Stormwater Management Plan · MCU18/0019

SC7440 – Goodchap St, Noosa                                                                               9




3.3.3.1 Rainfall Data
Rainfall data for the site was chosen to give the best representation of actual conditions. A time period of
10 years between 1973 and 1983 was selected from the Cooroy Composite station, using a six minute time
step. The Mean Annual Rainfall for this period is 1595mm, and the Mean Annual ET is 1201mm. See
attached Appendix B for details.


3.3.3.2 Treatment Nodes
The following devices have been used in the treatment train to reduce these pollutant loads to achieve WQO’s.


        SPEL ‘SPELFilter’ Cartridges – Standard underground cartridges were required to achieve the
        WQO’s. The filters use an upflow treatment process, through a spiral wrapped media configuration
        that maximises surface treatment area. Refer to Appendix D for specifications. The design
        proposed is:
            o   8 Cartridges;
        SPE ‘StormSacks’ GPT – A number of baskets installed to the top of field inlets to trap coarse
        sediment prior to entering the drainage system was modelled in line with the cartridge system. The
        design proposed is:
            o   3 Baskets;



3.3.4   Effectiveness in Pollution Reduction
The water quality development model was set up with the incorporation of the above devices to reduce
pollutant export to WQO levels. Table 3.6 indicates the predicted pollutant mean values of stormwater
discharged as calculated by MUSIC:


                                   Pollutant               Percentage Load Reduction

                       Total Suspended Solids (TSS)                    83.7%

                          Total Phosphorus (TP)                        61.3%

                              Total Nitrogen (TN)                      45.0%

                         Gross Pollutants (>5mm)                       100%

                                  Table 3.6 - Flow Based Pollutant Load Reduction



The MUSIC modelling results shown above indicate that the treatment train will adequately treat TSS, TP
and TN generated by stormwater runoff in accordance with the targets required under the water quality
objectives stated previously.