Scg 33132(L2)

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Further, the site is not located within the flood hazard overlay mapping and therefore this flood hazard overlay
code an is not applicable to this development.



Issue 14 – Roofwater Capture and Reuse
  Justification for the tank sizing has been provided based on an assumption that reuse is only required for
  communal landscaping. The Sustainable Building Design Code seeks to maximise water efficiency and
  requires non-potable reuse, which includes fixtures both external and internal to the dwelling.

Response

For QDC 4.2 (residential buildings), the requirement will only apply to new Class 1 and 10 buildings (i.e. houses
and their garages) and not multi-unit residential buildings (Class 2).

As per our previous response correspondence and meeting with Council engineers (Morgan Gaffney & Mark
Lewis), we have now revised our proposal to consider re-use for the following external purposes.
    -    Communal Landscaping
    -    Pool top up
    -    Communal WC’s


The following extract provides the criteria has been adopted and calculations of re-use quantities.




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We have amended our stormwater management plan to include additional storage to increase the total stored
volume to 32kl.


Issue 15 – Drainage Design
  No drainage design calculations are provided to demonstrate that the stormwater devices have been
  adequately sized to convey the critical minor and major rainfall events.

Response
Pipe long sections and HGL diagrams are provided on SCG DRG No. 33132-SW1.4 and as per the provided
SWMP the following design storms have been adopted.


    -    Minor Drainage System – 10% AEP
    -    Major Drainage System – 1% AEP.

As mentioned above, a rainfall multiplier of 1.2 has been applied to the PC DRAINS model and therefore the
provided HGL diagrams also include an increase to rainfall intensity of 20% to consider the impacts of climate
change. We confirm that both the major and minor drainage networks have been adequately designed to convey
the critical storm events mentioned above.

Issue 16 – Detention Tank and Bio-Detention Basin Details
  Several details are missing from the amended stormwater and engineering plans provided. Additional detail is
  required to address the following:




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Response
    a) In accordance with our standard construction notes all works are to comply with the relevant
       Australian standards. The provided detention tank detail is merely a typical detail to demonstrate how
       detention is achieved on site to satisfy Councils non-worsening requirement. The provided drawings
       are issued “For Approval” and are not construction detailed drawings.
    b) Following correspondence with Noosa Council’s engineering officer (Morgan Gaffney) we have
       amended our proposal to include further excavations to the road verge (as requested by council) to
       provide a 1m wide clearance between the batter toe and existing footpath with a maximum grade of
       2.5%.
    c) The provided section B & C on our stormwater management plan include bio-retention layer depths in
         accordance with the IPWEA standard drawings, pipe cover is only required to be 300mm for internal
         areas not subject to vehicle loading. Further in accordance with IPWEA STD DRG DS-078 the
         required minimum grade for the underdrains is 0.5%. the underdrain has a maximum pipe run of 6.5m
         which results in 32mm of fall. We do not feel this meticulous issue council has raised is going to
         impact the function of or ability to construct the bio retention basin. If required, there is scope to drop
         the invert levels to the bio basin during construction which will be under the direct supervision and
         instruction of the RPEQ.

Issue 17 – Bio Basin Design
  Development plans still include extensive retaining walls around the bio-retention basins which is not supported
  by Council. The proposed retaining walls do not comply with Acceptable Outcome 9.2 of the Water Quality
  and Drainage Code which requires;
  Developments are designed to eliminate retaining walls in excess of 0.8m for any water quality treatment device.
  A compliant design must be provided in accordance with the requirements of AO 9.2 and Bioretention
  Technical Design Guidelines Version 1.1 (WaterbyDesign). It is noted that batters within Council’s road reserve
  are not supported as an acceptable design outcome due to maintenance and amenity issues.

Response

The proposed basins are serving 2 purposes, bio retention and also onsite detention. the volume of detention
required is the design criteria that is driving the inclusion of the retaining walls & hence providing the storage
volume, not the bio retention. We have provided an additional plan (SCG Drg. No 33132-SW1,5) to include spot
levels to outline the extent of earth retaining vs the extent of block walls for the purpose of detention storage. The
revised plans outline that approximately 30% of detention basin A and 65% of Detention Basin B contained earth
retaining walls. It is also worth noting that the existing ground profiles at Detention Basin B (Headland Drive)
location contains retaining walls, therefore the adopted design is maintaining the existing site amenity.

The inclusion of batter slopes would have a major impact to the layout of the entire development due to the
required space. The Water Sensitive Urban Design section 3.3.5 references in some cases retaining walls may
be accepted on steep sloped sites. We feel the performance outcomes (functionality, safety & maintenance
access) have been achieved with the provided design. This proposed concept also follows the same principles of
the 2 recently council approved neighboring developments on Eumundi Noosa Road

Issue 18-20 – Operational Works Stormwater Detail
  With reference to Council’s Information Request Items 20-23, a sufficient level of detail must be provided by
  the applicant for Council to assess the Operational Works application. Submit to Council additional information
  to address the following:

Response

   17. We have revised our drawing (SCG DRG. No. 33132 – OW6.1) to clearly display the spot levels for the
       proposed kerb & Channel. No changes have been proposed to levels on the existing road profile, it is
       merely the addition of a kerb & channel.
   18. The proposed swale includes spot levels noted on sheet 33132 – SW1.1 Rev B. there is approximately
       4m of fall at a slope 5-6% which follows the natural ground profiles, we do not forsee any concerns


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        relating to adverse impacts to existing drainage conditions to adjacent properties.
   19. Please see revised plans attached to include additional pipe sections for the smaller drainage lines (2-2
       & 2-out)

If you require any further information, please do not hesitate to contact our office.


Yours faithfully




TOM HARRINGTON – RPEQ 27698
For and on behalf of
SCG CONSULTING ENGINEERS


Enc      SCG Drawings Numbers: 33132 – CD – 01.12.23




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