2503-45382 SRA - REPS Approved Plan and Documents

                                         STORMWATER MANAGEMENT PLAN

Client: Noosa Shire Council                                                                                 Location: Doonan


5.3    Proposed Stormwater Treatment Train
Stormwater runoff from the proposed development will be treated by two (2) bioretention basins prior to
discharging into the receiving environment. The proposed Bioretention Basin A will treat Sub-catchment A,
and Bioretention Basin B will treat Sub-catchment B. Table 5-3 details the associated bioretention basin
parameters used for the proposed treatment train.

                                Table 5-3 MUSIC Details for the Proposed Treatment Train

                                        Surface Area        Filter Area                      Extended
                      Bioretention                                           Filter Depth
                                                                                             Detention
                          basin             (m2)                (m2)              (m)
                                                                                             Depth (m)
                           A                122                 122
                                                                                 0.7             0.3
                           B                80                  80

Refer to the engineering plans in Appendix A for further details.


5.4    MUSIC Modelling Results
MUSIC modelling of the proposed catchments was performed to ensure the nominated treatment strategy
achieves the required pollutant reduction objectives listed in Table 5-1. The target reductions in stormwater
pollutants are based on a comparison of an unmitigated scenario, having no treatment on site, and the
mitigated scenario, which has stormwater treatment measures incorporated onto the site.

As per the SPP (2017), MUSIC modelling is performed to demonstrate the environmental values of receiving
waters are not negatively impacted through the release of nutrients and sediments into waterways. Table
5-4 provides the modelling results for the proposed development being treated by the proposed bioretention
basins. Table 5-4 provides MUSIC modelling results for the overall catchment and considers all sub-
catchments in Table 5-2 and the overall proposed treatment train.

                              Table 5-4 MUSIC Model Results for the Overall Treatment Train

                         Unmitigated          Mitigated               Reduction        Reduction
          Pollutant                                                                                    Compliance
                              (kg/yr)             (kg/yr)            Achieved (%)      Target (%)

             TSS               9590                1810                   81.1              80               Y
             TP                16.7                4.39                   73.1              60               Y
             TN                72.6                37.2                   48.8              45               Y
             GP                666                  0                     100               90               Y


The MUSIC modelling results in Table 5-4 demonstrate that the stormwater management strategy proposed
for the development site meets or exceeds the target reduction rates for major pollutants required by the
NSC and the SPP (2017).




                                                            9                                             Project No: 244035
                                                                                                         M25-0042 Rpt Issue A