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Home My WebLink About20221107_2-ESC_Calcs Attachment 2 Stormwater and Erosion Control Calculations > v n w p = r (p • 6 \ - i dir 7f r E ;f IN . .- � t a u s • to 6 q I � STEEL GRAY MINE �e N 7 ota2leto 3 FORF , =� 91 W BLUE RIDGE QUARRIES,INC, LANDCRAFT ENGINEERING PLLC urtc t couNTv NORTH CaR0l1NA FM WENSE Na P-0740 ��® Project No: otdwinq Title: 31 CROSS STREETSLHI a 000 DETAILS SPRUCE PMNBC 211M rI s I n I v I ,+ I w I a I x I g w r c s a• r Steel Gray Mine Sediment Trap Trap/ Surface Storage Spillway Skimmer Size Drainage Area Area Volume length T-1 16'X60'X4 0.6 acres 960ft2 3840ft3 4.0' T-IA 10'X33'X4' 0.12 acres 330ft2 1320ft' 4.0' T-2 20'x110'x4' 1.87 acres 2200ft2 8800ft3 6.0' T-3 26'x100'x3' 2.12 acres 2600ft2 10400ft3 6.0' T-4 36'x125'x4' 3.5 acres 4500ft' 18000w 10.0' T-5 36'x99'x4' 1.95 acres 3564ft2 14256ft3 9.54 Runoff Calculations for Trap T-1 Description Acres C-Value Coef. Bare Sandy Soil level 0 0.5 0 Bare Soil (sloping) 0.6 0.5 0.3 Grassland & disturbed Areas 0 0.5 0 Woodlands 0 0.3 0 Roadway ravel 0 0.65 0 Totals 0.6 0.3 C = 0.3 (coef) / 0.6 (acres) = 0.5 i = Rainfall Intensity for 10 year, 1 day storm = 7.06 inches Q = (C)(i)(A) = 0.5 X 7.06 X 0.6 = 2.118 cfs i = Rainfall Intensity for 2 year, 1 day storm = 5.21 inches Q = (C)(i)(A) = 0.5 X 5.21 X 0.6 = 1.563 cfs i = Rainfall Intensity for 25 year, 1 day storm = 8.09 inches Q = (C)(i)(A) = 0.5 X 8.09 X 0.6 = 2.427 cfs Sediment Trap Trap T=1 Trapping Effeciency Drainage Area Acres 0.6 A = 0.01 X (0) 1 2.118 = 0.0212 X 43560 _ 922.6 ft2 Required Basin Size 16'X60'X4'(minimum) Ft2 Surface area 980 Ft3 Storage area 3840 Trap to be deaned at the plont where the basin no longer functions well or Is at 60%capadty. Runoff Calculations for Trap T-1A Description Acres C-Value Coef. Bare Sandy Soil level 0 0.5 0 Bare Soil (sloping) 0.21 0.5 0.105 Grassland & disturbed Areas 0 0.5 0 Woodlands 0 0.3 0 Roadway ravel 0 0.65 0 Totals 0.21 0.105 C = 0.105 (coef) / 0.21 (acres) = 0.5 i = Rainfall Intensity for 10 year, 1 day storm = 7.06 inches Q = (C)(i)(A) = 0.5 X 7.06 X 0.21 = 0.7413 cfs i = Rainfall Intensity for 2 year, 1 day storm = 5.21 inches Q = (C)(i)(A) = 0.5 X 5.21 X 0.21 = 0.54705 cfs i = Rainfall Intensity for 25 year, 1 day storm = 8.09 inches Q = (C)(i)(A) = 0.5 X 8.09 X 0.21 = 0.84945 cfs Sediment Trap Trap T-1A Trapping Effeciency Drainage Area Acres 0.21 A = 0.01 X (0) 0.74 = 0.0074 X 43560 322.3 W Required Basin Size I VX3TXW(minimum) Ft2 Surface area 330 Ft3 Storage area 1320 Trap to be cleaned at the plant where the basin no longer funclions well or Is at 50%capacity. Runoff Calculations for Trap T-2 Description Acres C-Value Coef. Bare Sandy Soil level 0 0.5 0 Bare Soil (sloping) 0.75 0.5 0.375 Grassland & disturbed Areas 0 0.5 0 Woodlands 1.12 0.3 0.336 Roadway ravel 0 0.65 0 Totals 1.87 0.711 C = 0.711 (coef) / 1.87 (acres) = 0.3802139 i = Rainfall Intensity for 10 year, 1 day storm = 7.06 inches Q = (C)(i)(A) = 0.38021 X 7.06 X 1.87 = 5.01966 cfs i = Rainfall Intensity for 2 year, 1 day storm = 5.21 inches Q = (C)(i)(A) = 0.38021 X 5.21 X 1.87 = 3.70431 cfs i = Rainfall Intensity for 25 year, 1 day storm = 8.09 inches Q = (C)(i)(A) = 0.38021 X 8.09 X 1.87 = 5.75199 cfs \41W Sediment Trap Trap T 2 Trapping Effeciency Drainage Area Acres 1.87 A = 0.01 X (0) 5.02 = 0.0502 X 43560 - 2186.7 ft2 Required Bann Size 2VX11VXC(minimum) Ft2 Surface area 2200 FM Storage area 8800 Trap to be cleaned at the plont where the basin no longer functions wetl or is at 60%capacity. Runoff Calculations for Culvert C-1 Description Acres C-Value Coef. Bare Sandy Soil level 0 0.5 0 Bare Soil (sloping) 0.85 0.7 0.595 Grassland & disturbed Areas 0 0.5 0 Woodlands 1.12 0.3 0.336 Roadway ravel 0 0.65 0 Totals 1.97 0.931 C = 0.931 (coef) / 1.97 (acres) = 0.4725888 i = Rainfall Intensity for 10 year, 1 day storm = 7.06 inches Q = (C)(i)(A) = 0.47259 X 7.06 X 1.97 = 6.57286 cfs i = Rainfall Intensity for 2 year, 1 day storm = 5.21 inches Q = (C)(i)(A) = 0.47259 X 5.21 X 1.97 = 4.85051 cfs i = Rainfall Intensity for 25 year, 1 day storm = 8.09 inches Q = (C)(i)(A) = 0.47259 X 8.09 X 1.97 = 7.53179 cfs kqoV Project Description Worksheet Circular Channel-C-1 Flow Element Circular Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.010 Slope 0.010000 ftfft Diameter 15 in Discharge 7.53 cfs Results Depth 0.92 ft Flow Area 1.0 ft2 Wetted Perimeter 2.59 ft Top Width 1.10 ft Critical Depth 1.09 ft Percent Full 73.9 % Critical Slope 0.007304 ft/ft Velocity 7.74 ftfs Velocity Head 0.93 ft Specific Energy 1.86 ft Froude Number 1.45 Maximum Discharge 9.03 cfs Discharge Full 8.40 cfs Slope Full 0.008041 ft/ft Flow Type Supercritical 1 I 15in 0.9I It I VAL H:1 NTS Runoff Calculations for Ditch DB-2 Description Acres C-Value Coef. Bare Sandy Soil level 0 0.5 0 Bare Soil (sloping) 0.6 0.7 0.42 Grassland & disturbed Areas 0 0.5 0 Woodlands 0 0.3 0 Roadway ravel 0 0.65 0 Totals 0.6 0.42 C = 0.42 (coef) / 0.6 (acres) = 0.7 i = Rainfall Intensity for 10 year, 1 day storm = 7.06 inches Q = (C)(i)(A) = 0.7 X 7.06 X 0.6 = 2.9652 cfs i = Rainfall Intensity for 2 year, 1 day storm = 5.21 inches Q = (C)(i)(A) = 0.7 X 5.21 X 0.6 = 2.1882 cfs i = Rainfall Intensity for 25 year, 1 day storm = 8.09 inches Q = (C)(i)(A) = 0.7 X 8.09 X 0.6 = 3.3978 cfs Protect Description Worksheet Trapezoidal Channel-DB-2 Flow Element Trapezoidal Channel Method Manninds Formula Solve For Channel Depth Input Data Mannings 0.104 Coefficient Slope 0.020000 ft1ft Left Side Slope 2.00 V:H Right Side Slope 2.00 V:H Bottom who 2.00 ft Discharge 3.39 cfs Results Depth 0.97 ft Flow Area 2.4 IP Wetted Perimeter 4.17 ft Top Width 2.97 ft Critical Depth 0.43 ft Critical Slope 0.280312 ft/ft Velocity 1.40 ftfs Velocity Head 0.03 ft Specific Energy 1.00 ft Froude Number 0.27 Flow Type Subcritical Determine sheer stress:T 62.4X 0.97 X 0.02 a 1.21 ibIW Permissible Sheer Stress 4.0 IbffN Rip Rap Lining OK 0.97 rs ---------2.00 tt -----------� V:1 H2.0 NTS Runoff Calculations for Ditch DB-2A Description Acres C-Value Coef. Bare Sandy Soil level 0 0.5 0 Bare Soil (sloping) 0.24 0.7 0.168 Grassland & disturbed Areas 0 0.5 0 Woodlands 0 0.3 0 Roadway ravel 0 0.65 0 Totals 0.24 0.168 C = 0.168 (coef) / 0.24 (acres) = 0.7 i = Rainfall Intensity for 10 year, 1 day storm = 7.06 inches Q = (C)(i)(A) = 0.7 X 7.06 X 0.24 = 1.18608 cfs i = Rainfall Intensity for 2 year, 1 day storm = 5.21 inches Q = (C)(i)(A) = 0.7 X 5.21 X 0.24 = 0.87528 cfs i = Rainfall Intensity for 25 year, 1 day storm = 8.09 inches Q = (C)(i)(A) = 0.7 X 8.09 X 0.24 = 1.35912 cfs \w� \� Protect Description Worksheet Trapezoidal Channel-DB-2A Flow Element Trapezoidal Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.104 Slope 0.020000 tuft Left Side Slope 2.00 V:H Right Side Slope 2.00 V:H Bottom Width 2.00 ft Discharge 1.36 cfs Results Depth 0.55 ft Flow Area 1.3 ft2 Wetted Perimeter 3.24 ft Top Width 2.65 ft Critical Depth 0.24 R Critical Slope 0.305306 ft/ft Velocity 1.08 ft/s Velocity Head 0.02 ft Specific Energy 0.57 ft Froude Number 0.27 Flow Type Subcritical Determine sheer stress: To 62.4X 0.66 X 0.02 0 0.691bKO Pemlissible Sheer Stress 4.0 We Rip Rap Lining OK ' f 0.55[l .._i_ VA H2.0 NT8