Engineering Hydrology Plans (IWMP)

2.4 Treatment Measures

The various treatment measures proposed to be implemented within this
development are outlined below. They are made up of rainwater tanks and
bioretention system for stormwater reuse. The localities of the measures are
detailed in Figure 6.

2.4.1 Rainwater Tanks




Through appropriate design of rainwater tanks it has been found that significant
reductions in run-off can be achieved. Rainwater tanks not only provide temporary
detention of stormwater run-off, but also provide a significant alternative for water
supply uses. Collected roof water is suitable for garden irrigation or toilet flushing
with no additional treatment.
An additional benefit to rainwater tanks is that the detention of stormwater flows
can alter the pollutant transportation characteristics of a catchment. Rainwater
tanks can be incorporated into building design so that they do not impact on the
aesthetics of an urban development. Legislation introduced by the Queensland
State Government regarding water saving targets have mandated the inclusion of
rainwater tanks in all new developments state-wide unless an exemption has been
granted.
Rainwater tanks have been modeled as a lumped tank to represent the entire
development. Sizing of each tank volume has been modeled in MUSIC using
estimated demands for each use to achieve a minimum 80% reliability. The
demands of each use on the site are highlighted in below in Table 7. Irrigation of the
site landscape will be sourced from the Tavern tank. Landscaping area has been
estimated as 10% of the carpark area, irrigating at a rate of 548mm/yr. The annual
irrigation demand scaled by daily PET was calculated as 311KL/yr.




                                                                                         9