Response to Information Request Letter · OPW25/0057

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Response:

Amendments were undertaken to the 12dModel to ensure the culvert determining factor was inlet control and
corresponding upstream head loss coefficients used. Stormwater Calculation Results are contained on Covey Drawing
233467_C380_RevE.

ITEM – STORMWATER QUANTITY

Information Required:

3. Provide an update to the Flood Hazard Assessment report which specifically examines the impact resulting from
   changes in the site land use / imperviousness on stormwater characteristics within the downstream road
   network and downstream private land. Where unacceptable impacts are predicted to occur, these impacts are
   to be mitigated through the use of a detention basin or other means.

Response:

No hydraulic modelling has been undertaken to determine the detention requirements for each residential lot (if any).
The developer(s) of the individual lots must seek approval from Noosa Shire Council for any stormwater detention
infrastructure that may be required to facilitate the development of each lot. Stormwater detention infrastructure
must be contained within the lot that it serves.

The OPW application includes earthworks and civil infrastructure to suit a 1 into 3 development providing lots of similar
characteristics to those currently on site. The lots are to be stabilised with appropriate grass cover and retain the
‘Community Use’ zoning. Final development form of each lot is to be determined.

Flows generally move throughout the site in a similar manner to the existing regime, with Lot 1 and Lot 2 flows
converging towards the intersection of Lake Macdonald Drive and Dianella Court. Lot 3 continues to drain to the south
in line with the pre-developed case.

ITEM – CLIMATE CHANGE

Information Required:

4. Clarify what climate change assumptions have been adopted in the drainage design in order to meet PO2 of the
   Water Quality and Drainage Code. It is suggested that SPP2-4.5 and a planning horizon of 2100 be adopted
   consistent with the current methodology of ARR. This should be applied to both the drainage design and flood
   hazard assessment.

Response:

The stormwater design has been amended in consideration of the application of SPP2-4.5 and a planning horizon of
2100. To meet the flow requirements of the increased rainfall intensities, the following stormwater network
amendments have been applied:

-   4/A to 5/A increased from ø375 to ø450 for the increased stormwater flows
-   1/H to 2/G increased from ø450 to ø525 for the increased stormwater flows
-   Line K (Lot 3 outlet) increased from ø375 to ø450 for the increased stormwater flows
-   Q100 overland flows updated
-   Stormwater longitudinal sections updated for new pipe sizing and flows
-   HGL updated for increased stormwater flows
-   Swale calculations updated to suit increased flows – no change to swale sizing required
-   Bio-basin weir lowered by 100 mm to cater for increased 1 % AEP flows

ITEM – STORMWATER STRUCTURES 2/A & 4/A

Stormwater structures (2/A & 4/A) do not align with the 600 mm channel (900 mm x 900 mm structures).

Information Required:

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5. Provide a typical detail as they do not reflect standard drawing DS-050.

Response:

Stormwater structures 2/A and 4/A have been amended to reflect 900 x 600 pits in accordance with DTMR Std. Drg.
1309 with the inclusion of a ‘V’ type grate to suit the 600 mm channel profile.

ITEM – STORMWATER STRUCTURE 6/A

Structure 6/A appears to include two lateral inlets, typically this arrangement is avoided as per QUDM 7.6.3. It’s noted
outlet velocities to the bioretention sediment forebay (Structure 7/A) should be minimised. The design pipe flows from
6/A to 7/A appear to exceed the design pipe capacity at grade shown on drawing C320 Rev D.

Information Required:

6. Review the design and provide further engineering justification and / or amendments if required.

Response:

Lot 1 stormwater connection has been re-aligned to discharge directly to the bio-basin headwall / forebay, removing
the two lateral inlets previously reflected at structure 6/A.

At grade pipe capacity reflected on the longitudinal sections does not account for hydraulic head. In accordance with
the ‘Water by Design – Bioretention Technical Design Guidelines, Version 1.1, October 2014’ the bio-retention filter
media scour velocities have been checked as per Section 3.4.5.

-   Minor storm (2-10 year ARI)          = 0.585 m/s
-   Major storm (50-100 year ARI)        = 0.540 m/s

ITEM – EROSION AND SEDIMENT CONTROL (ESC)

The ESC plans include high efficiency sediment (HES) basins for catchment 1 & 2. HES Basin 1 shows overflow
discharging to an existing field inlet to the northeast. It’s unclear where the forebay is located and how runoff will be
directed through the basin.

Information Required:

7. Provide additional information addressing the above mentioned.

Response:

Erosion and Sediment Control Plans provided with the Operation Works application are indicative of the necessary
measures and controls typical of the earthwork’s construction package in accordance with the IECA Manual for Erosion
and Sediment Control. Clarification has been shown around the location of basins, forebay and outlets.

Completion of and submission of final construction Erosion and Sediment Control plans is the responsibility of the
awarded contractor. Plans are to be created in line with their proposed construction methodology, construction
sequencing and site management requirements. Erosion and Sediment Control plans are to be submitted to Council
prior to the Pre-Start meeting.

ITEM – EXTERNAL ROADWORKS

Further details are required for the Lake Macdonald Drive roadworks.

Information Required:

Provide amended plans addressing the following:

8. The pathway along Lake Macdonald Drive follows the TMR SEQ Principal Cycle Network and requires coloured
   treatments (e.g. CCS Black 44 colour treatment for footpath infrastructure along the Network).



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Response:

Lake Macdonald Drive is identified on the Department of Transport and Main Roads Priority Route Maps as ‘Route
Priority C’. As the development is providing shared use facilities to the frontage of Lake Macdonald Drive, i.e. 2.5 m
wide concrete pathway, standard finishes for the pathway would typically be plain concrete.

Coloured treatments (CCS Black 44) would be applicable to dedicated cycle facilities providing a contrasting surface to
delineate against plain concrete shared or dedicated pedestrian facilities.

9. Possibility for Cycle Green Treatment (line marking) along the 2.0 m cycle lane at the Dianella Court / Lake
   Macdonald Drive intersection.

Response:

Green cycle treatment has been included in the amended plans.

10. Kerb ramp and crossing TGSI’s are to be pavers (detail to be provided).

Response:

Kerb ramps have been nominated in accordance with Noosa Shire Council Standard Drawing SD: 9006 with a minimum
requirement for ‘BLACK poly adhesive TGSI on PLAIN concrete’.

ITEM – FAUNA MANAGEMENT

The application includes the removal of vegetation within Councils Road reserve and within the property to facilitate
road and bioretention basin infrastructure.

Information Required:

11. Provide to council for endorsement a fauna management plan, (or part thereof) prepared by a qualified person
    to address fauna management during the vegetation clearing of the site.

Response:

Refer to Fauna Management specialist engaged by the client.

ITEM – MISCELLANEOUS

Information Required:

12. All timber bollards / garden edging / etc. is to be ACQ treated (Not CCA treated).

Response:

Landscape plans have been amended accordingly.

ITEM – PORTABLE LONG SERVICE LEAVE LEVY

The provided DA Form 1 has nominated evidence of portable long service leave levy will be provided before the
application is decided.

Information Required:

13. Provide evidence the portable long service leave levy has been paid.

Response:

Refer to the client for further information.




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We trust this answers the Information Request fully, should any further information be required, please contact this
office.

Your faithfully
COVEY ASSOCIATES PTY LTD




CHRISTOPHER TEMMERMAN
Senior Civil Designer




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