Response to Information Request Letter · OPW25/0057

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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