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
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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