# Manual Calculation

The result of computation using MSMAware was checked using spreadsheet in this section.

### Project Data

The project area is located in Kuala Lumpur.

So from Figure 5.A1 which divides peninsula into 5 design regions, the project area is located in Region 1- West Coast.

The Project area is 547 m² which equal to 0.0547 ha.

The Terrain is mild.

The % imperviousness is 43.14 per cent.

### Refer table 5.A1

Table 5.A1 gives the maximum permissible site discharge (PSD) and minimum Site Storage Requirement (SSR) values in accordance with the five regions in Peninsular Malaysia.

From Table 5.A1, the Permissible Site Discharge (PSD)/ha= 64.29 l/s/ha.

For the project area, PSD= 0.0547 x 64.29 =3.5167 l/s= 0.0035 m³/s.

From Table 5.A1, the Site Storage Requirement (SSR)/ha= 372.67 m³/ha.

For the project area, SSR= 0.0547 x 372.67 = 20.39 m³.

### Refer table 5.A2

Table 5.A2 gives the maximum permissible site discharge (PSD), minimum Site Storage Requirement (SSR) and inlet values in accordance with the major towns in Peninsular Malaysia.

From Table 5.A2, the inlet flow/ha is 153.1 l/s/ha.

For the project area, inlet flow=0.0547 x 153.1 = 8.375 l/s= 0.0084 m³/s.

From Table 5.A2, PSD/ha=    61.59   l/s/ha.

For the project area, PSD= 0.0547 x 61.59 = 3.368 l/s =      0.0034 m³/s.

From Table 5.A2, SSR/ha= 356.37 m³/ha.

For the project area, SSR= 0.0547 x 356.37 = 19.49 m³.

Adopt smaller PSD value from Table 5.A1 and Table 5.A2 for subsequent sizing of outlet pipe= 0.0034 m3/s.

### Refer table 5.A3

Table 5.A3 gives the OSD volume, inlet size and outlet size for 5 different regions in Peninsular Malaysia.

From Table 5.A3, the inlet pipe= 140.71 mm diameter.

From Table 5.A3, the outlet pipe= 62 mm diameter.

### Refer table 5.A4

Table 5.A4 gives the discharge and pipe diameter relationship for low lying, mild and steep slopes.

From Table 5.A4, the inlet pipe for the inlet flow of 0.0084 m³/s computed in Table 5.A2= 236 mm diameter.

From Table 5.A4, the outlet pipe for the adopted PSD of 0.0034 m³/s = 236 mm diameter.

Adopt the PSD value which is the lower from Table 5.A1 and Table 5.A2= 0.0034 m³/s.

Adopt the SSR is the larger from Table 5.A1 and Table 5.A2= 20.39 m3.

### Sizing of OSD tank

The required storage is 20.39 m3.

Length = 4.25 m.

Tank Storage =1.2 x 4 x 45 = 24 m³ > 20.39   OK

Adopt inlet pipe: Inlet pipe is the smaller of Table 5.A3 and Table 5.A4 = 140.1 mm, adopted= 145 mm.

Adopt outlet pipe: Outlet pipe is the smaller of Table 5.A3 and Table 5.A4 = 62 mm, adopted= 65 mm.

The design is summarize as presented in table 5.42 below

Table 5.42 Summary of OSD Computation Using MSMA 2011 for Kuala Lumpur

Editor :- Dilah – 11 March 14

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