OPW16/0021- Operational Works Application 2 of 4

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and!discharged!into!a!small!bioretention!basin.!!Runoff!from!the!external!catchment!
will! be! bypassed! around! the! site! via! cut! off! drain! on! the! western! boundary.! Flows!
will!bypass!the!site!on!the!north!or!southern!boundary.!!This!external!catchment!will!
not!contribute!runoff!to!any!bioretention!or!detention!system!on!site.!!!
During! subsequent! design! phases! FLOTH! Sustainable! Building! Consultants! have!
undertaken! the! hydraulic! design! of! the! internal! stormwater! management!
infrastructure!and!it!is!proposed!that!runoff!from!the!‘hard’!roof!area!be!collected!
within! a! ‘Rainwater! Tank’! and! treated! for! internal! uses.! ! In! addition,! all! other! built!
areas!including!the!driveway!and!green!roofed!areas!will!be!collected!in!a!large!60!
m3! ‘Stormwater! Tank’! via! a! GPT! and! reused! within! the! site.! ! Tank! sizes! (including!
outlet!details)!and!reuse!estimates!have!been!provided!by!FLOTH!for!use!in!this!plan.!
FLOTH!Design!plans!are!provided!in!Appendix!1.!
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Figure!3:!Conceptual!Treatment!Train!


2.3 Modelling!Approach!
2.3.1 Philosophy!
As! discussed! above! a! conservative! approach! to! the! quantification! of! water! quality!
load! generation! and! treatment! as! a! result! of! the! proposed! living! ‘green’! roof! has!
been!adopted!for!this!investigation.!!The!areas!of!‘green’!roof!have!been!included!in!
the! MUSIC! model! as! forest! source! nodes! and! not! as! treatment! devices.! ! It! is!
proposed!that!the!roof!areas!be!planted!with!native!endemic!species!and!thus!will!
reflect! the! surrounding! forest! areas! rather! than! an! urban! garden.! The! ‘green’! roof!
areas! will,! in! fact,! provide! a! certain! level! of! water! quality! treatment! similar! to! a!
bioretention!garden;!however,!this!has!not!been!included!in!the!modelling.!!
Hydraulic! design! and! site! water! reuse! estimates! have! been! undertaken! by! FLOTH!
(see!Appendix!1).!!FLOTH!propose!to!capture!all!runoff!(up!to!and!including!the!1%!
AEP!event)!from!the!developed!areas!of!the!site!and!direct!to!either!a!rainwater!tank!



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