RFI - Engineering correspondence

Our Reference: 2023


14 October 2020

Billy Glover
Noosa Council
PO Box 141
Tewantin 4565
QLD, Australia

RESPONSE TO COUNCIL INFORMATION REQUEST

             PROPOSED INDUSTRIAL SUBDIVISION DEVELOPMENT
             AT 1 TAYLOR COURT,
             COOROY, QLD, 4563


This correspondence is provided as a partial response to Noosa Shire Council’s Information
request for the subdivision development at the above address (Council reference OPW20-0144),
dated 24th September 2020.

Issue:
The Earthworks Erosion and Sediment Control Plan is not reflective of the requirements for the
large site and has no information on the type of soil that will be exposed, timing and staging of
works or drainage management to prevent erosion. The State Planning Policy requires that all
exposed areas greater than 2500 metres2 must be provided with sediment controls which are
designed, implemented and maintained to a standard which would achieve at least 80% of the
average annual runoff volume of the contributing catchment treated (i.e. 80% hydrological
effectiveness) to 50mg/L Total Suspended Solids (TSS) or less, and pH in the range (6.5–8.5).

Response:
The Erosion and Sediment Control drawings on sheet R05 have been updated to include a
Type D sediment basin in proposed Lot 4 for the site earthworks. Calculations for the basin size
in accordance with the IECA guidelines are included with this correspondence.

Issue:
The application proposes construction of an approximately 500m2 hardstand driveway, allotment
reshaping and redirection of sheet flows to concentrated flow outlets. Where not appropriately
managed, these cumulatively will increase scour and impact the quality of runoff via increased
peak runoff from both the hardstand and outlet pipes. Further it is unclear how runoff from the
driveway will be treated to achieve the no worsening requirement for water quality in the drinking
water supply catchment.

Response:
Lawful points of discharge are required as part of the development works for these proposed lots
1-4. Lot 4 shall utilise the existing field inlet pit in the south-western corner of the property. Lots
1-3 are proposed to have piped connections (for future roofwater and/or site runoff) to the field
inlet pits 1/1, 2/1 and 3/1 on sheet R08. In response to ensuring a non-worsening of water quality,
a turfed swale drain has been included below the batter of Lot 4 to dissipate pipe flow velocities
and provide “scrubbing” of post development discharge runoff from the driveway and hardstands.
Please note that any future development of the proposed lots would be subject to a Material
Change of Use application that would determine whether additional, use -specific treatment
devices are required on each lot before discharge. The stormwater runoff from the swale is
recollected and discharged to the drainage reserve to the south of the property. Energy dissipation
by rock scour pad will be provided as shown on the civil drawings at each outlet to the swale and
the drainage reserve.



 2023 - Bullgate                                                                              Page 1 of 3