16-001014-01A (Swmp)

Basin and Bio-Pod D2 they have not been modelled. This will make the results more conservative, as GPT’s will capture
gross pollutants and some sediments.

4.5         MUSIC MODELLING RESULTS
Results for the proposed stormwater quality management strategy (without modelling the WQCP) is presented in
Table 4-5 below.

                                          Table 4-5:    MUSIC Modelling Results
                                                     TSS              TP              TN         Gross Pollutants
                  Description
                                                    (kg/yr)         (kg/yr)         (kg/yr)          (kg/yr)
    Developed Site Only (Without
                                                    29,700            65             425                4,270
    Mitigation)
    WQOs (Percentage Reduction)                      80%             60%             45%                90%
    Load Retention Target                           23,760            39             191                3,843
    Developed Site plus External Catchment
                                                    36,500            77             480                4,630
    (Without Mitigation)
    Developed Site plus External Catchment
                                                    12,700            33             289                 488
    (With Mitigation)
    Load Retention Achieved                         23,800            44             191                4,142
    Load Retention Achieved as % of
                                                       80%           68%             45%                97%
    Developed Site Load
    Objective Achieved?                                YES           YES             YES                YES


Two models have been provided to Council, the “Developed Site Only” model and the “Developed Site with External -
Mitigated” model. The methodology for demonstrating that WQOs for the site have been met is summarised below.

     The Load Retention Target (in kg/yr) for the site was determined using the “Developed Site Only” model, estimating
      the pollutants generated from the developed site only.

     The Load Retention Achieved (in kg/yr) was determined using the “Developed Site with External - Mitigated” model,
      estimating the amount of pollutants removed from site and External Catchment B1 and C1 as a result of the
      stormwater quality improvement devices.
A comparison between the targets and pollutant retention achieved demonstrate that WQO’s for the site have been
met. This approach is consistent with past DA approvals (for the interim layout) and earlier discussions with Council.
The above results indicate that the proposed strategy is effective in treating pollutant loads from the proposed
development to achieve the WQO’s as required under SPP 2014.



5           WATERWAY STABILITY MANAGEMENT
The SPP 2014 waterway stability requires the limiting of the 63% AEP post-development peak flows within the receiving
waters to be below a minimum of pre-development peak flows.

Section 3.2.6 of this report includes analysis of peak flows for a 63% AEP rainfall event in which developed peak flows
have been mitigated back to existing conditions in all recurrence intervals. Therefore, the waterway stability management
objectives has been met.




16-001014-01 | STORMWATER MANAGEMENT PLAN (SWMP)                 COOROY RETIREMENT COMMUNITY, TRADING POST
| PALM LAKE RESORTS                                                                          ROAD, COOROY                | 21