STP22-0347 DA Engineering Report RFI Response Rev C

                                                                                                                  STP CONSULTANTS




                                                                        Load Based                  Water Quality Objectives
                       Parameter                   Statistic
                                                                         Reduction

             Total Suspended Solids (TSS)        Mean Range                 80%                         Less than 5mg/L

                Total Phosphorous (TP)           Mean Range                 60%                   Less than 0.01 to 0.05mg/L

                  Total Nitrogen (TN)            Mean Range                 45%                    Less than 0.2 to 0.5mg/L

                           PH                    Mean Range                   -                         Between 7 and 8

                                                                                               Greater than 80% saturation during
                   Dissolved Oxygen                  Mean                     -
                                                                                                            daytime

                                                                                              Retention of litter greater than 50mm
                    Gross Pollutants                   -                    90%               for flows up to the 3-month ARI peak
                                                                                                                flow

                                                                                            Retention of sediment coarser than
                   Coarse sediment                     -                      -            0.125mm for peak flows up to the ARI
                                                                                                    3-month peak flow

            Table 9.2 – Water Quality Objectives for South-East Queensland


9.3      PROPOSED STORMWATER TREATMENT TRAIN ANALYSIS
         The proposed development site has sufficient area available to dedicate to stormwater treatment devices. Roof
         water will discharge via downpipes directly to the in-ground stormwater. The landscaped areas and pavements
         will discharge directly to field inlet pits or to overland flow. All grated field inlets will be fitted with filter baskets for
         removal of gross pollutants. Treatment is undertaken within the grassed swales which then discharge to the
         existing Lawful Points of Discharge to the north and east of the site.

9.4      MUSIC MODELLING

        MODEL PARAMETERS

                                   Input                                          Data Used

             Rainfall Station                                  40059 COOROY COMPOSITE

             Rainfall Period                                   01/01/1973 – 31/12/1983

             Mean Annual Rainfall (mm)                         1600mm

             Evapotranspiration                                1629mm

             Model Timestep                                    6 minutes

             Rainfall Runoff Parameters*                       Commercial

             Pollutant Parameters*                             Commercial (Split)

             Table 9.3 – Basic MUSIC Model Parameters




Civil Engineering Report & Site Based Stormwater Management Plan | STP22-0347                                                         22