Appendix C - Stormwater Management Plan

TfA Project Group Pty Ltd                                                                     Stormwater Management Plan
                                                                                                   Development Application




   Table 15: Required detention volume for the catchment

        Design Storm            Post Development          Allowable stormwater discharge      Required Detention volume
                                                            from the Detention Basin(s)*
                ARI                  Flow rate                         Flow rate                        Volume
                Years                   L/S                                L/S                              L
                 1                     55,25                             28.97                           10,410
                 2                     74,71                             39.02                           14,150
                 5                     102.47                            54.13                           19,118
                 10                    119.85                            63.15                           22,435
                 20                    142.62                            75.12                           26,713
                 50                    108.49                            95.35                           33,669
                100                    206.83                            109.68                          38,391
   *The figures are based on the stormwater runoff from the pre-development catchment less the stormwater runoff
   from the non-developed area at the back of the proposed building on the Southern corner of the post-development
   catchment.


   Therefore, a 38,400L detention storage volume is required to mitigate peak flows from the catchment. The outlet
   arrangement of the detention basin shall be designed at the Operational Works phase of the project and it will
   ensure that the design flow rates do not exceed pre-development flow rates for the nominated design storm events.


   Appropriate design software shall be used at the operational works stage to determine the actual design volume
   of the onsite detention basin required and a suitable outlet arrangement (e.g. orifice plate, culvert, etc.).



   7       WATER QUALITY ASSESSMENT


   7.1          Construction Phase
   Impacts on receiving waters and surrounding areas will be minimised during the construction phase with
   measures as outlined in this SBSMP and an Erosion and Sediment Control Plan to be developed at the
   Operational Works stage.


   7.1.1         Pollutants
   Typical pollutants generated during the construction phase of the development are shown below in Table 16.


   Table 16: Pollutant typically generated during the construction phase

       Pollutant                     Sources
       Litter                        Paper, construction packaging, food packaging, cement bags, off-cuts
       Sediment                      Unprotected exposed soils and stockpiles during earthworks and building
       Hydrocarbons                  Fuel and oil spills, leaks from construction equipment
       Toxic materials               Cement slurry, asphalt prime, solvents, cleaning agents, wash-waters
       pH altering substances        Acid sulphate soils, cement slurry and wash-waters




                            123 Eumundi Road (Cnr Walter Hay Drive), Noosaville QLD 4566                                Page 8