This is a OSD underground tank design result comparison between manual calculation with MES Software.
In this documentation, a comparison of results between manual calculation and MES Software result will be shown. This comparison will be based on SUStoM requirement which is now part of the submission requirement from DID Sarawak, whereby design engineer will be required to use SUStoM for their project submission.
Comparison between OSD sizing of 30m x 30m x 1.5m RC detention storage tank by manual calculation with MES Software.
OSD MSMA 2 – Simplified Method
Project file here
Summary Report here
Manual Excel Spreadsheet here
MES Software Textual Report vs Manual Spreadsheet #
| Reference | Calculation | Output |
Design Criteria #Design Manual = MSMA 2nd Edition Method = Simplified Method Type of OSD = Below Ground |
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| Figure 5.A1 |
Proposed Development #Location = Terengganu – Kuala Terengganu Region = Region 2 – East Coast Project Area = 2.564 ha Impervious Area = 1.923 ha Pervious Area = 0.641 ha Percentage of Impervious Area = 75% Terrain = Steep |
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From Client’s Manual Calc. Impervious = 75% | |
| Table 5A1 |
Permissible Site Discharge (PSD) #Permissible Site Discharge (PSD)/ha = For area of 2.564 ha, PSD = 2.564 x 69.30 = |
69.30 l/s/ha
177.69 l/s |
| Table 5A2 | Permissible Site Discharge (PSD)/ha =
For area of 2.564 ha, PSD = 2.564 x 69.30 = |
69.30 l/s/ha
177.69 l/s |
| Permissible Site Discharge (PSD) =
(whichever is smaller from Table 5A1 and A2) |
177.69 l/s | |
 |
From Client’s Manual Calc.Qpost =177.7l/s | |
| Table 5A1 |
Site Storage Requirement (SSR) #Site Storage Requirement (SSR)/ha = For area of 2.564 ha, SSR = 2.564 x 509.90 = |
509.90 m3/ha
1307.38 m3 |
| Table 5A2 | Site Storage Requirement (SSR)/ha =
For area of 2.564 ha, SSR = 2.564 x 509.90 = |
509.90 m3/ha
1307.38 m3 |
| Site Storage Requirement (SSR) =
(whichever is larger from Table 5A1 and 5A2) |
1307.38 m3 | |
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From Client’s Manual Calc. SSR = 1307.4m3 | |
OSD Tank Sizing #The required storage is 1307.38 m3 The dimension for the proposed below-ground storage tank: V = Length × Width × Depth = 30.00 × 30.00 × 1.60 = 1440.00 m3 |
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From Client’s Manual Calc. = 1350 m3 | |
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Table 5A3 |
Inlet & Outlet Sizing #Inlet Pipe Inlet pipe diameter = |
719 mm |
| Table 5A2 | Inlet/ha =
For area of 2.564 ha, Inlet Flow = 2.564 x 220.0/1000 = |
220.00 1/s/ha
0.564m3/s |
| Table 5A4 | Inlet Pipe diameter = | 786 mm |
| Required Inlet Pipe diameter =
(whichever smaller from Table 5.A3 and 5.A4) |
719 mm | |
| Provide 1 nos. 720 mm diameter pipe | 1 Nos. 720 mm | |
| Primary Outlet
Primary outlet discharge should not exceed the lesser PSD flow. |
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| Table 5A3 | Outlet pipe diameter = | 327mm |
| Table 5A4 | PSD = 177.6851/s =
Outlet pipe diameter = |
0.178 m3/s
418 mm |
| Required Outlet Pipe diameter =
(whichever smaller from Table 5.A3 and 5.A4) |
327 mm | |
| Provide 1 nos. 327 mm diameter pipe | 1 Nos. 327mm | |
| Ao = No. of Orifice × π × (D/2)2
= 1 × π × (0.327/2)2 = 0.08398m2 |
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| Ho = Depth – Diameter/2 – H
Ho = 1.6 – 0.327/2 – 0.900 Ho = 0.537 m |
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| Q = CdAo(2gHo)0.5
= 0.62 × 0.084(2 × 9.81 × 0.5365)0.5 = 0.172m3/s = 168.93l/s |
168.93l/s < 177..685/s
OK
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| Secondary Outlet | ||
| Table 5A3 | Required overflow pipe diameter = | 719 mm |
| Ao = π × (D/2)2
= π × (0.719/2)2 = 0.406 m2 |
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| Provide 1 nos. 720 mm diameter pipe | 1 Nos. 720mm | |
| Ao = No. of Orifice × π × (D/2)2
= 2 × π × (0.720/2)2 = 0.40715m2 |
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