08/1128 - Information Response to Biodiversity Items & Ecological Impact Items - Place Designs [As Published] · 132008.1128

BCROQ RFI Response to Council 20081126 Page 17 of 28

Biodiversity

Items 19 & 20 are to be addressed in a separate response by the Client’s Consulting Engineers - Cardno
(Qld) Pty Ltd.

Ecological Impacts
Item 42.

The discharge velocity for Q2 events in the developed scenario exceeds the undeveloped case.
Council also notes that the Lot 6 bioretention basin reduces the Q100 flows to velocities
experienced in Q10 events and Q10 flows to velocities experienced in Q2 events. Due to the
sensitivity of the area and number of significant species residing within the receiving
environment, Council requests comment regarding the impact of such event flow reductions on
the ecology on significant species.

Sensitivity of Significant Species

The significant species downstream of the bioretention basin include:
* Lewin’s Rail - These species are sensitive to maintenance of riparian areas for foraging whilst
having the quality of the wet heath maintained for shelter and nesting requirements.

« Acid frogs -
o Wailum Froglet, wallum sedgefrog and wallum rocketfrog;
o require water within breeding area to be below pH 6 to maintain the competitive

advantage over related non-acid tolerant species;

o potential utilising lower end of drainage lot in Lot 7; and
o core habitat is the wet /closed heath of the Noosa National Park.

Conclusion

The wet heath areas are adapted to the variable climatic conditions of drought and torrential rain, such
that any minor differences in discharge level as a result of rainwater tanks and bio- retention basins will not
be significant, subject to water quality meeting the modelled pollutant reductions are achieved.

As a result it is concluded that the overland flow after release from the bio-retention basins will allow pH to
be buffered as per natural flow through the 20m conservation buffer on the western boundary. Water
infiltrating within the basin should achieve natural pH level prior to reaching the open heath. The acidity in
waters favouring acid frog breeding is generated from humic acid in the breakdown of the vegetative
material within the wet heath.

It is recommended that water quality should be monitored to determine if acidity in the water changes as a
result of the development.