OPW16/0021- Operational Works Application 2 of 4

!




                                                                                                    !
Figure!4:!Model!Layout!
!
Note:!results!are!reported!at!the!“Junction”!node!which!captures!all!developed!areas!
of!the!site.!

2.4 Treatment!Measures!
Runoff!from!the!hard!roofed!area!will!be!collected!in!a!rainwater!tank!and!treated!
for! internal! reZuse.! ! Runoff! from! the! ‘Green! Roof’! areas! and! the! driveway! will! be!
collected!in!the!Stormwater!Tank!via!a!GPT!for!reuse!externally.!!Overflow!form!both!
tanks! are! directed! to! a! bioretention! basin! at! the! outlet! of! the! site.! The! location! of!
the!elements!are!shown!in!Figure!5.!

2.4.1 Rainwater!Tanks!




                                                                                         !
!
Through! appropriate! design! of! rainwater! tanks! it! has! been! found! that! significant!
reductions!in!runZoff!can!be!achieved.!!Rainwater!tanks!not!only!provide!temporary!
detention!of!stormwater!runZoff,!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.!!!


!                                                   !                                               ! 9!