Attachment 3 - Stormwater Management Plan 1856-SBSMP-01 v5 (December 2019) · RAL18/0023

All load-based pollutant reduction efficiencies are met in accordance with the Table A in
Appendix 2: Stormwater Management Design Objectives, Part G, SPP (2017) included in
Appendix B.


The bioretention treatment nodes for the car parking pavements in Lots 12-15 are modelled
as all the same size for consistency at planning stage. It is recommended that the MUSIC
file be updated as part of the Operational Works design to correctly capture batters and
extended detention, final pavement catchments etc. with the construction drawings for these
works.


The Noosa Plan, Division 20-Water Sensitive Design Code, table 14-61 Specific Outcome
S1.5 requires that stormwater discharging to naturally acidic areas are managed to prevent
eutrophication. Council representatives have identified that areas to the south of Lot 11 and
12, including the covenant land incorporated within Lot 12, are naturally acidic areas. To
manage this, it is recommended that stormwater outlets from post treatment systems and
runoff from both Lots 11 and 12 should occur to the surface at a lower level to the lot pad
so that discharged water has sufficient room to disperse across the ground, absorbing
nitrogen and reducing the runoff pH from contact with decomposing leaf litter. To achieve
this, a rock pad generally in accordance with the design specification in QUDM-2017 is
proposed at these outlet to the treatment system and pipe discharge for Lot 12, with the
exception that the rock pad flares at 1:1 instead of 1:5 to encourage flow dispersion.
The piped discharge for Lot 11 is to the drainage system in Road B. Any runoff from the
rear of the lot is to be buffered by groundcover vegetation areas either side of the bushfire
access track. This maintains the flow regime as sheet runoff and allows the surface water
to be in contact with the soils and natural vegetation of the area as it moves south, to
correctly balance the pH before entering the acidic areas.




Site Based Stormwater Management Plan                                            Page 18 of 22
1856-SBSMP-01_Version 5.0 (December 2019)