Appendix 4- SWMP

                                                                                                            ingeniir


Assessment). It is proposed that approximately 2,400L of retention volume be provided per unit, which will
provide more than 95% reliability and is deemed a suitable and practical outcome for installation.


6.    STORMWATER QUANTITY
The development is proposed to incorporate stormwater detention to mitigate the increase in peak discharge
from the site and maintain pre-developed stormwater performance.

The Bureau of Meteorology 2016 IFD service has been used for all analysis in this report.

A Rational Method estimation of the stormwater discharge has been used to estimate the pre-developed
runoff performance of the site. In accordance with Noosa Shire Council recommendations, the detention
analysis has been proportioned to match or improve on the pre-developed flows as determined by the
Rational Method. As it is only roof water that is proposed to be collected and detained, a linear methodology
has been employed with storage volumes calculated in accordance with AS3500.3.

Rational method and detention calculations are presented in Appendix 3 | Rational Method & Detention
Calculations.


6.1     Detention Sizing and Details

The required detention volume that was determined to maintain or improve the pre-development discharge
rates to Dvid Low Way is 7,500L per unit. This is proposed to be comprised of two Garantia Li-Lo Rainwater
Underground Tanks (or equivalent) with properties as listed in Table 1.

                                          DETENTION TANK PROPERTIES
                            Roof/Impervious Area Connected                        100%
                            Eaves Gutter Size                                 1% AEP
                            Number of Tanks                                        2
                            Storage Capacity                               7,500L
                                                                     1250mm (1565mm with
                            Height
                                                                            riser)
                            Length                                        3600mm
                            Width                                           2250mm
                                                                     Garantia Li-Lo Rainwater
                            Example Product
                                                                       Underground Tanks
                                             Table 1: Detention tank properties



The outlet configuration of the tanks is proposed to be constructed of an internal standpipe, with outlet
orifices drilled into the pipe prior to installation into the tank. The outlet details are presented in Table 2.




                                               Ingeniir Pty Ltd | 245001-SMP-01
                 ABN: 99 642 485 363 | PO Box 988 Maroochydore QLD 4558 | [email protected] | 0404157187
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