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

        The Lot 3 treatment model was developed with an additional source node that showed the road catchments where bio-
        retention pods are being removed, with stormwater being discharged from the private access road un-treated. This was
        done to provide an increased bio-retention area within Lot 3 to appropriately mitigate the increased pollutant run-off
        from the access roadway, with the total pollutant discharge from the entire development and the access roadway meeting
        the objectives noted in Table 23 above.


5.2.6   Treatment Nodes


        The MUSIC model consisted of 3 bio-retention treatment nodes as detailed in Table 28. Treatment node input parameters
        were based on the MUSIC Modelling Guidelines and Noosa Shire Council expectations. Refer to Appendix B for locations
        of the bio-retention treatment devices. Refer to the MUSIC information attached in Appendix G for further details.

                                      Table 28: Selected Stormwater Quality Treatment Devices
            Treatment Device           Discussion


           Bio-Retention Basins        A bio-retention system is a combination of vegetation and filter substrate that provides
                                       treatment of stormwater through filtration, extended detention and some biological
                                       uptake. Three Bio-retention systems are proposed across both Lot 3 and Lot 7 – as per
                                       the details below.


                                       Lot 3 Proposed Bio-Retention Area (as modelled):
                                           •      Filter Area = 560m2
                                           •      Surface Area = 560m2
                                           •      Filter Depth = 700mm
                                           •      Extended Detention Depth = 0.5m


                                       Lot 7 North Proposed Bio-Retention Area (as modelled):
                                           •      Filter Area = 27m2
                                           •      Surface Area = 27m2
                                           •      Filter Depth = 700mm
                                           •      Extended Detention Depth = 0.5m


                                       Lot 7 South Proposed Bio-Retention Area (as modelled):
                                           •      Filter Area = 33m2
                                           •      Surface Area = 33m2
                                           •      Filter Depth = 700mm
                                           •      Extended Detention Depth = 0.5m


                                    Note that per the MUSIC Modelling Guidelines, the filter media depth was increased to
                                    700mm to allow for tree and shrubbery planting within the bio-retention basins. This
                                    increase minimises the potential for tree roots damaging the filter media and sub-soil
                                    drainage systems. Larger trees within the proposed bio-retention basins allow for some
                                    landscape screening of the area, and improve the visual amenity of the bio-retention
                                    systems.


                                    Further details on planting schedules in the bio-retention system, including larger trees to
                                    provide landscape screening, will be determined in later detailed design phases.




                                                     www.bornhorstward.com.au                                                Page 18