Attachment 6 - Stormwater Management Plan and Engineering Response. · MCU23/0078

            •    Lot 7 (North) Catchment Tank Outlet:
                      o     Low-flow outlet: 90mm diameter orifice with invert at RL 6.50m;
                      o     Mid-flow outlet: 150mm diameter orifice with invert at RL 7.75m; and
                      o     High-flow weir: 2m long weir with crest height at RL 8.0m.


            •    Lot 7 (South) Catchment Tank Outlet:
                      o     Low-flow outlet: 100mm diameter orifice with invert at RL 6.50m;
                      o     Mid-flow outlet: 150mm diameter orifice with invert at RL 7.60m; and
                      o     High-flow weir: 2m long weir with crest height at RL 8.00m


        See Engineering Drawings in Appendix B for further information.


4.2.7   Results for Developed Scenario


        Tables 18, 19 and 20 indicates the developed total peak discharge rate from the development sites as outputted by XP
        storm. The peak flow rate indicated is the combined flow of the site and external catchments. To determine the critical
        storm event for the developed mitigated case, the 1-to-100-year ARI storm events for 20, 25, 30, 45, 60, 90, 120 and 180-
        minute durations were simulated in the model.


        From these simulations it was determined that the critical storm event for the Lot 3 Catchment was the 180-minute storm
        for all storm event ARIs, and for the two Lot 7 catchment, the critical storm event varied between the 45-minute storm and
        the 180-minute storm depending on the storm event ARI. The critical storm event results will therefore be compared
        against the existing scenario discharges for both catchments, as identified in Section 4.2.8.


        Further details of the outputs for the critical events have been located within Appendix F.


                                Table 18: XP Storm Developed Mitigated Peak Flow Results – Lot 3 (m3/sec)
                          Storm Duration                                    ARI (Years)
                                 (min)           1        2        5         10           20        50     100
                          20                   0.037     0.042   0.051     0.068         0.104     0.143   0.170
                          25                   0.041     0.045   0.061     0.099         0.137     0.174   0.193
                          30                   0.044     0.048   0.080     0.126         0.163     0.191   0.217
                          45                   0.049     0.055   0.132     0.179         0.203     0.280   0.337
                          60                   0.054     0.077   0.163     0.210         0.259     0.343   0.409
                          90                   0.075     0.107   0.194     0.270         0.338     0.419   0.563
                          120                  0.090     0.122   0.206     0.318         0.357     0.462   0.626
                          180                  0.102     0.132   0.220     0.327         0.373     0.481   0.628
                          Critical             0.102     0.132   0.220     0.327         0.373     0.481   0.628
                          Critical Event        180      180      180       180          180       180     180




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