Attachment C - Stormwater Management Plan - 30-32 Doonella Street_SMP-revA_full (00016826)

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2.4.2 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! or! a! weir.! ! 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.!!!
As! these! systems! take! approximately! 12"24hrs! to! drain,! the! maximum! depth! of!
pondage! allowed! to! occur! over! the! filter! area! has! been! limited! to! 300mm,! with! a!
minimum! filter! media! depth! of! 500mm.! ! Table! 6! summarises! the! proposed! design!
parameters!for!each!bioretention!system!for!this!development.!!In!conjunction!with!
the! bioretention! system,! the! detention! basin! has! also! been! represented! as! it! is!
located!directly!above!the!bioretention.!!The!bioretention!locations!are!highlighted!
in!Figure!2.!!!
Table!6:!Bioretention!Basin!Design!Parameters!

                                   Parameter!                         Basin!
                         Extended!Detention!Depth!(m)!                 0.30!
                                                         2
                           Storage!Surface!Area!(m )!                   33!
                                                     2
                             Filter!Media!Area!(m )!                    29!
                       Unlined!Filter!Media!Perimeter!(m)!             0.01!
                   Saturated!Hydraulic!Conductivity!(mm/hr)!           200!
                                Filter!Depth!(m)!                       0.5!
                       TN!Content!of!Filter!Media!(mg/kg)!             400!
               Orthophosphate!Content!of!Filter!Media!(mg/kg)!          50!
                            Exfiltration!Rate!(mm/hr)!                  0.0!
                               Overflow!Weir!(m)!                       2.0!
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