Swmp

5.1        State Planning Policy and Water by Design Assessment
The proposed development has been assessed against the State Planning Policy 2017 and the Water By
Design (Stormwater Quality Deemed to Comply Solutions – 2010).

The proposed residential development involves a land area greater than the trigger value of 2500m2 for
stormwater quality measures as required in the State Planning Policy 2017 and the Water By Design -
Stormwater Quality Deemed to Comply Solutions - 2010. Therefore, stormwater quality treatment is
warranted for the proposed development.

5.2        Construction Phase

Sediment generated during the construction phase shall be controlled in accordance with a site specific
Erosion and Sediment Control (ESC) Plan and kept on site throughout construction.

5.2.1      Silt and Sediment Erosion
A potential for sediment mobilisation/transportation exists during and beyond the construction of the
proposed development. This can elevate turbidity levels of stormwater runoff.

A RUSLE assessment of the site confirms proposed development is a Low Risk for soil loss (< 150
Tonnes).

Potential Causes

           •    Stormwater scour and erosion of excavated or stripped surfaces and stockpiled soils.
           •    Wind borne transportation of sediments.
           •    Disturbance/breakup of soil profile via vehicular traffic followed by stormwater scour
                and erosion.
           •    Transportation of sediments from site via excavation vehicles.

Mitigating Measures

           •    Construction of silt fences around the development site located to cut off all runoff.
           •    Construction of a sediment basin throughout construction at a low point of the
                development site.
           •    Provide 80-100mm crushed rock (no fines) hardstand under all vehicle paths expected
                during construction. Generally, this would be provided from the existing crossover and
                extended to a distance within the site that would accommodate the maximum delivery
                vehicle length expected.
           •    Provide rumble grates at exit points from the site for passing earthmoving vehicles.




SCG Consulting Engineers                    Page 8                                  SCG Ref: 33132(SWMP)