RFI Eng response notice items 4-19 MCU150111

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Item 15 Provide commentary to confirm that the Nodes proposed for the Bowling Green and Park will most
adequately represent the nutrient fluxes from those uses.

Our Response

The proposed bowling green is to be constructed with synthetic grass and has a roof. For the purposes of the MUSIC
model, the bowling green has been modelled as a roof.

As per the Stormwater Construction Management and Maintenance Plan, it is advised that landscaping areas directly
adjacent to the WQCP are not fertilized in order to minimise high nutrient runoff from entering the pond.

Item 16 Detail Invert Levels for outlet structures of all water quality treatment devices, along with surrounding
land surface levels to demonstrate that adequate fall is available for stormwater discharges.

Our Response

Invert levels have been added to the plans to show that there is adequate fall for all basin outlets. Refer attached
Drawings B14158.W Sheet SK103 and SK104.

Item 17 Demonstrate how the design of the bioretention basins, including location and heights of retaining walls
is consistent with the recommendations of the Water by Design Bioretention Technical Design Guidelines for
depth of filter media to surrounding areas and retaining wall heights.

Our Response

At the central bioretention basin the concept design plans for the site indicate a maximum wall height of 1.6m and 1.5m.
This is considered to be reasonable for such developments.

It is noted that the Water by Design Bioretention Design Guidelines recommend for wall heights exceeding 800mm that
multiple walls be used with a 3m wide terrace in between the walls. It is suggested that this is an onerous requirement
and not relevant where only one side of the bioretention basin is walled.



Item 18 Provide commentary regarding the functional consistency between proposed weir width details shown
on proposed detail design drawings and the MUSIC model weir width input data.

Our Response

The width of the weirs shown on plans are inconsistent with the MUSIC model. This issue has been corrected in MUSIC
model and has little impact on the results. All objectives have been achieved.



Item 19 Provide calculations in accordance with the Queensland Urban Drainage Manual to demonstrate that the
confluence of stormwater at the drainage easement will not cause scour and that any required dissipater/erosion
control can be contained wholly within the applicant’s property.

Our Response

We appreciate council’s concerns regarding scour protection. However it is possible that pipe network may change during
the detailed design phase. As such we would suggest that detailed calculations are provided to demonstrate scour risk
mitigation at the Operational Works phase. Please condition approval appropriately.