UPDATED 16.5.23 - 20210153 Maple St SWMP

Run-off from the drainage network and the attenuated outflows from the detention area will be
discharged through a bioretention swale along the south-eastern boundary of the development,
allowing for treatment of all flows from the development prior to discharge from the site. Under
extreme events, the swale also provides an overland flow path for larger storm events to discharge
from the site. The treated run-off will be collected by subsurface drainage and an inlet within the
garden to capture flows in excess of the extended detention depth. The drainage line discharging
from the bioretention area will be piped within Myall Street with new connection into the existing
kerb inlet pit downstream of the development.

The run-off from the reconfigured lot which retains the existing dwelling will be directed towards a
drainage pit at the rear of the dwelling. Similarly, the existing run-off from the upstream catchment
within the adjacent property will be collected by the proposed stormwater line. The pit will be
conveyed through the stormwater network for the remainder of the site and discharged into Myall
Street. As the proposed attenuation measures restrict stormwater quantity peak flows from the
development to existing levels, and the external catchment is not modified by the proposed
development there is considered to be no worsening to the downstream network within the state
controlled Myall Street to which the site will discharge and therefore sufficient capacity is available to
service the development.

The roof, reuse and allotment drainage systems for the proposed site shall be designed to comply
with:

     1. Noosa Shire Council Planning Scheme Policy (PSP) - Engineering Design Standards – Roads,
        drainage and earthworks;

     2. The Queensland Urban Drainage Manual (QUDM); and

     3. AS/NZS 3500.3:2015 - Plumbing and Drainage Part 3: Stormwater Drainage.

Refer to Appendix A Proposed Concept Plan for the proposed stormwater drainage layout plan
illustrating the concept described above.



          2.4.2 Stormwater Catchments
The stormwater catchments for the proposed development are provided within the design plans
contained within Appendix A Proposed Concept Plan.


          2.4.3 Lawful Point of Discharge
The existing site naturally to the south east towards it’s Myall Street Frontage. A number of drainage
outlets within the retaining wall along the eastern frontage currently discharge the roof run-off and
groundwater from the existing dwelling into the verge where it will flow into the kerb and gutter
drainage system of Myall Street.

The lawful point of discharge test, as described in Section 3.9.1 of QUDM, requires:

      •     The development does not change the flow characteristics leaving the site; or
      •     The proposed development will not alter the sites stormwater discharge in a way that may
            substantially damage a third-party property; or
      •     The location of the discharge from the site is under lawful control of the government or
            other statutory authority from whom permission to discharge has been received; or
      •     An authority to discharge has been obtained.

Modelling for peak flow attenuation has ensured that the site peak run-off rates will not exceed the
pre-development site conditions as discussed in Section 3 Stormwater Quantity. The development


Project number 20210153
File RECOR Preliminary Stormwater Management Report - 20210153.docx, 2022-03-31                                 Page 9 of 27
Revision 1

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