MCU14/0106 Appendix E - Engineering Report

Noosa Civic
Stormwater Management Plan




3                 Stormwater Quality Modelling
3.1               Environmental Values and Water Quality Objectives
In order to satisfy the requirements of the State Planning Policy (DSDIP, 2014) and Noosa Shire Council, it
will be necessary to treat runoff from the site to ensure that the Environmental Values of downstream
receiving waters are protected. To achieve this, it will be necessary to treat water to meet the water quality
objectives defined in the State Planning Policy.
The relevant load based water quality objectives applicable to the site are listed in Table 3-1.
Table 3-1         Operational Phase Performance Criteria

               Pollutant            Load Based Reduction Target
      Total Suspended Solids               80% reduction
          Total Phosphorus                 60% reduction
            Total Nitrogen                 45% reduction
    Litter (sized 5mm or greater)          90% reduction


The following section details the modelling undertaken to confirm that an appropriate level of treatment can
be achieved.
For the analysis, two solutions were considered.
          Full site treatment
           For this option, it was assumed that runoff from the entire site would be treated in bio-retention
           basins located on site. As the locations of these basins within the car park are currently undefined,
           the entire system was modelled as one treatment area in the analysis.
          Water re-use and treatment
           For this option, a 300kL water tank was added that collected water from the roofed areas of the site
           for use limited to suitable non-potable water purposes. Runoff from the remainder of the site and
           any overflow from the water tank were then treated by the bio-retention system as in the full site
           treatment option.
It is intended that a decision will be made at the detailed design stage in relation to the preference of
collecting runoff for reuse purposes in a rain water tank and the appropriate locations for bio-retention
basins.

3.2               Pollutant Impact Assessment
A detailed pollutant export analysis was carried out using eWater’s Model for Urban Stormwater
Improvement Conceptualisation (MUSIC) v6.01. The analysis was carried out in accordance with the latest
guidelines and data as defined in:
          ‘Water Sensitive Urban Design Technical Design Guidelines for South East Queensland’ (Healthy
           Waterways, 2006); and
          ‘MUSIC Modelling Guidelines Version 1.0’ (Water By Design, 2010).
In accordance with the above guidelines, the meteorological data and rainfall-runoff parameters adopted for
modelling are detailed in Table 3-2 below. The catchments adopted for the MUSIC model are shown on
Figure 4.




QIC Noosa Civic Pty Ltd                              Version 1                                     November 2014
Appendix D - SMP.docx                                                                                    Page 5