Information Request Response Lot 22 · MCU22/0038

         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.




Council Item 6.1 – 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.


Our Response

MPN Consulting have prepared an attached letter responding to this specific RFI item, refer Appendix
B, with the relevant commentary extracted below.


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.




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