2014022_71_SeaviewTce_SWMP-revC_full · OPW16/0021

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2.4 Treatment!Measures!
Runoff! from! the! development! will! be! treated! via! two! bioretention! basins.! ! The!
location! of! the! basins! is! shown! in! Figure! 5.! ! The! area! of! concrete! roof! will! also! be!
captured!in!a!rainwater!tank!for!reuse!within!the!development.!

2.4.1 Rainwater!Tanks!




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Through! appropriate! design! of! rainwater! tanks! it! has! been! found! that! significant!
reductions!in!runToff!can!be!achieved.!!Rainwater!tanks!not!only!provide!temporary!
detention!of!stormwater!runToff,!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.!!!
The!modified!OPW!treatment!train!proposes!one!tank!to!be!utilised!for!stormwater!
treatment! (the! Rainwater! Tank).! ! A! second! tank! (Stormwater! Tank)! will! be! utilised!
for!detention!purposes!only!and!does!not!form!part!of!the!water!quality!treatment!
train.!!The!size!and!outlet!pipework!included!in!the!MUSIC!model!as!shown!in!Table!
4.!!As!the!proposed!reuse!from!the!tank!is!now!to!be!limited!to!nonTpotable!internal!
use!and!external!use!there!is!no!additional!treatment!of!the!water!proposed!prior!to!
use.!!!
Estimates!of!reuse!have!been!reduced!to!500!L/d!which!is!considered!reasonable!for!
the!size!and!scale!of!the!proposed!development!and!are!modelled!as!noted!Table!4.!
Table!4:!MUSIC!Rainwater!Tank!Parameters!


                                                                  Rainwater!
                                   Parameter!
                                                                    Tank!

                               Tank!Volume!(kL)!                      25!
                                                 2
                               Surface!Area!(m )!                    12.5!
                       Equivalent!Overflow!Pipe!(mm)!                212!
                       Constant!Daily!Outflow!to!Reuse!
                                                                      0.5!
                                  (kL/d)!#!
#!ReTuse!estimates!applied!as!a!constant!daily!demand.!



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