Amended Stormwater Management Report

2. 2       Law fu l P oint of D is ch ar ge

Roofwater runoff from the existing dwelling is assumed to discharge to ground level and discharge to
the east with ground level runoff as sheet flow.
The proposed lawful point of discharge for the roofwater from the proposed development shall be The
Esplanade kerb and channel via the construction of a new kerb outlet. Runoff from the upper impervious
ground level areas shall be directed to a soakage trench with the remaining lower pervious areas
continuing to discharge to the east as sheet flow. Roofwater runoff from the proposed development
shall be collected on site and directed to the new outlet via the construction of new on site drainage.
Refer to Appendix B for further information regarding the proposed stormwater works for the
development.

2. 3       Ups tr e am D r ain ag e C onne ct ion

The development site does not have any upslope properties unable to gravity drain to a lawful point of
discharge.

2. 4       Flood ing

The proposed development site is not impacted by any NC flood mapping and is therefore considered
to be flood free.

3      STO R M WAT E R Q UA N TIT Y M AN AG E ME NT


A detailed stormwater quantity analysis of the existing and developed site conditions has not been
undertaken as the proposal is for a residential dwelling on an existing residential lot with final impervious
area fraction being generally in line with lump C10 values for low density residential lots.

4      W AT ER Q U AL IT Y M A NAG E M EN T


4. 1       O pe r at io na l Ph a se

The development is not required to meet the Queensland Government’s State Planning Policy (July
2017) as the site does not exceed the 2,500m2 minimum site area. However stormwater quality
management must still be undertaken via the application of best management practices (BMPs) to
ensure no adverse impacts to the downstream environment.

Pollutants typically generated during the operational phase of the development include:

       •    Litter/gross pollutants;

       •    Sediment;

       •    Nutrients (N & P);

       •    Hydrocarbons (oils and grease); and

       •    Heavy metals.

Stormwater quality best management practices may be implemented for the development as follows:

       •    First flush diversion system for roof water diverting the roof water for irrigation purposes

       •    Rainwater storage tanks may be used to collect rainwater for landscape irrigation.
Best management practices have been deemed sufficient for the site area and land use. Refer to
Appendix B for the stormwater management drawing.



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