SWMP change reps

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.
           •    Where possible maintain existing landscaping/grasses downslope from construction areas
                to act as buffer/silt trap.
           •    Install temporary downpipes from completed roof structures and ensure runoff passes
                through silt fences.
           •    Minimise concentrating surface flows.
           •    Place silt barriers around council stormwater pits that the site drains to.
           •    Cover soil stockpiles with hessian or similar.

SCG Consulting Engineers                      Page 9                             SCG Ref: 33132(SWMP).RevC