1909-13367 SRA referral response approved docs

4      ST O RM W AT E R Q U AL I T Y M AN AG EM ENT


NSC requires that new developments achieve the assessment benchmarks laid out in part 14 of the
Noosa Plan. Stormwater water quality specifically relates to Work Code I (Water Sensitive Design
Code). Accessible developments are required to meet the performance outcomes of the QLD state
planning policy, Appendix 2 SPP Code: Water Quality. The QLD state planning policy operational phase
stormwater management design objectives are triggered when:



       (1) A material change of use for an urban purpose that involves premises 2500m2 or greater in size
           and :
            (a) Will result in six or more dwellings; or

            (b) An impervious area greater than 25% of the net developable area.

       (2) Reconfiguring a lot for urban purposes that involves premises 2500m 2 or greater in size and
           will result in six or more lots.

       *Taken directly from the QLD state planning policy Appendix 2 Table B.



4. 1       O pe r at io na l Ph a se

The proposed development requires a MCU and:

           Has a developable area greater than 2500m 2 and

           Will result in the creation of 6 or more dwellings and

           Will result in an impervious area greater than 25% of the net developable area

The proposed development therefore triggers the requirement for stormwater quality management
(from NSC). These objectives are based upon the Queensland Governments State Planning Policy
(SPP July 2017) table B the reductions in mean annual load from unmitigated development (%) are
outlined below:

           80% reduction in Total Suspended Solids (TSS)

           60% reduction in Total Phosphorous (TP)

           45% reduction in Total Nitrogen (TN)

           90% reduction in Gross Pollutants > 5mm (GP)

           Limit the peak 1 year ARI event discharge within the receiving waterway to the pre-development
            peak 1 year ARI discharge.

The proposed development shall utilise bioretention basins in order to achieve the required pollutant
load reductions stipulated above to treat stormwater flows prior to discharge off site. Each proposed
catchment shall be directed to a bioretention basin.

The proposed layout of the stormwater treatment train in presented below in figure 3 and in Appendix
AC.

4. 2       Sto rmw at e r Q ua lit y T re at me nt so luti on

The developed site has been modelled using the stormwater quality modelling program MUSIC.


                                              Stormwater Management Report                             13
S19-007                                         122 & 144 Myall St, Cooroy