18-0165B Stormwater Management Report_Issue D

8   STORMWATER QUALITY MANAGEMENT


This Stormwater Management Plan is to demonstrate how the proposed stormwater management strategies for this
development, achieves the pollutant load reduction targets of the Noosa Shire Council (NSC) and the State Planning
Policy (2014) through the use of appropriate modelling software.

The Water Sensitive Urban Design Technical Design Guidelines for South East Queensland recommends the
following minimum reductions in the annual pollutant loads leaving a development site compared to the developed
unmitigated case:

            •   ≥80% reduction in Total Suspended Solids Load (TSS);
            •   ≥60% reduction in Total Phosphorus Load (TP);
            •   ≥45% reduction in Total Nitrogen Load (TN);
            •   ≥90% reduction in Gross Pollutant Load (GP).




8.1 Site Stormwater Water Quality Objectives


Taylor Court, Cooroy is located within the Mary River Basin Catchment Plan. The nearest water course to the
development is Six Mile Creek and is identified as being ‘lowland freshwaters’ as defined by the Environmental
Protection Water Policy 2009 South East Queensland Map Series (Plan WQ1381).

Within the Mary River Basin Environmental Values and Water Quality Objects – Basin No. 138 (part) including all
tributaries of the Mary River (Department of Environment and Resource Management, 2010), the following specific
performance criteria is required for lowland freshwaters:

                                        Table 2 - Site Stormwater Quality Objectives


                             Pollutant              Water Quality Objectives
                                                    Lowland Freshwater Values
                     Suspended Solids (SS)          <6 mg/L (annual mean concentration)
                     Total Phosphorus (TP)          <0.05 mg/L (annual mean concentration)
                     Total Nitrogen (TN)            <0.5 mg/L (annual mean concentration)
                     Turbidity                      <50 NTU
                     Hydrocarbons                   Aim for no visible oils, petrochemicals, films or
                                                    odours
                     Dissolved Oxygen               85 – 110% saturation
                     Chlorophyll-a                  0.005 mg/L
                     pH                             6.5 – 8.0
                     Litter                         Aim for no anthropogenic material greater than
                                                    5mm in any dimension




HR DESIGN                                         Reference No: 18-0165D                                 Page 7 of 15