RFI - 20210153 Maple St SWMP

The bioretention area has been modelled based on the sizing determined through MUSIC modelling
to deliver the required stormwater quality improvements. A 20m² area is modelled with two low flow
100mm diameter slotted ag pipe at the base of the garden, and the inlet pit operating as a weir inlet
overflow route. A 1m media filter depth and 200mm drainage layer are modelled with a typical
porosity of 0.3, along with the extended detention depth of 200mm which provides the storage
capacity for the bio-garden.

Using this mitigated development model, the proposed developed flows were again compared to
the existing state as shown below in Table 3.2 Existing and proposed mitigated site peak discharge
rates.

                      Table 3.2 Existing and proposed mitigated site peak discharge rates

                                                                 Maple Street
                                                                                             Qchange
                                 A.E.P               Qexisting     Qmitigated     Qchange     (%)
                                                     (m³/s)        (m³/s)         (m³/s)
                                   1EY                0.058         0.047         -0.011      -19%
                                  50%                 0.068         0.057         -0.011      -16%
                                 0.2 EY               0.125         0.102         -0.023      -18%
                                  10%                 0.156         0.129         -0.027      -17%
                                   5%                 0.192          0.16         -0.032      -17%
                                   2%                 0.235         0.197         -0.038      -16%
                                   1%                 0.262         0.218         -0.044      -17%



As the total peak flows are equal to or below the existing site conditions, the proposed OSD area will
provide the mitigation required for the peak flow storm events from the development.

Myall Streets is proposed as the lawful point of discharge for the development. As the existing site
run-off drains and is discharged towards the Myall Street verge, it will be captured by the existing
kerb and channel and conveyed to the existing downstream kerb inlet pit in Myall Street to which the
proposed site will discharge. The peak site discharges are below the existing peak flow rates
including the upstream external catchments which drain through the site, therefore the proposed
development will result in an improvement to the stormwater drainage conditions along the state
controlled Myall Street.


     3.1. Rainwater Reuse
In accordance with the Noosa Shire Council Sustainable Building Design Code AO2.1, the
development will require a minimum of 3,000L of rainwater capture per dwelling. With a total of 11
new dwellings proposed, the site will require 33,000L of rainwater storage. The development will
comply with provision of 50kL of rainwater tank storage connected to the roof drainage system to
capture the maximum possible rainwater from the development.
The rainwater reuse tank will be plumbed internally to supply non-potable demands throughout the
development. This includes external irrigation and wash down areas, as well as internal uses for
toilets and laundries. The tank is to be fitted with an automatic switching device that will revert to
the reticulated water supply should water levels in the rainwater tank be unable to meet demand.




Project number 20210153
File RECOR Preliminary Stormwater Management Report - 20210153.docx, 2022-03-31                                     Page 14 of 27
Revision 1

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