Stormwater Management Plan

6.3.3.2 Detention tank design

In order to limit the site stormwater discharge, stormwater runoff from the development will be detained
in a detention tank located towards the south-western side of the site.

The location of the detention tank is shown on MPN Plan 10256-DA.03 with the detention tank properties
shown in Table 3 below.
                                 Property                                                                    Detention Tank
         Max. Detention Volume (Incl. Freeboard)                                                                   10.68m3
               Max. Water Depth (100 Year ARI)                                                                      0.75m
                Max. Water Depth (20 Year ARI)                                                                      0.45m
                        Detention Base Level                                                                    28.7m AHD
                      Detention Ceiling Level                                                                   29.6m AHD
                         Outlet Arrangement                                                   1 x 120mm Orifice [email protected]
                                                Table 3 - Detention Tank Design Properties

The elevation-area-volumes used for the modelling of the detention tank are listed in Table 4 below.
 Height Above Tank Invert (m)                         Elevation (m AHD)                   Staged Area (m2)               Cumulative Volume (m3)
                        0                                        28.7                                11.87                                0
                     0.45                                        29.15                               11.87                               5.34
                      0.9                                        29.6                                11.87                               10.68
                                     Table 4 - Detention Tank Staged Elevation-Area-Volume


Storm events for Annual Recurrence Intervals from 2 to 100 years were calculated to ensure that peak
runoff flows from the post development site would not exceed peak runoff flows from the pre-
development site.




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Inspired engineering

22 May 2025
https://mpncnetau.sharepoint.com/sites/Administration/Shared Documents/10000-10999/10200-10299/10256/Report/22-05-25 SWMP_Issue A.docx