2014022_71_SeaviewTce_SWMP-revC_full · OPW16/0021

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Executive!Summary!
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AquaIntel! has! been! commissioned! by! TOD! Consulting! Engineers! on! behalf! of! Universal!
Property! Company! Establishment! to! prepare! a! Stormwater! Management! Plan! (SWMP)! to!
support! the! Operational! Works! Approval! for! the! residential! development! at! 71! Seaview!
Terrace,!Sunshine!Beach!(Lot!1!RP197117).!!This!document!supersedes!both!the!original!the!
stormwater! management! plan! (Rev! A)! prepared! by! AquaIntel! (January! 2014)! in! support! of!
the! Material! Change! of! Use! application! and! the! previous! Stormwater! Management! Plan!
(RevB)! submitted! with! the! Operational! Works! application! for! the! site.! ! This! document! is!
prepared! to! address! the! RFI! for! the! Operational! Works! application! and! specifically! Items! 1!
and!3!(Doc!Ref!MLEWIS:OPW16/0021,!issued!5!April!2016).!
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The!site!is!currently!undeveloped!and!well!vegetated.!!The!site!is!located!adjacent!to!Noosa!
National!Park.!There!is!a!small!external!catchment!draining!through!the!site!from!the!west.!!
The! site! grades! from! the! west! to! the! east! and! currently! runoff! from! the! site! collects! in! a!
drainage!line!near!the!eastern!boundary!of!the!site!and!discharges!to!the!beach.!!!
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It!is!proposed!that!the!residence!be!constructed!with!a!living!‘green’!roof!consisting!of!up!to!
200!mm!of!planted!material!covering!the!shell!like!structure.!!The!roof!will!drain!via!an!under!
surface!drainage!network!and!a!series!of!intercept!drains!to!the!edges!of!the!roof.!!
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Environmental! best! management! practices! are! proposed! for! treatment! of! stormwater!
generated!by!the!site.!Stormwater!will!be!treated!using!a!number!of!treatment!devices!prior!
to!discharge!to!the!receiving!environment.!The!stormwater!treatment!train!for!the!site!will!
consist! of! a! combination! of! areas! treated! within! two! separate! bioretention! basins,! water!
harvesting!and!reuse!on!site,!and!maintenance!of!discharge!from!the!green!roof!into!natural!
gullies.! ! While! it! is! not! proposed! to! direct! all! site! runoff! through! a! formal! water! quality!
treatment!device,!this!report!demonstrates!that!the!Water!Quality!Objectives,!defined!in!the!
SPP,!will!be!met!by!the!overall!treatment!train!proposed!for!the!developed!portion!of!the!site.!
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Non_worsening!of!peak!flows!from!the!site!has!been!demonstrated!through!the!incorporation!
of!a!detention!basin!and!stormwater!tank.!!Runoff!from!the!external!catchment!to!the!west!
of! the! site! will! be! managed! by! diverting! the! existing! drainage! paths! along! the! western!
boundary!and!allowing!flow!to!continue!through!the!area!of!the!site!to!the!north!which!will!
not!be!developed.!Runoff!from!the!driveway!will!be!captured!initially!in!a!detention!basin!(to!
be!co_located!with!a!bioretention!basin)!then!discharge!will!be!returned!to!sheet!flow!prior!to!
entering!natural!drainage!gullies!below!the!development!footprint.!!The!grassed!area!on!the!
southern!side!of!the!proposed!building!and!pool!deck!area!will!be!captured!via!a!bioretention!
basin! for! treatment! (but! limited! detention)! prior! to! exiting! the! site! via! a! piped! outflow! to!
below! RL26! and! a! spreader! at! that! location! to! minimise! the! risk! associated! with! flow!
concentration.!!In!order!to!achieve!non_worsening!of!peak!flows!from!the!site!it!is!necessary!
to!capture!flow!from!the!southern!part!of!the!green!roof!and!pass!them!through!a!detention!
tank.! ! The! detention! tank! (denoted! Stormwater! Tank)! will! discharge! via! the! same! level!
spreader!as!that!which!outlets!the!southern!bioretention!basin.!!To!reduce!concentration!of!
flows! and! to! maintain! the! natural! hydrologic! regime! as! far! as! possible! it! is! proposed! that!
runoff! from! the! Green! roof! (North)! and! Lower! Lawn! (North! and! South)! be! return! to! sheet!
flow! prior! to! exiting! at! the! environmental! line.! ! Runoff! from! the! hard! roof! area! will! be!
directed!to!a!rainwater!tank!for!reuse!on!site,!with!overflows!directed!to!the!stormwater!tank!
that!also!services!the!Green!Roof!(South).!



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