SC3395-SWMP Rev A

SC3395-Lot 4 Hofmann Drive, Noosaville                                                                      9




Under the proposed conditions, the site was ‘split’ into three land use catchment nodes; the roofed area,
driveways and ground level uses. The pollutant export parameters utilised were based on the Urban
Residential pollutant loads, refer Table 3.3.


                                               TSS Log                TP Log                    TN Log
 Flow Type       Surface Type
                                     Mean          Std Dev.   Mean        Std Dev.      Mean        Std Dev.
                      Roof               N/A         N/A       N/A             N/A       N/A             N/A
  Baseflow
                   Driveways             1.00        0.34     -0.97            0.31      0.20            0.20
Parameters
                 Ground Level            1.00        0.39     -0.97            0.31      0.20            0.20
                      Roof               1.30        0.39     -0.89            0.31      0.26            0.23
 Stormflow
                   Driveways             2.43        0.39     -0.30            0.31      0.26            0.23
Parameters
                 Ground Level            2.18        0.39     -0.47            0.31      0.26            0.23
                         Table 3.3 – Pollutant Export Values Adopted (Urban Residential)



3.3.2.1 Rainfall Data
Rainfall data for the site was chosen to give the best representation of actual conditions. A time period of
10 years between 1973 and 1983 was selected from the Cooroy Composite station, using a six minute time
step.


3.3.2.2 Treatment Nodes
The following devices have been used in the treatment train to reduce these pollutant loads to achieve WQO’s.


        Bio-Retention Basin – A combined area of 90m2 of designated Bio-retention to treat carpark,
        landscape, and roof catchments to achieve the WQO’s was modelled. An extended detention
        depth of 200mm with a filter media of 180mm/hr sandy loam hydraulic conductivity has been
        modelled. The location of this device is shown on the attached Appendix A.


        Gross Pollutant Traps – Baskets installed to the top of each gully pit receiving to trap coarse
        sediment prior to entering the drainage system. These GPT’s were modelled with the pollutant
        removal characteristics of a Stormwater 360 ‘EnviroPod’ (i.e. retains 100% of gross pollutants and
        coarse sediment within the range of 0.5mm to 5mm for all flows up to and including the design
        storm event for the catchment).