Attachment 5 - Stormwater Managment Plan · 132007.12.8

2 Stormwater Quality
2.1 Design Objectives
This report identifies the stormwater quality management objectives for the
operational phase (post-construction phase) of the proposed development.
Construction based stormwater quality management objectives will need to be
addressed as part of operational works documentation.
The load based Water Quality Objectives (WQO’s) stipulated in the State Planning
Policy – July 2014 for the South East Queensland region will be adopted for the site.
The applicable water quality design objectives for the site are shown in Table 1 below.
Table 1: Site stormwater quality objectives (operational phase)

      Minimum reductions in mean annual loads from unmitigated development (%)
   Total Suspended      Total Phosphorous        Total Nitrogen      Gross pollutants
     Solids (TSS)              (TP)                   (TN)               >5 mm
          80                    60                     45                   90

2.2 Stormwater Quality Treatment
2.2.1 Strategy
The objective of this report is to assess the stormwater quality measures required
based on the development layout prepared in order to support the Material Change
of Use application for the site. The site will consist of a multi-story carpark, with
majority of the site being roofed, which will be collected and directed to a bioretention
system located near the outlet of the site prior to discharge from the site.

2.3 Modelling Approach
2.3.1 MUSIC Parameters
An assessment of stormwater runoff quality from the proposed development site has
been assessed using the Model for Urban Stormwater Improvement
Conceptualisation (MUSIC) – Version 6.20, released in 2016.
Climate data for the catchment was sourced from the MUSIC model database. The
rainfall and evaporation data template for this site has been based on data from
Cooroy (040059) from 1/1/1973- 31/12/1983 with six (6) minute rainfall duration.

Table 2Table 2 and Table 3 outline the adopted source node parameters from “MUSIC
Modeling Guidelines” (Water By Design, 2010) that were used in the MUSIC model.
The site will consist of a multi-story carpark and has been represented using
commercial runoff parameters.




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