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

        The permeable pavement has been modelled with the following properties:

                   Filter media                        Sandy Loam;
                                                        5 – 10% Organic Content in accordance                   with
                                                        AS1289.4.1.1;
                                                        Average D50 0.45 mm;
                                                        Ksat 360 mm/hr;
                   Filter media depth                  0.40 m;
                   Extended detention depth            0.1 m;
                   Seepage                             0 mm/hr;
             
                                                                        2                 2
                    Filter Area                         Pavement 1: 69m , Pavement 2: 150m ;
             
                                                                        2                 2
                    Surface Area                        Pavement 1: 69m , Pavement 2: 150m .



5.4.3   Post Development Modelling Results - Mitigated
        The stormwater quality improvement device (SQID) will reduce the amount of sediments and
        nutrients discharging from the proposed residential development. Table 15 illustrates the treatment
        train effectiveness of the proposed SQID’s.

        Table 15:       Treatment Train Effectiveness of Proposed SQID

                    Parameter                Post         Post Mitigated   Reduction (%)     Water Quality Objectives
                    Flow (ML/yr)             6.24              6.19             0.8                       -
                     TSS (kg/yr)             1400              154              89                      80%
                     TP (kg/yr)              2.73             0.654             76                      60%
                     TN (kg/yr)               13               7.06            45.8                     45%
             Gross Pollutants (kg/yr)         144               0              100                      90%

        The results demonstrate that the proposed SQID meet the intended water quality objectives for flow,
        suspended solids, phosphorous and nitrogen levels.



6.0 OPERATIONAL PHASE MAINTENANCE REQUIREMENTS
        The proposed stormwater management devices will require maintenance and monitoring to ensure
        that they function as designed. The following section provides an outline of the necessary
        maintenance tasks for the proposed devices.

6.1     Bio-retention Basin Maintenance
        The most intensive period of maintenance is during the plant establishment period (first two years)
        when weed removal and replanting may be required. It is also the time when large loads of
        sediments could impact on plant growth particularly in developing catchments with poor building
        controls.

        Maintenance is primarily concerned with:
            Maintenance of flow to and through the bio-retention basin;
            Maintaining vegetation;
            Preventing undesired overgrowth vegetation from taking over the bio-retention basin;
            Removal of accumulated sediments; and
            Litter and debris removal.




K4277-0002                                           14 March 2018                                       Page 14 of 16