Scg 33132(L2)

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


SCG Consulting Engineers                              Page 4 of 5                                    SCG Ref: 33132(L2)