24-7-19 Attachment F Rev Stormwater Mgmt Plan

18 July 2019



                                            Existing Discharge                         Proposed Discharge
         ARI Year
                                            From Site (m3/sec)                          From Site (m3/sec)

             2                                       0.196                                   0.192

             5                                       0.271                                   0.249

            10                                       0.310                                   0.306

            20                                       0.359                                   0.355

            50                                       0.390                                   0.369

           100                                       0.435                                   0.413

                                      Table 1 – Existing and Developed Peak Flows

5.3.3 Stormwater Quality Management Strategy

In order to satisfy the requirements of the State Planning Policy July 2017 for the adequate
treatment of stormwater runoff, natural treatment solutions have been provided to remove
hydrocarbons, suspended solids and nutrients prior to being discharged from site.

5.3.3.1 Potential Pollutants Generated
The pollutants that could be potentially generated as a result of the development use are as
follows:

          Litter
          Sediment
          Nutrients (Nitrogen and Phosphorous)
          Hydrocarbons (oils and grease)
          Surfactants
          Pathogens/Faecal Coliforms (bacteria and viruses)

The MUSIC computer modelling program developed by the Co-operative Research Centre for
Catchment Hydrology was used to predict the performance of the proposed stormwater treatment
train.

At this stage the pollutants modelled in MUSIC are Total Suspended Solids (TSS), Total
Phosphorous (TP) and Total Nitrogen (TN).

5.3.3.2 Rainfall
The rainfall data used in the model was based on the Bureau of Meteorology data from rainfall
station 40059 Cooroy Composite. The model was run for a 10-year period from 1 January 1973 to
31 December 1983. The modelling time step was 6 minutes.




5.3.3.3 Rainfall Runoff Properties


Excellence with Economy in Engineering                                                                       10
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