Further Advice Assessment Manager OPW21 0272

Officer: 	Laurie Schreck
Direct Telephone: 	07 53296223
Our Reference:	OPW21/0272
Your Reference:	OPW21/0272
11 January 2022
Deluca Charitable Foundation Limited
C/- Deluca Corporation Pty Ltd
PO Box 1514
MILTON   QLD  4064
[email protected] Sir/Madam
Further Advice – Development Application
I refer to your application and advise that Council wishes to provide you with further advice about the application in accordance with the provisions of the Development Assessment Rules 2017.
application details
Application No.	OPW21/0272 MCU20/0128
Street Address:	Reservoir 32 Viewland Dr Noosa Heads Qld 4567
Real Property Description:	Lot 1 RP 226728
Planning Scheme:	Noosa Plan 2020 (25 September 2020)
further advice
You are advised that:
The response to the information request received on 10 December 2021 has not addressed all concerns with the proposed development. Please see the further information request items below to be addressed for the development.
Water Quality and Stormwater
Issue – Severe Storms or Severe Blockage
Concern is raised over the potential of the proposed design to result in a new concentrated discharge location to downstream properties (specifically 28 Viewland Dr) under conditions of either a severe storm or severe blockage of the low-flow outlet from the detention tank. The absence of any secondary outlet or weir from the detention tank exacerbates this risk.
Consideration should be made to providing a high flow weir from the detention tank such that flows will preferentially continue to Viewland Dr in the case of a severe blockage rather than over the retaining wall in Bio Basin 1.
Advice Required
Provide both severe storm and severe blockage assessments for the site drainage system, conducted in accordance with QUDM. For the severe storm assessment, a 1:2000yr ARI is recommended with design blockage, while a severe blockage assessment is recommended to be based on the 1%AEP (at year 2100) plus complete blockage of the low-flow outlet from the detention tank.
The assessment should demonstrate that floor levels of the units are not inundated and should quantify any impacts or unexpected flow paths to downstream properties. Where new overland flow paths or concentrated discharge locations are identified, measures should be undertaken to mitigate.
Issue – Drainage Calculations for Internal Works
Concerns have been raised around elements of the drainage calculations for the internal works.
Advice Required
Provide the 1%AEP (2100) peak water surface levels modelled for the detention tank, Bio basin1 and Bio basin 2.
Clarify how the detention tank is able to fill to full capacity, given that the top of the tank internally is at 74.50mAHD while the top of retaining wall for Bioretention Basin 1 sits lower at 74.20mAHD.
Provide drainage calculation tables for the internal drainage network.
Issue – Drainage Calculations for External Works
No drainage calculations are provided to accompany the long-sections for the external drainage works in Viewland Drive.
Advice Required
Provide drainage calculation tables for the external drainage works in Viewland Drive. The calculations are to include at least the first gully pit in the existing drainage network which the new works will connect into and is to demonstrate that the additional flows from the site will not cause surcharging of this gully.
Issue – Drainage Design
A number of issues have been identified or require further clarification in the amended drainage design.
Advice Required
Provide updated plans which address the following issues:
Provide additional level details showing how flow will be managed to not pond against or enter building Apt01 (currently several areas grade towards the building);
Provide either forebays or rock energy dissipaters at the inflow points to the bioretention basins;
Revise the design to reduce retaining wall heights to a maximum of 0.8m adjacent to bioretention basins as required by Condition 47.4 or otherwise identify how access to each basin for maintenance will be achieved? As the filter areas of the bio basins appears to be over-sized, consider converting the eastern-leg of bio basin 1 into an access ramp so the device can be accessed and maintained;
Provide details (i.e. depth, longitudinal grade, side slope) and supporting calculations for the eastern swale drain. Demonstrate that the swale can convey the 1%AEP (2100) flows from the external catchment;
The swale is shown as leaving the subject site and passing through the Unity Water site before re-entering the subject site. Provide approval from Unity Water for works within their site;
Provide further details for the end of the swale, showing how flows will be transitioned back to distributed sheet flows at the location nominated, given the very small area available to achieve this. If this is not achievable, continue swale to an area of the site where flow distribution is more achievable;
For the bioretention basins, provide a plan view showing sub-soil drain layout;
Revise the detail for the sub-soil drain cleanouts on the bioretention sections so there are no 90-degree bends;
Nominate material type and size for sub-soil drains for the bioretention basins; and
Revise the bioretention basin levels so that a free-draining outlet from the subsoil drains is possible. Currently there is only 600mm of fall from bio surface to outlet pipe invert even through there is 700mm of fall required to the base of the drainage layer (even without allowing for 0.5% fall).
Landscaping
Issue
The higher order MCU includes conditions 14, 15 and 16 regarding fencing and landscaping requirements. The application material and information request response do not appear to have included these requirements in particular condition 15 requiring the area of land between the fence and the front property boundary must be densely landscaped to screen any fencing from the street. The planting included within the Planting Plan (601 and 602 D) appears to stop at the front fence with no landscaping between the fence and property boundary.
Advice Required
Amend the application material to include the 1m setback between the boundary and the front fence being densely landscaped to screen any fencing from the street.
Issue
The higher order MCU include condition 17b which requires 1 street tree within the road reserve for every 8 metres of road frontage. It has been proposed that existing street trees are to be removed therefore it is particularly important to ensure the MCU condition has been met and the street trees are included within the application material.
Advice Required
Amend the application material to ensure MCU condition 17b has been met including the location, species and any other relevant detail.
due date for response to further advice
A response to the further advice is required by 27 January 2022. Email your response to [email protected] details
Should you have any further queries in relation to the above, please do not hesitate to contact me on the number above.
Yours faithfully,

Laurie Schreck
Development Engineer

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PO Box 141		P. (07) 5329 6500	[email protected]	
	TEWANTIN  QLD  4565	F. (07) 5329 6501	www.noosa.qld.gov.au
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