Stormwater Management Plan (Quantity)

 

Our Ref: B09182.W.01.MS.ip.Authorities.docx
Contact: Andrew McPhail B - OW N
Smart Consulting

RPS Australia Asia Pacific

C/- Brown Consulting (QLD) Pty Ltd
PO Box 997

BUDDINA QLD 4575

17 April 2013
Attention: Sian Davis

Deat Sian,

Proposed Residential Development — Lake Doonella, Noosa Stage C
Stormwater Management Plan (Quantity)
Updated Management Strategy

Brown Consulting (QLD) Pty Ltd have previously prepared a Flood Investigation & Stormwater
Management Plan (Report No. B09182.W-02A dated October 2011) for Stockland Pty Ltd for the
proposed Stage C Residential Development at Lake Doonella, Noosa.

A hydrological analysis was previously undertaken to determine the change in peak flows from the
ptoposed Doonella Subdivision and the mitigation provided by the proposed stormwater detention
measures. Hydraulic modelling was also undertaken to determine post development flood levels to
confirm proposed lot and road levels had appropriate flood immunity along the environmental corridor
through the site.

Since the submission of this report, Sunshine Coast Regional Council (SCRC) has indicated that the use
of the environmental corridor for detention (referred to as the Dodonaea Close Detention Basin)
outlined in the Stormwater Management Plan was not acceptable. Subsequent meetings with SCRC
have led to the design change process. New peak flow management options have been proposed, with
Option 3 deemed to be viable. This was indicated in an email from Senior Development Planner
Dennis Wallace dated 30 March 2013 (refer to Attachment 1) in which it stated:

Of the SWM options submitted, only Option 3 was a presented as viable and doesn’t appear to provide significant
benefits over the original proposal in regard to soil hydrology and impacts of existing vegetation. On this basis, council
would be willing to amend the approval(s) to allow for the originally proposed Dodonaea detention area, provided we
can also do the following:

© = Allow for fauna passage, including a fauna underpass;

© Rehabilitate the fauna corridor area post construction disturbances and the changes to the soil hydrology

and vegetation that will result from the detention area;
© Obtain an Op Works revegetation/ rehabilitation approval for the above.

This letter report presents the analysis and results for the new peak flow management strategy
(Option 3) for the proposed residential subdivision as requested by Council. It is noted that post
construction rehabilitation of the environmental corridor is outside the scope of this letter.

Level 6, 199 Grey Street South Brisbane QLD 4101 Australia Brown Consulting (QLD) Pty Ltd 1
PO Box 10349 Adelaide Street Brisbane QLD 4000 Australia ABN 38 109 428 506
Telephone +61 7 3895 3444 Facsimile +61 7 3895 3400 brownconsulting.com.au