Appendix B - Stormwater Management Report

TABLE 1 PRE AND POST COMPARISON OF PEAK DISCHARGE RATES

The effect of the rainwater tanks is effective attenuation of discharge rates to maintain existing rates
or even a reduction of the pre-development rates.

Controlled flows from the outlets of these tanks will be discharged to the LPOD via a level spreader
device to maintain the pre-development drainage regime.


3.2. Quality

        3.2.1.Construction Phase
To fulfill the General Environmental Duty, a person “…must not carry out any activity that causes or is
likely to cause environmental harm, unless measures to prevent or minimise the harm have been taken…”. It is
necessary to manage and mitigate these impacts through best practise erosion and sediment controls.
Due to the development area being less than 2,500 m2 the construction impacts will be managed
using the principles aligned with the desired outcomes of Appendix 2 of State Planning Policy (SPP).

A site-specific erosion and sediment control plan must be prepared and submitted as part of the
Operational Works approval.


        3.2.2.Operational Phase
This development consists of an additional dwelling as part of the subdivision and is consistent in
character with the existing residential dwelling and environment. As the development proposal is not
considered to significantly alter the potential for pollutant generation, stormwater quality treatment
processes are not proposed for the development.


4. Conclusion and Recommendations
This Stormwater Management Report demonstrates how the stormwater run-off from the site is to be
managed to comply with the relevant requirements and mitigate adverse impacts to the downstream
catchment.

       The proposed site stormwater run-off maintains the existing drainage regime. The existing
        surface runoff from the upstream properties remains unchanged compared to the existing state.

       Pre and post development modelling of the resultant peak flows has been carried out, with
        attenuation using two 3kL rainwater tanks identified to mitigate peak flows. Outlets from the
        tanks discharge via a level spreader device to the LPOD, to maintain the pre-development
        drainage regime.

       A site-specific erosion and sediment control plan is to be prepared and submitted with the
        Operational Works approval to mitigate impacts to the receiving catchments and fulfil the
        general environmental duty of care and Appendix 2 of the SPP.

       The proposed development is not considered to significantly alter the pollutant generating
        potential of the site; therefore, stormwater quality treatment processes are not proposed for the
        development.