MCU14/0106 Appendix E - Engineering Report

Noosa Civic
Stormwater Management Plan



For this scenario, stormwater quality treatment will be provided by multiple bio-retention basins located in the
surface car parks and other appropriate areas. It is considered conservative to model all bio-retention areas
as a single node in the MUSIC model due to a drop in treatment effectiveness with larger basin sizes. The
adopted bio-retention parameters and required total treatment area are listed in Table 3-4.
Table 3-4         Full Site Treatment Basin Details

 Design Parameters                                         Value
 Filter Area (m2)                                           850
 Filter Depth (m)                                           0.4
 Extended Detention Depth (m)                               0.2
 Saturated hydraulic conductivity (mm/hr)                   200
 TN content of filter media (mg/kg)                         400
 Orthophosphate content of filter media (mg/kg)             50


Table 3-5 presents the results obtained from the MUSIC model.
Table 3-5         Full Site Treatment Basin MUSIC Model Results

             Pollutant           Proposed without     Proposed with         Reduction        Target Reduction
                                    treatment           treatment           Achieved                (%)
                                      (kg/yr)             (kg/yr)              (%)
  Total Suspended Solids              14200                2710                81.0                  80
  Total Phosphorous                    31.7                 12.3               61.2                  60
  Total Nitrogen                       231                  107                53.6                  45
  Gross Pollutants                     1520                  0                 100.0                 90


With reference to Table 3-5, it can be concluded that bio-retention basins with a cumulative filter media
surface area of 850 m2 will be sufficient to satisfy the water quality objectives applicable to the site. The
proposed locations of the basins are shown on Figure 6.

3.2.2             Water Re-use and Treatment
For this option, a 300 kL rainwater tank is proposed to be installed to capture runoff from all roof surfaces for
subsequent re-use in irrigation and toilet flushing. Runoff from the remainder of the site, including overflow
from the tank, will be directed to bio-retention treatment as per the full site option.
Typical irrigation rates for landscaped areas are in the order of 2mm/m 2/day. For those days of moderate to
heavy rainfall it is not necessary to provide additional irrigation of landscaped areas.
Cooroy Composite rainfall station statistics from the Bureau of Meteorology indicate that there are 89 days
per year on average where rainfall exceeds 2mm.
It has conservatively been estimated that irrigation of the landscape area will be required for an average 276
days per year.
The resultant water usage for irrigation of landscape areas is shown in Table 3-6.
The typical water usage rates for toilet flushing purposes in retail and restaurant areas were taken from
Table A of DNRW’s Planning Guidelines for Water Supply and Sewerage (2014). The average water use
ranges and the adopted values were:
           Major Shopping Development: 300 to 800 L/day/100m2 (550 L/day/100m2 adopted)
           Restaurant: 800 to 1800 L/day/100m 2 (1300 L/day/100m 2 adopted)
Approximately 50% of the water demand was assumed to be non-potable.
The resultant water usage for retail and public buildings is shown in Table 3-6.


QIC Noosa Civic Pty Ltd                               Version 1                                    November 2014
Appendix D - SMP.docx                                                                                    Page 7