# OSD Spreadsheet Computation – MSMA 2011

This column, explain details on steps by steps procedure for designing storage system of OSD using spreadsheet computation.

Step 2:- Insert the location, region, project are, terrain and the percentage of impervious area.

[Refer figure 5.A1 to identify the region for your site project.]

Step 3:- Determine permissible site discharge (PSD) per hectares (PSD/ha) from table 5.A1. Insert the value in yellow box as shown below.

[Refer to table 5.A1 in MSMA (2011).]

***Outlet discharge for PSD will be automatically calculated for you as shown in figure below.***

Step 4:- Determine site requirement (SSR) per hectares (SSR/ha) from table 5.A1. Insert the value in yellow box as shown below.

[Refer to table 5.A1 in MSMA (2011).]

Step 5:-Identify the major town of the detention site in Table 5.A2 and determine inlet flow per hectares from Table 5.A2Insert the value in yellow box as shown below.

[Refer to table 5.A2 in MSMA (2011).]

***Inlet flow will be automatically calculated for you as shown in figure below.***

Step 6:- Determine PSD per hectares (PSD/ha) from Table 5.A2. Insert the value in yellow box as shown below.

[Refer to table 5.A2 in MSMA (2011).]

***Outlet discharge for PSD will be automatically calculated for you as shown in figure below.***

Step 7:- Determine SSR per hectares (SSR/ha) from Table 5.A2. Insert the value in yellow box as shown below.

[Refer to table 5.A2 in MSMA (2011).]

***The value for adopt smaller PSD for subsequent sizing of outlet pipe will be automatically calculated for you as shown in figure below.***

Step 8:- Determine the inlet pipe diameter from table 5.A3. Insert the value in yellow box as shown below.

[Refer to table 5.A3 in MSMA (2011).]

Step 9:- Determine the outlet pipe diameter from table 5.A3.  Insert the value in yellow box as shown below.

[Refer to table 5.A3 in MSMA (2011).]

Step 10:- Determine the inlet pipe diameter from table 5.A4 by using the inlet flow value from step 5.1 as discharge. Insert the value in yellow box as shown below.

[Refer to table 5.A4 in MSMA (2011).]

Step 11:- Determine the outlet pipe diameter from table 5.A4 by using the inlet flow value from step 9 as discharge. Insert the value in yellow box as shown below.

[Refer to table 5.A4 in MSMA (2011).]

***Adopt PSD and SSR will be automatically calculated for you as shown in figure below***

Step 12:- Change the value for depth and width as shown in figure below. Length will be automatically calculated for you.

Step 13:- Rounded length value and insert the value in adopt length box as shown in figure below.

Step 14:- Make sure your tank storage is larger than sizing of OSD tank as shown in figure below. If the value smaller, you need to change the size.

Step 15:- The value for Adopt inlet and outlet pipe need to refer to value get from table 5.A3 and table 5.A4 as shown below

Editor:- Dilah – 18 Feb 14

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