Information Request OPW25 0057 (As Published) · OPW25/0057

                 Issue - 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 landuse/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.


                 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.


                 Item – Stormwater Structures 2/A & 4/A
                 Stormwater structures (2/A & 4/A) do not align with the 600mm channel (900mm x 900mm
                 structures).
                 Information Required
                 5.     Provide a typical detail as they do not reflect standard drawing DS-050.


                 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.


                 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 filed inlet to the northeast. It’s unclear where the
                 forebay is located and how runoff will be directed through the basin.
                 Information Required
                 7.     Prove additional information addressing the abovementioned.


                 Item – External Roadworks
                 Further details are required for the Lake Macdonald Drive roadworks.
                 Information Required
                 Provide amended plans addressing the following;




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Document Set ID: 23708018
Version: 5, Version Date: 13/05/2025