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HomeMy WebLinkAboutStormwater Design Report - Appendix A DRAINAGE AREA # 1 (POND 1) 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft2) C *Area Hardscape 0.95 6016 5715 Landscape 0.2 5395 1079 Roof 0.95 514 488 Total 11924 7282 A =Area(acres) 0.27 C = Weighted C Factor 0.61 2. Calculate Required Volume Q = CIA V=72000 C = Weighted C Factor 0.61 1 = intensity (in/hr) 0.41 (10 yr, 2hr storm) A = Area (acres) 0.27 Q = runoff(cfs) 0.07 V = REQUIRED STORAGE VOL. (ft') 493 PROVIDED VOLUME (ft-) 690 DRAINAGE AREA # 2 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft`) C *Area Hardscape 0.95 18813 17872 Landscape 0.2 7881 1576 Roof 0.95 9362 8894 Total 36056 28342 A =Area (acres) 0.83 C = Weighted C Factor 0.79 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc= 1.87 (1.1-CCr)D112/S13 - ----------------------- rm S = Slope of Basin (%) 1.19 !Return (yrs) C, C = Rational Method Runoff Coefficient 0.95 :2 to 10 1 C,= Frequency Adjustment Factor 1.1 :11 to 25 1.1 D = Length of Basin (ft) 114 126 to 50 1.2 ;51 100 1.25 Tc Overland Flow(minutes) 1.88 ----to---100-------------1.25 Tc Gutter Flow Tc= UV/60 V= (1.486/n)R2/1 S12 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb) S = slope (ft/ft) 0.0088 L = length of gutter(ft) 110 V= mean velocity (fUs) 2.82 Tc Gutter Flow(minutes) = 0.65 Tc Total = 2.53 DRAINAGE AREA # 3 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft 2) C "Area Hardscape 0.95 16408 15588 Landscape 0.2 11144 2229 Roof 0.95 2843 2701 Total 30395 20518 A =Area (acres) 0.70 C= Weighted C Factor 0.68 2. Calculate Tc (Time to Concentration) Tc Overland Flow Tc= 1.87 (1-1-CC')D112/S'/' -- ------------------------- torm S = Slope of Basin (%) 1.68 :Return (yrs) C, C = Rational Method Runoff Coefficient 0.95 :2 to 10 1 Cf= Frequency Adjustment Factor 1.1 :11 to 25 1.1 D = Length of Basin (ft) 103 126 to 50 1.2 51-to-1 00 1.25 7-c Overland Flow(minutes) 1.60 Tc Gutter Flow Tc= LN/60 V= (1-486/n)R2/1 S112 n = Mannings Coefficient 0.013 R = Hydraulic Radius A/P (ft) 0-13 (0.15' below top of curb) S = slope (ft/ft) 0.014 L = length of gutter(ft) 359 V = mean velocity (ft/s) 3.54 Tc Gutter Flow(minutes) = 1.69 Tc Total= 3.29 DRAINAGE AREA # 4 1. Calculate Area and Weighted C Factor Contributing Area C Area (ft`) C 'Area Landscape 0.2 6793 1359 Roof 0.95 2712 2576 Total 9505 3935 A =Area (acres) 0.22 C= Weighted C Factor 0.41 2. Calculate Required Volume Q = CIA V=72000 C = Weighted C Factor 0.41 1 = intensity (in/hr) 0.41 (10 yr, 2hr storm) A= Area (acres) 0.22 Q = runoff(cfs) 0.04 V = REQUIRED STORAGE VOL. (ft) 267 POND 2 - DETENTION REQUIRED VOLUME 1. Calculate Area and Weighted C Factor(Post-Development) Contributing Area C Area (ft 2) C *Area Hardscape 0.95 18813 17872 Landscape 0.20 7881 1576 Roof 0.95 9362 8894 Total 36056 28342 .-------------------------- A =Area (acres) 0.83 Storm C = Weighted C Factor 0.79 ;Return (yrs) C, :2 to 10 1 2. Calculate Tc (Pre-Development) 11 to 25 1.1 Tc Overland Flow :26 to 50 1.2 Tc = 1.87 (1.1-CCr)D1r2/S13 151 to 100 1.25 S = Slope of Basin (%) 2.713 C = Rational Method Runoff Coefficient 0.2 C, = Frequency Adjustment Factor 1.1 D = Length of Basin (ft) 265 Tc (Pre-Development) (minutes) 19 3. Calculate Rainfall Intensity(Duration = Pre-Development Tc) i = 0.64x 0.6' (10-yr Storm, Fig. 1-3, COB Design Standards) x = storm duration (hrs) 0.32 (Tc Pre-Development) i= rainfall intensity(in./hr.) 1.34 4. Calculate Runoff Rate (Pre-Development) Q = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr-) 1.34 (calculated above) A= Area (acres) 0.83 (calculated above) Q =Runoff Rate (Pre-Development) (cfs) 0.22 5. Calculate Required Pond Volume Total Area (acres) = 0.83 acres Weighted C = 0.79 Discharge Rate (cfs) = 0.22 cfs (Equal to Pre-Development Runoff Rate) Duration(min) Duration(h Intensity Q Runoff Release Required Storage rs) (in/hr) (cfs) Volume Volume 3 ft 25 0.42 1.13 0.74 1103 333 770 26 0.43 1.10 0.72 1119 347 772 27 0.45 1.08 0.70 1134 360 774 28 0.47 1.05 0.68 1148 373 775 29 0.48 1.03 0.67 1162 387 776 30 0.50 1.00 0.65 1176 400 776 31 0.52 0.98 0.64 1190 413 777 32 0.53 0.96 0.63 1203 427 777 33 0.55 0.94 0.61 1216 440 776 341 0.571 0.931 0.601 12291 4531 776 PROVIDED VOLUME (ft 3 810 OUTLET STRUCTURE SLOT Q=CLH Q = Discharge (cfs) 0.22 C = Weir Coefficient 3.33 (per COB Design Standards) H = Head (ft) 1.5 L = Horizontal Length (ft) 0.04 L =Slot Width (inches) 0.4 POND 3 - DETENTION REQUIRED VOLUME 1. Calculate Area and Weighted C Factor(Post-Development) Contributing Area C Area (ft2) C Area Hardscape 0.95 16408 15588 Landscape 0.20 11144 2229 Roof 0.95 2843 2701 Total 30395 20518 •-------------------------- A =Area (acres) 0.70 Storm C= Weighted C Factor 0.68 ;Return (yrs) Ct 12 to 10 1 2. Calculate T° (Pre-Development) 111 to 25 1.1 Tc Overland Flow :26 to 50 1.2 Tc= 1.87 (1.1-CCt)D12/513 :51 to 100 1.25 -------------------------- S = Slope of Basin (%) 4.02 C = Rational Method Runoff Coefficient 0.2 Cf= Frequency Adjustment Factor 1.1 D = Length of Basin (ft) 199 Tc (Pre-Development) (minutes) 15 3. Calculate Rainfall Intensity(Duration = Pre-Development Tc) i = 0.64xo.65 (10-yr Storm, Fig. 1-3. COB Design Standards) x= storm duration (hrs) 0.24 (Tc Pre-Development) i= rainfall intensity(in./hr.) 1.60 4. Calculate Runoff Rate(Pre-Development) O = CiA C = Rational Method Runoff Coefficient 0.2 (open land) i = rainfall intensity (in./hr.) 1.60 (calculated above) A= Area (acres) 0.70 (calculated above) Q = Runoff Rate (Pre-Development) (cfs) 0.22 5. Calculate Required Pond Volume Total Area (acres) = 0.70 acres Weighted C = 0.68 Discharge Rate (cfs) = 0.22 cfs (Equal to Pre-Development Runoff Rate) Duration(min) Duration Intensity Q,n (cfs) Runoff Release Required Storage (hrs) (in/hr) Volume Volume ft3 15 0.25 1.58 0.74 668 201 467 16 0.27 1.51 0.71 683 215 468 17 0.28 1.45 0.68 698 228 470 18 0.30 1.40 0.66 712 242 470 19 0.32 1.35 0.64 726 255 471 20 0.33 1.31 0.62 739 269 470 21 0.35 1.27 0.60 752 282 470 22 0.37 1.23 0.58 764 295 468 23 0.38 1.19 0.56 776 309 467 24 0.40 1.16 0.55 787 322 465 PROVIDED VOLUME (ft ) 582 OUTLET STRUCTURE SLOT Q=CLH ` Q = Discharge (cfs) 0.22 C = Weir Coefficient 3.33 (per COB Design Standards) H = Head (ft) 1.5 L = Horizontal Length (ft) 0.04 L =Slot Width (inches) 0.4 PIPE A (OS A Outlet Pipe) 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor A =Area (acres) 0.83 C= Weighted C Factor 0.79 2. Calculate Rainfall Intensity(Duration =Max Tc from Contributing Drainage Areas) i = 0.78x 0 b4 (25-yr Storm, Fig_ 1-3, COB Design Standards) x = storm duration (hrs) 0.04 i= rainfall intensity(in.1hr.) 5.91 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.79 (calculated above) i = rainfall intensity (in./hr.) 5.91 (calculated above) A= Area (acres) 0.83 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 3.85 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) Pipe A Location: OS A Outlet Pipe 0 INPUT D= 12 inches d= 11.26 inches Mannings Formula d n= 0.013 mannings D 0= 57.7 degrees Q=(1.486/n)ARh2/S1f2 S= 0.015 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh213S112 S=slope of channel Q=V x A n=Manning's roughness coefficient Solution to Mannings Equation Manning's n-values z Wetted Hydraulic Area,ft Perimeter, ft Radius,ft velocity ft/s flow,cfs PVC 0.013 0.77 2.64 0.29 6.13 4,69 PE(<9"dia) 0.015 PE(>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Conc 0.013 PIPE B (OS B Outlet Pipe) 25-YR OUTFLOW RATE REQUIRED CAPACITY 1. Calculate Area and Weighted C Factor A =Area (acres) 0.70 C = Weighted C Factor 0.68 2. Calculate Rainfall Intensity(Duration = Max Tc from Contributing Drainage Areas) i = 0.78x 0 ' (25-yr Storm, Fig, 1-3. COB Design Standards) x = storm duration (hrs) 0.05 i = rainfall intensity(in./hr.) 5.00 3. Calculate 25-yr Pond Outflow Rate Q = CiA C = Rational Method Runoff Coefficient 0.68 (calculated above) i = rainfall intensity (in./hr.) 5.00 (calculated above) A= Area (acres) 0.70 (calculated above) Q 25-yr Pipe Flow Rate (cfs)= 2.36 MANNING'S EQUATION FOR PIPE FLOW (PROVIDED CAPACITY) Pipe B Location: OS B Outlet Pipe H INPUT D= 12 inches d= 11.26 inches Mannings Formula d n= 0.013 mannings D 0= 57.7 degrees Q=(1.486/n)ARr,z/3S,z S= 0.02 slope in/in R=A/P A=cross sectional area P=wetted perimeter V=(1.49/n)Rh 2/3 Sil2 S=slope of channel Q=V X A n=Manning's roughness coefficient Solution to Mannings Equation Manning's n-values a Wetted Hydraulic Area,k Perimeter, k Radius,ft velocity ft!s flow,cfs PVC 0.013 0.77 2.64 029 7.08 5.42. PE(<9"dia) 0.015 PE(>12"dia) 0.02 PE(9-12"dia) 0.017 CMP 0.025 ADS N12 0.012 HCMP 0.023 Concl o.013