20220171 - 14 Wyandra St SWMP

The result of the iterative sizing process determined that the OSD storage will need to provide an attenuation
capacity of 3,000L/unit for the proposed roof area with the maximum possible roof area to be plumbed to the tank.
A low flow outlet consisting of a 42mm orifice plate is to be provided to the base of the OSD storage of each tank,
and a 100mm high flow outlet at the head of the tank will provide discharge for larger storm events.

Using this mitigated development model, the proposed developed flows were again compared to the existing state
as shown below in Table 3.2 Existing and proposed mitigated site peak discharge rates.

                                Table 3.2 Existing and proposed mitigated site peak discharge rates

                                                                      Wyandra Street
                                                                                                      Qchange
                                           A.E.P               Qexisting    Qmitigated   Qchange       (%)
                                                               (m³/s)       (m³/s)       (m³/s)
                                             1EY                0.022        0.022        0.000         0%
                                            50%                 0.025        0.025       0.000          0%
                                           0.2 EY               0.037        0.033       -0.004        -11%
                                            10%                 0.047        0.041       -0.006        -13%
                                             5%                 0.056        0.046       -0.010        -18%
                                             2%                 0.064        0.060       -0.004         -6%
                                             1%                 0.070        0.070       0.000          0%



As the total peak flows are equal to or below the existing site conditions for all storm events, the proposed OSD area
will provide the mitigation required for the peak flow storm events from the development.




Project number 20220171
File RECOR Preliminary Stormwater Management Report - 20220171.docx, 2022-08-24                                   Page 9 of 15
Revision 1


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