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

5. STORMWATER QUALITY

5.1     CONSTRUCTION PHASE

        As a result of the proposed development, contaminants will be generated during the construction phase. A
        comprehensive Erosion and Sediment control plan including the construction process will be prepared during the detailed
        design. This is to be kept on site during the construction phase and will be in accordance with the State Planning Policy
        2017 and Noosa Shire Planning Scheme.


5.2     OPERATIONAL PHASE

        As the proposed development includes building work that involves greater than 2,500m2 of land the State Planning Policy
        (2017) and Noosa Shire Council Planning Scheme requirements for water quality are applicable to the proposed
        development.


5.2.1   Pollutants of Concern


        The key pollutants to be targeted and the minimum reductions in mean annual loads described in Table 9.4.8.3 the State
        Planning Policy (also consistent with the Noosa Shire Council Requirements) are outlined in Table 24 below.


                                          Table 24: Noosa Shire Council Water Quality Objectives
                                                                          Reduction in Mean
                                            Pollutant
                                                                             Annual Load
                                            Total Suspended Solids (TSS)          80%

                                            Total Phosphorus (TP)                 60%

                                            Total Nitrogen (TN)                   45%

                                            Gross Pollutants (GP)                 90%


5.2.2   Modelling/Assessment Approach


        A quantitative assessment of stormwater runoff quality was considered for the catchments ultimate developed scenario.


        The predicted reductions in mean annual loads of key pollutants have been identified using the “Model for Urban
        Stormwater Improvement Conceptualisation” (MUSIC), Version 6 (6.3.0). MUSIC is a stormwater quality modelling program
        that provides estimates of stormwater pollution generation and the performance of stormwater management measures
        used in series or parallel to form a ‘treatment train’.


5.2.3   Meteorological Data


        The first step in creating the MUSIC model was to select the appropriate meteorological data set (period and time step) to
        be used as the basis for the runoff algorithms. Section 3.1 – Meteorological Data and Section 3.2 – Modelling Period and
        time-step, of the MUSIC Modelling Guidelines details the Rainfall Data and Time Step process requirements of the model,
        respectively.


        The time step used for the MUSIC modelling process was: Tewantin RSL Park 6 Minutes, Station No: 040908.




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