RFI - Appendix B Civil Engineering Report · MCU22/0038

 13 May 2022



Response:

The proposed pump out tank will be located under the basement slab and will have no impact on the car
parking layout of the basement. The pumps utilised will be submerged pumps which can be accesses
through a maintenance opening in the basement slab. The final sizing of the tank will be completed as
part of the detail design stage of the development.

The tank will only contain the treated flows from the bioretention basin 1 subsoil drainage and as such
the volume of water flowing into the tank will be minimal. No bioretention basin overflows or roofwater
flows will enter the tank.

The pump out system will be powered from the building power supply. No back up power supply will be
provided for the pump out system. Redundancy will be provided within the tank.


        Issue
        The submitted documentation (drawing “Stormwater Treatment Plan”, CP.1.01, Rev A,
        prepared by MPN Consulting) indicates that the existing footpath, to the frontage of the subject
        property, is to be removed and replaced with a new 1.8m wide one. The existing footpath is
        2m wide.

        Information Required
        7. Submit amended plans showing all proposed footpaths to be 2m wide.

Response:
Path Widths have been amended to 2m wide on the revised plans.

        Issue - Stormwater Management Plan - Quality
        The biobasins have been designed without a free draining outlet to an existing stormwater system.

        Information Required
        Provide justification that the biobasins need to drain to the basement carpark pump out system. Include
        information on discharge pit invert levels.
        Provide the MUSIC model for the proposed development.
        Provide sizing details of the high flow stormwater pipes inlet and outlet pipes for biobasin 1.

Response:
As depicted on the revised layout plans the invert levels at the downstream connection point for bio
basin 1 are higher than the base of the bio retention basin by 400mm. As a result the subsoil drainage
from the bio basin will need to connect into the basement for pump out to the external network.

Details on the pipe sizes and invert levels for the bioretention basins have been provided on the revised
plans.

The site MUSIC model was previously submitted to council and has been issued again as requested.




 Excellence with Economy in Engineering                                                                    2
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