B07056.W-01A Complete - Stormwater [As Published] · 132007.2398

Concept Stormwater Management Plan
RSL Care – Cooroy Retirement Village

6.4                MUSIC Modelling Results
Computer modelling using MUSIC was undertaken for the existing and developed scenarios as described in
Section 6.3. The results of the various scenarios are compared in this section to show the effects of the
proposed water quality treatment train on pollutant loads and concentrations.

Results from modelling of the various scenarios are presented in Table 6.7 below. Load retention targets were
derived from the percentage reduction required from the developed site only (without mitigation). These have
then been compared with the load retention achieved from the total catchment (i.e. including some external
catchment areas).
                              Table 6.7: Load Reduction Results for Various Scenarios

                                                     TSS                TP              TN           Gross
 Description                                                                                        Pollutants
                                                    (kg/yr)           (kg/yr)         (kg/yr)        (kg/yr)
 Existing Site (Agricultural Node)                    9190             25.7             180              0

 Developed Site Only (Without Mitigation)             8280             21.8             174             1410

 WQOs (Percentage Reduction)                          80%              60%              45%             90%
 Load Retention Target                               6624              13.1            78.3            1269
 Developed Site plus External Catchment
                                                     12500             30.6             221             1490
 (Without Mitigation)

 Developed Site plus External Catchment
                                                      4160             16.1             143             0.1
 (With Mitigation)
 Load Retention Achieved                             8340              14.5             78             1490
 Load Retention Achieved as % of
                                                     101%              67%             45%             106%
 Developed Site Load
 Objective Achieved?                                  Yes              Yes              Yes            Yes
These results show the load retention achieved for the site and external catchments exceed that which is
required for the site only catchment. Proposed mitigation measures are therefore effective in reducing pollutant
loads to meet WQOs. It is also noted that the developed site plus an external catchment (with mitigation)
produces lower pollutant loads than the existing site.

The median concentration results from the developed site plus an external catchment are presented in Table 6.8
as required by Noosa Council. Results from the MUSIC model show that WQO’s as per Table 6.1 are not met
for the pollutants analysed.




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