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7 SWALE AT 1.0 SOUTH Stage 1 - Calculate Treatment Volume (1/1 Year Return Period) V T= Treatment Volume = A P * I / 1000 Where: A P = Catchment Area (m 2 ) = 800 V T= Treatment Volume = m 3 /hr I = Average annual rainfall for 1/1 year strom (mm/hr) = 27 Stage 2 - Calculate Velocity (V) / Treatment Flow (Q F ) / Residence Time (R T ) (1/1 Year Return Period) Swale Dimensions MANNING'S EQUATION V = 1 Base (b) 0.75 n R2/3 1/2 S o Water Height (h A) 0.1 Side length actual (L A) 0.9 Side length - Wet (L W) 0.30 Where: answer dimension Swale height (h) 0.3 Mannings Angle Length (A L) 0.32 Roughness (n) 0.30 m -1/3 s Hydraulic Radius (R) 0.08 m Where: Cross sectional area of swale n = from CIRIA, 2004 guidance where water is running (A) m 2 R = A/P W Wetted Perimeter of A = (b*h A)+(2*h A*h/2) Swale (P w) 1.38 m P W = A L+A L+b Swale Slope (S o) SO = 1 in 99 (0.0101) Velocity (V) 0.06 m/s Volume of Flow = Q F = V * A * 60 * 60 QF m 3 /hr Where: Residence Time = (R T) = SL / V / 60 Swale Length (SL) (m) = 73 RT mins Stage 3 - Checks - (1/1 Year Return Period) Type Purpose Pass? Velocity V < 0.3m/s yes Volume V T < Q F yes Residence Time R T > 10mins yes Comments

8 SWALE AT 1.0 SOUTH Stage 4 - Calculate Volume (1/30 Year Return Period) QF(1/30)= Flow of 1/30 return period = AP * I / 1000 Where: A P = Catchment Area (m 2 ) = 800 Q F(1/30)= Flow of 1/30 return period = m 3 /hr I = Average annual rainfall for 1/30 year strom (mm/hr) = 65 Stage 5 - Calculate Velocity (V) / Swale Flow Capacity (Q SFC(1/30) ) for 1/30 Year Return Period Swale Dimensions MANNING'S EQUATION V = 1 Base (b) 0.75 n R2/3 1/2 S o Water Height (ha) 0.3 Side length actual (L A) 0.9 Side length - Wet (LW) 0.90 Where: answer dimension Swale height (h) 0.3 Mannings Angle Length (AL) 0.95 Roughness (n) 0.30 m -1/3 s Hydraulic Radius (R) 0.12 m Where: Cross sectional area of swale n = from CIRIA, 2004 guidance where water is running (A) m 2 R = A/P W Wetted Perimeter of A = (b*h A)+(2*h A*h/2) Swale (P w) 2.65 m P W = A L+A L+b Swale Slope (S o) S O = 1 in 99 (0.0101) Velocity (V) 0.08 m/s Swale Flow Capacity = Q SFC(1/30) = V * A * 60 * 60 Q SFC(1/30) m 3 /hr Stage 6 - Checks - (1/30 Year Return Period) Type Purpose Pass? Velocity V < 1.0m/s yes Volume QF(1/30) < Q SFC(1/30) yes Comments

9 Branch L (m) Grad (1 in?) D (mm) V (m/s) T f (min) T c (min) I (mm/hr) A P (hec) εa P (hec) Q (m 3 /s) All Q (m 3 /s) Remarks Pass Pass Pass Pass Pass Fail Pass

10 PIPE DESIGN - USING RATIONAL METHOD Rational Method =Q = Flow in pipe (m 3 /s) = C * A P * I Where: C = (If AP is in hectares) T = duration of storm = T c AP = Impermeable Area (Hectares) Tc = Time of Concentration (minutes) = T f (of all connecting pipes) + 4mins(T e - time of entry 30 * 25.4 I = Rainfall intensity (mm/hr) = Where: into pipe system) T + 10 Tf = Time of Flow (minutes) = L / V / 60 Additional information L = Length (m) Grad = Gradient (1 in? Slope)= Determined as per CIRIA, 2005 Guidance D = Diameter of pipe (mm) V = Velocity (m/s) = interpolated from hydraulic charts εap = summation of impermeable areas for all connecting pipes (Hectares) All Q = Allowable Flow capacity of pipe = interpolated from hydraulic charts Catchment A Outfall Branch L Grad D V Tf Tc I Ap εap Q All Q Remarks Pass Catchment B Outfall Pass

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