Stormwater Management Plan

Good Shepherd Lutheran College                                                                  Odyssey Consulting Group
Proposed Unit Development                                                        Conceptual Stormwater Management Plan
Lot 30 on SP170751                                                                                     Project No: K4277
115 EUMUNDI NOOSA ROAD, NOOSAVILLE

        Table 11:      Detention Tank A Parameters
                                                                                                2
          Detention Tank Surface Area                                                   100 m
          Detention Tank Invert Level                                                    9.14 m
          Detention Tank Height                                                          1.26 m
          Low Flow Outlet Pipe Diameter                                       300 mm @ Invert of tank
          Low Flow Orifice Diameter                                                     210 mm
          High Flow Orifice Diameter                                                    110 mm
          High Flow Outlet Pipe Invert Level                                             9.63 m
          Over Flow Outlet Diameter                                                     150 mm
          Over Flow Outlet Pipe Invert Level                                             9.95 m
                                                                                                3
          Detention Volume                                                              126 m
        The 25 minute design storm was the critical storm event for determining the required volume within
        the tank. A comparison of the pre development, post development and mitigated flow rates based on
        the above arrangement is shown in Table 12 followed by the hydrograph in Figure 3 for the critical
        duration of the Q100 storm event.
        Comparison of Pre Development, Post Development and Mitigated Flow Rates for Catchment B
        Table 12:      Comparison of Pre Development, Post Development and Mitigated Flow Rates for Catchment B
                    Average Recurrence Interval                          2                   10                 100
                    DRAINS Pre Development                  3
                                                           m /s          0.104               0.169              0.277
                    Flow Rate
                    DRAINS Post Development
                                                            3
                    Flow Rate                              m /s          0.174               0.280              0.448
                    Catchment A Q100
                    DRAINS           Mitigated              3
                                                           m /s          0.104               0.169              0.277
                    Development Flow Rate




        Figure 3:      Mitigated Post Development Catchment Q100 Flow Rates
        Catchment A will be collected by a detention tank to mitigate flows to less than that of the pre
        development scenario and will discharge to a LPOD on Eumundi Noosa Road. With reference to Figure
        3 the detention arrangement can be seen to effectively mitigate the post development flows in all
        storm events for the proposed site.


K4277-0002                                           14 March 2018                                          Page 9 of 16