5. Attachment D - Stormwater Response

23 September, 2016                             -3-
Our File Ref: B16239CL002
Contact: Kym Huddart



Item 7

Issue
Specific Outcome O9 of the Water Sensitive Design Code requires that runoff from the
site is treated through natural treatment strategies. It is noted that the proposal is for all
runoff to either be treated via a non-natural device or enter the receiving stormwater
network directly.

The Water by Design Deemed to Comply Solutions applies to this site and provides that
a bio retention basin with filter media area of 2.2% of the catchment area (i.e. 53m²) will
achieve the water quality reduction targets. Treatment via this method will facilitate
compliance with Specific Outcome O9 of the Water Sensitive Design Code.

In addition ongoing maintenance of the water quality treatment device will be
responsibility of the property owner. Given the underground nature of the proprietary
stormwater quality treatment device, a condition requiring for the applicant to enter into a
contract for ongoing maintenance of the device will be needed.

Information Required
Where it is demonstrated it is not feasible for all runoff to be treated via natural treatment
strategies, provide a letter signed by the applicant acknowledging the ongoing
maintenance responsibilities and costs for a proprietary device compared to a natural
treatment option.

Lambert & Rehbein Response
In regards to providing a natural stormwater treatment strategy, the proposed
landscaping at the rear of the site is allocated for retaining the existing trees. The
remaining landscaping locations at the entrance from Eumundi Noosa Road would not
provide the area required for bioretention treatment. In addition, in this instance it is
considered impractical to direct surface and piped roof runoff to separate landscaped
areas for treatment.

It is proposed provide stormwater quality treatment via Stormwater 360 Enviropods (gully
pit filter baskets) and Stormwater 360 StormFilters (filter cartridges located within the
detention tank) to meet the water quality objectives for the site. A letter signed by the
applicant acknowledging this treatment train method and the ongoing maintenance will
be provided separately.