MCU14/0106 Appendix E - Engineering Report

Noosa Civic
Engineering Report




7                    Stormwater Management Plan
A Stormwater Management Plan (see Appendix D) has been prepared to support the proposed Noosa Civic
expansion. The key findings of the investigation are detailed below.
            Regional Flooding
The Regional flood and storm tide mapping indicates that the proposed development will be above the
regional flood events.
            Stormwater Quantity
Without active mitigation, the proposed development is predicted to increase the peak rate of stormwater
runoff from the site. Various detention basins utilising the surface car park areas and at the south-western
corner of the site have been formulated to mitigate these increases in flow, as shown in Figure 2. Based on
this analysis (see Appendix D), sufficient storage volume is available to adequately mitigate peak rates of
stormwater discharge flows from the site. No adverse flooding impacts will occur external to the site.
            Stormwater Quality
It will be necessary to treat runoff from the site to satisfy the water quality objectives defined by the State
Planning Policy (DSDIP, July 2014) and Noosa Shire Council (Water Sensitive Design Code).
Modelling of two approaches for the treatment of runoff was completed using the industry-standard MUSIC
software.
o            Bio-basin Treatment
For this scenario, runoff from the entire site was considered to be treated by a series of bio-retention systems
as shown on Figure 3.
o            Water Re-use Tank and Bio-Basin Treatment
For this scenario, a 300 kL rainwater tank capturing runoff from roof surfaces for suitable re-use purposes,
with the remaining water to then be treated by bio-basins to the required standards, was considered.
Both treatment scenarios were found to satisfy the applicable water quality objectives. A decision will be
made at detailed design in relation to the solution to be ultimately adopted.
Given the results obtained with respect to stormwater quality and quantity, it is considered that the site can
be developed from a stormwater management perspective without producing unacceptable impacts.




QIC Noosa Civic Pty Ltd                             Version 1                                     November 2014
engineering report_final.docx                                                                           Page ix