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2. STORMWATER QUALITY
   MANAGEMENT
2.1          Overview
This proposed development was originally approved for 50 low density residential lots and associated new road. Since the initial
development, a portion of the Site – 6 lots (refer Figure 1.2), is proposed to be converted to a townhouse site consisting of 11 dwellings. This
stormwater quality assessment proposes to confirm the existing bioretention constructed as part of the original development (OPW15/0133)
still achieves load-based Water Quality Objectives (WQO’s) for the Site with the inclusion of the new townhouse area.


2.2          Operational Phase
The WQO’s stipulated in the State Planning Policy – July 2017 for the South-East Queensland region will be adopted for the Site. The NSC
Planning Scheme provides stormwater management design objectives for the operational phase of developments. The applicable Water
Quality Objectives (WQO’s) for the Site are shown in Table 2.1.

TABLE 2.1: WATER QUALITY OBJECTIVES

 Pollutant                                                             Minimum Load Reduction Target (%)


 Total Suspended Solids (TSS)                                          80


 Total Phosphorus (TP)                                                 60


 Total Nitrogen (TN)                                                   45


 Gross Pollutants (GP)                                                 90



2.3          Model Development
  2.3.1       Catchments
The representation of the post-development catchments (approved development and new townhouse) has been split into three catchment
source nodes, being road, roof and ground. The development site area then reports to a bioretention basin. Catchment properties have
been summarized in Table 2.2Error! Reference source not found. and a catchment plan shown in Figure 2.1.

TABLE 2.2: TREATED CATCHMENT PROPERTIES

 Land Use                       Approved Development (ha)          Bypass (ha)            New Townhouse (ha)          Total Impervious (%)

 Roof                           0.766                              0.060                  0.239                       100

 Road / Hardstand               0.920                              -                      0.080                       100

 Ground                         1.905                              0.147                  0.187                       20

 Park                           0.348                              -                      -                           0

 Total                          3.936                              0.207                  0.506                       -



73 EUMUNDI - NOOSA ROAD, NOOSAVILLE I BBNE00529_0002_0001-REP-001-0                                                                           4