bellair street rain gardens - melbourne, australia

8/3/2019 Bellair Street Rain Gardens - Melbourne, Australia

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Project summary

WSUD Type: Raingarden tree pits

Scale: Streetscape

Land Use: Residential

Constraints: Space, Topography, Vegetation

Cost: $272,000

Perormance: Stormwaterquality47.2%TN,74.9%TP,88.7%TSS,100%GrossPollutants

Site description

LocationThe project is located in Bellair Street,Kensington, between Arden Street andOrmond Street as circled right.

Figure 1. Map showing location o theBellair St, Kensington WSUD Raingardens

Part 3

Sample Case Study

Bellair Street Raingardens

112

MacaulaySt

Bella

irSt

Bella

irSt

Wolsel

eyRd

OrmondSt

DerbySt

Hampde

nRd

Kensington


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Site area

The road reserve is approximately 280m long by 15m wide.

Site land use

Bellair Street is a low density residential street with residential properties abutting the western edgeand a railway reserve on the eastern edge.

The project proposed to:

Renewtheroadsurface,kerbandchannelandfootpath

Replacesomematurestreettreessufferingfromstructuraldefectsandpoorhealth.

Catchment description

The treatable catchment is 6540m2, comprising the road reserve and abutting residential properties.The existing stormwater drainage system was used where available, however sections o new drainagewere still needed. The high point is situated between Tennyson St and Arden St.

Part o the drainage runs to the existing drain in Arden St. The remainder was directed north to connectto the existing drain in Bellair St near the corner o Tennyson St. The treated water will ultimately enterMoonee Ponds Creek.

Topography/Terrain

Bellair St is relatively fat with a slight high point between Tennyson and Arden St.

Tennyson St slopes down to Bellair St rom Southey St, orming part o this treatment catchment.

Site constraints

Drainagegradientswerelimitedbytherelativelyatsitetopography

Shallowstormwaterpipeexistforapproximatelyhalfofthesite,withtherestrequiringnewstormwater pipe connection

Notallexistingtreescouldberemoved,duetocommunityrequest

WSUDpitlocationandnumberwasoptimisedtomaximiseparkingandtreespacing

Existingbluestonechannelpitchersneededtobereplaced

Parkingspaceswerenottobereduced.

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Model WSUD Guidelines Part 3 Case Studies

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Extended Detention Depth(edd) depth from road levelto top of soil.Min 100mm, max 150mm

Steel edge on 3 sidesto form pit. Asphaltflush to steel edge

Precast concrete spike downkerb to match main kerb

Transition Layer: Approveddrainage sand only

Filltration Layer: Approvedfast draing Soil only

Drainage Layer: Approved gravelonly. Preforated pipe at 1:100 grade

Precast concrete kerb

Bluestone pitcher channellowered locally by - 100mm

Connect solid UPVC pipeto stormwater as perengineers spesification

Advanced tree - stake with50 x 50 x 2000mm hardwoodstakes & secure with 50mmwide hesslan ties

Plant groundcovers at300mm centres

Mulch with 50mm depth7-19mm recycled nofines rock aggregate

(Alex Fraser or equiv)

road

WSUD Design

Objectives

The project objectives were to:

Treatthestreetasholisticallyaspossible;

Upgradethestreetscapeandrenewinfrastructureandvegetation; Treatstormwatertobestpractice;

MaximiseWSUDtreatmentsizewhilstnotreducingavailableparking;and

Ensurealowcostdesign.

Opportunities

I possible, the removal o all existing trees would:

Provideaconsistentaestheticforthestreetscaperenewal(whichalsoincludedtheroad,footpath,kerb and channel in addition to the tree renewal)

Alloweasiercivilworks.

The project also oered the opportunity to design and trial a larger version o the tree pit raingardenin a residential street setting. This context would require a less intensive treatment then the City o

Melbournes CBD tree pits thus a lower cost, raingarden that was not grated could be used.

Design development

Through extensive community consultation, the design was altered to allow our healthy plane treesto remain.

The kerb outstand raingarden also proved too dicult to include due to steep level changes andpedestrian crossing issues at a street intersection.

Final design

The nal design included 19 raingardens, our less then the original concept design. It also excluded thekerb outstand raingarden.

Six o the raingardens required a reduced lter media depth due to the shallow depth o the existing

stormwater pipe that was used to drain the raingardens. The nal design still met the stormwaterquality best practice treatment targets.

Figure 2. Section detail o Raingarden


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Figure 3. Plan view o raingarden showing drainage layout

Figure 4. Plan view o raingarden showing surace details

Cost and timelines

The construction and installation costs o the raingardens have been kept at a minimum totalingapproximately$1,300persquaremetre.Thiscostcanbefurtherreducedwherenewstormwaterdrainage

and boring is not required.

Table 1. Project cost and timelines

Task Cost ($) Completion dates Undertaken by

Invest igation (inc luding concept des ign) 8 ,000 Late 2007 City o Melbourne Landscape design team withassistance rom Melbourne Water

Detailed Design WSUD 9,000 Feb 2008 City o Melbourne Engineering Services Group /Citywide / Connell Wagner

Detailed Design Conventional 15,000 Feb 2008 City o Melbourne Engineering Services Group /Citywide / Connell Wagner

Construction WSUD 90,000 June 30, 2008 City o Melbourne Engineering Services Group /Citywide / Ruccia Paving

Construction Conventional 150,0 00 June 30, 20 08 Cit y o Melbourne Engineering Ser vices Group /Citywide / Ruccia Paving

Implementation (non-structural) June 2008 City o Melbourne Tree Planning & WSUD Ocer

Consultation/ Community Engagement Feb June 20 08 Cit y o Melbourne Tree Planning

Other (e.g. Evaluation) July Dec 2008 City o Melbourne Tree Planning & WSUD ocer

Total cost 272,000

Transition single bluestone picherset and angled 150mm below channellevel on either side of tree pit,refer detail 4

Connect slotted pipe tounderground stormwater drain

45 UPVC T connection

Flushout riser standpipewith suitable cover upstreamof tree pit

150x3mm galvanised steeledging on 3 sides to form pit

Proposed plane tree (by others)2000

1800

flow

DETAIL1:20

3-

45flow

Precast concrete spike downkerb to match colour & finishof main kerb (have not provedsuccessful and have neededa re-design to cast in-situ exposed concrete kerbs)

UPVC slotted subsoil drain(no sock)

UPVC unslotted standpipe riserwith suitable removable grateto top of pipe

UPVC sewer class stormwaterdrain where shown

Single row bluestone pitcherchannel

Lift and reset existing precast

exposed agregate kerb

Remove bluestone pitcherchannel (subject to meetingheritage requirements)

45 UPVC T connection with150mm to 75mm connection fitting

C

-

2000

1800

Bluestone pitcher channellowered by - 100mm.Transition on sides

Centre of pit to be finished100mm below roadway height.Transition height from pit edges

Mulch with 50mm depth7-19mm recycled no finesrock aggregate(Alex Fraser or approved equiv)

Steel edge on 3 sidesto form pit. Ashphalt flushto steel edge

Advanced tree plantingin centre of tree pit

Plant groundcover at300mm centres

Precast concrete spikedown kerb to match colour& finish of main kerb

footpath

precast concrete kerb

channel


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Model WSUD Guidelines Part 3 Case Studies

116

Perormance

The WSUD design exceeded the best practice stormwater quality pollutant load reduction targets,as evaluated by the stormwater quality model, MUSIC.

Table 2 below show the MUSIC model results.

Table 2. MUSIC modelling

PollutantTreatment perormance

(kgs reduced)Treatment perormance

(% reduced)Best Practice Target

(% reduced)

Total Suspended Solids 565.7 88.7 80

Total Phosphorous 0.987 74.9 45

TotalNitrogen 4.51 47.2 45

Gross Pollutants 122 100 70

Note:Loadreductionsarebasedonthetypicalurbanannualload,asmodelledbyMUSIC.

Greenhouse impact

There are no ongoing CO2 emissions rom this project. Embodied energy impacts exist rom:

Materialchoice(e.g.PVCpipes,sandandgravel) Transport.

Risk management/issues

The construction o raingardens into the streetscape alls into the usual scope o works or streetscapesand does not thereore pose any greater risk to trac or pedestrians than usual civic works.

The sunken design o the raingardens has been mitigated as a pedestrian risk by the use o mulchtopping and dense planting. This will need to be maintained.

The end use o the water is not or reuse purposes. It will be entering the stormwater and ultimately thewaterway and will not be directly in contact with people. This negates the need to treat to high Class Astandards. The design o the raingardens will treat the stormwater to a standard that reduces the risk tothe environment by removing pollutants that would have otherwise entered the waterways.

Applicability

The project was designed so this orm o raingarden could be used in other residential streetscapesoutside the CBD area, where new trees need to be installed in the parking lane.

Post-project reection

The exclusion o the kerb-outstand raingarden is regrettable. This could be avoided in the uture by:

Improvedanalysisoflevelchangesbetweenfootpath,roadandraingardensurface

FirmCouncilpolicyonpedestriansafetyforsuchsystems.

Maintenance requirements and issues

WSUD tree pit maintenance tasks are described in the table below.

Table 3. WSUD Tree Pit Maintenance Tasks

Parks Activity reports Every 12 weeks

ESG Activity reports Every 12 months

Inspection items Works tasks Frequency

Sediment accumulation at infow points? Remove or suck out sediments.Notifycouncilifrecurringproblemtoenableinvestigationo sediment source

12 weeks

Litter within pit? Remove litter 4 weeks

Erosion at inlet or around tree? Invest igate why erosion is occur ing .Top-up missing gravel mulch, top-up missing media(FAWB specication)

4 weeks

Trac damage present? Repair / replace missing or damaged partsBollards needed?

4 weeks

Evidence o dumping (e.g. building waste)? Re-instate media and vegetation as required to originalspecications (FAWB specication).

4 weeks


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Inspection items Works tasks Frequency

Tree condition satisactory(Foliage, bark, roots)?

Weed growth should be minimal.Spray with herbicide i necessary

4 weeks

Replanting required? Re-instate and water as necessary. 4 weeks

Clogging o drainage points(sediment or debris)?

Remove leaves, litter or sediments 4 weeks

Evidence o ponding? Rack top layer o the media and replace by sandy soil(FAWB specication). Inltration testing may be required

12 weeks

Set down rom pit cover still present? Maintain / reinstate as per design level. 12 weeks

Damage/vandalism to structures present? Repair / replace missing or damaged parts.Talk to an enorcement ocer

12 weeks

Surace clog ging visible? Testing o inltration media to ensure perormance asspecied.

12 months

Drainage system inspected? Lit lids and inspect pits. 12 months

Resetting o system required? Engage designer / consultant 5 -10 years

Diagrams o treated areas


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Household

1. Water sensitive homes

2. Household rainwater tanks

3. Sizing a rainwater tank

4. Porous paving

5. Site layout and landscaping

Developers, Council planners, architects, engineers

6. Water conservation initiatives

7. Waterway rehabilitation

8. Rainwater tanks

9. Gross pollutant trap

10. Sedimentation (settling)11. Ponds and lakes

12. Vegetated swales and buer strips

13. Raingardens

14. Raingarden tree pit

15. Surace wetlands

16. Subsurace ow wetlands

17. Suspended growth biological processes

18. Fixed growth biological processes

19. Recirculating media flter

20. Sand and depth fltration

21. Membrane fltration

22. Disinection

Part 4

Water Sensitive

Urban Design (WSUD)Fact Sheets

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Introduction

Part 4 o the Model WSUD Guidelines includes a list o Fact Sheets or either households or developers/

council sta. They describe the likely benets, dierent congurations, constraints and designconsiderations or a range o WSUD elements and include:

HouseholdFactSheets(FactSheets1-5)

Waterconservationinitiatives(FactSheet6)

Waterwayrehabilitationprograms(FactSheet7)

Treatmenttechnologies:

Stormwater treatment (Fact Sheets 8 to 16)

Wastewater treatment or reuse (Fact Sheets 16 to 22).

WSUD elements discussed in this section cover a wide range o applications at dierent project (land)scales, including:

Sitelevelrunofffromsinglesites

Precinctgroupsofhousesorstreetscapescale

Regionalapplicableforlargerscaleswherelargercatchmentareasareinvolved.WSUD elements can also be categorised according to the user and application type to which they aretypically relevant, as shown in the table below.

Application scale Users Development Type

Small Householders Residential

Medium DevelopersArchitectsLandscapearchitectsEngineers

Multi-unit and mixed use development

Large DevelopersArchitectsLandscapearchitects

Engineers

GreeneldsBrowneldsLargescaleredevelopment

CommercialandindustrialdevelopmentBroad Council sta, including:

EngineersParksofcersDesignersPlanners

Council landscapes such as parks andgardens, streetscapes, and public squaresand plazas

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Model WSUD Guidelines Part 4 Fact Sheets

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Table 1 .WSUD elements, their Fact Sheet number and key selection characteristics

User

FactSheet

number Fact Sheet

Stormwater

W

astewater

A

esthetic

v

alue

Application Type

Q

uality

R

etention

S

mall

M

edium

Large

B

road

Household 1. Water sensitive homes

2 . Household rainwater tanks

3 . Sizing a rainwate r tank

4. Porous paving

5. S ite layout and landscaping

Developers,Council planners,architects, engineers

6. Water conservation ini tiatives

7. Waterway rehabilitation

8. Rainwater tanks

9. Gross pollutant trap ? 10. Sedimentat ion (settl ing) ? ?

11. Ponds and lakes

12. Vegetated swales and buer str ips

13. Raingardens

14. Raingarden tree pit

15. Surace wetlands ? ?

16. Subsur ace fow wetlands ? ? ?

17. Suspended growth biological processes ?

18. Fixed growth biological processes ?

19. Reci rculat ing media lter ?

20. Sand and depth ltration ?

21. Membrane ltration ?

22. Disinection ?

= Primary purpose ? = Some impact but not primary purpose = Does not contribute=notapplicable?=possiblyapplicable=applicable


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Fact Sheet 1: Water sensitive homesSmall Medium Large Broad

What is a Water Sensitive Home?

Beore we built houses, rainall would naturally soak into the ground and slowly fow to our creeks and rivers.

Today, with so many houses and concrete suraces, rain all ing onto a houseblock or runo rom watering gardensfows to the nearest underground drain and piped quickly to the nearest creek carrying with it pollution that can harmour waterways.

The main components ound in stormwater pollution are large quantities o substances such as nitrogen and phosphorus,heavy metals and ne sediments. Some o these pollutants are rom natural sources, such as nitrogen rom atmosphericdeposition. Most however, are rom garden ertilizers, litter, construction sites and cars. All o these are washed intowaterways ollowing rainall.

The amount o stormwater pollution that is actually generated rom a single house and garden is not high, but collectivelyour entire neighbourhood hurts our local waterway.

A suite o initiatives through Local Government, State Government and Melbourne Water are encouraging developers and

builders to protect our waterways and bays rom stormwater pollution through onsite Water Sensitive Urban Designstormwater treatment (WSUD). WSUD measures are simple treatment measures that collect, reuse and treat rainall thatalls onto your block. By improving the quality o stormwater beore it reaches the local waterway, you are helping to:

Delayandreducethevolumeofstormwaterdischargetostreams Improvewaterqualityinstreamsandgroundwater Usewaterresourcesmoreefciently Protectstreamandriparianhabitats Preventerosionofwaterways Protectthescenicandrecreationalvaluesofstreams

How do I make my home stormwater sensitive?

A stormwater sensitive home is one in which the dwelling and itssurrounding land are designed and used so as to minimise harmul

impacts on the natural water cycle.By collecting and reusing stormwater in the home, and treating thestormwater to improve its quality beore it leaves the houseblock,a stormwater sensitive home will help keep our rivers, streams andbays healthy.

The solution is simple and you are part o it.

How do I improve the quality o stormwater leavingmy block?

Improving the quality o stormwater that leaves your block can beachieved simply. Victorian standards or treating stormwater now existandrequiretheremovalof80%ofsuspendedsolids,45%oftotalNitrogenand45%oftotalPhosphorusfromstormwaterrunoff.

There is enormous scope or creativity when designing new homesor rebuilding an old one so that they incorporate a variety o WSUDtreatments to meet the standards. Treatments can include rainwatertanks plumbed to a toilet, raingardens, or porus pavements installedinstead o concrete pavements.

There are 4 additional act sheets in this series that outline someo the commonly used stormwater treatment measures suitable ormaking your home stormwater sensitive.

Fact sheets include:

1. Rainwater tanks 2. Porus Paving 3. Raingardens 4. Site layout and landscaping

Changes to water fowsin urban areas


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122

Fact Sheet 2: Household rainwater tanksSmall Medium Large Broad

How does a rainwater tank help protect our

local streams?Most people install a rainwater tank primarily to harveststormwater rom their roo and conserve their mainswater use. In addition to conserving water, a rainwatertank also helps treat stormwater and protect localstreams rom high storm fows by reducing the volumeo stormwater and quantity o pollutants coming roma house block that would otherwise be delivered to thelocal stream.

What do I use my tank water or?

Garden irrigation, laundry and toilet fushing consume much o our home water use. In most cases these uses do notrequire the water to be o drinking quality standard that is provided by mains water. By plumbing your rainwater tank to

your toilet or laundry and substituting these mains water needs with the rainwater harvested rom your roo, you canconserve mains water whilst reducing the amount o stormwater that enters our streams.

Why cant I use my rainwater tank or my garden alone?

So that your tank is not too ull to collect rainwater when it rains, you need to be consistently using your tank waterall year round.

I tank water is used or your garden alone, your tank will remain ull and unused during the winter months when yourgarden does not require watering. With a ull tank, your capacity to capture and store the regular winter rainall and thusbenet the local waterway is signicantly reduced.

By plumbing your rainwater tank to your toilet or laundry, your tank water is used consistently all year round allowingrainall to rell the tank more oten especially in winter. This ultimately reduces the volume o stormwater that is deliveredto the stream and the quantity o pollutants that are washed with it.

The Victorian Government has recognised the importance o plumbing your tank to your toilet and oers a cash rebateor the installation o connected rainwater tanks (www.dse.vic.gov.au). In addition, a 5 star energy standard has beenintroduced that requires a connected 2000Lt rainwater tank or solar hot water service to be installed in all new housesand apartments (class 1 and 2 buildings). (www.buildingcommission.com.au).

How do I choose a rainwater tank?

The most important thing to consider when choosing a rainwater tank is to rst identiy what you want rom yourrainwater tank. The size and type o rainwater tank you choose will vary depending on your homes water needs and thereliability you seek rom your rainwater tank supply. There are a number o actors that may infuence this and theollowing questions should be considered when planning your tank installation:

whatisthewaterdemandofyourhome? howmanypeoplearelivinginyourhome?

whatisyourintendeduseofrainwater? whatreliabilitydoyouwantfromyourtank? whatisthetotalareaofroofdrainingintoyourtank? whatisaveragerainfallofyourarea? doyouneedextraslikeapressurepump,theabilitytotopupyourtankwithdrinkingwater,abackowprevention

device or a rst fush device? arethematerialsusedonyourroofsuitabletocollectrainwater? aretherephysicalconstraintsofyourpropertythatmayinuencethetypeofrainwatertankyouneed?

Once you know how much water you can collect and how much water you are going to use then a tank size can beselected to provide the reliability o water supply that you need.


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Types o rainwater tanks

Rainwater tanks come in a variety o materials, shapes and sizes and can be incorporated into building design so theydont impact on the aesthetics o the development. They can be located above ground, underground, under the house orcan even be incorporated into ences or walls.

There are three main tank systems to consider and a variety o materials to choose rom. Features o these are outlinedbelow and in the pictures above:

Tank systems:

Gravity Systems - rely on gravity to supply rainwater to the household and the garden by placing the tank on a standat height.

Dual Supply Systems - top your rainwater tank with mains water when tank level is low ensuring reliable water supply.

Pressure Systems - use a pump to deliver rainwater to household and garden xtures.

To reduce the amount o sediment and debris entering a tank, mesh screens and rst fush diverters can be tted.A screen will lter large debris such as leaves and sticks while rst fush diverters store the rst fush o the rainall thatcarries the sediment and other pollutants initially washed rom your roo (see gure below).

Costs & rebates

Costsofinstallingatankvaryhoweverastandard2000Lttankorbladderwillcostaround$1000.

Additional plumbing and/or Abovegroundtankscostapproximately$250fora500litretank. Belowgroundtankscostbetween$300-$600per1000litresofstorage Thecostsofpumpsstartfrom$200.

Additional plumbing and/or excavation costs vary on intended use, pipe layout, materials and site accessibility.

TheVictorianGovernmentoffersatotalrebateof$300fortheinstallationofarainwatertankthatisplumbedtotoiletandconnected by a licensed plumber. For urther details reer to the Department o Sustainability and Environment websitewww.dse.vic.gov.au.

First flush diverter added to a tank

to tankfrom roof

tank

Fact Sheet 2: Household rainwater tanksSmall Medium Large Broad


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The eectiveness o a rainwater tank installation is infuenced by:

Howoftenitrains(rainfallpatternsorrainfallfrequency) Howharditrains(rainfallintensity).

There are two key questions that aect the size o the tank: Howbigisyourroof? Howwillthewaterbeused(fortoiletushingorgardenwatering)?

How to calculate appropriate tank size

1. Calculate roo area (m2)2. Decide i you are using the water or toilet fushing, garden use, or both.

Toilet ushing Calculatehowmanypeopleper100m2 o roo area Readoffthesupplyreliabilityfordesiredtanksize.

Outdoor use Calculatethegardenareathatyouwater Determinegardenareaper100mofroofarea

Fact Sheet 3: Sizing a rainwater tankSmall Medium Large Broad

Example: Toilet ushing

A typical household example is shown below. Roofarea=250m2 Desiredreliabilityofsupply(tomeetdemand)=90% Rainwateristobeusedfortoiletushing

Therearefourpeopleinmyhousehold.

Step 1 Convert the number o people to per 100m 2roo area: 4 people per 250 m2 = 1.6 people per 100m2

Step 2 Use the toilet fushing tank sizing curve belowtoworkouthowtoachieve90%reliability: Ineedatankthatisapproximately0.8%of250m 2 = 2 m2

Step 3 Calculate the tank area: 2m2 x depth 1m = 2m3 (2 kL).

Result On average, a 2kL rainwater tank will meet myhouseholds fushing requirements.

Example: Outdoor useA typical household example is shown below. Roofarea=150m2 Desiredreliabilityofsupply(tomeetdemand)=50% Rainwaterisusedforoutdooruse Gardenareais250m2 but I only water 120m2 o my

garden (so I use this gure).

Step 1 We need to work out the amount o garden areaper 100m2 o roo area. Divide garden area by roo areaand multiply by 100m2, i.e: 120m2/1.5 = 80 m2 garden areaper 100m2 o roo area

Step 2 Use the outdoor tank sizing curve below to work out

howtoachieve50%reliability: Ineedatankthatisapproximately1.5%ofthe150m2 = 2.25 m2.

Step 3 Calculate the tank area: 2.25m2 x depth 1m = 2.25m3 (2.25 kL)

Result Onaveragea2.25kLrainwatertankwillsupply50%ofmy outdoor watering requirements.

100

90

80

70

60

50

40

30

20

10

0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Tank size as % of roof area (tank assumed to be 1m deep)

Tank sizes for outdoor use Melbourne

Figure 2: Rainwater tank sizing curve foroutdoor use in Melbourne

25m garden/100m roof50m garden/100m roof

75m garden/100m roof100 garden/100m roof

Reliability

(%o

fsupply)

100

90

80

70

60

50

40

30

20

10

0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0


Tank sizes for toilet flushing reuse Melbourne

Figure 1: Rainwater tank sizing curve fortoilet flushing in Melbourne

0.8 people/100m roof1.6 people/100m roof2.4 people/100m roof3 people/100m roof4 people/100m roof5 people/100m roof

Reliability

(%o

fsupply)


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MUSIC and STORM modelling programs

MUSIC is a stormwater modelling program which can calculate sizing curves or tanks based onhistorical rainall data or a location. The water use can be set as constant (e.g. toilet fushing) or to varywith the season such as garden watering. Outdoor use is typically greater in summer and the outdoor

curve accommodates this variation.MUSIC can be accessed at http://www.toolkit.net.au/music, but requires a licence (a trial version isavailable ree or a limited time).

STORM is an online calculation tool rom Melbourne Water which is based on MUSIC results.This provides reliability estimates or tanks based on roo area, tank size and location within Victoria.Changing these parameters until the desired reliability is achieved will provide the tank size required.

STORM can be accessed ree at: http://storm.melbournewater.com.au/.

Installation

A licensed plumber is required to install the rainwater tank with all installations conorming toAustralian standards (AS3500.1.2 Water Supply: Acceptable Solutions)37.

Planning approvalInstallation o tanks within Heritage Overlay areas and tanks larger than 4,500 litres in the City oMelbourne require a planning permit.

Tanks outside Heritage Overlay areas, and smaller than 4,500 litres, have Victorian Governmentexemption (Clause 62.02 o the Victoria Planning Provisions).

The City o Melbourne can advise on exemptions and planning permit requirements.

Planning permits

Most properties must lodge a planning permit or a rainwater tank due to the heritage nature o theCityofMelbourne.Forworkslessthan$10,000onasingledwellingonalot,thereisnofeeforaplanning permit. The planning permit only needs to address issues relating to heritage. This usuallyconcerns the visibility o the tank rom streets or laneways, and its eect on existing building abric.

Heritage Victoria permits

Buildings listed on the Victorian Heritage Register will require a Heritage Victoria permit under theHeritage Act 1995. Once approved, a planning permit is not required.

Building permits

The weight o a water tank can impact on a buildings structure. For water tanks installed withinthe building abric, such as in a roo space, under raised foors or in the upper foors o an apartmentbuilding, a building permit may be required. The City o Melbourne can provide urther advice.

37 Reer to the Green Plumbers (ww w.greenplumbers.com.au) and the Plumbing Industry Commission (www.pic.vic.gov.au) or additional inormation.


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126

Fact Sheet 4: Porus pavingSmall Medium Large Broad

Why install porous pavements?

In urban environments, paved suraces such as roads,driveways and courtyards cover a signicant area.These impervious suraces do not allow rainall to soakthrough them to the underlying soil and as a resultcontribute to larger amounts o stormwater enteringinto our streams than would otherwise naturally occur.These stormwater fows carry with them pollution thathas been washed o rom roads, pavements and roos.The rapid pace that stormwater is delivered to the streamcontributes to bank erosion and habitat scouring.

To protect our streams rom this occurring, we need to reduce the amount o impervious suraces in our urbanareas so that less water and pollutants are washed o and delivered quickly to the stream.

One way to do this is to install porous pavements instead o traditional concrete pavements in our backyards anddriveways. Porous pavements reduce the amount o runo by allowing water to soak through the surace and into theunderlying soil.

How porous paving works

By using porous paving that allows rainwaterto soak through to the soil instead o standardconcrete or block pavers, you can:

reducetheamountofimpervioussurfaceson your block

increasegroundwaterrechargebyallowingthe water to soak through the soil

improvestormwaterqualitybyltering

stormwater and reducing pollutant loads reducehighowsenteringthewaterway

rom urban areas causing stream erosion andhabitat scouring

How does porous paving work to treat stormwater?

Porous paving is installed just like traditional paving and comes in many orms. It can be asphalt, or modular pavers that areconcrete, ceramic or plastic.

Porous paving contains surace voids that are lled with sand or gravel that lter the stormwater. They overlay a gravelretention trench that allows greater capacity to retain stormwater. During heavy rain, excess stormwater overfows to thestreet drainage systems when the trench becomes ull.

To maximise its capacity to allow water to soak through to the underlying soil, porous pavements should not be installed

over rock or other substrate that has little or no capacity to allow water to inltrate through it.

Maintenance

Concrete grid, ceramic and modular plastic block pavers require less maintenance than asphaltic porous paving as they areless easily clogged by sediments. To ensure their eectiveness and liespan, porous paving should be:

Protectedfromshocksedimentloadsespeciallyduringandshortlyafterconstructionwhencloggingmayoccur Inspectedforcracksandholesandreplacedasnecessary Cleanedfromaccumulateddebrisandsediment Weededormowedwhereappropriate(largelyforaestheticpurposes)

When properly maintained porous paving should have an eective lie span o at least 20 years.

Costs

Costsofporouspavingdependonthetypeofmaterialusedandrangefrom$70-$120persqm.(MelbourneWater,2005).Cost to install porous pavements are similar to other pavements.

Porous pavers

Sand/gravel

Geotextile fabric

Geotextile fabric

Infiltration to subsoil

Retention trench(coarse gravel)

Overflow pipe

Rain


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Incorporating water sensitive measures

There is enormous scope when designing new homes and retrotting existing homes to incorporate water sensitivemeasures such as rainwater tanks, porous pavements and raingardens. By thinking about your site and its eatures beoreyou begin, you can make the most o layout opportunities or your treatment measures. Things to consider when makingyour home stormwater sensitive include:

1.Naturalsitefactors2. Choice o treatment measures3. Plant selection4. Protection during construction

What to consider when designing the layout o your stormwater sensitive site

1. Natural site actors

Understanding your sites topography, rainall, existing drainage patterns, expected fows, soil, vegetation and sun/shade

patterns beore you begin can help you plan the layout o your stormwater treatment measures. By understanding andincorporating the natural site eatures o your site into your design, you can maximize the eectiveness o your treatmentmeasures whilst creating aesthetically pleasing surroundings or your home.

2. Choice o treatment measures

Runo rom your block mainly comes rom your roo and pavement. Rainwater tanks, raingardens, buer strips and porouspavements call all be used to treat rainwater runo. Exactly how your site ultimately looks will depend on your creativity,individual needs and the individual site actors you are working with. There is a lot o scope to be creative in your layoutand it is important to remember that you are not constrained by using just one treatment measure. You may choose tocollect runo rom your roo and direct it to a raintank to supply water or toilet fushing, or you may choose to direct yourroo runo to a raingarden. You may even choose to do both. By knowing the amount o rain and runo you receive andwhere you sun and shady areas are will help you to design the best layout or your stormwater treatments whilst creatingthe home surroundings you desire.

3. Plant selectionA wide variety o plants are suitable or your stormwater treatment measures with characteristics that incorporate thenecessary treatment unction and your aesthetic preerences. Choice o plants will depend on your visual preerencescoupled with their suitability to your sites soil and climatic conditions whilst withstanding periods o soil saturation andanaerobic conditions. Preerence should be given to local native species and it is wise to check with your council that theplants you choose are not environmental weeds in your area.

4. Protection during construction

It is important to protect both your stormwater treatment measures and the stormwater drains rom excess sedimentbeing washed into them during the construction phase o your site. Without adequate protection during this time,stormwater treatment measures can become clogged with dirt and soil washing rom your site. Clogging risks their abilityto adequately treat stormwater and it is likely that the clogged treatment measure will will need to be cleaned out.Using sediment ences to capture dirt and soil coming rom your site is an easy way to protect your stormwater treatment

measures, and your local stream rom being smothered by i loads are not captured along the way.By considering your site actors beore you begin it ispossible to create a stormwater sensitive home that suitsyour individual needs. The gure (right) shows one possibleoverall water sensitive strategy or a typical suburbanhome. A rainwater tank collects hal o the roo runo andis plumbed to supply rainwater or toilet fushing andoutdoor use. The remaining roo runo is directed into araingarden. Stormwater runo rom paths, driveways andlawns is directed to garden areas. Concrete imperviouspavements have been replaced with porous pavements anda buer garden area is protecting any excess runo romreaching the road and into the conventional stormwaterdrainage system.

Fact Sheet 5: Site layout and landscapingSmall Medium Large Broad

Road

Grassed area

Garden

Garden buffering edge of property

Garden planted

with native

species

TankRoof water drain totank plumbing inside

Roof drainingto rain garden

Carportdirectedto gardenarea

Rain gardenplanter box

Porous paving

Porous paving


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Fact Sheet 6: Water conservation initiativesSmall Medium Large Broad

Supplying potable (drinking) water to Melbourne is increasingly becoming a dicult task. There is already a strain on

existingwaterresources.Newdevelopmentwillputfurtherpressureonpotablewaterresourcesunlessdemandisreduced.

Finding sources o potable and reusable water

Matching the intended use o the water to its required quality (and thereore its source) achieves the most signicantsavings or potable water demand. Most domestic, commercial and industrial water does not need to be o potable quality.Depending on what water is required or, it could come rom dierent sources.These include: Roofrunoff/rainwatertanks Greywater(fromlaundryandbathroom) Reclaimedwater(fromlocalwastewatertreatmentplants) Recycledplantwater(atanindustrialpremise).

Consider the ollowing issues when determining an appropriate source o reuse water: Availabilityofsecondarysource Proximitytouse Potentialcostofconstructionofextrainfrastructure Riskofcrossconnectionsbetweenpotableandreusedwater(healthimpacts) Treatmentrequirementsbeforereuse Applicationusageandmethodofthereusedwater Broaderenvironmentalobjectives(includinggreenhouseemissions).

Prioritising options or water reuse

A hierarchy o options or water reuse is listed below. The options are ordered rom the easiest to implement to the mostextensive water reuse. To determine the best option or a development, consider the: Scaleofthedevelopment Proximitytotreatmentfacilities Pressureonpotablewaterdemand.

The recommended hierarchy or household reuse options is:1. Rainwater reuse or the toilet and garden2. Rainwater or hot water, household greywater or garden and toilet3. Stormwater reuse or garden4. Recycled water to toilet and garden, rainwater or hot water.

The alternative water source hierarchy has been set out in a broader context in Module 2.2 Scoping the Options o theWSUD Guidelines.

Managing demand

Make better use o water to achieve signicant savings through: Changesinconsumerbehaviour

Useofwaterefcientdevices.Education initiatives are the best way to change behaviour. Usually they are carried out by local water authorities.

Examples o education initiatives on demand management include: raisingawarenessoftheimportanceoftapmaintenanceandleakagedetectiontosavepotablewatersupplies educatingcommercialbuildingsofopportunitiesforincreasedefciencyintheircoolingtowers,toiletsandotherwater

using areas raisingawarenessofchangestoregulationsandstandardsimpactingwateruse,suchashasrecentlyoccurredwithre

testing in commercial buildings educatingCityofMelbournestafftoparticipate,collaborateandinnovateinsustainability.


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The WELS (Water Efciency Labelling and Standards) scheme

Melbourne households generally dont use water eciently. The WELS (Water Eciency Labelling and Standards)scheme rates the water eciency o water appliances such as:

Showerheads

Washingmachines

Toilets

Dishwashers(onetosixstarsaregiven).

The scheme increases the use o water ecient devices and encourages improved practices in residential dwellings.

Water usage (per litre) must be part o product labelling, according to the scheme. The more water ecient the product is,the more stars it will have. This is similar to the energy eciency rating.

More inormation on the WELS scheme can be ound online at www.waterrating.gov.au. The Green Plumbers are a goodsource o water saving assistance in the household. Call 1800133871 or log onto: www.greenplumbers.com.au

Reducing consumption

Areductionofaround15-40%inwaterconsumptioncanbeobtainedby:

Adoptingwaterefcientappliancesandttings

Changingbehaviour.

Garden designs that use water eciently through plant selection and zoning o vegetation types can also reduce waterdemands considerably. Using indigenous vegetation can vastly reduce irrigation.

For advice on sustainable gardening, visit a nursery that is accredited by Sustainable Gardening Australiawww.sgaonline.org.au

For more inormation on householder initiatives, reer to Fact Sheets 1-4.

Fact Sheet 6: Water conservation initiativesSmall Medium Large Broad


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Fact Sheet 7: Waterway rehabilitationSmall Medium Large Broad

Waterway rehabilitation aims to mimic the natural

waterway system. Important considerations include: Vegetationselection

Stabilisationofthewaterway

Adequateoodconveyance

Appropriatehydrologicregime.

Community value

Rehabilitated waterways can be very popular recreationareas within communities (e.g. Moonee Ponds Creek and theYarra and Maribynong Rivers). Frequently used as linearparks, they:

Attractwalkers,bikeriders,birdwatchers

Provideurbanretreats

Helptopromoteappreciationofwaterwaysandtheirecologicalvalues

Canimprovepropertyvaluesofsurroundingareas.

Hydrologic conditions

In the City o Melbourne, the hydrologic regime o waterways has been drastically changed. In the short term, its notpossible to return a waterway to pre-urbanisation conditions.

Pollutant control

Upstream runo requently requires some pollutant control, particularly or litter, debris and coarse sediments. These canimpact the aesthetics o a waterway as well as smothering habitats, generating odours, attracting pests and depositingdangerous materials.


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Fact Sheet 8: Rainwater TanksSmall Medium Large Broad

Rainwater tanks collect water runo rom roo areas.

They can provide a resource o non-potable water in theCity o Melbourne.

Tank design

Tanks can be incorporated into building design so theydo not impact on the aesthetics o a development or thesurrounding environment. They can be: Sympathetictoheritageareas Locatedunderground Incorporatedintofenceorwallelements.

Tank sizing

In general, tanks are sized according to their intended demand

and available roo catchment. For example, i tank water willbe used or toilet fushing and hot water systems, the right sizeo tank can achieve the desired level o reliability.

Figure 1 use Melbourne rainall data and typical demandvalues (rom 3 star rated appliances). The curves size tanksrelative to the roo area and the occupancy rate. Generallyrainwater harvesting becomes uneasible i the roo areais less than 15m2 per person.

I the water demand (or occupancy number) and roo areasare known, a tank can be selected with reerence to Figure 1.Use the reliability o supply (percentage o water needssupplied) to work out optimal tank size. Marginal gain isattained by installing a tank larger than approximately2-4%ofroofarea(dependentondemand).Theincreasedtanksize and cost must be evaluated against additional potablewater conservation.

Inner city residential tanks

An inner city residential tank is usually 1.5 to 3 kL (kilolitres). However this depends on roo area and water use.

Use a top up rom potable water supplies to cover the shortall in demand. This is achieved by: Plumbingpotablewaterintothetankwithanairgap Havingaoatactivatedswitch Preventingcrosscontaminationbyusingappropriatevalves.

Integrated management systems are available that can automate rainwater use throughout the household.

Installation

Rainwater tanks can be tted with rst fush diverters. These are simple mechanical devices that divert the rst portiono runo volume (that typically carries debris and contaminants) away rom the tank. Ater the rst fush diversion, waterpasses directly into the tank. Collected roo runo water is suitable or direct use or garden irrigation or toilet fushingwith no additional treatment. Tank water can also be used in hot water systems, although some additional treatment toremove the risk o pathogen contamination is required. This generally involves UV disinection, and ensuring that the hotwater service maintains a temperature o at least 60-70C, subject to City o Melbourne approval. A licensed plumber isrequired to install the rainwater tank with all installations conorming to Australian standards (AS3500.1.2 Water Supply:Acceptable Solutions)45.

120L/day/100m roof140L/day/100m roof160L/day/100m roof180L/day/100m roof200L/day/100m roof

20L/day/100m roof40L/day/100m roof60L/day/100m roof80L/day/100m roof100L/day/100m roof

100

90

80

70

60

50

40

30

20

10

00.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0


Tank sizes for general water reuse Melbourne

Figure 1: General use tank sizing curve

for Melbourne

Reliability

(%o

fsupply)

44 Reer to the Green Plumbers (ww w.greenplumbers.com.au) and the Plumbing Industry Commission (www.pic.vic.gov.au) or additional inormation


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Planning approval

Installation o tanks within Heritage Overlay areas and tanks larger than 4,500 litres in the City o Melbourne require aplanning permit.

Tanks outside Heritage Overlay areas, and smaller than 4,500 litres, have Victorian Government exemption (Clause 62.02o the Victoria Planning Provisions).

The City o Melbourne can advise on exemptions and planning permit requirements.

Planning permits

Most properties must lodge a planning permit or a rainwater tank due to the heritage nature o the City o Melbourne.Forworkslessthan$10,000onasingledwellingonalot,thereisnofeeforaplanningpermit.Theplanningpermitonlyneeds to address issues relating to heritage. This usually concerns the visibility o the tank rom streets or laneways, and itseect on existing building abric.

Heritage Victoria permitsBuildings listed on the Victorian Heritage Register will require a Heritage Victoria permit under the Heritage Act 1995.Once approved, a planning permits not required.

Building permits

The weight o a water tank can impact on a buildings structure. For rainwater tanks installed within the building abric,such as in a roo space, under raised foors or in the upper f oors o an apartment building, a building permit may berequired. The City o Melbourne can provide urther advice.

Fact Sheet 8: Rainwater TanksSmall Medium Large Broad


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Fact Sheet 9: Gross Pollutant Traps (GPTs)Small Medium Large Broad

Gross pollutant traps (GPTs) are commonly installed by council and developers to manage stormwater pollution.

GPTs retain litter and debris rom stormwater systems primarily through screening. Some GPTs also remove bed loadsediments and some suspended sediments through rapid sedimentation.

GPTs are mainly used in existing conventional drainage systems either in pipes, at outalls, or in open channels. However,they can also be used as pre-treatments or other WSUD elements. They aim to retain solid litter that has washed into thesystem but not retard fows or increase water levels in the drainage system considerably.

Many WSUD elements dont need a GPT. In particular, when there is streetscape and source control measures buering thestormwater drainage system rom contributing areas, the entry o litter and debris to the stormwater system is restrictedby ltration media. However, GPTs can be used in WSUD as a pre-treatment device when piped systems discharge intowaterways or wetlands.

Selecting a GPT product

Unlike other WSUD elements, a wide range o commercial GPT products are available rom more than 15 suppliers in

Australia. Dierent GPTs employ varying mechanisms o l itter separation and containment and their perormances canvary greatly. There are also GPTs intended or dierent catchment scales rom less than one hectare to more than100 hectares. Its important to select an appropriate GPT depending on specic conditions.

Sizing

Isolating high pollutant load generation areas is the key to locating a GPT. Use hydraulic considerations to size a GPTand minimise the amount o clean water that is treated. GPTs are generally sized to treat between the three-month toone-year ARI peak fow and work best with catchment areas less than 100 hectares. These design fow rates are basedontreatingmorethan95%ofannualrunoffvolume.

Type and brand

To decide on the type (and brand) o GPT, you need to balance:

Lifecyclecostsofthetrap(i.e.bycombiningcapitalandongoingcosts)

Expectedpollutantremovalperformance(inregardtothevaluesofthedownstreamwaterbody) Anysocialconsiderations(e.g.publicsafetyandaesthetics).

Cost

Use a lie cycle cost approach that considers ongoing operation costs and the benets o dierent traps assessed over alonger period. The overall cost o GPTs is oten more heavily infuenced by maintenance rather than capital costs.

Maintenance

Regular maintenance (cleaning) o GPTs is essential or their successul operation.

There is a maintenance commitment when a GPT is installed. Generally, this is at least a clean out every three months.However, it depends on the catchment characteristics and any source reduction initiatives that may be active in the area.

A poorly maintained GPT will not only cease to trap pollutants, but may release contaminants by allowing leaching romthe collected pollutants.


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Waterway Sedimentation removes pollutants in water through gravity settling. Sedimentation systems reduce fow

velocities and encourage particles to settle out o the fow. Coarse particles are removed more easily than ne particles.However a well perorming sedimentation system will let ner particles aggregate and then settle.

Sedimentation happens in many WSUD elements.For example: Sedimentbasins Tanks(storagetanks,balancingtanks,rainwatertanks,stormwatertanks) Pondsandlakes Wetlands.

All elements reduce fow velocity, increasing the retention time o the water and the settling o particles.

Design considerations

The key design parameters are: Sedimentsterminalsettlingvelocity(primarilydependentonparticlesize)

Hydraulicinformation(watervelocity,owrateandretentiontime).The sediment separation device can then be sized. For ner particles, characteristics such as their size, shape, structureand charge have a greater impact on removal.

Sediment basins

Sediment basins are used to retain coarse sediments rom runo. They are typically incorporated into pond or wetlanddesignssuchastheexclamationmarkwetlandattheNationalAustraliaBankforecourtatDocklands.

During periods without rainall, the basins can drain and then ll during runo events. They are oten used duringconstruction activities and as pre-treatment or elements such as wetlands (e.g. as an inlet pond).

Sizing

Basins are sized according to the design storm discharge, and generally designed to trap coarse sediments only (particle sizegreater than 0.125mm diameter). The large volumes o coarse sediments carried in stormwater require regular removal

rom the basin. These have generally low contaminant concentrations and should be kept separate rom the ne sediments.Fine sediments have the highest contaminant (hydrocarbon and metal) concentrations and higher waste disposal costs.Thereore sediment basins are mainly designed to retain coarse sediment.

Maintenance

Sediment basins must be maintained every two to ve years, depending on the catchment. This generally involvesdraining the basin and excavating collected sediments or landll. To drain the basin, either a sump is required in thedesign, or the sediment can be pumped, depending on the size. An access point or suitably sized excavators is also needed.For construction sites that produce very large sediment loads, de-silting is required more requently. A sediment basin willgenerally require resetting ater construction in the catchment area is complete.

Location

Available space and suitable topography are the two main considerations when locating a sediment basin. Howevertemporary basins can be constructed as turkey nest basins. Outlet controls are important or the basins extended

detention unction, as well as ensuring adequate settling time. Outlet structures should be designed or even detentiontimes. For example, a multiple level o-take riser will regulate fow to a wetland or pond.

Design

Depth can minimise vegetation (weed) growth and allow or adequate collected sediments storage, usually a minimum oone metre. Detailed design specications are available rom the WSUD Engineering Procedures: Stormwater manual46 .

Tanks, ponds and wetlands

Physical separation by sedimentation occurs in tanks, ponds and wetlands, primarily due to reduced fow velocities andstill conditions. For more inormation, reer to the appropriate Fact Sheet.

Advanced sedimentation systems

More advanced sedimentation devices such as clariers can be incorporated into black , grey and sewer mining watertreatment processes. These devices are typically a combination o mechanical and physical designs that enhance

sedimentation and reduce the necessary ootprint.

Fact Sheet 10: Sedimentation (Settling)Small Medium Large Broad

46 Available or purchase rom Melbourne Waters website (http://wsud.melbournewater.com.au)


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Fact Sheet 11: Ponds and LakesSmall Medium Large Broad

?

Ponds and lakes are articial bodies o open water usually

ormed by a simple dam wall with a weir outlet structure.Ponds in the City o Melbourne can be integrated intotheWSUDstrategy.Notonlydotheyprovideanaestheticquality, but they also provide a unction.

Typically the water depth is greater than 1.5m. There isusually a small water level fuctuation, although newersystems may have riser style outlets. This allows orextended detention and longer temporary infows storage.

Usage and benefts

Ponds promote:

Particlesedimentation

Adsorptionofnutrientsbyphytoplankton UVdisinfection.

Ponds provide valuable water storage that can potentially be reused as irrigation. Oten wetlands will fow into ponds andthe water body enhances the local landscape and can provide a wildlie habitat. Ponds or lakes can also be ocal points indevelopments, with houses and streets having aspect over open water.

Ponds can be used or water quality treatment. In particular, ponds are useul in areas where wetlands are uneasiblee.g. very steep terrain. In these cases, ponds should be designed to settle ne particles and promote submergedmacrophyte growth.

Vegetation

Aquatic vegetation has an important unction in water quality management in ponds and lakes. Fringing vegetation isnecessary to reduce bank erosion, and is aesthetically pleasing. However it has minimal contribution to water quality

improvement.

Stormwater treatment

Ponds are seldom used as stand-alone stormwater treatment measures. As a minimum, ponds require pre-treatmentwith sediment basins. These basins require regular sediment removal (reer to the Sedimentation (Settling) Fact Sheet ormore details).

Hydrologic conditions and inow water quality

There have been cases where water quality problems in ornamental ponds and lakes are caused by poor infow waterquality, especially high organic load, inrequent water body turnover and inadequate mixing. Detailed modelling may beneeded to track the ate o nutrients and consequential algal growth in the water body during periods o low infow(and thereore long detention period).

As a general rule, the mean turnover period or lakes during the summer periods should be less than 30 days, i.e. the lakevolume should not be greater than the volume o catchment runo typically generated over a 30 day period in thesummer months.

In the absence o these hydrologic conditions, it may be necessary to introduce a lake management plan to reduce the risko algal blooms during the dry season. In spite o this, there is oten an urban design desire to maximise the size o thepond as a ocal water eature or a residential development.

Further inormation

Additional Inormation or developers can be obtained rom Melbourne Waters Constructed Shallow Lake Systems DesignGuidelines or Developers available online at www.melbournewater.com.au/content/library/rivers_and_creeks/wetlands/Design_Guidelines_For_Shallow_Lake_Systems.pd


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Fact Sheet 12: Vegetated swales and buer stripsSmall Medium Large Broad

Swales

Vegetated swales can be used instead o pipes to conveystormwater and provide a buer between the receivingwater(e.g. Port Philip Bay, river, wetland) and the imperviousareas o a catchment.

Swales can be integrated with:

Landscapefeaturesinparksandgardens

Streetdesignstoaddtotheaestheticcharactero an area.

Pollutant settlement

As water fows over vegetation, its evenly distributed and the fow retarded. This encourages pollutant settlement andretentioninthevegetation.Totalnitrogen(TN)isgenerallythehardestpollutanttoremoveinswalesystems.

Flood ows

Pits draining to underground pipes can be used to convey food fows, in excess o the treatment design fow. Water overfowsrom the swale into a pit.

Slope

Thelongitudinalslopeofaswaleisanimportantconsideration.Slopesfrom1%to4%arerecommended.Slopesmilderthan this can become waterlogged and have stagnant ponding (although the use o subdrains can alleviate this problem).Whereslopesaresteeperthan4%,checkbanksalongswales,densevegetationand/ordropstructurescanhelptodistribute fows evenly across the swales and slow velocities.

Cross-section

Swales with trapezoidal cross-sections usually achieve better treatment outcomes than those with triangular cross sections.

Design issues

Design or swale, road or driveway cross overs must be careully considered. Driveway cross overs can be:

Anopportunityforcheckdams(toprovidetemporaryponding)

Constructedatgradetoactlikeafordduringhighows.

Vegetation type

Many dierent vegetation types can be used in swales. Vegetation should:

Coverthewholewidthoftheswale

Becapableofwithstandingdesignows

Beofsufcientdensitytoprovidegoodltration

Beselectedtobecompatiblewiththelandscapeoftheareaandmaintenancecapabilities.

For best perormance, vegetation height should be above the treatment fow water level. Some examples are shown inthe pictures.

Maintenance

Maintenance requirements are typical o standard landscaping. Vegetation growth and litter removal are the key objective.

Nitrogen removal

Swales are typically limited by their eectiveness in reducing total nitrogen levels. A bioretention swale may help i greaternitrogen removal is required (see the Raingardens Fact Sheet or urther details).

Sizing curves

Sizing curves relate the swale perormance to a percentage o the impervious catchment area to be treated. They relate thevegetationheight(Figure1)andtheswaleslope(Figure2)totheTNremoval.Thesizingcurvesareusedtoassessthetopwidth o the vegetated swale.


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Buer strips

Buer strips aim to provide discontinuity between impervious suraces and the drainage system. The key to their operation,like swales, is an even shallow fow over a wide vegetated area. Buers are commonly used as a pre-treatment or otherstormwater measures.

Set downs

Set down buer strips rom the road surace to:

Accountforsedimentaccumulationovertime

Allowfortheheightofthegrass(oncegrown)tobeslightlysetdownfromtheroadlevel.

The required set down is a trade o between creating scour rom runo and providing sucient build up space oraccumulated sediment. Generally between 40 and 50 mm set down rom the paved surace will be adequate with apavement surace that is tapered down towards the buer strip (as illustrated in Figure 3).

For detailed inormation, reer to Chapter 8 o Melbourne Waters Technical manual WSUD Engineering Procedures:Stormwater (2005).

Figure 3 Typical buer strip arrangement

Maintenance

Maintenance costs tend to be higher in the rst ve years, while the swale or buer is becoming established.

Grassedswalescostabout$2.50to$3.13/m2/year or the establishment period (approximately ve years) but i residents mow regularly, there is less cost to local authorities

Vegetatedswalescostabout$9/m2/year, ongoing.

Afterveyears,thecostforgrassswalesdecreasestoroughly$0.75$1.50/m

2

/year

40

.For a maintenance checklist, reer to the WSUD Engineering Procedures or Stormwater Manual41.

0.05m vegetation0.15m vegetation0.25m vegetation0.5m vegetation

0 1 2 3 4 5 6 7 8 9Swale Size (% of Impervious Catchment)

1% slope3% slope5% slope

100

90

80

70

60

50

40

30

20

10

0

Swale TN Reduction (varying slope)Swale TN Reduction (varying vegetation height)

Figure 2. TN reduction by a swale in Melbourneas slope varies (0.25m vegetation height)

%T

N

Reduction

0 1 2 3 4 5 6 7 8 9Swale Size (% of Impervious Catchment)

100

90

80

70

60

50

40

30

20

10

0

Figure 1. TN reduction by a swale in Melbourneas vegetation varies (3% slope)

%T

N

Reduction

40 EPA 2008, Maintaining water sensitive urban design elements, publication 122641WSUD Engineering Procedures: Stormwater, CSIRO 2005.

Road surface Sediment accumulation area

40-50 mm set down

Road edge Buffer strip

Fact Sheet 12: Vegetated swales and buer stripsSmall Medium Large Broad


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Fact Sheet 13: RaingardensSmall Medium Large Broad

In raingardens, stormwater runo is ltered through a

vegetated sand media layer. Its then collected throughperorated pipes so it can fow to downstream waterwaysor into storage or reuse. Temporary ponding above thesand media provides additional treatment.

Raingardens are not intended to be inltration systems asthe dominant path or water is not discharge intogroundwater. Any loss in runo is mainly attributed tomaintaining lter media moisture (which is also thevegetations growing media).

Vegetation

Vegetation that grows in the lter media enhances its unction by:

Preventingerosionoftheltermedium

Takingupnutrientsandwater Continuouslybreakingupthemediathroughplantgrowthtopreventcloggingofthesystem

Providingbiolmsonplantrootsontowhichpollutantscanadsorb.

Filtration media

Selection o an appropriate ltration media is a key issue that involves a trade-o between providing sucient:

Hydraulicconductivity(i.e.passingwaterthroughtheltrationmediaasquicklyaspossible)

Waterretentiontosupportvegetationgrowth(i.e.retainingsufcientmoisturebyhavinglowhydraulicconductivities)and remove pollutants.

Typically a sandy type material with a hydraulic conductivity o 100-300mm/hr is suitable. However media can be tailoredto a vegetation type.

Pollutant removal and sizing curvesRaingardens are typically limited in their ability to reduceTotalNitrogen(TN).Figure1showsadesigncurveforpreliminary sizing o rain gardens in Melbourne, relatingtypical perormance to a percentage o the imperviouscatchment. Best practice targets are the removal o:

45%TN

45%TotalPhosphorus(TP)

80%TotalSuspendedSolids(TSS).

Raingarden basins

The treatment process in rain garden basins uses physical

ltration o sediments through the lter media and theremoval o nutrients through the biological and chemicalinteractions, primarily again in the lter media.

Typically, food fows bypass the basin, preventing high fowvelocities that can dislodge collected pollutants or scour outmedia or vegetation.

These devices can be installed at various scales. For example:

Planterboxes

Retardingbasins

Streetscapesintegratedwithtrafccalmingmeasures.

0 0.2 0.4 0.6 0.8 1.6 1.8 2

0mm extended detention100mm extended detention200mm extended detention300mm extended detention

TN is generally thelimiting pollutant inbioretention systems

1 1.2 1.4

100

90

80

70

60

50

40

30

20

10

0

Bioretention System Surface Area (as a % of Impervious Catchment)

Melbourne (reference site) Bioretention TN Removal

Figure 1: TN removal by Raingardens in Melbourne

TN

Removal(%)


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Raingarden swales

Swale raingardens (reer to Figures 2 and 3) provide both stormwater treatment and conveyance unctions.

A raingarden is installed in the swales base. The swale component provides stormwater pre-treatment to remove coarse tomedium sediments while the raingarden removes ner particulates and associated contaminants.

A raingarden can be installed in part o a swale, or along the ull length o a swale, depending on treatment requirements.

Typically,thesesystemsshouldbeinstalledwith1-4%slopes.Insteeperareas,checkdamsarerequiredtoreduceowvelocities. For milder slopes, its important to ensure adequate drainage is provided to avoid nuisance ponding (a raingardenalong the ull length o the swale will provide this drainage).

Runo can be directed into raingarden swales either through direct surace runo (e.g. with fush kerbs) or rom an outleto a pipe system.

Figure 2: Typical swale raingarden section drawing

Figure 3: typical swale raingarden system adjacent to roadside plan and section drawing

Maintenance

Thetypicalannualmaintenancecostforaraingardenisapproximately5-7%oftheconstructioncost.Maintenancecostsare likely to be higher in the rst ew years due to the more intensive eort needed to establish the system.

The maintenance cost or mature raingardens are:

$2.50/m2 or grassed systems

$9/m2 or vegetated systems using native vegetation42.

For a maintenance checklist, reer to the WSUD Engineering Procedures or Stormwater Manual43.

0.3- 0.7m Filler media(approved filter sand)

Perforatedcollection pipe

Possibleimpervious liner

0.1m Transition layer(coarse sand)

0.15-0.2m Drainage layer(coarse sand/gravel)

0.2-0.5m

1-3m

0.6-2.0m

Vegetated swale Bioretention

Road surface

Overflow pit

Vegetated swale Bioretention

42 EPA 2008, Maintaining water sensitive urban design elements, publication 122643WSUD Engineering Procedures: Stormwater, CSIRO 2005.

Fact Sheet 13: RaingardensSmall Medium Large Broad


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Fact Sheet 14: Raingarden tree pitSmall Medium Large Broad

Raingarden tree pits are one option or stormwater

treatment. They can be congured to suit landscape andstreetscape design even when its highly urbanised, orwheregradesaresteeperthan4%.Below,Figure1showssome examples.

Street trees can be designed to incorporate a raingardenstormwater treatment where street runo is diverted to astreet tree pit. The street tree is lowered to allowstormwater runo to enter the tree pit and lter throughthe vegetated media beore being discharged into thestormwater system.

Figure 1. Examples o raingarden tree pits, confgured indierent landscape fnishes

Design considerations

Raingarden tree pits have similar design and operational principles as other raingardens. The key dierences are:

Vegetationselection(i.e.thetreespecies)

Smallerfootprint

Structuralsoilproperties(media)

Landscapenishes.

Built environment

For retrot sites, the interaction with existing built environment is an important design and implementation consideration.In high density urban areas, such as Melbourne, there is a high competition or open and underground space.

A typical raingarden tree pit

Figure 2 shows a diagram o a typical raingarden tree pit. Raingarden tree pits work like raingarden basins. The tree pitlters stormwater runo through the vegetated lter media. Temporary ponding above the lter media provides additionaltreatment within a small space. An extended detention depth is needed. Importantly or rain garden tree pits, the tree mustbe set down, typically below the invert o the kerb.

Cremorne St, Richmond (VIC)

Marwal Ave, North Balwyn (VIC) Batmans Hill Dr, Docklands (VIC) Little Collins St, Melbourne (VIC)


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Figure 2. Diagram o raingarden tree pit cross section

Key design issues

Tree media surace layer

The top o tree media surace layer should be set a minimum o 50mm below the invert o the slot cut in the kerb andchannel. This allows or the extended detention depth around the tree.

Inrastructure interace

Consider the relationship with surrounding inrastructure including: Roadsurfacegrading(selectionofeithersinglecrossfallorcrownedroad) Locationofstreettreestointegratewithexistingstormwaterinfrastructure,inparticular:

location o stormwater pits levels at the road surace levels or the stormwater lines that will receive treated water rom street tree drainage.

Identicationandlocationofexistingservices,forexample: gas electricity (underground and above ground) telecommunication

water sewerage.

Stormwater catchment area

Identiy the stormwater catchment area that will be directed to the street trees. This includes downpipes rom adjacentbuildings discharging to kerb and gutter drainage.

Inlet design

Design the inlet so it operates appropriately in relation to: Receivingstormwater Velocitycontrolandsedimentationissues Maintenanceimplication(includingstreetcleaning) Pre-treatmentrequirements(litterandsedimentcapture).

High ow events

High fow bypass is needed to make sure high fow events are saely conveyed to the conventional drainage system.Typically this is provided by side entry pits located downstream o inlets to the raingarden tree pits.

44 As per FAWB lter media guidelines revised March 2008.


Perforated pipe located todrain filtered stormwater

Air void

Filtration Media

Dense ground planting is optional,companion planting will assist in breakingup the soil surface and maintain

Connect to stormwaterto Engineers specifications,

contact local authority

0.15m

0.5m

0.15m

Filtration layer (approved filter sand) for tree growth

Transition layer 0.1m

Drainage layer perforated pipe orequivalent at min 0.5% grade surrounded within150mm layer of 2.5mm gravel sand


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Underdrainage

Typically a perorated pipe is incorporated into the design to provide underdrainage. The underdrainage is connected to theconventional drainage system. This ensures treated stormwater is conveyed to the receiving waterways and prevents waterlogging the tree. One end o the underdrainage is exposed to allow periodic fushing, i required.

Selection o tree species

Use expert advice to assess the suitability o tree species to the raingarden tree pits. Suitability depends on:

Rootstructure

Climaticcondition

Interactionwithsurroundinginfrastructure.

The selection o the tree species requires consultation between the landscape architect, arborist and WSUD specialist.

Filter media specifcations

Consult media specications to get the desired perormance and structural conditions (see WSUD Engineering Procedures:Stormwater, Melbourne Water pp 89-90). A hydraulic conductivity o 100-30044 mm/hr is typically recommended orstreet tree bioretention pits (this normally reduces with time to a minimum 50-100mm/hr).

Basin confguration

Raingarden tree pits can be congured in a basin. This involves setting down o the tree and integrating the surace withthe surrounding street level. An example o a raingarden tree pit integrated into the streetscape is shown in Figure 3 below.

Figure 3. Raingarden tree pit integrated into the streetscape situated roadside o kerb

a. Plan section

b. Cross section

Granite pavers to appropriate specification

Area of ground cover planting(1m by 1m)

Tree Guard to appropriatespecification

Street Tree to appropriatespecification placed in centreof tree pit

Gutter

Kerb

road

Granite Pavers to appropriatespecification

Filtration Layer 0.5 to 1.2m(depth will depend on invert level of stormwater pipethat drainage will connect with)

Transition Layer 0.1m

Drainage Layer 0.1m

footpath

Structural Soil(to appropriate spec.)

Optional root barrier(also acts as impervious liner)

90mm perforated pipe

0.1m



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Treatment size

The design curves or raingardens are also used to size raingarden tree pits. The catchment is dened by the impervioussurace area draining to each raingarden tree pit.

The typical road runo catchment area is small or an individual raingarden tree pit. The street trees are spaced at a highrequency, so they have sucient treatment or their catchment.

A typical street layout is shown in Figure 4 below.

Figure 4. Typical street layoutor raingarden tree pit roadside o the kerb

Saety considerations

Raingarden tree pits must be set below the kerb invert and the design must also integrates pedestrian saety.Examples o designs incorporating saety measures include:

Concealmentofextendeddetentiondepthwithframe(e.g.LittleCollinsSt)

Integrationoflandscapedesignwithretainingwall(e.g.BatmanDrive)

Useofpebblemulch(e.g.BatmanDrive&MartinSt)

Installationofahandrail(e.g.CremorneSt).

Openings in pit lids around tree trunks must not be less than 0.75m in diameter. Grates should be provided over theopenings to prevent human injury. Concentric rings can be used and cut out sequentially to provide more room as thetree grows.

Street sweeping

Regular maintenance regimes are essential to remove gross pollutants. Thereore street sweeper access is required,particularly or designs which incorporate kerb outstand. Sharp curves should be avoided, as they can collect grosspollutants.

Maintenance

Raingarden tree pits are designed or minimal maintenance. Street sweeper access is needed to clean litter rom the inletand enable stormwater to runo to the tree.

Thetypicalannualmaintenancecostofatreepitis5-7%ofthetotalconstructioncosts45.

Covering the tree pit will prevent litter accumulation. Periodic cleaning will be needed and depends on the design o thetree pit cover and location o the street tree.

Raingarden tree pits are designed to collect sediments and nutrients rom the stormwater runo. Over a long period otime (greater than 30 years) these sediments will accumulate, particularly in the top lter layer (200-300mm). The toplayer o the media will require replacement and hence also involves replanting the tree. The top lter media layer willrequire suitable disposal.

For a maintenance checklist, reer to the WSUD Engineering Procedures: Stormwater manual46.

Protection during the build out phase

Excessive sediment load, or example during construction phases, will cause the raingarden tree pit lter media to clog.Best practice site management during construction is required to minimise sediment load. During the construction phase,

the raingarden tree pit can be protected by a geotextile layer. This is placed on top o the lter media and then covered bytur. At the conclusion o the construction, the tur can be removed and tree planted. This enables the inrastructure to beconstructed during the build out phase, yet the media protected rom excessive sediment loads.

Stormwater pipe Stormwater pit

Subsoildrainage

SSD

10m 10m

Fall

45 EPA 2008, Maintaining water sensitive urban design elements, publication 1226.46WUSD Engineering Procedures: Stormwater, CISRO 2005.



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Fact Sheet 15: Surace wetlandsSmall Medium Large Broad

?

Constructed surace wetland systems use enhanced sedimentation, ne ltration and biological uptake processes to

remove pollutants rom stormwater. They generally consist o an inlet zone (a sediment basin to remove coarse sediments see Fact Sheet 9 Sedimentation (settling)), a macrophyte zone (a shallow heavily vegetated area to remove neparticulates and soluble pollutants) and a high fow bypass channel (to protect the macrophyte zone).

The wetland processes are engaged by slowly passing runo through heavily vegetated areas where plants lter sedimentsand pollutants rom the water. Biolms that grow on the plants can absorb nutrients and other associated contaminants.While wetlands can play an important role in stormwater treatment, they can also have signicant community benets.They provide habitat or wildlie and a ocus or recreation, such as walking paths and resting areas. They can also improvethe aesthetics and orm a central landscape eature.

Wetland systems provide food protection when incorporated into retarding basins. Additionally an open water bodyor pond at the downstream end o a wetland can provide water storage or reuse, such as irrigation. Wetlands can beconstructed on many scales, rom small house blocks (pictured let) to large regional systems. In highly urban areasthey can have a hard edge orm and be part o a streetscape or building orecourts. In regional settings they can be over10 hectares in size and provide signicant habitat or wildlie.

Inlet zone

The wetland inlet zone (or sediment basin) is designed to regulate fows into the macrophyte zone and remove coarse sediments.The inlet zone also enables a bypass pathway to be engaged once the macrophyte zone has reached its operating capacity.

The inlet zone reduces fow velocities and encourages settling o sediments rom the water column. They can drain duringperiods without rainall and then ll during runo events. They are sized according to the design storm discharge and the targetparticle size or trapping. Sediment basin maintenance is usually required every two to ve years. Sediment basins should bedesigned to retain coarse sediments only (recommended particle size is greater than 0.125mm). The highest contaminantconcentrations are associated with ne sediments and thereore waste disposal costs or this material can be much higher.

Macrophyte zone

An important operating characteristic o macrophyte zones is even, well distributed fows, that pass through various bands

o vegetation. Strong vegetation growth is required to perorm the ltration process as well as withstand fows through thesystem. Vegetation selection is heavily dependant on the regional climate. Flow and water level variations and maximumvelocities are important considerations and can be controlled with an appropriate outlet structure.

Dierent zones in a macrophyte system perorm dierent unctions. Ephemeral areas are oten used as organic mattertraps. These areas wet and dry regularly and thus enhance the breakdown process o organic vegetation. Marsh areaspromote epiphyte (biolms) growth and ltration o runo. Epiphytes use the plants as substrate and can eectivelypromote adhesion o ne colloidal particulates to wetland vegetation and the uptake o nutrients. Generally, there areareas o open water surrounding the outlet o wetlands. These can increase UV disinection and provide habitat or shand other aquatic species, as well as providing greater aesthetic appeal.

Optimal detention times in the wetland (typically 72 hours 12 in the inlet zone and 60 in the macrophyte zone) ensuredesired perormance. The macrophyte zone outlet must be sized accordingly. Multiple level orice riser outlets areconsidered to give the most uniorm detention times or wetlands. Sizing curves or wetlands are presented in Figure 1,withTNthelimitingdesignparameter.Foradesiredperformance(typically45%TNreduction),therequiredwetlandsurace area is calculated as a percentage o the impervious catchment area to be treated.


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Figure 1 Sizing curve or wetlands in Melbourne

Maintenance

To cost wetlands, the treatment device includes an inlet zone sediment basin/ pond and macrophyte zone, without a grosspollutant trap. Wetlands typically cost between two and six per cent o the construction cost to maintain each year.Generally, there is a very strong correlation between typical annual maintenance costs and the surace area o the wetland.Smaller wetlands are cheaper to maintain. Maintenance costs increase where there are:47

Introducedaquaticweeds

Sedimentsarecontaminated

Upstreamcontrolofsedimentispoor

Accessisdifcult

Dewateringareasarelimited.

For a maintenance checklist and more inormation on wetland design, reer to the WSUD Engineering Procedures:Stormwater manual48.

100

90

80

70

60

50

40

30

20

10

00 0.5 1 1.5 2 4 4.5 5

Wetland Surface Area (% Impervious Catchment)

TN is generally the limiting pollutant in wetlands

Melbourne Wetland TN Removal

250mm extended detention500mm extended detention750mm extended detention

TN

Removal(%)

2.5 3 3.5

47 EPA 2008, Maintaining water sensitive urban design elements, publication 1226.48 WUSD Engineering Procedures: Stormwater, CISRO 2005.

Fact Sheet 15: Surace wetlandsSmall Medium Large Broad


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Fact Sheet 16: Subsurace ow wetlandsSmall Medium Large Broad

?

Wetlands are a complex assemblage o:

Water Soils

Microbes

Plants

Organicdebris

Invertebrates.

Subsurace wetlands are a proven technology to adequately remove organic matter and suspended solids.Subsurace fow wetlands provide a low cost, very low energy, natural treatment system.

Subsurace wetlands and surace wetlands

Subsurace wetlands are typically applied in wastewater treatment systems where there is a relatively consistent infuentfow rate. In comparison, surace wetlands used to treat stormwater fows must be able to cope with variations in fows as

a results o rainall patterns.

Soil substrata

In subsurace fow wetlands, all the fow is through the soil substrata (reer to Figure 1). The soil typically has a highpermeability and contains gravel and coarse sand. The bed is planted out with appropriate vegetation.

As the fow percolates through the wetland, biological oxygen demand (BOD) and total suspended solids (TSS) are mainlyremoved by biological decomposition.

Figure 1 Typical subsurace ow wetland section drawing

Treatment o greywater and blackwater

Subsurace wetlands are a proven technology to adequately remove organic matter and suspended solids rom greywaterand blackwater. Subsurace wetlands provide a good quality efuent with typical average efuent BOD and TSS less than20 mg/l. They are commonly used in Europe to treat greywater in high density developments.

Subsurace wetlands have also been used in Australia to treat greywater rom colleges and buildings at Charles SturtUniversity. In Melbourne, a subsurace wetland treats laundry water rom the Department o Human Services ArthertonGardens housing estate. The water is then used to drip irrigate the surrounding reserves garden beds.

Pollutant removal

Subsurace wetlands are eective in the removal o nitrogen. The environment within a subsurace wetland is mostlyanoxic or anaerobic. Some oxygen is supplied to the roots which is likely to be used up in the bio mass growth, ratherthan penetrate too ar into the water column.

Water percolatesupwards throughthe media

Outlet drainageSlotted pipe on underside only running

across width of wetlandsVegetation

Wetland Soil Media

Perforated pipe equallyspaced across width

Inlet Drainage Media


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Design

Primary design criteria or subsurace fow wetlands are as ollows: Detentiontime

Mediasize

Hydraulicloadingrate

Organicloadingrate

Beddepth

A

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