08/1128 - Response to Information Request [As Published] · 132008.1128

Page 7

From Table 2.10 of the Engineering Report:

Peak 100 year ARI discharge from southern basin is 0.28 m/s, which
gives velocity = 0.09 m/s.

Peak 100 year ARI discharge from northern basin is 0.05 m/s, which
gives velocity = 0.017 mis.

The model was reviewed. The model indicated that the peak velocity in the
southern basin would be 0.135 m/s and the peak velocity from the northern
basin would be 0.025 m/s.

Scour due to flow velocities is considered to be negligible.

39. It is proposed that grease and oil filtration devices will be installed on
GPTs.

40. All basement car parks, including the RAC basement will drain by
gravity means to the bioretention basins. Refer to attachment for further
details.

41. RAC basement plans now include gated drains to facilitate gravity
feed of stormwater as per item 40 above.

Ecological Impacts

42. It is suggested that single high ARI events (Q1 and above) have
minimal long term ecological impact. The bio-retention basin acts to
attenuate the peak discharges for high ARI events such that flow volume in
equals flow volume out, less minor infiltration or evaporation losses. Refer to
attached letter from Place dated 25"" November 2008.

43. This item has been addressed fully in the attached letter by Place
dated 25'" November 2008.

44. The proposed spreader channels will act to redistribute collected
stormwater in a manner which, as much as possible, emulates the natural
runoff conditions for the site.

45. The proposed pergola (open nature) would not impact on MUSIC
modelling or bio-retention treatment functionality providing adequate light is
allowed for plant requirements. Shade tolerant species may be used as
outlined in the Healthy Waterways Guidelines.

46. The location of the bio-retention basin has been constrained by the
development layout. Construction and vegetation management plans to be
conditioned as part of the Operational Works application.

External Traffic Generation

47 - 52 Please refer to the attached report prepared by Arup addressing
these points.

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