Computations\PA 17, 26\STORMWATER\Stormwater Calculations BASIN E Post-Development Weighted C-Value (Cw) Area Runoff (Acres) Coefficient Calculations Asphalt/Concrete 0.27 0.90 0.25 Dense Residential 0.04 0.50 0.02 Open Land 0.10 0.20 0.02 Totals 0.42 0.29 Cw =0.69 L:\203430\Computations\PA 17, 26\STORMWATER\Stormwater Calculations Equations Used: Qp = C i A (Modified Rational Method) i = a * (DURATION) ^ -(b) (City of Bozeman) Overland Flow tc=((1.8)*(1.1-C)*(D^(1/2)))/(S^(1/3)) (City of Bozeman) Gutter Flow V=3.28*k*(S^(1/2), where k=0.618 (paved) (FHWA HEC 22, Eqn 3-4) BASIN A Basin Area (ac): 4.69 Storm Event Intensity Post-Dev C (weighted): 0.40 (yr) (in/hr) A B Overland Distance (ft): 137 2 0.51 0.36 0.6 Overland Slope (%): 0.7 5 0.75 0.52 0.64 Gutter Flow Distance (ft): 2120.0 10 0.93 0.64 0.65 Gutter Flow Slope (%): 1.0 25 1.13 0.78 0.64 Post-Dev. Tc (min): 33.7 50 1.35 0.92 0.66 100 1.49 1.01 0.67 Storm Event (yr): 2 10 25 100 Storm Coeff. A: 0.36 0.64 0.78 1.01 Storm Coeff. B: 0.60 0.65 0.64 0.67 Composite C: 0.40 0.40 0.40 0.40 Storm Intensity (in/hr): 0.51 0.93 1.13 1.49 Post-Dev Qp (cfs):0.96 1.75 2.12 2.79 BASIN B Basin Area (ac): 4.38 Storm Event Intensity Post-Dev C (weighted): 0.53 (yr) (in/hr) A B Overland Distance (ft): 70 2 0.77 0.36 0.6 Overland Slope (%): 0.7 5 1.18 0.52 0.64 Gutter Flow Distance (ft): 868.0 10 1.46 0.64 0.65 Gutter Flow Slope (%): 1.0 25 1.76 0.78 0.64 Post-Dev. Tc (min): 16.8 50 2.13 0.92 0.66 100 2.37 1.01 0.67 Storm Event (yr): 2 10 25 100 Storm Coeff. A: 0.36 0.64 0.78 1.01 Storm Coeff. B: 0.60 0.65 0.64 0.67 Composite C: 0.53 0.53 0.53 0.53 Storm Intensity (in/hr): 0.77 1.46 1.76 2.37 Post-Dev Qp (cfs):1.80 3.41 4.10 5.52 BASIN C Basin Area (ac): 0.82 Storm Event Intensity Post-Dev C (weighted): 0.62 (yr) (in/hr) A B Overland Distance (ft): 115 2 0.88 0.36 0.6 Overland Slope (%): 0.5 5 1.35 0.52 0.64 Gutter Flow Distance (ft): 251.0 10 1.69 0.64 0.65 Gutter Flow Slope (%): 1.3 25 2.03 0.78 0.64 Post-Dev. Tc (min): 13.5 50 2.46 0.92 0.66 100 2.75 1.01 0.67 Storm Event (yr): 2 10 25 100 Storm Coeff. A: 0.36 0.64 0.78 1.01 Storm Coeff. B: 0.60 0.65 0.64 0.67 Composite C: 0.62 0.62 0.62 0.62 Storm Intensity (in/hr): 0.88 1.69 2.03 2.75 Post-Dev Qp (cfs):0.45 0.86 1.03 1.40 BASIN D Basin Area (ac): 3.48 Storm Event Intensity Post-Dev C (weighted): 0.54 (yr) (in/hr) A B Overland Distance (ft): 65 2 0.89 0.36 0.6 Overland Slope (%): 0.7 5 1.36 0.52 0.64 Gutter Flow Distance (ft): 524.0 10 1.70 0.64 0.65 Gutter Flow Slope (%): 1.1 25 2.05 0.78 0.64 Post-Dev. Tc (min): 13.3 50 2.49 0.92 0.66 100 2.77 1.01 0.67 Storm Event (yr): 2 10 25 100 Storm Coeff. A: 0.36 0.64 0.78 1.01 Storm Coeff. B: 0.60 0.65 0.64 0.67 Composite C: 0.54 0.54 0.54 0.54 Storm Intensity (in/hr): 0.89 1.70 2.05 2.77 Post-Dev Qp (cfs):1.66 3.19 3.83 5.19 URBAN + FARM POST-DEVELOPMENT SUB BASIN FLOWS MAJOR SUBDIVISION Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) Storm Coeff. (i) L:\203430\Computations\PA 17, 26\STORMWATER\Stormwater Calculations BASIN E Basin Area (ac): 0.42 Storm Event Intensity Post-Dev C (weighted): 0.69 (yr) (in/hr) A B Overland Distance (ft): 61 2 1.14 0.36 0.6 Overland Slope (%): 0.7 5 1.78 0.52 0.64 Gutter Flow Distance (ft): 245.0 10 2.23 0.64 0.65 Gutter Flow Slope (%): 0.8 25 2.67 0.78 0.64 Post-Dev. Tc (min): 8.8 50 3.27 0.92 0.66 100 3.66 1.01 0.67 Storm Event (yr): 2 10 25 100 Storm Coeff. A: 0.36 0.64 0.78 1.01 Storm Coeff. B: 0.60 0.65 0.64 0.67 Composite C: 0.69 0.69 0.69 0.69 Storm Intensity (in/hr): 1.14 2.23 2.67 3.66 Post-Dev Qp (cfs):0.33 0.64 0.77 1.05 Storm Coeff. (i) L:\203430\Computations\PA 17, 26\STORMWATER\Stormwater Calculations Existing Detention Pond Sizing (From Norton Ranch Phase 5 Design Report) Contributing Area C Area (ft2)C*Area Phase 5 ROW 0.74 358934 264714 OS 0.2 206332 41266 Low-Med Residential 0.35 720728 252255 Norton Phase 3 and Future Planning Area Composite 0.49 1474393 722453 (From Existing/Planned Norton Ranch Phase 3) Total 2760387 1280688 A = Area (Acres)63.3698 C = Weighted C Factor 0.46 Tc = Time to Concentration 50 min Tc = Time to Concentration 0.84 hrs. i = intensity 0.72 in/hr Q (Pre-Development)9.09 cfs Detention Pond Volume Total Area = 63.37 Acres Weighted C= 0.46 Discharge Rate = 9.09 cfs Required Storage = 37018 cu ft Provided Storage = 47688 cu ft Norton Ranch Phase 5 Existing Detention Pond MAJOR SUBDIVISION URBAN + FARM Phase 1 Required Detention Pond Sizing Contributing Area C Area (ft2)C*Area Norton Phase 5 ROW 0.74 358934 264714 * Open Space 0.2 206332 41266 * Low-Med Residential 0.35 720728 252255 * Norton Phase 3 Composite 0.49 1194415 585263.4 * Urban + Farm Phase 1 Hardscape 0.90 83745.80 75371.22 High Density Residential 0.50 170193.27 85096.635 Opens Space 0.20 107875.33 21575.0664 Totals 2842224 1325541 A = Area (acres)65.25 C = Weighted C Factor 0.47 Discharge Rate (cfs) =9.09 * i = 0.64x-.65 (COB DESIGN STANDARD, Fig. I-3 , 10 yr Storm) Q = CiA Duration Duration Intensity Q Runoff Release Required min hr in/hr cfs Volume Volume Storage 31 0.52 0.98 29.92 55643 16907 38736 32 0.53 0.96 29.30 56265 17453 38812 33 0.55 0.94 28.72 56874 17998 38876 34 0.57 0.93 28.17 57472 18544 38928 35 0.58 0.91 27.65 58058 19089 38969 36 0.60 0.89 27.14 58633 19634 38998 37 0.62 0.88 26.67 59198 20180 39018 38 0.63 0.86 26.21 59753 20725 39028 39 0.65 0.85 25.77 60299 21271 39028 40 0.67 0.83 25.35 60835 21816 39019 41 0.68 0.82 24.94 61363 22361 39002 42 0.70 0.81 24.56 61883 22907 38976 43 0.72 0.79 24.18 62395 23452 38943 44 0.73 0.78 23.83 62899 23998 38901 45 0.75 0.77 23.48 63396 24543 38853 * From Norton Ranch Phase 5 Design Report, C&H Engineering URBAN + FARM Phase 1 MAJOR SUBDIVISION Required Detention Pond Volume Required Detention Pond Sizing Norton Ranch Pahse 1 Planned Drainage Area #18 Norton Ranch Phase 3 Contributing Area C Area (ft2)C*Area ROW/Hardscape 0.95 30016 28515 * Open Space 0.2 11097 2219 * Low-Med Residential 0.35 48520 16982 * Totals 89633 47717 A = Area (acres)2.06 ac C = Weighted C Factor 0.53 i = 0.64x-.65 (COB DESIGN STANDARD, Fig. I-3 , 10 yr Storm)0.41 in/hr Q = CiA 0.45 cfs V= 7200Q 3217 ft3 Actual Drainage Area Contributing Area C Area (ft2)C*Area Hardscape 0.95 22668 21534.6 High Density Residential 0.50 1531 765.5 Low-Med Density 0.35 44742 15659.7 Opens Space 0.20 16330 3266 Totals 85271 41226 A = Area (acres)1.96 ac C = Weighted C Factor 0.48 i = 0.64x-.65 (COB DESIGN STANDARD, Fig. I-3 , 10 yr Storm)0.41 in/hr Q = CiA 0.39 cfs V= 7200Q 2779 ft3 * From Norton Ranch Phase 3 Design Report, C&H Engineering URBAN + FARM Phase 1 MAJOR SUBDIVISION Retention Pond Volume Storm Drain Inlet ID#Basin 10-Yr Flow (cfs) 25-Yr Flow (cfs) 100-Yr Flow (cfs) SDI-1 Basin C 0.86 1.03 1.40 SDI-2 Basin D 3.19 3.83 5.19 Existing SDI 1 Basin B 3.41 4.10 5.52 Existing SDI PH. 5 Basin A 1.75 2.12 2.79 URBAN + FARM PHASE 1 MAJOR SUBDIVISION SDI FLOWS Label Inlet TypeDischarge (ft³/s)Spread (ft)Gutter Width (ft)Road Slope (%)Gutter Cross Slope (%)Road Cross Slope (%)Grate Width (ft)Grate Length (ft) Grate TypeCurb Opening Length (ft)Opening Height (ft)Inlet Efficiency (%)Water Depth at Curb (in)SDI-1 - 25YR ON GRADE 1.03 4.5 1.5 1.14% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 79.68 2.2SDI-1 - 100YR ON GRADE 1.40 5.2 1.5 1.14% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 74.59 2.4SDI-2 - 25YR ON GRADE 3.83 7.8 1.5 1.33% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 56.35 3.4SDI-2 - 100YR ON GRADE 5.19 8.8 1.5 1.33% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 51.8 3.8EXISTING SDI-1 - 25YR ON GRADE 4.10 8.4 1.5 1.10% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 55.4 3.6EXISTING SDI-1 - 100YR ON GRADE 5.52 9.5 1.5 1.10% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 50.67 4EX. PHASE 5 - 25YR ON GRADE 2.12 6.8 1.5 0.80% 6.25% 3.00% 1.5 3 Curved Vaned 2.75 0.5 66.3 3EX. PHASE 5 - 100YRON GRADE5.529.51.50.80%6.25%3.00%1.53Curved Vaned2.750.550.674URBAN + FARM PHASE 1STORM DRAIN INLET SPREAD CALCSMAJOR SUBDIVISION