Workshop E6: WSUD Will it work? 28th August 2008

Prepared for: Hunter & Central Coast Regional Environmental Management Strategy (HCCREMS) Presenter: Rod Wiese STORM_CONSULTING PTY LTD

Prepared by: STORM_CONSULTING PTY LTD

Head Office Suite 3, 6 West Street PYMBLE NSW 2073 Australia T +61 (02) 9499 4333 F +61 (03) 9499 4311 www.stormconsulting.com.au

Workshop E6: WSUD

Prepared for HCCREMS 28/08/08 1

Presented By: ROD WIESE

Managing Director, Principal Engineer

STORM_CONSULTING PTY LTD

WSUD Workshop 6: Will it Work?WSUD device performance and lifecycle costs

http://www.stormconsulting.com.au

STORM_CONSULTING – various projects(Project information, life cycle costing, graphics, photos)http://www.stormconsulting.com.au

Google Earth (Aerial photos)http://earth.google.com

Managing Urban Stormwater Treatment Techniqueshttp://www.environment.nsw.gov.au/stormwater/usp/docs.htm

Western Sydney WSUD Technical Guidelineshttp://www.wsud.org/tech.htm

BCC WSUD Design Guidelines and Practice Noteshttp://www.brisbane.qld.gov.au/BCC:BASE:2067326321:pc=PC_1898

MUSIChttp://www.toolkit.net.au

http://www.wsud.org (photos)

References

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Agenda

Mapping WSUD15:30 – 15:40

Sandfilters & exfiltration systems15:00 – 15:30

Discuss regional examples & experience15:40 – 16:00

Afternoon Tea14:45 – 15:00

Mapping WSUD14:15 – 14:45

Raingardens13:30 – 14:15

Lunch12:30 – 13:30

Discuss regional examples & experience12:00 – 12:30

Mapping WSUD11:45 – 12:00

Bio-retention basins & trenches11:10 – 11:45

Morning Tea10:50 – 11:10

Mapping WSUD10:40 – 10:50

Swales10:10 – 10:40

Buffer (Filter) strips09:45 – 10:10

Buffer (Filter) Strips

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Typical application

Buffer strips

Application

Buffer Strips

• Generally used adjacent impervious surface – typically a road

• Catchment areas less than 2 Ha including allotment level

• Removal of coarse to medium sized sediments

• Typically used in conjunction with swales as an alternative to kerb

and gutter and can form part of a multi-use corridor

• Typically used as a pre-treatment for other stormwater treatment

devices, such as bioretention and infiltration systems

• Retrofitting considerations – relatively easy to do, e.g. in association

with re-construction of a road

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Geelong & Brisbane examples

Buffer strips

Bio-retention trenchBio-swale

Buffer strip

Gerringong

Buffer Strips

Brisbane

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Limitations

Buffer Strips

1. Site limitations that may preclude their use:– suitable only for relatively flat or gradually

sloping areas up to 5% grade– require adequate sunlight for vegetation

growth

2. Vehicular and pedestrian traffic

3. Vegetation must be established and then maintained

4. Dispersed pollutant storage

Construction

Buffer strips

Use during or after construction? Must allow for vegetation establishment

If used during construction, may need to be restored once development construction is complete

Protection from construction-site runoff and heavy vehicles

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Performance

Buffer strips

Gross Pollutants* 50 – 80% Coarse Sediment* 30 – 50% Medium Sediment 10 – 50% Fine Sediment 10 – 50% Free Oil and Grease 10 – 50% Nutrients, Metals 10 – 50%

* Assumes gross pollutant pre-treatment provided.

Western Sydney WSUD Technical Guidelineshttp://www.wsud.org/tech.htm

Soils & plantsSoilsnon-erosive soils support vegetation growthpossibly limited in saline areasconsider vehicular traffic (foundation)

Planting optionstypically turfcould be other mixes of groundcoverscompatibility of species (endemic, domination, wetting)

Buffer Strips

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Lifecycle Costshttp://www.stormconsulting.com.au

Over 10 years –

construction $12/m2

mowing and weed removal $200/m2

decommissioning/replacement $12/m2

Total $224/m2

Buffer Strips

Tips for review/inspection

Buffer strips

Look for concentrated flow paths

Compatibility of plant species

Ensure drop from impervious surface

Plant establishment plan

Foundation of vehicular traffic

Commitment to maintenance

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Hunter example

Buffer strips

Swales

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Typical swale

Swales

Swales

Fundamentals

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Swales

Fundamentals

Swales

Bio-swales

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Swales

Swale vs bio-swale

Managing Urban Stormwater Treatment Techniqueshttp://www.environment.nsw.gov.au/stormwater/usp/docs.htm

Swales

Fundamentals• Longitudinal grades ideally 2-4% but can be 6%• Check dams may be required for steeper grades• Flatter grades may require SSD • Side batters 1:3-6• Max velocity 0.5 – 3 m/s• Swale length min. 30m• Treatable design flow depth approx. 75mm (30-50% plant height)• Residence time 5-9 mins• Max width 2.5m• Appropriate soils for vegetation growth• Adequate sunlight• Driveway crossovers (generally 1:13)

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Swales

Performance

Gross Pollutants* 50 – 80% Coarse Sediment* 30 – 50% Medium Sediment 10 – 50% Fine Sediment 10 – 50% Free Oil and Grease 10 – 50% Nutrients, Metals 10 – 50%

* Assumes gross pollutant pre-treatment provided.

Western Sydney WSUD Technical Guidelineshttp://www.wsud.org/tech.htm

Swales

PerformanceManaging Urban Stormwater Treatment Techniqueshttp://www.environment.nsw.gov.au/stormwater/usp/docs.htm

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Swales

ConstructionTiming of swale construction, i.e. during or after construction

Depending on the site runoff, sediment loads and flow rates, swales may need to be restored once development construction is complete.

If the swale is to be constructed for use after development completion, it should be protected from construction-site runoff and should be fenced during the construction period to prevent damage from heavy plant and vehicles.

Swales

Vegetation

• Most often grassed (turf)

• Can be wetland plants, other herbaceous plants, groundcovers

• Hydraulic conveyance must be considered

• Flow depth 30-50% of plant height

• Must grow in specified media – frequently wetted

• Trees and shrubs can cause shading

• For general landscape/aesthetics reasons

• Use more substantial plants and shrubs to limit access.

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Coomera & Bowral examples

Swales

Swales

Driveway treatment

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Swales

Driveway treatment

Swales

Driveway treatment

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Swales

Issues?

Swales

Alternative to turf - Thredbo

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Swales

Port Stephens area

Bio-swales

Melbourne

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Tips for review/inspection

Swales

Swale slope and width

Length of flow path (capacity)

Swale vs bioswale (slope, traffic, soils)

Compatibility of plant species

Ensure drop from impervious surface

Potential for vehicular traffic (especially clay soils)

Driveway crossings

Mapping WSUD

Morning Tea

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Bio-retention basins & trenches

Fundamentals

Western Sydney WSUD Technical Guidelines, 2004.

Bio-retention

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• Catchment – area and characteristics, location of device

• Inflows – get water in

• Drainage – get water out

• Extended detention

• Vegetation

• Filter media

• Site Function: Users, maintenance, interpretation.

Bio-retention

Key considerations

Bio-retention

Key elements

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Fundamentals

Bio-retention

Fundamentals

Bio-retention

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• Trench slope (generally < 6%)

• Scour velocities in trenches

• High flow bypass

• Filter media specification (CRITICAL – refer to raingardens)

• Shallow ponding depths

• Liner? groundwater interaction, adjacent infrastructure

• Significant head requirement – vertical flow through filter

• Rule of thumb - 1% of catchment area

• Maintenance access

Fundamentals

Bio-retention

Plants and soils

Bio-retention

• Vegetation:• root depth• moisture requirements• sunlight• plant height and stiffness• growing media vs filter media

• Maintenance access

• Pedestrian movement and safety

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Performance

Managing Urban Stormwater – Treatment techniques, 2007

http://www.environment.nsw.gov.au/stormwater/usp/docs.htm

Bio-retention

Performance

Bio-retention

Managing Urban Stormwater – Treatment techniques, 2007

http://www.environment.nsw.gov.au/stormwater/usp/docs.htm

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(Managing Urban Stormwater Treatment techniques, 2007)

Bio-retention

Bio-retention

Brisbane

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(From MUSIC Manual, 2005 - could add 50% with recent increases)

• Most importantly: highly variable - based on materials, landscaping, size, retrofit and catchment characteristics.

• Basins > 100m2 $125 – $150/m2

• Basins < 100m2 $225 - $275/m2

• Linear systems $100 - $410/m (depends on trench width)

• Annual maintenance 5% – 7% of construction cost (Taylor and Wong, 2002)

• Media and plant replacement every 15-25 years.

Cost estimates

Bio-retention

http://www.toolkit.net.au

Melbourne

Bio-retention

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Bio-retention

ThredboAlpine Resort

Bio-retention

Delta area car park - Thredbo

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Bio-retention

Delta car park - Site issues

Bio-retention

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Delta Car Park In summer

Bio-retention

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Bio-retention

Bio-retention

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Mapping WSUD

Workshop sessionDiscuss regional examples & experience

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Lunch

Raingardens

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Raingardens

• Catchment – area and characteristics, location of device

• Inflows – get water in

• Drainage – get water out

• Extended detention

• Vegetation

• Filter media

• Site Function: Users, maintenance, interpretation.

Raingardens

Key considerations

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Raingardens

Key elements

Raingardens

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Raingardens

Raingardens

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Raingardens

Raingardens

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Raingardens - Examples

Highest hydraulic conductivityAg drain/slotted pipe – connected to drainTypically

90-100mm ag pipe or slotted PVC4 to 7 mm clean gravel150+ mm thick layer

Potential pitfallsAvoid scoria – it creates fines - blockingDo not use filter socks on ag – blockingLayer thickness – thick layers can be difficult to accommodate in sites with limited depth

Raingardens

Drainage Layer

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Raingardens

Raingardens

Drainage layer media

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Raingardens – Transition layer

Raingardens – Transition layer

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Raingardens

Main element of the system• Provides treatment• Supports plant growth

Typical properties• Washed sandy material

• Drainage rate – 100 – 200 mm/h

Saturated hydraulic conductivity (AS 4419)

• Needs to have sufficient nutrients to support plant growth

• 300 – 500+ mm layer thickness

Filter Media

Raingardens – Upper Filter

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Raingardens

Potential pitfalls

• Filter does not meet specifications

No checking of material prior to or after delivery

• Surface grading and levels of filter – adequate ETD

• Fines block filters

Avoid using topsoil or soils with clay content

• Lack of nutrients resulting in poor plant growth

Filter layer

Raingardens

Is this filter media ok?

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Raingardens – Filter Media

Raingardens

Roles• Reduce erosion• Some extended detention• Reduce area of growth for weeds• Plant growth – retains moisture

Typically• 10 - 20 mm diameter washed aggregate (non floating)• 50 - 75 mm layer, placed clear of plant stems

Potential pitfalls• Timber mulch – it floats• Fines included – which clog surface layer• Too thick – collar rot against plants; lose EDD• Jute – hydraulic conductivity, degradation, aesthetics

Mulch Layer

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Raingardens

Raingardens

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Raingardens

Fundamentals

Raingardens

Role• Maintains porosity of soil• Improves pollutant removal• Aesthetics• Roots prolong life of filter by creating drainage pathways• Community appreciation of garden and environmental qualities

Specification• Plants that are suited to temporary inundation• Free draining soils• Low nutrient soil properties

Vegetation

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Raingardens

• Plant selection to suit wet / dry period

• Horticultural requirements of each species, pruning, watering and

seasonal change

• Larger plants or trees can reduce through traffic and unintentional

damage

• Selection of some plants as indicator species for filter functionality

Vegetation considerations

Raingardens

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Most importantly: highly variable - based on materials, landscaping, size, retrofit and catchment characteristics.

From STORM_CONSULTING:Construct Raingardens $500 - $1,000 /m2

Construct tree pits $3,000 - $5,000 /tree incl. landscape and drainage

From City of Kingston (pers. Comm.):• Construct small roadside raingardens $700/m2

• Maintain these same raingardens $17/m2 pa (2.5%)

Cost estimates

Raingardens

Raingardens

Raingardens

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Mapping WSUD

Afternoon Tea

Sandfilters & Exfiltrationsystems

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Definition

Sandfilter – stormwater enters system at the surfaceExfiltration – stormwater distributed into filter below surface via

distribution pipes

Not to be confused with “infiltration systems”

Porous Section

Impermeable Section

Sandfilters

Sandfilters

Sandfilter Configuration

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Exfiltration

Native Soil

Media

1

2

3

4

6

Note: Diagram is not to scale

5Groundwater

Step One:

Litter / Sediment

Traps

Step Two:Pit

Step Three:

Porous Concrete

Pipe

Step Four:Substrate

Media Material

Step Six:

Flushing Pit / Pipe

Step Five: Collection Pipes or

Surrounding Soil /

Groundwater

Porous Section

Impermeable Section

ExfiltrationConfiguration

http://www.hydrocon.com.au

Sandfilters

Application• Best close to source – to prevent overloading

• Best for fine sediment and attached pollutants (nutrients, hydrocarbons and heavy metals)

• High pollutant removal

• Subsurface allows multi-use of space

• Useful tool for retrofitting

• Vertical flow through filter, therefore requires significant head

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Fundamentals• Pre-treatment – remove gross pollutant and coarse to medium

sediment down to 125 micron (generally) prior to filter

• HOW?• Sediment basin• GPT • Permeable pipe• Vegetation

• Due to susceptibility for blocking - generally situated “off-line”

• Even distribution of inflows

• Maintenance may be confined space

• Can surcharge above ground to increase performance

Sandfilters

Exfiltration

Elambra Estate, Gerringong

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Exfiltration

Gerringong

Exfiltration

Asquith

This was one of 3 research sites under ARC via Linkage Project grant 0454374. Papers may be found at: http://www.hydrocon.com.au

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Exfiltration

Asquith (Photo Source: Alison Dunphy)

Exfiltration

Station 1 –Inlet Pit

Upstream Manhole

Downstream ManholeOverflow Outlet

Sand Media

Gravel Media

HydroCon Infiltration Pipes

Not To Scale

Station 2B –Standpipe

Station 3B –Standpipe

Station 2A –Standpipe

Station 3A –Standpipe

Station 4 –Manhole

Asquith(Photo Source:

Anthony Collins)

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Ashgrove Ashgrove estateestate

Duck RiverDuck River

Exfiltration

Ashgrove - pre-development

Basin C – Detention with Exfiltration

800 m3 concrete storage tank buried next to filters Trunk drainage and

detention in box culvert

Basin A – Detention with Exfiltration

Basin B – Exfiltration and Detention

Exfiltration

Flow

Flow

Flow

Basin C

Basin B Basin A

Flow

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Basin C – Detention with Exfiltration

Basin A – Detention with Exfiltration

Basin B – Exfiltration and Detention

Exfiltration

Ashgrove’s Basin A

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800 kL u/grndStormwater Storage Tank

Pump Station

Reticulation to lots

Ground level

Exfiltration

Ashgrove construction

Exfiltration

Ashgrove Basin A - constructed

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Exfiltration

Performance• Treatment through physical filtration and adsorption• High level of sediment, nitrogen and phosphorous removal

depending on configuration.• Detention and retention of flows

Sandfilters

Managing Urban Stormwater – Treatment techniques, 2007

http://www.environment.nsw.gov.au/stormwater/usp/docs.htm

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Sandfilters

Sandfilter Performance

Most importantly: highly variable - based on materials, landscaping,size, retrofit and catchment characteristics.

• $300 - $700/m2 excluding pre-treatment

• 2001 Newcastle 5,000m2 catchment $36,153 (say $700/m2)

• 2003 Sydney $1,500/m2

• Linear systems $250 - $450/m (trench width? Ex pre-treatment)

• Maintenance depends on above ground use & configuration

• Top layer of media replaced every 5-15 years in exfiltration• Regular raking of sand media in package configuration and

replacement of top layer every few years (11-13% of capital)

Cost estimates

Sandfilters

http://www.stormconsulting.com.auhttp://www.toolkit.net.au

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Exfiltration

Kinross

Exfiltration

Kinross(Photo Source: Alison Dunphy)

This was one of 3 research sites under ARC via Linkage Project grant 0454374. Papers may be found at: http://www.hydrocon.com.au

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Exfiltration

Grasmere, Camden

Exfiltration

Grasmere construction

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Exfiltration

Grasmere, Camden

Exfiltration

Construction Issues

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Exfiltration

Kiama CBD

Exfiltration

Kiama

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Exfiltration

Exfiltration

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Exfiltration

Pre-treatment

Exfiltration

Kiama

This was one of 3 research sites under ARC via Linkage Project grant 0454374. Papers may be found at: http://www.hydrocon.com.au

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Exfiltration

Kiama

Exfiltration

Maintenance / construction issues

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Exfiltration

Maintenance - Eduction of pits and pipes

Infiltration

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Infiltration

InfiltrationFundamentals:• Treated flows are permitted to infiltrate into ground• May be applied to most systems presented earlier• Work best in permeable soils• Not to be adopted if harvesting water is proposed

Benefits:• Allows groundwater recharge• Reduces runoff volume• Effective pollutant reduction downstream

Key Considerations:• Pre-treatment (prevent pollution of groundwater & clogging)• Quality of groundwater• Soil types (hydraulic conductivity)• Site slope• Distance from site infrastructure

Infiltration

Infiltration

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Infiltration

Infiltration

Managing Urban Stormwater Treatment Techniqueshttp://www.environment.nsw.gov.au/stormwater/usp/docs.htm

Workshop sessionDiscuss regional examples & experience

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Workshop CompleteThank you for your participation

www.stormconsulting.com.au