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3. STORMWATER QUALITY
3.1.        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.

NSC Planning Scheme (2020) defines the post-construction phase Water Quality Objectives as shown in
Table 3-1.

Table 3-1: 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



3.2.        Stormwater Quality Treatment
3.2.1.      Strategy
The objective of this report is to assess the stormwater quality measures required based on the
development layout to support the development application. Runoff from the development will be
collected in a stormwater drainage system and discharged into a bioretention basin prior to being
discharged from the site, with the existing bioretention basin associated with 25 Pavilion Street, being
extended.

3.2.2.      MUSIC Parameters
An assessment of stormwater runoff quality from the existing conditions and proposed developed
conditions has been undertaken using the Model for Urban Stormwater Improvement Conceptualisation
(MUSIC) – Version 6.3, released in 2018.

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 from 1/1/1973- 31/12/1983 with six (6)
minute rainfall duration.

Table 3-2 and Table 3-3 outline the adopted source node parameters from “MUSIC Modelling Guidelines”
(Water By Design, 2010) that were used in the MUSIC model.

The site density of 10 dwellings per hectare, with the source nodes being assigned percentage impervious
values based on 10 dwellings per hectare




23-0167SMP01-V2 | Stormwater Management Plan | 33 Pavilion Street, Pomona                             Page 23