Stormwater Management Plan

6.3       Operational Phase
6.3.1     Lawful Point of Discharge

The lawful point of discharge for the site is to the existing underground stormwater drainage network in
Bottlebrush Avenue.

6.3.2 Proposed Site Drainage

Stormwater and roofwater runoff from the development will be collected and conveyed in a new
stormwater pit and pipe network to underground detention tank located near south-western side of the
site. Detained flows from the tank will outlet to a new stormwater manhole in Bottlebrush Avenue located
at opposite verge of road.

A Trapezoidal catch drain will be constructed along the north-eastern boundary to collect and convey
upstream catchment runoff. This runoff will be collected in a stormwater pit at the eastern end of the
catch drain and conveyed through the internal drainage system.

The proposed site stormwater infrastructure is shown on MPN Plan 10256-DA.03 attached in Appendix C.

6.3.3 Stormwater Quantity Management Strategy

Stormwater detention is proposed to be provided to limit discharge of site to the pre-development
discharge.

For the management of stormwater quantity for the proposed development, the DRAINS computer
model was used to calculate the stormwater runoff quantity for the pre-developed site and proposed
development. Runoff flows for 2 to 100 year Average Recurrence Interval storm events with durations of 5
minutes to 2 hours were calculated to ensure that peak runoff flows from the proposed site would not
exceed peak runoff flows from the pre-development site.




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Inspired engineering

22 May 2025
https://mpncnetau.sharepoint.com/sites/Administration/Shared Documents/10000-10999/10200-10299/10256/Report/22-05-25 SWMP_Issue A.docx