Stormwater Management Plan 12_05_26

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Stormwater Management
The existing site has been developed in accordance with council’s approved development
OPW/25/0057. This development provides a stormwater outfall and water quality treatment for the site.
The minor storm event is defined as the 10% AEP storm plus climate change, with the major event
being the 1% AEP storm plus climate change.

4.1     Drainage Network & Legal Point of Discharge
Runoff from within the subject site is to be captured by a proposed underground pipe drainage network
and is to be conveyed to a future stormwater pit (provided by the surrounding subdivision), which shall
form the Legal Point of Discharge for the development. The proposed and future surrounding network
(as per OPW/25/0057) is shown in in the civil engineering concept plans, refer Appendi A.

4.2     External Catchments
The site is not impacted by external drainage catchments, as per the approved Operational Works
drawings for the surrounding development (OPW/25/0057). A future cutoff drain shall protect the site
from runoff from the west, and the neighbouring lot to the south predominately grades towards the new
subdivision road. A new cut-off drain along the southern boundary will be provided to redirect any minor
flows from the south, as per the civil engineering concept plans (refer Appendix A).

4.3     Flooding
The site is not impacted by flooding and is not covered by Council’s Flood Hazard Overlay.

4.4     Stormwater Quality Management
Stormwater quality is to be provided by a future bio-retention basin directly north of the subject site. The
bio-retention basin is to be built as a part of the surrounding subdivision works (refer OPW/25/0057)
and has been sized to cater for the fully developed catchment. As such, no additional stormwater quality
is proposed for the development.
4.4.1 Construction Phase Stormwater Quality Management
Stormwater quality management during the construction phase is critical to ensuring water quality
standards are achieved during the full life of the development. Implementing best practice Erosion and
Sediment Control techniques is imperative to managing the runoff quality affected by construction
works. Appendix B outlines best practice measures for stormwater quality during construction.

4.5     Stormwater Quantity Management
4.5.1 General
In accordance with the NSC Planning Scheme, stormwater quantity management is required for the
proposed development. To achieve compliance, an on-site detention (OSD) tank will be provided to
mitigate post-development peak flows.




12 May 2026