24-7-19 Attachment F Rev Stormwater Mgmt Plan

18 July 2019



Land Use – Commercial                    Log10 TSS (mg/L)                   Log10 TP (mg/L)           Log10 TN (mg/L)


                                        Base             Storm             Base          Storm        Base         Storm
                                        Flow              Flow             Flow           Flow        Flow          Flow

Roof                Mean                    0             1.30                0          -0.89         0           0.37

                    Std. Dev.               0             0.38                0           0.34         0           0.34

Roads               Mean                 0.78             2.43              -0.6         -0.30        0.32         0.37

                    Std. Dev.            0.39             0.38              0.5           0.34        0.30         0.34

Ground              Mean                 0.78             2.16              -0.6         -0.39        0.32         0.37
Level/Open
Space               Std. Dev.            0.39             0.38              0.5           0.34        0.30         0.34
                                Table 3 – Pollutant Export Parameters (Commercial)

5.3.3.5 Water Quality Objectives
The Water Quality Objectives of the receiving waters for the proposed development have been
obtained from State Planning Policy July 2017. The State Planning Policy load reduction targets are
summarised in Table 4 below.


                                                WATER QUALITY OBJECTIVES


Total Suspended                                               Total                    Litter/Gross
                              Total Nitrogen
 Solids (TSS) %                                           Phosphorous                  Pollutants %          Oils/Grease
                            (TN) % Reduction
   Reduction                                            (TP) % Reduction                Reduction

                                                                                                       No visible films or
          80                           45                          60                      90
                                                                                                            odours

                               Table 4 – Water Quality Objectives
5.3.3.6 Treatment Plan
In order to achieve the Water Quality Objectives for the proposed development, it is proposed to
use natural treatment methods to treat the runoff prior to discharge from the site.

Stormwater runoff from the roof and suspended carpark will be captured in a new pit and pipe
network which will discharge to a bioretention basin located along the Northern boundary of the
site.

Runoff from the landscape areas at the front of the site will be treated by grassed swales.

Stormwater runoff from the courtyard area and carpark access driveway will bypass treatment.

Treated and detained water will discharge off site via a proposed stormwater connection to the
existing stormwater pits constructed as part of the masterplan ROL.




Excellence with Economy in Engineering                                                                                       12
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