P0198-25-001_12_Gympie_Street_Tewantin_SWMP

4.3         Stormwater Pollutant Reduction Performance
The following Table 4-1 presents the pre-treatment pollutant loads, residual loads post-treatment, and the
percentage reductions achieved through implementation of the bio-retention system.
Table 4-1: Pollutant Load Reduction

 Parameter                              Pre-Treatment Load        Post-Treatment Residual Load      Reduction
                                          (kg/yr or ML/yr)               (kg/yr or ML/yr)              %

 Total Suspended Solids (kg/yr)                1273.00                            50.60              96.03%

 Total Phosphorus (kg/yr)                        2.15                             0.24               88.66%

 Total Nitrogen (kg/yr)                         12.34                             4.70               61.95%

 Gross Pollutants (kg/yr)                       29.71                             0.00               100.00%



4.4         Analysis and Compliance with Water by Design Guidelines
The Urban Stormwater Quality Planning Guidelines 2010 set out the minimum pollutant reduction targets for
Southeast Queensland developments as follows:

     •    Total Suspended Solids (TSS): 80% reduction

     •    Total Phosphorus (TP): 60% reduction

     •    Total Nitrogen (TN): 45% reduction

     •    Gross Pollutants: 90% reduction

The results of the MUSICX model confirm that the proposed stormwater treatment system meets or exceeds
these regulatory targets, ensuring compliance:

     •    TSS reduction of 96.03% (exceeding the 80% requirement)

     •    TP reduction of 88.66% (exceeding the 60% requirement)

     •    TN reduction of 61.95% (exceeding the 45% requirement)

     •    Gross Pollutant reduction of 100% (exceeding the 90% requirement)


4.5         Stormwater Management Implications
The results indicate that the bio-retention basin effectively treats stormwater runoff, significantly reducing
pollutant loads before discharge. The high-performance efficiency of the system ensures that the development
achieves full compliance with stormwater quality regulations while protecting receiving waterways and
maintaining sustainable urban drainage practices.

By implementing this stormwater treatment strategy, the proposed development at 12 Gympie Street ensures:

     •    Optimal sediment and pollutant retention through the bio-retention basin.

     •    Hydrological neutrality, with controlled flow rates post-development.

     •    Alignment with best-practice water-sensitive urban design (WSUD) principles.

This outcome demonstrates a clear commitment to sustainable urban development and reinforces the site’s
long-term environmental performance and regulatory compliance.



 12 GYMPIE STREET, TEWANTIN
 Stormwater Management Plan                                                                                   18
 Client Reference: P0198-25-001          4 November 2025
 Prepared for Novato Group