MCU25 0079 - Negotiated Reference Documents (As Published)

                 The total impervious area of the existing site was extrapolated from the survey plan and was found to
                 be approximately 40% impervious area (fi=0.40) which equates to approximately 370m2 of impervious
                 area.
                 Roofwater runoff from the existing dwelling appears to discharge to Clipper Street via kerb outlets.
                 Ground level runoff will also discharge to Clipper Street via overland flow.
                 Time of Concentration (tc)

                 The time of concentration is determined by using a combination of standard inlet time and pipe /
                 overland flow time as described in QUDM.

                 A time of concentration of 5 minutes has been deemed appropriate for the existing site as it is improved
                 with a detached dwelling and the natural topography is relatively steep:

                            tc, existing = 5 minutes
                 3.1.1 DR AI NS re su lt s f o r e xi st i ng s ite

                 The existing site catchment is summarised below:

                        •     Area – 0.0921Ha

                        •     Total time of concentration (tc) – 5 minutes

                        •     Percent Impervious (fi) – 40%

                 Peak flow rates from the existing site have been determined by modelling various storm durations for
                 each AEP storm ensemble. The peak flow rate for the median AEP storm event are given in Table 1
                 below.

                 Table 1 - Existing site peak flow rates.

                                       AEP Storm Event                               Peak flow rate (L/s)

                                               1EY                                            20

                                              0.5EY                                           26

                                              0.2EY                                           36

                                               10%                                            40

                                                5%                                            47

                                                2%                                            59

                                                1%                                            66

                 3. 2       De v elo ped Sit e
                 Catchment Area

                 The proposal involves the construction of three residential units including access driveway and ground
                 level features. The final catchment area will remain unchanged at approximately 921m2. The proposal
                 also will take into account the proposed development within the upper half of Lot 183, which is a
                 residential development.




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Document Set ID: 23959990
Version: 1, Version Date: 23/07/2025