2014022_71_SeaviewTce_SWMP-revC_full · OPW16/0021

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2 Stormwater!Quality!Improvement!Devices!

2.1     Bioretention!System!




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Bioretention! systems! use! ponding! above! a! treatment! surface! to! maximise! the!
volume! of! runoff! flowing! through! the! filtration! media.! They! typically! convey! flows!
above! the! design! event! through! overflow! pits.! ! The! treatment! system! operates! by!
firstly!filtering!surface!flows!through!surface!vegetation!and!then!percolating!runoff!
through! prescribed! filtration! media.! ! This! media! provides! treatment! through! fine!
filtration,!extended!detention!and!biological!uptake!of!nutrients.!!They!also!provide!
flow! retardation! for! smaller! events! and! are! particularly! efficient! in! removing!
nutrients.! ! These! devices! can! be! installed! at! various! scales,! from! planter! boxes! in!
streetscape!to!within!large!detention!basins.!!
The! bioretention! systems! proposed! to! treat! the! runoff! generated! from! the!
development! site! before! being! discharged! into! the! natural! overland! flowpath!
downstream!of!the!site.!
As! these! systems! take! approximately! 12X24hrs! to! drain,! the! maximum! depth! of!
pondage! allowed! to! occur! over! the! filter! area! has! been! limited! to! 200mm.! ! The!
depth!of!the!filter!media!has!been!limited!to!400mm.!!The!basin!is!to!be!planted!out!
with! native! species! which! are! adaptable! to! a! wet/dry! soil! environment.! The! basin!
will! require! maintenance! such! as! weeding! and! replanting! if! plants! are! damaged! or!
die.!!
An!overview!of!the!bioretention!basin!is!provided!in!the!table!below.!!Locality!plans!
of!the!basin!is!attached!in!Appendix!1.!
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                                                               Bioretention!Filter!Area!
                   ID!               Catchment!Area!(ha)!
                                                                        (m2)!
             Driveway!Bio!                   0.026!                       5!
               Lower!Bio!                    0.057!                       12!
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