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Designer: My Name Date: 7 July, 2014 Calculation

1. Desi gn Crit eria Design Manual : MSMA 2nd Edition Design Type : Dry Sediment Basin Outlet Design Storm ARI : 10 years

2. Dete rmi nati on Tim e of Con cent rati on a) Overland Flow Time, to (minutes) Table 2.1 Friend's Equation Table 2.2 to = (107 × n* × L1/3)/S1/2 = (107 × 0.015 × 400.0001/3)/2.0001/5 = 10.29 min File Path : D:\msma\1\1.doc

Checker: Date: Output

2 Hence, standard storm duration =

15 min

3. Dete rmi nati on Typ e of Soil Table 12.16

Soil Type = Coarse-grained sand, sandy loam; less than 33% 0.3 m

1750.00 = V2>1750.00 m3 OK 1y23 148.80y22 + 3510.36y2 For y2 = 0.60m, V2 = 2052.86 m3 c) Overall Basin Dimensio n

Total Basin Dimension

Top Water Level: Top Width =

WT = 30.60 m

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5 W1 + 2 × Z × y1/2 = 30.00 + 2 ×1× 0.60/2 = 30.60 m Top Length = L1 + 2 × Z × y1/2

LT = 120.60 m

= 120.00 + 2×1× 0.60/2 = 120.60 m Base Bottom WB = 28.20 m Width = W1 - 2 × Z × y1/2 + y2) = 30.00 - 2 ×1× (0.60/2 + 0.60) = 28.20 m Bottom Length = L1 - 2 × Z × y1/2 + y2)

LB = 118.20 m

= 120.00 - 2 ×1× (0.60/2 + 0.60) = 118.20 m Depth: Settling Zone, y1 = 0.6 m

y1 = 0.60 m

Sediment Storage Zone, y2

y2 = 0.60 m

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6 = 0.60 m Side Slope: Z = 1(H): 1(V)

Z=1(H):1(V)

4. Sizi ng of Basi n Outl et The Spillway is designed for 10 year ARI flood. Qrequired = Q10 - Qriser a) Design rainfall intensity equation Eq. 2.2

i = λTK/(d + θ)ƞ where: i = average rainfall intensity (mm/hr) for selected ARI (T) and storm duration (d) T = average recurrence interval, ARI (years) d = storm duration (hours); 0.20 ≤ d ≤ 72 λ , K, θ and ƞ = fitting constants dependent on the rain gauge location Location

i = 52.823 × 100.167/ (15.00/60 +

Negeri Sembilan Setor JPS Sikamat i=160.220mm/hr

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ARI, T Storm λ (years) duratio n, d(min) 10 15.00 52.823

K

θ

ƞ

0.167

0.159

0.811

7 0.159)

0.811

= 160.220 mm/hr b) Determin e runoff coefficien t, C Table 2.6

C (Impervious) = 0.90 (Landuse = Commercial and Business Centres) C (Pervious) = 0.00 ()

Eq. 2.3

Q10

= CIA/360 = [(0.00 × 0.90) + (10.00 × 0.00)] × 160.220/360 = 0.000 m3/s

Q10=0.000 m3/s

c) Determination of Outlet Pipe Sizing and Qriser Outlet Riser: 900 mm diameter perforated pipe. Average Surface Area, Aav = [(30.60 × 120.60) + (118.20 × 28.20)]/2 = 3511.80 m2 Orifice Area, Atotal = (2Aav/tCd√2g) × √y = (2 × 3511.80)/(24 × 60 × 60) × 0.6 × √(2 × 9.81)) × √(0.60 + 0.60) = 0.03351 m3 Using an orifice of 50 mm, area of each orifice is Ao = (π × D2)/4 = (3.142 × 0.0502)/4 = 0.00196 m2 Total number of orifice required = 0.03351/0.001963 = 18 Eq. 2.6

Qriser

= CoAo(2gHo)0.5 = 0.6 × (3.142 × 0.902)/4 × (2 × 9.81 × 0.250)0.5 = 0.845 m3/s

d) Spillway Sizing Qrequired = Q10 - Qriser = 0.000 0.845 = -0.845 m3/s

Qrequired=-0.845 m3/s

Eq. 2.10

Qspillway = CspBH1.5

Table 2.7

B = 2.00 m, H = 0.25 and Csp = 1.49 from Table 2.7

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Qriser=0.845 m3/s

8 Qspillway = 1.49 × 2.00 × 0.251.5 = 0.371 m3/s

Qspillway=0.371 m3/s>-0.845 m3 OK

Total Basin Depth including spillway = 0.60 + 0.60 + 0.30 + 0.25 = 1.75 m

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