Design, Construction and
Establishment of
Constructed Wetlands:
Design Manual
Executive Summary
Urban development places significant pressure on waterways and their environmental
and social value. The increased flow and frequency of urban stormwater can be a
major force in stream erosion and habitat disturbance. In addition, stormwater
contains considerable levels of contaminants and pollutants that can further degrade
the health of waterways.
In 2013, a number of key strategies were released. These strategies have influenced
urban development and the approach to managing stormwater within Melbourne. In
July, the State Government released Melbourne’s Water Future for consultation; a new
approach to managing the urban water cycle in Melbourne. One of this strategy’s key
objectives is to make better use of all available water sources, including recycled
water, rainwater and stormwater. The volume of stormwater runoff from Melbourne’s
rainfall is greater than the amount we use from our dams. This quantity of water is
more than enough to provide both an alternative supply for non-drinking purposes
and a healthy flow to our waterways and bays. The Melbourne’s Water Future strategy
outlines an alternative approach to stormwater management and seeks to manage the
various stormwater objectives of flood reduction and waterway protection through
strategies that reduce the volume of stormwater (e.g. through harvesting) and
improve management of flows.
The government also released Plan Melbourne – Metropolitan Planning Strategy, a key
document that provides a clear vision for the city to 2050 and responds to the
challenges of population growth, urbanisation, driving economic prosperity and
liveability while protecting our environment and heritage. Customers and communities
are increasingly demanding clever, affordable and local solutions that enhance
liveability in their suburbs.
Within this changing world, Melbourne Water is a key player; we now need to rethink
our approach in delivery of valued services. There is a need for change in the way that
Melbourne Water delivers services and we are responding by changing our business
model to exhibit three focus areas:
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Servicing customers in addition to managing assets;
Delivering operational excellence in core services; and
Optimising the value created through new services and extended roles.
The primary focus for realising this business model is outlined in our new Service
Delivery Strategy and our new Asset Management Strategy, which have the business
shifting from a world where we build and manage assets, to one which also focusses
on the delivery of valued services for all customers and stakeholders.
Design, Construction Design Manual Melbourne Water
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Melbourne Water has also recently released our Stormwater Strategy, which outlines
our role in managing stormwater to protect and improve the ecosystem health of
waterways and bays. It is closely linked to the Healthy Waterways Strategy, which
focuses on managing rivers, estuaries and wetlands in the Port Phillip and Westernport
region. The Stormwater Strategy articulates our high-level strategic direction and
approaches in managing stormwater in rural and urban areas. It sees us working with
others to achieve multiple community outcomes for stormwater management, in
relation to healthy waterways and bays, wellbeing and amenity, alternative water
supply and public safety.
Constructed wetlands have always been considered as one possible option to improve
stormwater quality within a suite of other treatment measures. This method can help
urban development achieve some of the objectives outlined in the Stormwater and
Healthy Waterways strategies.
Constructed wetlands are built to remove pollutants carried via fine sediments and
water soluble nutrients, primarily nitrogen and phosphorous. These wetlands are
shallow, vegetated systems that fill and drain in a controlled manner following rain
events. The design hydrological regime and vegetation configuration throughout the
wetland is critical to the treatment function of the system. Vegetation in the wetland
has a direct relationship to the treatment performance. If the vegetation does not
meet the design configuration it is unlikely that the wetland is performing the
treatment required.
This manual has been prepared to assist the land development industry when
designing, constructing and establishing constructed wetlands on behalf of Melbourne
Water. This document has been developed with a strong focus on:
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Designing and building robust wetland systems;
Ensuring safety for both the community and maintenance staff;
Cost effective asset management through design, construction, operation and
maintenance;
Improvements and efficiencies to the design acceptance process and when
dealing with Melbourne Water;
Clarity and consistency in decision making; and
Training and guidance to the land development industry with tools, templates,
and checklists.
This document can be used as a reference for external stakeholders, such as
developers and consultants, and council.
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Melbourne Water Design, Construction and Establishment of Constructed Wetlands
Table of contents
Introduction
Introduction to the manual
Process of the manual
How to use the manual
Supporting resources
Support resources
Templates
Standard drawings
Part A1: Constructed wetlands form and function
Table of contents
Water Sensitive Urban Design
Protection of waterways
Management of stormwater in urban landscapes
Provision of multiple benefits
Natural Wetlands
Constructed Wetlands
Stormwater treatment mechanisms
Components of a typical constructed wetland
Amenity in constructed wetlands
Hydrodynamic design considerations
Constructed wetlands in retarding basins
Designing to avoid mosquitoes
Designing for maintenance access
Climate change
Safety in design
Part A2: Planning, funding and management
Table of contents
Introduction
Melbourne Water’s statutory role in new development
Water Industry Act (1994)
Water Act (1989)
Planning and Environment Act (1987)
Subdivisions Act (1988)
Legislation and constructed wetlands
State Environment Protection Policy (Waters of Victoria)
Living Victoria Policy
Design, Construction and Establishment of Constructed Wetlands Melbourne Water
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Melbourne’s Water Future
Plan Melbourne
Victorian Planning Provisions
Urban Stormwater Best Practice Environmental Management
Guidelines for stormwater treatment
Melbourne Water policies and strategies
Enhancing life and liveability
Relationship Strategy
Service Delivery Strategy
Asset Management Strategy
Waterways and Drainage Strategy
Healthy Waterways Strategy
Flood Management and Drainage Strategy
Planning and Building (Land Development Manual) website
Planning for constructed wetlands
Development Services Schemes
Funding constructed wetlands
Development contributions
Scheme reimbursements
Waterways and drainage charge
Financial principals
Managing constructed wetlands
Delineation of Melbourne Water and Council ownership
Ownership of wetland systems
Ownership of the wetland and surrounding open space area
Part B1: Vision, core outcomes and aspirational outcomes
Table of contents
Introduction
Vision
Core outcomes
Effective pollutant removal
Community safety
Maintenance and operational staff safety
Cost effective asset management
Aspirational outcomes
Wellbeing, liveability and amenity
Alternative water supply
Recreational
Landscape and cultural objectives
Accessibility
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Melbourne Water Design, Construction and Establishment of Constructed Wetlands
Table of contents
Conservation
Part B2: Deemed to comply design criteria
Table of contents
Introduction
Deemed to Comply conditions
General
Maintenance provisions
Gross pollutant management
Sediment pond
Macrophyte zone
Bypass
Inlets and outlets
Vegetation
Liner and topsoil
Landscape design structures
Edge treatment
Part C: Design acceptance process
Table of contents
Introduction
Two submission/acceptance pathways
Deemed to Comply
Alternative approach
Working with Melbourne Water
Concept design stage
Concept design steps
Function design stage
Functional design steps
Detailed design stage
Detailed design steps
Pre-construction stage
Pre-construction steps
As-construction and establishment stage
As-constructed steps
Part D: Technical design, construction and establishment
approach
Table of contents
Introduction
Design, Construction and Establishment of Constructed Wetlands Melbourne Water
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Concept design
MUSIC Modelling
Hydrologic and hydraulic modelling
Functional design
Detailed design
Pre-construction
Construction and establishment
Part E: Design tools, resources and glossary
Table of contents
Introduction
Design Tools
Hydrological modelling
Continuous simulation modelling
Hydraulic analysis of flow velocities
Resources
Planning
Design
Maintenance
Construction and establishment
Glossary
Part F: Forms, templates and example plans
Table of contents
Introduction
Design acceptance process – forms, templates and checklists
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Melbourne Water Design, Construction and Establishment of Constructed Wetlands
Constructed Wetlands Design Manual Melbourne Water
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Constructed Wetlands
Design Manual
Introduction
Table of contents
Introduction to the manual
1 Purpose of the manual
1 How to use the manual
3 Supporting resources
4 Support resources ..................................................................................4 Templates.............................................................................................4 Standard drawings .................................................................................5 Constructed Wetlands Design Manual Melbourne Water
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Introduction to the manual
Introduction to the manual
Melbourne Water recognises the importance of constructed wetlands and their role
and function within urban environments. In consultation with the land development
industry and other stormwater management professionals, we have reviewed the
existing “Constructed Wetlands Guidelines” (2010) and prepared a new design manual
to assist the industry to deliver best practice wetland designs. We expect this will help
us to achieve our shared objectives for the treatment of stormwater and improvement
of our urban waterways.
The purpose of the manual, titled “Design, Construction and Establishment of
Constructed Wetlands: Design Manual” (‘the manual’), is to provide greater
transparency of the design requirements for the construction of wetland systems in
the Port Phillip and Western Port region.
This manual should be read in conjunction with the following documents (or current
versions of these documents):
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Melbourne Water’s Planning and Building website [quick link]
Urban Stormwater: Best Practice Environmental Management Guidelines
(Victorian Stormwater Committee, 1999) [quick link]
WSUD Engineering Procedures: Stormwater (MWC, 2005) [quick link]
This document is a revision of the previous Melbourne Water Constructed Wetlands
Guidelines and provides the current best practice in constructed wetlands. Any
variations between this document and those listed above are superseded by this
manual.
Purpose of the manual
The manual is intended for use by the land development industry who design,
construct and establish constructed wetlands on behalf of Melbourne Water. This
manual is also a resource for other professionals working within the stormwater
management, drainage and land development industry (including other authorities
and interested community members).
The manual facilitates the consistent delivery of high quality constructed wetlands
across the Port Phillip and Westernport region and will improve the customer
Constructed Wetlands Design Manual Melbourne Water
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experience of working with Melbourne Water during the design, construction and
establishment process.
The manual:
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Defines best practice in constructed wetland design;
Describes the approach and tools necessary to deliver best practice wetland
design;
Articulates the requirements of Melbourne Water’s constructed wetlands design
approach and design acceptance process, including the deemed to comply
approach; and
Articulates why it is important to implement best practice design standards, in
terms of values of and objectives for constructed wetlands.
The manual is structured in a similar format to the Constructed Waterways in New
Urban Developments: Design Manual (2014) to provide consistency for the land
development industry in the design approach and design acceptance process for both
constructed urban waterways and constructed urban wetlands.
The manual has evolved from previous guidelines and documents, the latest being the
Constructed Wetlands Guidelines (2010). Wetland guidelines have been refined over
many years, since the industry publication Managing Urban Stormwater Using
Constructed Wetlands in 1998. Since this publication, the stormwater industry has
matured through advancements in engineering practice, practical knowledge and
further understanding of natural ecosystems. This manual reflects current thinking
and best practice design.
The manual responds to a range of needs within the land development industry,
including:
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Melbourne Water’s need to see consistent improvement in the quality of
constructed wetland designs being submitted for review and approval; and
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The need from the land development industry for clear guidance from
Melbourne Water regarding:
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Expectations and requirements for constructed wetlands;
o
The appropriate and efficient design approach required of consultants;
and
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The design acceptance process for constructed wetland designs.
Melbourne Water Constructed Wetlands Design Manual
Meeting the above needs provides greater certainty and confidence within the industry
that the designs submitted to Melbourne Water will be accepted. This will increase the
efficiency of the design acceptance process, potentially saving time and money.
How to use the manual
The manual is structured as a series of parts and associated products to maximise the
flexibility of its use within the land development industry.
There are six main Parts within this manual, each with a distinct purpose:
Part A: Constructed wetlands fundamentals:
o
Part A1: Constructed wetlands form and function describes the
fundamentals of constructed wetlands. A detailed overview of the physical
features available to wetland designers and the drivers of wetland design
and treatment are provided.
o
Part A2: Planning, funding and management outlines the planning,
funding and management arrangements for constructed wetlands as
supported by relevant legislation, policy, strategy and guidelines.
Part B: Constructed wetlands outcomes:
o
Part B1: Vision, core outcomes and aspirational outcomes sets out
Melbourne Water’s required outcomes for constructed wetlands.
o
Part B2: ‘Deemed to comply’ design criteria presents the design criteria
that must be met to achieve ‘deemed to comply’ acceptance, and
demonstrates how this criteria aligns with the design objectives.
Part C: Design acceptance process details the concept, functional and
detailed design stages and the associated requirements of Melbourne Water’s
constructed wetland design acceptance process.
Part D: Technical design, construction and establishment approach
provides resources for designing, constructing and establishing constructed
wetlands.
Part E: Design tools, resources and glossary outlines the various analytical
design tools, information sources and Melbourne Water resources that can be
used to develop a best practice constructed wetland design.
Constructed Wetlands Design Manual Melbourne Water
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Part F: Forms, templates and example plans provides all the forms,
checklists and templates to assist with the submission of information through
the design acceptance process as part of land development.
Familiarity with the manual will allow the land development industry to gain a full
understanding of Melbourne Water’s requirements for best practice constructed
wetland design. However, the manual has been written in a way that the Parts can be
used independently as required.
Supporting resources
The design approach set out in the manual draws on a large body of existing
information and design tools, many of which will be familiar to the land development
industry. However, there are several new concepts and tools. A range of supporting
resources has also been developed to assist designers to completely understand
Melbourne Water’s requirements for constructed wetlands and apply them to their
work.
Support resources
A number of resources have been developed to support the design approach set out in
the manual:
•
MUSIC Auditing tool
•
Hydrological event modelling
•
Continuous simulation (water quality, residence time and water level analysis)
•
Hydraulic analysis of flow velocities
Templates
The following templates have been produced to assist the designer package their
design reports and plans to Melbourne Water’s satisfaction:
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Design report template – a blank word template with key headings and a table
of contents to guide the structure and content of the concept and functional
design reports.
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Design checklists
•
Example design plans – sample plans illustrating the level of detail typically
shown on wetland design plans from concept, through function to detail.
Melbourne Water Constructed Wetlands Design Manual
Standard drawings
A number of standard drawings to accompany the manual are available on Melbourne
Water’s website.
Constructed Wetlands Design Manual Melbourne Water
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Constructed Wetlands
Design Manual
Part A1: Constructed wetlands form and function
Table of contents
Water Sensitive Urban Design
1 Protection of waterways ..........................................................................1 Management of stormwater in urban landscapes .........................................1 Provision of multiple benefits ...................................................................2 Natural wetlands
2 Constructed wetlands
3 Stormwater treatment mechanisms ..........................................................4 Components of a typical constructed wetland .............................................5 Amenity in constructed wetlands ............................................................ 13 Hydrodynamic design considerations ....................................................... 14 Constructed wetlands within retarding basins ........................................... 15 Designing to avoid mosquitos ................................................................ 15 Designing for maintenance access .......................................................... 16 Climate change .................................................................................... 16 Safety in Design .................................................................................. 17 Constructed Wetlands Design Manual Melbourne Water
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Constructed wetlands form and function
Water Sensitive Urban Design
Water Sensitive Urban Design (WSUD) integrates water cycle management with urban
planning and design, and utilises natural processes to help mitigate the impacts of
stormwater runoff on waterways and bays.
The key principles of WSUD outlined in the Urban Stormwater: Best Practice
Environmental Management (BPEM) Guidelines (Victorian Stormwater Committee,
1999) are to:
 Protect and enhance natural water systems within urban environments;
 Integrate stormwater treatment into the landscape, maximising the visual and
recreational amenity of developments;
 Improve the quality of water draining from urban developments into receiving
environments;
 Reduce runoff and peak flows from urban developments by increasing local
detention times and minimising impervious areas; and
 Minimise drainage infrastructure costs of development due to reduced runoff
and peak flows.
Protection of waterways
Stormwater management, through the adoption of WSUD principles, helps to protect
urban waterways so they remain valuable community assets that enhance community
liveability and support the ecosystems that rely on them.
The physical characteristics and catchment properties within a region, such as land
use, amount of impervious area, and rainfall characteristics, strongly influence the
amount of stormwater that is generated and the subsequent impacts on waterway
health.
Management of stormwater in urban landscapes
The management of stormwater in the landscape using WSUD initiatives (stormwater
treatment, harvesting and reuse systems) reduces the volume and frequency of
stormwater runoff and increases the quality of stormwater before it is discharged to
downstream waterways.
The management of stormwater in urban landscapes may also include:
Constructed Wetlands Design Manual Melbourne Water
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Integrated management with groundwater, potable water and wastewater to
protect water related environmental, recreational and cultural values;
Storage, treatment and beneficial reuse of stormwater runoff; and
Use of vegetation for improving stormwater quality, providing water efficient
landscaping and enhancing biodiversity.
Provision of multiple benefits
The adoption of WSUD principles can provide a range of other benefits such as
alternate water supply, improved landscape amenity, and contribution to enhanced
liveability by highlighting natural features such as waterways and the surrounding
open spaces.
The use of WSUD treatment systems can also help to minimise drainage infrastructure
development costs by reducing pipe sizes and potentially replacing large scale
reticulated water systems with local solutions where appropriate.
Natural wetlands
The term ‘wetland’ is used to describe places within the landscape that are inundated
with water for all, or at least part, of the year. Wetlands encompass a diverse range of
aquatic ecosystems, ranging from permanently inundated environments (such as
freshwater lakes and estuaries) to variably inundated environments (such as
freshwater marshes/swamps and salt marshes).
Shallow freshwater wetlands (less than two meters deep) are present throughout
Australia and are defined on the basis of wetting and drying cycles (referred to as the
wetland water regime - timing, frequency, duration, extent and depth of inundation).
Many shallow freshwater wetlands are highly ephemeral, often comprising of large
shallow areas that regularly dry out during summer, and pockets of deeper permanent
water. A major feature of shallow freshwater wetlands is the presence of emergent
aquatic plants (plants that grow above the water surface and are commonly referred
to as macrophytes).
Shallow freshwater wetlands are characterised by a diverse range of physical,
chemical and biological processes that are dependent upon the wetland water regime,
wetland soils, microbial processes and the types of aquatic vegetation present.
Freshwater wetlands are generally characterised by the presence of highly organic,
reduced (anoxic) sediments due to regular inundation of the wetland soils. Wetlands
play an important role in nutrient cycling, acting as a sink for phosphorus and
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Melbourne Water Constructed Wetlands Design Manual
providing conditions where organic carbon, nitrogen and sulphur is transformed to
gaseous forms and released back into the atmosphere.
The aquatic plants that grow in wetlands have adapted to survive both inundated and
dry conditions. The biochemical, molecular and morphological adaptations of aquatic
plants to inundation include tolerance to anoxia (metabolic regulation), the presence
of aerenchyma (air spaces which extend throughout the plant and allow the plant to
supply oxygen to submerged tissues) and the ability to elongate inundated shoots (to
renew contact with the aerial environment).
Constructed wetlands
This document refers to removing stormwater pollutants and providing other WSUD
benefits to wetlands that are constructed within urban areas.
The capacity of wetlands to remove pollutants (nutrients, suspended solids and
metals) from water has led to the widespread use of constructed wetlands to improve
the quality of stormwater runoff from urban catchments.
Constructed wetlands are typically shallow, extensively vegetated freshwater bodies
that use enhanced sedimentation, fine filtration, chemical and biological uptake
processes to remove pollutants from stormwater runoff.
As complex and highly active biological systems, constructed wetlands rely heavily
upon microbial processes to intercept, transform and remove pollutants from
stormwater. Constructed wetlands are robust and dynamic systems that can cope with
large variations in flow and water quality. The presence of emergent aquatic plants
within constructed wetlands is crucial to the long term performance of the wetland
system, as the plants play a major role in the uptake of nutrients, and the health of
the wetland sediments and microbial communities. Constructed wetlands therefore
need to be carefully designed to provide the best conditions for plant growth to ensure
the long term performance of the wetland.
A well-designed constructed wetland can remove pollutants under varying hydraulic
conditions. If a constructed wetland is not designed appropriately, the wetland
vegetation may fail to establish, sediment/microbial health will be poor, and the
wetland may provide limited treatment of pollutants, or actually become a source of
pollutants itself.
Constructed wetlands are commonly used for stormwater treatment by developers
and councils due to their amenity and recreational value to the community. They also
provide a range of benefits such as wildlife habitat, management of stormwater runoff
Constructed Wetlands Design Manual Melbourne Water
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volumes and frequency, stormwater harvesting and reuse opportunities, and minimal
maintenance requirements once established.
Stormwater treatment mechanisms
Constructed wetlands are commonly used to treat stormwater to best practice
standard by removing:
 Gross pollutants
 Sediments
 Nitrogen
 Phosphorus
Stormwater treatment wetlands are also known to be efficient at removing a number
of other pollutants associated with urban stormwater runoff including:
 Metals
 Pathogens (e.g. E Coli)
 Organic compounds
The key treatment mechanisms associated with constructed stormwater treatment
wetlands are summarized below:
Physical
 Trap sediments – vegetation in the wetland facilitates
sedimentation of particles down to the fine colloidal fractions
enhanced
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Trap adsorbed pollutants – traps a high proportion of adsorbed pollutants
through high capture of fine particles
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The presence of vegetation minimises the likelihood of widespread reentrainment of trapped sediments
Biological and chemical uptake
 Trap dissolved pollutants – vegetation provides surfaces for epiphytic
biofilms which take up dissolved pollutants

Chemical adsorption of pollutants to fine suspended particles which are
trapped through enhanced sedimentation and adhesion facilitated by
macrophytes and biofilms
Pollutant transformation
 The regular wetting and drying cycle within wetlands leads to more stable
sediment fixation of contaminants (such as phosphorus and metals) in the
substratum
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Microbial processes such as nitrification and denitrification result in
nitrogenous pollutants such as ammonium and nitrate being converted to
nitrogen gas and being dispersed into the atmosphere

UV treatment in an open water area provides some disinfection
Melbourne Water Constructed Wetlands Design Manual
Components of a typical constructed wetland
Constructed treatment wetlands comprise of three major components: sediment pond,
macrophyte zone and bypass route (channel or pipe). Figure 1 and Figure 2 show an
indicative plan view and section of a typical wetland layout. All inflows enter a
sediment pond and are subsequently split between the macrophyte zone and bypass
route. These three components are important for all wetlands, even if some or all of
the wetland sits within a retarding basin.
Figure 1 Indicative plan view of a typical wetland layout
Figure 2 Indicative section of a typical wetland layout
Constructed Wetlands Design Manual Melbourne Water
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Sediment Pond
The sediment pond is an open water body where stormwater runoff enters the
constructed wetland system (refer Figure 3). The sediment pond reduces the velocity
of inflows, traps coarse sediments and generally protects the macrophyte zone.
Figure 3 Example sediment pond (Banyan Reserve, Carrum Downs)
Stormwater enters the sediment pond via a drainage inlet pipe or a
waterway/drainage channel. The sediment pond is sized to promote settling to
capture coarse sediments.
Generally, gross pollutants are removed using gross pollutant traps located in the
catchment upstream of the sediment pond. In cases where no upstream gross
pollutant traps are present, the inlet pipes to the sediment pond may be fitted with
litter traps.
The sediment pond is connected to the macrophyte zone by a connection sized to pass
the three month ARI flow. This protects the vegetation and deposited fine particulates
in the macrophyte zone from scour. Isolation of the sediment pond from the
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Melbourne Water Constructed Wetlands Design Manual
macrophyte zone is important, as this enables the water level within the sediment
pond to be reduced during maintenance without impacting on the water level in the
macrophyte zone.
When flows entering the sediment pond exceed the three month ARI flow, or the
extended detention depth of the macrophyte is full, stormwater is discharged from the
sediment pond via an overflow weir into a bypass channel. The bypass channel
conveys high flows around the macrophyte zone. The key features of a sediment pond
are shown in Figure 4 and Figure 5.
Constructed Wetlands Design Manual Melbourne Water
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Figure 4 Indicative plan view of a typical sediment pond layout
Figure 5 Indicative section of a typical sediment pond
A maintenance access track to the base of the sediment pond is required for vehicular
access to the sediment pond during sediment cleanout events. A sediment dry out
area must be provided in an area adjacent to the sediment pond. The accumulated
sediment removed from the sediment pond is stockpiled on the sediment dry out area
to allow sediment dewatering to occur prior to the sediment being removed
elsewhere.
Sediment ponds are maintained as open water systems, however emergent aquatic
plants (macrophytes) are normally planted around the shallow margins of the
sediment pond to assist with bank stability, improve visual amenity and to discourage
public access.
Macrophyte zone
The macrophyte zone consists of one or more densely planted linear cells (refer Figure
6).
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Melbourne Water Constructed Wetlands Design Manual
Figure 6 Densely planted macrophyte zone (Narre Warren North)
The function of the macrophyte zone is to provide a low velocity environment where
the smaller suspended particles are able to settle out of suspension or adhere to the
vegetation. Soluble pollutants, such as nutrients, are adsorbed onto the surfaces of
suspended solids and entrained within the wetland sediments, or biologically absorbed
by the biofilms (algae, bacteria) present on the macrophytes-or by the macrophytes
themselves. Microbial activity within the biofilms or within the sediment helps to
decompose organic matter and is crucial to the transformation and export of carbon,
nitrogen and sulphur (in gaseous forms) from the wetland.
The presence of macrophytes is also important in maintaining positive redox potential
in the sediments, thereby controlling the release of phosphorus from the sediments.
The macrophyte zone also provides a valuable habitat for aquatic fauna such as
invertebrates, waterbirds and amphibians.
It is important that the macrophyte zone is protected from high flows so that the
biofilms present upon the macrophytes are not removed. Fine sediments accumulated
within the wetland and the macrophytes themselves can also be scoured from the
wetland by high flows.
Constructed Wetlands Design Manual Melbourne Water
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Stormwater enters the macrophyte zone inlet pool where energy is dissipated and the
velocity of inflowing stormwater is reduced. The bathymetry of the macrophyte zones
is designed so that stormwater passes through a sequence of densely vegetated
marsh zones (shallow, deep and submerged) prior to exiting the macrophyte zone via
the outlet pool. The key features of a macrophyte zone are shown in Figure 7 and
Figure 8.
Figure 7 Indicative plan view of a typical macrophyte zone layout
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Melbourne Water Constructed Wetlands Design Manual
Figure 8 Indicative section of a typical macrophyte zone
The marsh zones are arranged in a banded manner, perpendicular to the flow
direction, so that stormwater can flow evenly through the macrophyte zone
vegetation, and interact with the biofilms present upon the surfaces of the
macrophyte stems. The treatment performance of the wetland is highly dependent
upon flows passing through dense vegetation distributed across the entire macrophyte
zone (Figure 9). Clumped vegetation and open water flow paths result in the short
circuiting of flows within the wetland and reduced treatment performance.
Open water areas (comprising of submerged marsh) should not exceed more than
20% of the wetland area. Open water areas should be provided as inlet and outlet
pools, and as intermediate pools in larger wetlands.
The distribution of wetland vegetation is typically determined by inundation depth,
frequency and duration. In constructed wetlands, these features are determined by
the permanent pool depth of the various macrophyte zones (submerged marsh, deep
marsh, shallow marsh, ephemeral marsh) and the amount of time inflows engage the
extended detention.
Constructed Wetlands Design Manual Melbourne Water
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a)
b)
Figure 9 Treatment performance of the wetland is highly dependent upon the presence
of dense vegetation: a) Good performance - dense vegetation and even flow path
through the wetland, b) Poor performance - clumped vegetation and multiple open
water flow paths.
The vegetation planted within the macrophyte zone should be selected based on
predicted water levels relative to the height of the plant species. Emergent
macrophytes are sensitive to excessive inundation depths and durations. Macrophyte
species planted within the shallow and deep marsh zones should be sufficiently robust
to cope with the expected hydrologic regime within the macrophyte zone.
The macrophyte zone (and planted margins of the sediment pond) must be lined with
topsoil to enable plants to grow and protect the wetland liner (generally compacted
clay) from being eroded.
Outflows from the macrophyte zone are regulated by a controlled outlet located
within, or adjacent to, the outlet pool. The controlled outlet sets the normal water
level within the macrophyte zone and is configured so that stormwater will take
approximately three days to pass through the system (residence time). The controlled
outlet is also configured to enable the water level in the macrophyte zone to be
lowered during the establishment phase to assist with the development of the
macrophytes.
The controlled outlet generally comprises of a weir, riser or plate with orifices, and is
housed within an outlet pit. Only water that has been treated in the wetland for
approximately three days is released through the controlled outlet and conveyed via
an outlet pipe to the downstream waterway.
When the top extended detention (TED)
further inflows are discharged from the
overflow weir. In most cases, the outlet pit
and also act as an overflow pit. However,
overflow pit.
12
of the macrophyte zone is exceeded, all
macrophyte zone via an overflow pit or
is configured to house the controlled outlet
large wetlands may also have a dedicated
Melbourne Water Constructed Wetlands Design Manual
Bypass route
The bypass route allows flows to be diverted around the macrophyte zone when the
water level is at TED. The bypass route protects the macrophyte zone from scour
during high flow events, and enables the wetland to be temporarily taken off-line for
maintenance or water level regulation (i.e. it may be beneficial to dry the wetland out
periodically to stimulate plant regeneration).
The bypass generally consists of a vegetated channel, but could also involve pipes,
culverts, etc. For wetlands within retarding basins, the bypass operates until it is
inundated by water filling up the retarding basin.
Amenity in constructed wetlands
Constructed wetlands are a valued asset to urban communities, providing open space
areas with formal and informal recreational benefits. Well-designed constructed
wetlands incorporated into new urban environments are often highly valued natural
assets.
The amenity associated with constructed wetlands is a commonly expressed reason
for community visitation to these areas and is therefore an important value that needs
to be managed and protected.
The landscape values associated with constructed wetlands delivered by Melbourne
Water are generally provided via planting vegetation and facilitating and/or carefully
managing public interactions with the wetland area in the form of paths, boardwalks
and pedestrian bridges. Please note that Melbourne Water does not fund or maintain
boardwalks and pedestrian bridges associated with constructed wetlands.
Landscape values are also delivered through the interface between Melbourne Water’s
interests and any Council requirements for adjacent public open spaces where
physical infrastructure may be provided (e.g. open mown grassed areas, seating,
playgrounds and barbeques). With all these elements being closely related, amenity
values can be created through the landscape design process.
Wetland amenity values are diminished by the presence of unpleasant or intrusive
development, odour, colour, litter, noise, mosquitoes and other pests.
The design of constructed wetlands and the surrounding urban environment requires
an integrated approach where the requirements of Melbourne Water and Council
influence each other to support a common vision.
Constructed Wetlands Design Manual Melbourne Water
13
A clear demarcation between the roles and responsibilities of Melbourne Water and
Council is essential to effectively deliver amenity in constructed wetlands.
Responsibility for different parts of the constructed wetland system and surrounding
open spaces must be clearly defined to enable effective asset ownership and
maintenance, especially at the interface between these two areas. See Part B1 of this
manual for amenity design objectives.
Hydrodynamic design considerations
The hydrodynamic design of constructed wetlands is crucial to the successful
establishment of emergent and submerged vegetation, and the ongoing performance
of the wetland. Poorly designed wetlands often result in ongoing operational and
management problems and do not provide the intended level of water quality
treatment.
A summary of the major hydrodynamic requirements which should be considered
during wetland design are provided in the table below:
14
Flow distribution

The wetland shape, bathymetry and placement of the inlet and
outlets must facilitate uniform flow across the wetland. This will
help avoid short circuiting of flows and poorly mixed zones.
Permanent pool
depth

The wetland bathymetry must facilitate establishment of
emergent and submerged macrophytes throughout the
wetland. Macrophyte species are sensitive to permanent pool
depth, and the depth ranges provided within each marsh zone
should be suitable for the types of macrophytes to be planted.
Hydrologic regime

The
wetland’s
extended
detention
hydrologic
regime
(inundation depth, duration and frequency) has a major
influence on the establishment and persistence of macrophytes
within the wetland. The hydrological characteristics of the
wetland’s extended detention (depth, inlet and outlet
properties) therefore play a major role in the sustainability of
vegetation cover within the wetland and the ongoing water
quality treatment performance of the wetland system.

Wetlands should be designed to enable the permanent pool to
be occasionally drawn down, as this replicates the hydrological
regime of natural wetlands through regular wetting and drying
of the wetland sediments (important to nutrient uptake) and
the long term sustainability of the wetland vegetation
(macrophyte regeneration and growth).
Melbourne Water Constructed Wetlands Design Manual
Constructed wetlands within retarding basins
Constructed wetlands are often located in the base of a retarding basin to reduce the
total amount of land required for stormwater treatment and flood mitigation. Wetlands
located within a retarding basin are prone to greater inundation depths when
retarding basins are engaged during intense rainfall events. Whilst the drawdown of
water levels in a retarding basin is normally short (less than 12 hours), it will take at
least another three days for water levels in the wetland to return to NWL, meaning
that the wetland vegetation may be inundated for extended periods of time.
It is important that the hydraulic and hydrologic conditions within retarding basins are
checked during the design process to ensure that the wetland vegetation is protected
from high inflow velocities and that the expected inundation depth, frequency and
duration will not be detrimental to the long term health of the wetland vegetation.
Designing to avoid mosquitos
Mosquitos are a natural component of wetland fauna. The construction of any water
body will create a habitat suitable for mosquito breeding and growth. Healthy, well
vegetated wetlands function as balanced ecosystems and have predators that control
mosquito populations. The risk of mosquito breeding can be addressed through:
 Ensuring all parts of the wetland are well connected to provide access for
mosquito predators to all inundated areas of the wetland;
 Providing areas of permanent open water that provide refuges for mosquito
predators (even during long dry periods);
 Ensuring wetland water quality is adequate for the support of mosquito
predators (this is normally the case for wetlands where stormwater is the
dominant inflow);
 Providing a bathymetry that ensures that regular wetting and drying is achieved
and water draws down evenly so isolated pools are avoided;
 Ensuring wetland configuration does not provide dead spots or open areas away
from normal direction of flow;
 Maintaining water level fluctuations that disturb the breeding cycle of some
mosquito species;
 Providing gross pollutant control upstream of the wetland so that gross
pollutants do not accumulate and provide mosquito breeding habitat within the
wetland; and
 Ensuring that maintenance procedures do not result in wheel ruts or other
localised depressions that create isolated pools when wetland water levels fall.
Constructed Wetlands Design Manual Melbourne Water
15
Designing for maintenance access
Constructed wetlands must be designed to facilitate maintenance access to all areas
of the wetland. Maintenance requirements should be considered through all phases of
wetland design, as it may be too late to modify a wetland design to accommodate
maintenance access during detailed design.
A summary of the major wetland maintenance access requirements that should be
considered during wetland design are provided in the table below:
Sediment pond
Macrophyte zone

Access track between external site access and sediment pond,
capable of supporting large vehicles.

Ramp to base of sediment pond to enable heavy machinery to
enter sediment pond for clean out operations (except for small
ponds that may be edge cleaned).

Track between sediment pond and dewatering area capable of
supporting large vehicles.

Access to hydraulic structures, e.g. inlet and outlet pipes,
bypass weir, pits, etc.

Gentle batter slopes to enable maintenance access to the
perimeter of the sediment pond.

Access track around the perimeter of the wetland for weeding,
replanting and litter collection. Perimeter access tracks are
often integrated with the landscape design, e.g. pedestrian
pathway networks can also be used for maintenance vehicle
access.

Access to wetland outlet structures (pits) and water level
gauge.

Gentle batter slopes to enable the macrophyte zone to be
readily accessed from all locations.
Climate change
An assessment of the potential impacts of climate change on constructed stormwater
treatment wetlands was undertaken by Melbourne Water (EDAW, 2010). Predicted
long term changes in climate for Melbourne include:
 Long term increase in temperatures and evapotranspiration, particularly during
summer;
 Reduced mean annual rainfall, particularly during winter and spring; and
 Infrequent but more intense storms and longer dry spells with heavy rainfall
events, particularly during summer.
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Melbourne Water Constructed Wetlands Design Manual
A range of climate change scenarios were modelled, based upon synthetic rainfall
datasets created to simulate predicted seasonal changes in rainfall and
evapotranspiration for 2030 and 2070.
The modelling indicated that climate change would result in a slight increase in
treatment performance of stormwater wetlands. However, this was offset by the
combined effect of decreased mean annual rainfall and increased evapotranspiration.
The modelling indicated that increased evapotranspiration would result in increased
permanent pool drawdown; however this also enabled wetlands to be able to cope
with more intense storms.
The study concluded that no design response is required to protect stormwater
treatment wetlands from the potential impacts of climate change, and that potential
issues associated with water level drawdown could be managed by slightly increasing
the normal water level of a wetland.
Safety in Design
As part of Melbourne Water’s ‘Zero Harm’ culture, ‘Safety in Design’ is a paramount
consideration. We ensure our designs are safe for the contractors to build, safe for
people to use, and safe for people to maintain in the future. Our management of risks
and hazards include eliminating, through design, as many risks as possible that may
be encountered during construction, maintenance or demolition.
Wetland designs must comply with the Melbourne Water Safety in Design Audit to
ensure that projects are undertaken in accordance with the Melbourne Water Safety in
Design Management Procedure.
Constructed Wetlands Design Manual Melbourne Water
17
Constructed Wetlands
Design Manual
Part A2: Planning, funding and management
Table of contents
Introduction
1 Melbourne Water’s statutory role in new development
1 Water Industry Act (1994) ......................................................................1 Water Act (1989) ...................................................................................2 Planning and Environment Act (1987) .......................................................2 Subdivisions Act (1988) ..........................................................................3 Legislation and constructed wetlands
3 State Environment Protection Policy (Waters of Victoria) ..............................3 Living Victoria policy ...............................................................................6 Melbourne’s Water Future .......................................................................6 Plan Melbourne ......................................................................................6 Victorian Planning Provisions ...................................................................7 Urban Stormwater Best Practice Environmental Management Guidelines for
stormwater treatment........................................................................... 10 Melbourne Water policies and strategies
10 Enhancing Life and Liveability ................................................................ 10 Relationship Strategy ........................................................................... 11 Service Delivery Strategy ...................................................................... 11 Asset Management Strategy .................................................................. 11 Waterways and Drainage Strategy .......................................................... 12 Stormwater Strategy ............................................................................ 13 Healthy Waterways Strategy .................................................................. 13 Flood Management and Drainage Strategy ............................................... 13 Planning and Building (Land Development Manual) website ........................ 13 Planning for constructed wetlands
14 Development Services Schemes ............................................................. 14 Funding constructed wetlands
14 Development Contributions ................................................................... 15 Scheme Reimbursements ...................................................................... 15 Waterways and Drainage Charge ............................................................ 15 Financial principles ............................................................................... 16 Managing constructed wetlands
17 Delineation of Melbourne Water and council ownership .............................. 17 Ownership of wetland systems ............................................................... 17 Ownership of the wetland and surrounding open space area ....................... 17 Design Manual Melbourne Water
i
Part A2: Planning, funding and
management
Introduction
Melbourne Water is the waterway, floodplain and drainage management authority
across the entire Port Phillip and Westernport region.
Melbourne Water’s statutory role in new development
Melbourne Water performs waterway, floodplain and drainage management functions
under the Water Act (1989) and Water Industry Act (1994). Melbourne Water is also a
Referral Authority for Town Planning applications from Councils under the Subdivision
Act (1988) and Planning and Environment Act (1987).
Melbourne Water plays an important role in coordinating the planning, design and
delivery of a variety of stormwater management infrastructure. This infrastructure
services new urban development, including the many proposed future constructed
wetlands that have been planned in our Development Services Schemes across the
region’s growth areas.
There are also a number of regulatory considerations for stormwater management.
They include water policy, such as the State Environment Protection Policy – Waters
of Victoria, as well as key government strategies and the Victoria Planning Provisions.
The following sections outline in further detail some of the regulatory considerations
for stormwater management.
Water Industry Act (1994)
Under Section 42(1) of the Water Industry Act (1994), the Minister for Water is
responsible for issuing Melbourne Water with a ‘Statement of Obligations’. Section 6-3
of the Statement of Obligations sets out Melbourne Water’s responsibilities with
respect to ‘Waterways and Drainage’ and requires that Melbourne Water prepare,
implement and report on a Waterways and Drainage Strategy. Melbourne Water has
addressed this obligation by producing the following strategic documents:

Waterways Operating Charter

Healthy Waterways Strategy

Stormwater Strategy

Floodplain and Drainage Strategy
Constructed Wetlands Design Manual Melbourne Water
1
The Charter and accompanying Strategies provide important context for a series of
other related plans and guidelines, including our Development Services Schemes. This
information assists Melbourne Water and our customers to deliver the waterway,
floodplain and drainage management services we are obligated to provide the
community.
Water Act (1989)
Melbourne Water has a range of powers under the Water Act (1989) that enable us to
carry out a broad range of functions. Part 10 of the Water Act (1989) relates
specifically to Melbourne Water’s waterway, floodplain and drainage management
functions.
Provisions exist under Section 199 of the Water Act (1989) to establish Development
Services Schemes, which are the principal planning tool Melbourne Water uses to
assist in implementing our waterway, floodplain and drainage management functions
within the growth areas across the Port Phillip and Westernport region.
This legislation is currently being reviewed.
Planning and Environment Act (1987)
Under Section 55 of the Planning and Environment Act (1987), the Responsible
Authority must refer all Planning Permit applications to Melbourne Water for proposed
buildings and works: on:
 properties covered by Land Subject to Inundation Overlays (LSIO), Special
Building Overlays (SBO), Floodway Overlays (FO);
 land designated as an Urban Floodway Zone (UFZ);
 land within 30 metres of a designated waterway;
 floodplains within Melbourne Water’s waterway management district.
Under Section 56 of the Planning and Environment Act (1987), Melbourne Water may
place conditions on Planning Permits that require the applicant to meet certain
obligations with respect to drainage, floodplain and waterway management.
Melbourne Water may request functional designs be prepared to our satisfaction, prior
to being able to respond to a Planning Permit application. An example of a situation
where this might occur is where development layouts are required to incorporate
stormwater management assets such as retarding basins, wetlands and waterways,
which all require the appropriate land area to ensure proper functioning of these
assets.
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Melbourne Water Constructed Wetlands Design Manual
Subdivisions Act (1988)
Under Section 8 of the Subdivision Act (1988) the Responsible Authority must refer
Plans of Subdivision to Melbourne Water for consent prior to Certification. As part of
the referral process, Melbourne Water may request more information or require a
stormwater management strategy and/or engineering functional design plans to be
prepared prior to being able to provide a Letter of Consent for the Certification of a
Plan of Subdivision.
Melbourne Water always requires Reserves to be created over existing and
constructed wetlands on Plans of Subdivision. Typically, the Reserves vested to the
local Council, with Melbourne Water requiring a Memorandum of Common Provisions
(MCP) Easement (AA1107) to be created over the Reserve in our favour.
Legislation and constructed wetlands
State Environment Protection Policy (Waters of Victoria)
The State Environment Protection Policy (SEPP) (Waters of Victoria) is a state wide
policy that requires runoff from urban and rural areas not to compromise the
beneficial uses of receiving waterways. This policy specifically refers to stormwater
pollution and requires the implementation of measures to control its environmental
impact. Water Sensitive Urban Design and constructed wetlands are two tools used to
comply with this Policy.
The SEPP sets a statutory framework for the protection of the uses and values of
Victoria’s fresh and marine water environments. As required by the Environment
Protection Act (1970), the SEPP includes:

uses and values of the water environment that the community and government
want to protect-these are known as beneficial uses;

objectives and indicators that describe the environmental quality required to
protect beneficial uses;

guidance to catchment management authorities, coastal boards, water
authorities, communities, businesses and local government and state
government agencies to protect and rehabilitate water environments to a level
where environmental objectives are met and beneficial uses are protected-this
is known as The Attainment Program.
The SEPP is based on the principles of the Environment Protection Act (1970) and
reflects the community's expectations of how we should continue to provide for
Victoria’s economic and social development while sustaining our environment. The
Constructed Wetlands Design Manual Melbourne Water
3
principles are listed in Part II (Clause 5) of the SEPP and should be considered when
making decisions on implementing the SEPP. Essentially, the principles promote the
adoption of sound environmental practices and procedures as a basis for ecologically
sustainable development. They promote a 'triple bottom line' approach by integrating
the consideration of environmental, social and economic values in planning and
decision-making processes.
To protect its beneficial uses, water needs a certain level of health. Water must not
carry pollutants (e.g. nutrients, sediment, salt and toxicants):
 at levels that are harmful to humans, plants and animals
 that result in an objectionable colour or odour,
 that renders the water unsuitable for the many uses that depend on healthy
water.
In addition, water needs to be free of human impacts detrimental to beneficial uses.
The SEPP provides a measure of the health of water environments by nominating core
objectives and indicators that can be used to assess the key risks to beneficial uses.
These objectives and indicators describe the level of health required to ensure
beneficial uses. Indicators relevant to stormwater, including water within constructed
waterways and wetlands, are: nutrients (phosphorus and nitrogen), turbidity, salinity,
pH, dissolved oxygen, toxicants (in water and sediments) and biological indicators.
The biological indicators and objectives are especially important, as they provide a
direct means of assessing the health of an ecosystem as affected by water quality,
flow and habitat.
The SEPP also contains a series of actions encapsulated as clauses. Those relevant to
constructed wetlands are outlined here:
Clause 10: Beneficial uses
Artificial stormwater drains and artificial wetlands are exempt from having to meet
beneficial uses as per natural surface water systems. These artificial environments
need to be managed for the purpose for which they were constructed. They must be
designed and managed so as not to be harmful to humans or have unacceptable
impacts on animals, and they must minimise impact on surface waters.
Clause 43: Surface water management and works
Works on or adjacent to surface waters must be managed to minimise environmental
risks to the aquatic ecosystem and to protect other beneficial uses. To enable this,
surface water managers need to:
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Melbourne Water Constructed Wetlands Design Manual
1. ensure works within or adjacent to surface waters are managed so that
unnatural erosion, sediment re-suspension and other environmental risks to
aquatic habitats are minimised; and
2. ensure existing and new in-situ structures do not pose a barrier to native fish
movement.
Clause 46: Urban stormwater
Although the beneficial use of the aquatic ecology is not protected in artificial
stormwater drains, stormwater run-off from urban areas can have a significant impact
on rivers, streams, lakes, estuaries, wetlands, bays and coastal waters. These
environments must be protected for the purpose for which they have been
constructed (i.e. the transport of stormwater) and must not have unacceptable
impacts on animals.
The SEPP supports the development and implementation of municipal stormwater
management plans and the implementation of effective management practices,
particularly for new residential developments and drainage systems.
The SEPP makes reference to the Urban Stormwater Best Practice Management
Guidelines (1999), which includes actions to minimise the pollution of stormwater as
well as guidance on the content of stormwater management plans. In addition, the
SEPP identifies the need for EPA to work with municipal councils and DSE to ensure
new developments include practices to minimise stormwater runoff volumes and the
impacts of urban stormwater.
Improved stormwater management will contribute to the protection of the ecological,
economic, recreational and aesthetic values of Victoria’s waters.
Clause 56: Construction activities
Construction practices that fail to control pollution can cause damage to waterways
and wetlands and disturb aquatic ecosystems by smothering habitats and contributing
nutrients that may have significant impacts on fish, plants and other aquatic life.
To protect beneficial uses, all construction activities must be managed to minimise
impacts on aquatic environments, particularly if works cross or adjoin surface waters.
By enabling the reduction of sediment, nutrient, litter and contaminated water runoff
from construction sites, the Clause contributes to the protection of the ecological,
economic, recreational and aesthetic values of Victoria’s water environments.
Consideration of these issues at the planning phase of a project will help ensure that
Constructed Wetlands Design Manual Melbourne Water
5
measures to prevent pollution are built into the project’s design, work schedule and
budget.
Living Victoria policy
Living Victoria is the Government’s 2010 election commitment to urban water reform.
It is an effective new way of planning and servicing our urban water cycle – drinking
water, stormwater, wastewater, the environment and urban amenity. The Living
Victoria policy involves using more of the water available within our urban areas and
less use of water from outside the urban catchment. Research shows that urban areas
have significant alternative water sources, such as rainwater, stormwater and
wastewater, which can meet our non-potable water needs.
Melbourne’s Water Future
Melbourne’s Water Future is the beginning of a new era in water cycle planning and
management. This new approach looks at how the different parts of the whole water
cycle work together. All parts of the water cycle-drinking water, rainwater, stormwater
(which runs off our hard surfaces), wastewater, groundwater, natural waterways and
green open spaces-are connected in ways that best deliver liveable, sustainable,
resilient and productive communities. Some of the key vision statements guiding the
document include:

Lower costs for water and infrastructure (large water augmentation projects)

Secure drinking water supplies

Improved environment, and waterway health

Green neighbourhood parks and gardens
Plan Melbourne
Plan Melbourne is the Victorian Government's metropolitan planning strategy to guide
the city's growth to 2050. It is a strategy to house, employ and move more people
around the metropolitan area and beyond.
The strategy explains that Melbourne’s sustainability is defined by the strength, health
and beauty of our natural environment, and the resilience of our built environment.
Key to sustainability is the way in which we manage our water, energy and waste
resources. As the city grows, it will become increasingly important to maintain the
health of urban waterways, enhance our biodiversity values and ensure a balanced
approach to coastal protection. We need to change the way we plan and manage both
urban development and water services to enable a more comprehensive and
innovative approach to using stormwater and recycled water.
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Melbourne Water Constructed Wetlands Design Manual
Victorian Planning Provisions
The Victoria Planning Provisions (VPP) contains a number of clauses that support the
sustainable management of stormwater runoff from development, including the use of
constructed wetlands. Clauses include the State Planning Policy Framework Clauses
10, 11, 12, 14, 15 and 19, which pertain to all types of development within Victoria.
Councils are responsible for administering planning policies, and these clauses ensure
the planning schemes sent to Councils and Melbourne Water appropriately apply water
quality requirements to all developments, including residential, industrial and
commercial uses.
Clauses 56.07 and 56.08 of the VPP were introduced on 9 October 2006 and provide
greater standards and requirements around the sustainable management of
stormwater runoff from developments. Clause 56.07 relates to integrated water
management in residential subdivisions, and Clause 56.07-4 and Standard 25
mandate best practice targets for pollutant load reductions and flow discharges to be
met in such developments.
In most cases, these guidelines require the incorporation of water quality treatment
systems and constructed wetlands into subdivision design. Clause 56.08 establishes
requirements for site management during residential subdivision works and includes
many issues relevant to the protection of water quality treatment systems, such as
site sediment control.
All of the abovementioned planning policies relating to stormwater management apply
state wide. Further information on these policies is provided below.
Clause 10 – Operation of the State Planning Policy Framework
This Clause, and the following Clauses, establishes the link between the planning
system and the state requirements for environmental protection, and provides
guidance for developers from a planning perspective.
Clause 11 – Settlement
Clause 11 aims to ensure a sufficient amount of land is available for residential,
commercial, industrial, recreational, institutional and other public uses within urban
areas. Clause 11 aims to contribute towards:

“A high standard of urban design and amenity;

Prevention of pollution to land, water and air; and

Protection of environmentally sensitive areas and natural resources.”
Constructed Wetlands Design Manual Melbourne Water
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Clause 12 – Environmental and Landscape Values
Clause 12 aims to “protect the health of ecological systems and the biodiversity they
support” and to “conserve areas with identified environmental and landscape values”.
It states that “Planning must implement environmental principles for ecologically
sustainable development that have been established by international and national
agreements”.
Clause 14 – Natural Resource Management
Clause 14 aims to “assist in the conservation and wise use of natural resources
including energy, water, land, stone and minerals to support both environmental
quality and sustainable development”.
Clause 14.02, Water, outlines objectives, strategies and policy guidelines for
catchment planning and management, water quality and water conservation. This
clause includes protecting and restoring waterways, catchments and other water
bodies, protecting water quality, and encouraging the use of alternative water
sources.
Clause 15 – Built Environment and Heritage
Clause 15 aims to protect “sites with significant heritage, architectural, aesthetic,
scientific and cultural value”. It sets out to achieve high quality urban design to
contribute positively to communities, enhance liveability, reflect cultural identity, and
promote attractive and high amenity communities.
Clause 19 – Infrastructure
Clause 19 aims to ensure social and physical infrastructure is provided in an “efficient,
equitable, accessible and timely” way.
Clause 19.03-2, Water supply, sewerage and drainage, requires that planning and
responsible authorities ensure:
1. “Water quality in water supply catchments is protected from possible
contamination by urban, industrial and agricultural land uses.”
2. Urban stormwater drainage systems take into account the catchment context,
and “include measures to reduce peak flows and assist screening, filtering and
treatment of stormwater, to enhance flood protection and minimise impacts on
water quality in receiving waters” and prevent intrusion of litter.
Clause 19.03-3, Stormwater, has a key objective to “reduce the impact of stormwater
on bays and catchments” with strategies to:
1. “Support integrated planning of stormwater quality through a mix of on-site
measures and developer contributions.
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Melbourne Water Constructed Wetlands Design Manual
2. Mitigate stormwater pollution from construction sites.
3. Ensure stormwater and groundwater entering wetlands do not have a
detrimental effect on wetlands and estuaries.
4. Incorporate water-sensitive urban design techniques into developments to:
-
Protect and enhance natural water systems.
-
Integrate stormwater treatment into the landscape.
-
Protect quality of water.
-
Reduce run-off and peak flows.
-
Minimise drainage and infrastructure costs.”
Clause 56.07-4 and Standard C25
Under Clause 56.07-4, local councils are responsible for ensuring urban runoff from
new residential subdivisions of 2 lots or more meets best practice water quality and
flow requirements. The objectives of Clause 56.07-4, which must be met, are:
1. “To minimise damage to properties and inconvenience to residents from urban
run-off.
2. To ensure that the street operates adequately during major storm events and
provides for public safety.
3. To minimise increases in stormwater run-off and protect the environmental
values and physical characteristics of receiving waters from degradation by
urban run-off.”
Standard C25 sets out the normal way of meeting the Clause 56.07-4 objectives. In
addition to other requirements, Standard C25 requires that urban stormwater
management systems must be:
1. Designed to meet current best practice performance objectives for stormwater
quality, as outlined in the Urban Stormwater: Best Practice Environmental
Management Guidelines (Victorian Stormwater Committee, 1999) as amended.
2. Designed to ensure that flows downstream of the subdivision site are restricted
to predevelopment levels unless increased flows are approved by the relevant
drainage authority and there are no detrimental downstream impacts.
Standard C25 requires that urban stormwater management systems are designed and
managed to the requirements of the relevant drainage authority. This is typically
Council, with the exception of catchments of 60ha or more within the Melbourne
Constructed Wetlands Design Manual Melbourne Water
9
Water drainage boundary, in which case
Melbourne Water.
the relevant drainage authority will be
Urban Stormwater Best Practice Environmental Management Guidelines for
stormwater treatment
The objectives for on-site treatment relating to urban stormwater quality, as outlined
by the Urban Stormwater: Best Practice Environmental Management Guidelines
(Victorian Stormwater Committee, 1999), are:

80% retention of the typical urban annual load for Total Suspended Solids
(TSS)

45% retention of the typical urban annual load for Total Phosphorus (TP)

45% retention of the typical urban annual load for Total Nitrogen (TN)

70% retention of the typical urban annual load for gross pollutants (litter).
The guidelines prescribe that discharges for 1.5 year ARI (Average Recurrence
Interval) be maintained at pre-development levels for stormwater treatments.
Delaying regular low flow events reduces in-stream erosion that can often result from
urban development.
These stormwater quality objectives reflect the level of stormwater management
necessary to meet the SEPP (Waters of Victoria) (EPA Victoria, 2003) requirements
and are the target design criteria for WSUD treatments.
This document is currently being reviewed and new objectives and guidelines will soon
be available.
Melbourne Water policies and strategies
Melbourne Water has a series of policies, strategies and guidelines that support the
implementation and management of constructed wetlands across the Port Phillip and
Westernport region as part of the delivery of our waterway, drainage and floodplain
management functions.
Enhancing Life and Liveability
Water is central to living. It sustains the communities we live in, the natural
environment we value and the economy we depend on.
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Melbourne Water Constructed Wetlands Design Manual
Melbourne Water will improve the quality of life and prosperity of the region by
providing safe, secure and reliable water services, desirable urban spaces and thriving
natural environments supported by healthy waterways and bays.
Every day, Melbourne Water will work with others to develop shared solutions to
manage rainwater, seawater, stormwater and treated sewage as one integrated
system. This approach will deliver the best economic, social and environmental
outcomes for all, now and in the future.
Melbourne Water’s Strategic Direction (2012)
Relationship Strategy
Relationships with customers and stakeholders are critical to Melbourne Water’s
success and reputation. The Relationship Strategy supports major change, by
transforming Melbourne Water into a truly customer-centric organisation. This
strategy puts customers at the centre of all we do and focuses our efforts on
delivering value for them.
Service Delivery Strategy
Melbourne Water is a service delivery organisation; this is reflected in our vision of
Enhancing Life and Liveability. Melbourne Water operates in a changing world with
changing expectations, with increasingly vocal customer and consumer groups,
population growth, climate change and technological developments. These issues
highlight the need to re-think Melbourne Water’s approach to the delivery of valued
services to our customers.
The Service Delivery Strategy identifies what our customers want, anticipates evolving
requirements, and explores the capabilities we require to deliver these services. The
key outcome of the Service Delivery Strategy is the Customer Service Charter
(Customer Charter), which defines the expected, measureable customer outcomes.
This strategy will transform the way that Melbourne Water does business and will
drive the achievement of our vision of Enhancing Life and Liveability. Our commitment
to the delivery of current core services is unchanged. This strategy unlocks new value
for our customers by ensuring that our services continuously evolve.
Asset Management Strategy
The Asset Management Strategy enables the business to unlock value for our
customers through applying the Asset Management Principles and Service Lifecycle to
Constructed Wetlands Design Manual Melbourne Water
11
core services, and using them to deliver new and evolving services; we will deliver on
the promises within the Customer Service Charters.
This strategy presents a wider view of asset management that incorporates existing
built assets, natural assets, and “softer” assets such as people, systems, processes
and information. This expanded view, combined with a Service Lifecycle approach,
provides a greater array of alternative solutions for consideration, including non-asset
solutions and multi-agency approaches for shared services.
Much of the value identified within Service Delivery Strategy requires implementation
through the Asset Management Strategy.
Waterways and Drainage Strategy
The Waterways and Drainage Strategy, formally known as the Waterways Operating
Charter, outlines our responsibilities, goals, services and work programs in managing
waterways, drainage and floodplains.
The strategy is Melbourne Water’s commitment to customers, stakeholders and the
community. It sets robust key performance indicators, presented as 39 targets (and
associated performance measures) against which progress is independently assessed
every year.
It also shows how Melbourne Water’s waterway, drainage and floodplain management
services:
1. contribute to Melbourne Water’s vision of 'Enhancing Life and Liveability'
2. relate to each other
3. are integrated with services to be delivered by other organisations.
The strategy outlines a five year program of works and brings together commitments
in strategies developed with input from customers and stakeholders. Costs associated
with undertaking work programs and fulfilling responsibilities in the strategy are
primarily met by the Waterways and Drainage Charge, which is paid by all property
owners in the Port Phillip and Westernport region.
Melbourne Water's legislated Statement of Obligations, which is a requirement of the
Water Industry Act 1994, specifies that the Waterways and Drainage Strategy must
be developed and implemented.
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Melbourne Water Constructed Wetlands Design Manual
Stormwater Strategy
The Stormwater Strategy focuses on managing stormwater to protect and improve the
ecosystem health of waterways and bays. The strategy articulates Melbourne Water’s
high-level strategic direction and approaches in managing stormwater in rural and
urban areas. It involves Melbourne Water working with others to achieve multiple
community outcomes for stormwater management, in relation to:

healthy waterways and bays;

wellbeing and amenity;

alternative water supply; and

public safety.
Healthy Waterways Strategy
The Healthy Waterways Strategy outlines Melbourne Water’s role in managing rivers,
estuaries and wetlands in the Port Phillip and Westernport region. It is closely linked
to the Stormwater Strategy, which focuses on managing stormwater to protect and
improve the health of waterways and bays. The strategy outlines that wetlands are
not just purely stormwater treatment systems but also ecological and amenity assets
for the community. Some of the key vision statements guiding the strategy include:

to connect diverse and thriving communities of native plants and animals;

to provide amenity to urban and rural areas and engage communities with their
environment; and

to sustainably manage balancing environmental, economic and social values.
Flood Management and Drainage Strategy
The Flood Management and Drainage Strategy aims to minimise flooding risks to
public health and safety, property and infrastructure, and to increase community
understanding and preparedness for floods.
The strategy defines five flood management objectives, and outlines actions to
achieve these and guide our priorities and expenditure.
Planning and Building (Land Development Manual) website
The Planning and Building (Land Development Manual) website provides Melbourne
Water’s policies, standards, specifications, guidelines, forms and documents to help
the land development industry provide a safe effective system for dealing with runoff, ensuring appropriate flood protection and providing drainage services in the
Constructed Wetlands Design Manual Melbourne Water
13
existing and growth areas of Melbourne. The information provided on this website
helps us to protect our civil assets, waterways and floodplains in order to meet the
environmental, economic, recreational and cultural needs of current and future
generations.
For more information on any of the documents, please visit Melbourne Water’s
website. www.melbournewater.com.au
Planning for constructed wetlands
Melbourne Water’s principle planning tool for stormwater management infrastructure
in new growth areas are our Development Services Schemes (DSS). When
development planning is undertaken outside a DSS area or in advance of a DSS being
prepared, the developer should contact Melbourne Water to discuss the proposed
stormwater management strategy.
Development Services Schemes
Melbourne Water’s approach to managing constructed wetlands in growth areas is
guided by our Development Services Schemes (DSS).
DSS provide an integrated plan of the drainage, waterway, water quality and flood
protection works that are required to provide the most hydraulically and cost effective
and environmentally sound stormwater management services to new developments
within an urbanising catchment.
At the high-level of a DSS, constructed wetlands are conceptually designed and
represented on Scheme plans. Melbourne Water uses a simple MUSIC model to predict
the wetland area needed to meet stormwater management standards.
For more information on Melbourne Water’s DSS, please refer to:
www.melbournewater.com.au\Planning-and-building
Funding constructed wetlands
Melbourne Water has three funding mechanisms in place for constructed wetlands. The
first, our DSS, funds the planning, design and construction of stormwater
infrastructure, such as constructed wetlands, via the collection and reimbursement of
development contributions. The second, assets, are 100% developer funded. The
developer designs and constructs a constructed wetland in accordance with their
subdivision (often outside a DSS) and once constructed, the asset is handed over to
Melbourne Water. The third, our Waterways and Drainage Charge, can fund the
delivery of constructed wetlands but also funds the ongoing operation and
14
Melbourne Water Constructed Wetlands Design Manual
maintenance of wetlands once they have been constructed and handed over to
Melbourne Water from developers.
Development Contributions
Melbourne Water’s DSS distribute the cost for the entire infrastructure required to
service the catchment across all of the developable land within the catchment on a per
hectare basis. The amount landowners must pay Melbourne Water when they develop
is based on this apportioned cost spread over the life of the DSS, which is typically 25
years, adjusted for the time value of money or ‘Net Present Value’ (NPV).
Melbourne Water advertises the contribution rates applicable for each DSS via our
website. Please refer to our website and ‘Principles’ document for further information.
These contributions go towards funding the capital cost of designing and constructing
wetlands.
Scheme Reimbursements
The reasonable cost of designing and constructing wetlands is reimbursed by
Melbourne Water via the DSS. Please refer to Melbourne Water’s reimbursement
principles on our website for further information.
Reimbursements for building assets - Melbourne Water
Waterways and Drainage Charge
Under the Water Act (1989), Melbourne Water undertakes waterway, floodplain and
drainage management within the Port Phillip and Westernport catchment boundaries.
Melbourne Water imposes a Waterways and Drainage Charge to all serviced properties
located within our waterway management district. This funds the range of programs to
protect and improve the health of our rivers and creeks, and to provide regional
drainage services, flood protection and flood warning systems throughout the Port
Phillip and Westernport region, The monies raised are collected on our behalf via the
retail water companies.
Prior to the commencement of each operating period, which is usually 3 to 5 years in
duration, Melbourne Water prepares and submits a Water Plan to the Essential Services
Commission for approval. The Water Plan summarises the outcomes, activities and
expenditures Melbourne Water proposes to deliver, and the prices it proposes to
Constructed Wetlands Design Manual Melbourne Water
15
charge for the life of the plan, which includes the amount of the Waterways and
Drainage Charge.
The Waterways Operating Charter sits alongside the Water Plan and establishes a
blueprint for Melbourne Water's management of rivers, drainage and floodplains over
the Water Plan period. It sets out our responsibilities and priorities, and supports the
detailed financial and pricing information outlined in the Water Plan.
Financial principles
The following supporting financial principles apply to determining cost effective
constructed wetland design, construction and maintenance:
1. Cost-benefit: Decisions about financially feasible design objectives beyond the
non-negotiable are made based on a measure of the cost-benefit of achieving
those objectives and willingness to pay.
2. Willingness to pay: The importance of achieving certain design objectives and
outcomes will dictate whether Melbourne Water or the developer will be willing
to pay to realise the outcome being sought.
Melbourne Water may be willing to pay where it is demonstrated that a wetland
will manage impacts of urbanisation beyond the development itself.
If a land developer proposes enhancements to a wetland that are not required
by Melbourne Water, but which will provide aesthetic and/or amenity benefit to
the residents within their particular development, then the land developer
should be willing to pay for the design and construction cost associated with
those enhancements.
If Melbourne Water agrees to the enhancement, it will be Melbourne’s Water’s
responsibility to maintain the enhanced wetland.
Melbourne Water will not be willing to pay for the design, construction or
maintenance costs of any enhancements within the wetland reserve that are
required by Council and/or will form area of Public Open Space that Melbourne
Water will not maintain.
3. Beneficiary pays: Depending on who is willing to pay for which aspect of any
proposed enhancement, the cost-benefit and extent of benefit will ultimately
determine the beneficiary and therefore the party who ultimately pays. In many
cases, it might not be a simple distinction between Melbourne Water and the
land developer. Therefore, some form of cost share will need to be proposed.
The basis of any cost share will take into account the principal driver behind the
enhancement (i.e. who is proposing it and why) before factoring in where
benefits are derived.
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Melbourne Water Constructed Wetlands Design Manual
Managing constructed wetlands
The majority of regional constructed wetlands have catchment areas that place them in
Melbourne Water’s responsibility for ownership and maintenance. However, Council is
likely to take ownership over constructed wetlands if the catchment area is smaller and
the treatment is more localised. The catchment area for the constructed wetland is
usually the main factor used when determining the asset owner.
Delineation of Melbourne Water and council ownership
Melbourne Water and the relevant council are the two key authorities with a
management interest in constructed wetlands. This section provides a brief overview of
this shared management interest in constructed wetlands.
Ownership of wetland systems
In 1928, the Melbourne Metropolitan Board of Works (MMBW) established an
agreement with the then 38 metropolitan municipalities about the distinction between
drains and main drains to be applied to pipelines, based on calculations of flow
capacity. The agreement was supported by a hydraulic engineer’s report which
determined that a main drain was classified where the catchment area exceeded 60
hectares. Assets in catchment areas greater than 60 hectares became MMBW (now
Melbourne Water) assets, and those assets with catchment areas less than 60 hectares
became municipal (Council) assets.
As MMBW’s, and subsequently Melbourne Water’s, management responsibility evolved
over time, the 60 hectare ‘rule’ has since been generally applied to all stormwater
quality treatment assets such as wetlands.
Ownership of the wetland and surrounding open space area
In developing areas, Council or Melbourne Water can own wetlands and surrounding
open space area. Ownership is created via a Reserve vested in either Council or
Melbourne Water. Typically, the preference is for Council to own the Reserve and
Melbourne Water to have maintenance rights to the wetland via the creation of a
Memorandum of Common Provisions Easement (MCP AA1107). The extent (coverage)
of this Easement is generally the same as the extent of the Reserve or, as a minimum,
the Easement must cover the flood extent of a 1 in 100 year ARI flood event.
A key part of constructed wetland design is the delineation of which components of the
wetland and surrounding open space area are to be owned and maintained by Council
and Melbourne Water. The preparation and execution of a ‘Maintenance Agreement’ is
a key requirement of the wetland design process. Each Council may have different
Constructed Wetlands Design Manual Melbourne Water
17
requirements when it comes to their maintenance and ownership obligations. Further
information on the creation of Maintenance Agreements is detailed on Melbourne
Water’s Land Development Manual website, or outlined in Part E.
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Melbourne Water Constructed Wetlands Design Manual
Constructed Wetlands
Design Manual
B1: Vision, core outcomes and aspirational outcomes
Table of contents
Introduction
1 Vision
1 Core outcomes
2 Effective pollutant removal ......................................................................3 Community safety ..................................................................................3 Maintenance and operational staff safety ...................................................4 Cost effective asset management .............................................................4 Aspirational outcomes
4 Wellbeing, liveability and amenity.............................................................4 Alternative water supply .........................................................................5 Recreational ..........................................................................................5 Landscape and cultural objectives ............................................................5 Accessibility ..........................................................................................5 Conservation .........................................................................................5 Constructed Wetlands Design Manual: Part B1 Melbourne Water
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B1: Vision, core outcomes and aspirational
outcomes
Introduction
Constructed wetlands should be designed to respond to the opportunities and
constraints of a particular site. The design response will be informed by characteristics
of the site (e.g. its topography, point of discharge, existing vegetation, geomorphic
character and soils) and the requirements of an urban development.
The design process and final form of a constructed wetland will be influenced by the
wetland vision. In addition to improving water quality, a vision typically includes
regulating flow rates, enhanced landscape and ecological values, and provides a range
of passive recreational and aesthetic benefits to the community.
This Part of the manual describes core outcomes that must be achieved for all
Melbourne Water constructed wetlands. The Deemed to Comply standards (refer
Part B2 of this manual) specify wetland properties that we are confident will achieve
the core outcomes. The Alternative Approach provides the option of proposing
wetland elements that differ from the prescriptive Deemed to Comply approach, but
still achieve the required core outcomes.
Aspirational outcomes are also described in this Part of the manual. Achieving these
aspirational outcomes is encouraged by Melbourne Water, however we will not accept
good performance relative to aspirational outcomes in lieu of compliance with the
required core outcomes.
The aim of this manual is to facilitate consistent delivery of best practice constructed
wetland designs. It is therefore important to define what is meant by best practice
constructed wetland design in clear terms, so that the expectations and requirements
of Melbourne Water for constructed wetlands are clear to all involved.
Vision
There are a range of strategies and resources that are relevant to defining a
constructed Wetland vision, but especially Melbourne Water’s Stormwater Strategy
(2012). The Stormwater Strategy states that sustainable stormwater management is
expected to protect people, property and receiving waters, enhance liveability and
supply fit-for-purpose cost-effective water.
Melbourne Water is working to achieve multiple community outcomes by considering
stormwater within an integrated water management framework, alongside water
Constructed Wetlands Design Manual: Part B1 Melbourne Water
1
supply, sewerage, drainage and waterway health. The desired community outcomes
are:

Healthy waterways and bays

Alternative water supply

Wellbeing and amenity

Public safety

Financially stable assets that can be maintained
Our vision for stormwater management proposes that:
“Sustainable stormwater management supports prosperous communities,
thriving landscapes and healthy waterways and bays.”
Melbourne Water has prepared the “Design, Construction & Establishment of
Constructed Wetlands” (the manual) to assist future constructed wetland designs to
achieve the vision, and the four community outcomes:
Figure 1: Community outcomes
(Stormwater Strategy Figure E1)
from
sustainable
stormwater
management
Core outcomes
All Melbourne Water constructed wetlands must achieve the following core outcomes:
1. PDeliver effective pollutant removal and flow regime management;
2. Offer a safe environment for the community to interact with;
3. Provide a safe environment for Melbourne Water officers and contractors; and
2
Melbourne Water Constructed Wetlands Design Manual: Part B1
4. Enable cost effective, long-term asset management over a life span of at least
25 years.
These core outcomes are described in more detail in the following pages.
Effective pollutant removal
The primary function of constructed wetlands is to mitigate the impacts of
urbanisation by reducing pollutant loads in stormwater runoff. The State Environment
Protection Policy Waters of Victoria (SEPP WoV) sets out base statutory requirements
for the quality of stormwater runoff. The Victorian Planning Provisions (Clause 56-07)
mandate the treatment of urban stormwater to best practice standards for all
residential subdivisions; constructed wetlands are often used for this purpose.
The Best Practice Environmental Management Guidelines for Urban Stormwater
describe the level of stormwater treatment necessary to comply with these regulatory
requirements (refer Table 1). In some circumstances, a wetland may need to be
designed to meet a higher or different level of performance than Table 1 to address
local environmental objectives, Development Services Scheme targets or other
pollutant control issues. Note that these Victorian stormwater standards are currently
being revised.
Table 1: Victorian Best Practice stormwater treatment standards (in review)
Pollutant
Performance objective
Total suspended solids
80% reduction from typical annual urban load
Total phosphorous
45% reduction from typical annual urban load
Total nitrogen
45% reduction from typical annual urban load
Litter
70% reduction from typical annual urban load
Source: (Urban Stormwater: Best Practice Environmental Management Guidelines – Victorian Stormwater
Committee, 1999)
Community safety
Many people find wetland environments appealing. It is important that aquatic safety
risks are managed appropriately, and that the safety of people around constructed
wetlands, especially when in flood, is a central focus of any design. Standing water,
pipe/pit inlets and overland flow paths must be considered as part of aquatic safety
risk management.
A safety design audit may be required to ensure that the unmitigated and mitigated
risk profiles of a design are within acceptable levels.
Constructed Wetlands Design Manual: Part B1 Melbourne Water
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Maintenance and operational staff safety
Constructed wetland designs must provide a safe environment for Melbourne Water
officers and contractors. Measures include stable access routes for vehicles, ability to
inspect key wetland components without heavy lifting and/or confined space access
requirements, and maximising the proportion of maintenance tasks that can be
undertaken from dry land.
Cost effective asset management
Constructed wetlands must be cost effective to:

design

construct

operate

maintain
The developer contribution approach provides a cost effective mechanism for the
delivery of constructed wetlands in tandem with new development. The aim is to
balance the benefits being derived from the constructed wetland with the costs of
delivering it.
The cost of maintaining constructed wetlands is ultimately borne by the community
through the Waterways and Drainage Charge that Melbourne Water collects via the
Water Retailers. We are obligated to ensure constructed wetlands are cost effective to
maintain.
Aspirational outcomes
Wetland designers should strive to achieve a range of aspirational outcomes in
addition to the required core outcomes described above. These aspirational outcomes
are summarised in the following section.
Note: Aspirational outcomes are not reimbursable. Designers should work with the
local council to ensure that desired aspirational outcomes correspond with council
recreational and public open space policies.
Wellbeing, liveability and amenity
4

Create greener urban spaces.

Provide the community with amenity and passive and active recreational
opportunities.
Melbourne Water Constructed Wetlands Design Manual: Part B1

Improve visual amenity through reduction in litter and pollutants.

Complement the amenity values of the broader landscape; particularly those
related to adjacent public open space and associated passive and active
recreation.

Ensure efficient use of space through the integration of wetlands with flood
management areas.
Alternative water supply

Provide a water supply for uses such as irrigating open spaces and streetscape
vegetation.
Recreational

Provide recreational opportunities, including walking, bird watching, picnicking
and other forms of passive recreation.

Provide an appropriate level of direct and indirect access to the wetland.
Landscape and cultural objectives

Retain, enhance and interpret existing ecological, landscape and cultural values,
such as trees and other native vegetation and sites of archeological significance.
These are valuable assets to the local community and help to create a unique
sense of place.
Accessibility

Provide public access to the wetland and associated open spaces including those
with limited mobility such as the disabled and elderly. The provision of public
access requires consideration of potential hazards associated with access paths,
provision of passing areas, ramps, hand/grab rails where needed, and the types
of surfaces used on paths including the use of tactile ground surface indicators.
Conservation
Wetlands often represent important biological ‘hot spots’ in urban areas, as they
encompass a wide range of aquatic and terrestrial habitats and may support diverse
flora and fauna communities.
Whilst stormwater treatment wetlands are not specifically designed to meet
conservation objectives, the general provision of habitat within and around a wetland
may be provided by:
Constructed Wetlands Design Manual: Part B1 Melbourne Water
5

Rocks or logs placed in or around a wetland to provide shelter, perches and
basking areas for native wildlife. Logs must be suitably anchored to avoid
movement.

Terrestrial planting of indigenous tree, shrub and groundcover species to
provide additional habitat for some wetland animals, such as feeding and
resting sites for waterbirds and over-wintering shelter for frogs.

Enhancing any adjacent riparian habitats and creating ecological linkages
(corridors) between waterways and other vegetation patches.
The creation of structural complexity in riparian and wetland vegetation is important
for ecological diversity and landscape amenity. This may be achieved by including a
range of plant life forms on the planting schedule. The use of locally indigenous
species ensures that plants are adapted to local environmental conditions and that the
character of the wetland is in keeping with the surrounding landscape.
When designing riparian communities, care needs to be taken so as to not create
nesting sites for colonial bird species, as resident populations of colonial bird species
can have a significant detrimental effect on wetland water quality.
It should be noted that constructed water bodies can attract flocking birds, which may
pose a hazard to airports. Local council planning schemes should be consulted when
considering whether to locate a constructed wetland near an airport.
Constructed wetlands have a primary function of treating stormwater and improving
water quality to receiving waterways and bays; they do not have a primary function of
constructing habitat and/or conservation zones. Therefore, maintenance and ongoing
functionality of the asset is often more important than habitat or biodiversity
protection or preservation in these works.
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Melbourne Water Constructed Wetlands Design Manual: Part B1
Constructed Wetlands
Design Manual
Part B2: Deemed to comply design criteria
Table of contents
Introduction
1 Deemed to Comply conditions
1 General ................................................................................................1 Maintenance provisions ...........................................................................1 Gross pollutant management ...................................................................3 Sediment pond ......................................................................................3 Macrophyte zone ...................................................................................4 Bypass .................................................................................................6 Inlets and outlets ...................................................................................6 Vegetation ............................................................................................9 Liner and topsoil .................................................................................. 12 Landscape design structures .................................................................. 13 Edge treatment ................................................................................... 13 Constructed Wetlands Design Manual: Part B2 Melbourne Water
i
Part B2: Deemed to comply design criteria
Introduction
This section presents an overview of the design criteria that need to be met in order
to achieve the design objectives. Clear links between the design criteria and
objectives are illustrated, assisting the designer to check that their design is meeting
Melbourne Water’s requirements.
These design criteria are expanded upon in this Part of the manual and are also
included in the relevant sections of Part D as part of the technical design approach.
Please refer to Part C for more information on the Deemed to Comply approach and
the Alternative Approach as part of the design acceptance process. The Deemed to
Comply conditions are also included in the design checklists provided in Part F of the
manual.
Deemed to Comply conditions
General
GN1
The treatment and flow regime performance of the wetland must be
modelled in MUSIC.
GN2
The meteorological data in the MUSIC model must be:
 Based on at least 10 years of historical records
 Recorded at six minutes intervals
 Sourced from a pluviographic station as close as possible to the
wetland site
 Have a mean annual rainfall depth equal to the long term rainfall
depth at the rainfall station closest to the wetland site
GN3
The system configuration shown on the design plans must be consistent
with the MUSIC model (including the stage/discharge relationship).
GN4
Peak design flows must be estimated in accordance with methods in
Australian Rainfall and Runoff.
Maintenance provisions
MN1
Sediment ponds must be able to be drained whilst maintaining the
macrophtye zone water level at NWL.
MN2
All parts of the base of a sediment pond must be accessible:
 Within seven metres of a designated hard stand area for excavation
vehicles (“edge cleaned”) OR
 Via a maintenance access ramp into the base of the sediment pond
Constructed Wetlands Design Manual: Part B2 Melbourne Water
1
2
MN3
The base of the sediment pond must extend vertically up the batter by 300
mm and comprise of:
 Concrete – steel reinforced minimum 150 mm thick
 400 mm compacted rock d50 ≥ 50 mm
MN4
‘Edge cleaned’ sediment basins must have hardstand areas (e.g. crushed
rock covered in topsoil) for excavation vehicles to park. A maintenance
track must be provided around the perimeter of the sediment pond.
MN5
Maintenance access ramps are required on all sediment ponds greater than
14 metres wide. The maintenance access ramp into a sediment pond must:
 Extend from the base of the sediment pond to at least 0.5 metres
above TED,
 Be at least 4 metres wide,
 Be no steeper than 1:5
 Be capable of supporting a 20 tonne excavator
 Constructed of either:
- 200 mm deep layer of cement treated crushed rock (6%), or
- 200 mm compacted FCR
 Have a barrier to prevent unauthorised vehicle access (e.g. gate,
bollard and/or fence).
MN6
A maintenance access track must be provided to the sediment pond
maintenance access ramp and to enable maintenance vehicles to safely
access and exit the site. The maintenance access track must be:
 Be at least 4 metres wide
 Comprise of compacted FCR minimum 200 mm depth
 Reinforced to take a 20 tonne vehicle
 At the road edge have an industrial crossover to Council standard
and rolled kerb adjoining it.
MN7
A hardstand area with a minimum turning circle appropriate to the types of
maintenance vehicles to be used must be provided adjacent to the
sediment pond maintenance access ramp to enable maintenance vehicles to
safely reverse and exit the sediment loading area.
Note: The turning circle must be in accordance with the Austroads Design
Vehicles and Turning Path Templates Guide
(http://www.austroads.com.au/images/stories/ap-g34-13.pdf)
MN8
Intersections between pedestrian pathways and site maintenance access
tracks should be clearly marked (i.e. using markers or different coloured
concrete on the pedestrian paths).
MN9
Dedicated sediment dewatering areas must be provided and:
 Be accessible from the maintenance ramp,
 Have a length to width ratio no narrower than 10:1,
 Able to contain all sediment removed from the sediment
accumulation volume spread out at 500 mm depth
 Located above the peak 10 year ARI water level and within 25 metres
of each sediment pond or as close as possible,
 The location of sediment dewatering areas must consider the odour
Melbourne Water Constructed Wetlands Design Manual: Part B2


MN10
issues for local residents and appropriate buffers from residential
areas and public access areas (like pathways, roads, playgrounds,
sports fields etc).
Consider public safety and potential impacts on public access to open
space areas,
Free from above ground obstructions (e.g. light poles) and be an
area that Melbourne Water has legal or approved access to for the
purpose of dewatering sediment.
The wetland must be configured to enable maintenance vehicles to drive
around at least 50% of the wetland perimeter. Vehicular access must be
provided as close as possible to wetland structures that may catch debris
(e.g. provide access to the closest bank where structure are within the
water body).
Gross pollutant management
GP1
Where the wetland’s catchment includes ≥ 1 ha of commercial and/or
industrial land, appropriately sized gross pollutant traps must be located
between any commercial or industrial land use and the wetland. Gross
pollutant removal closer to the source via distributed treatments is
preferred over a GPT located immediately upstream of a wetland.
GP2
Where GPTs are used adequate maintenance access routes must be
provided.
Sediment pond
SP1
Sediment ponds must be located offline of waterways1 but online to the
pipe or lined channel they are treating water from.
SP2
Sediment ponds must be located at each point stormwater enters the
“wetland system” unless:
 The catchment of the incoming stormwater is < 1 ha OR
 The incoming stormwater has already passed through a
bioretention system or wetland immediately upstream
SP3
Sediment ponds must be sized to:
 Capture 95% of coarse particles ≥ 125 µm diameter for the peak
three month ARI AND provide adequate sediment storage volume
to store between three to five years sediment. The sediment
accumulation zone must be assumed to be 500 mm below NWL
(refer to Figure 1).
 Ensure that velocity through the sediment pond during the peak
100 year ARI event is ≤ 0.5 m/s. (The flow area must be assumed
to be the EDD multiplied by the narrowest width of the sediment
1
A waterway is defined as either a natural or constructed waterway. Melbourne Water’s
Development Services Schemes define a ‘Constructed Waterway’ as reaches of a waterway that
are required to be fully or partially constructed to service new development.
Constructed Wetlands Design Manual: Part B2 Melbourne Water
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
SP4
pond, at NWL, between the inlet and overflow outlet) AND
Sediment ponds must be ≤ 120% of the size needed to meet the
limiting of the above three criteria. Compliance with the above
criteria must be demonstrated using the methods described in
WSUD Engineering Procedures: Stormwater (Melbourne Water,
2005). Alternatively, the velocity criteria can be checked using a
hydraulic model such as HEC-RAS. Refer to Part E of this Manual
for guidance on undertaking velocity checks).
The sediment pond EDD must be ≤ 350 mm.
Figure 1 Sediment pond storage
Macrophyte zone
4
MZ1
At least 80% of the area of the macrophyte zone at NWL must be ≤ 350
mm deep to support shallow and deep marsh vegetation. The wetland
bathymetry should provide approximately equal amounts of shallow
marsh (≤ 150 mm deep) and deep marsh (150 mm to 350 mm deep).
MZ2
The macrophyte zone EDD must be ≤ 350 mm.
MZ3
Macrophyte zones must be located offline from all waterways and drains
(i.e. there must be a bypass route around the macrophyte zone).
MZ4
The length of the macrophyte zone must be ≥ four times the average
width of the macrophyte zone.
MZ5
Major inlets to the macrophyte zone (i.e. those draining > 10% of the
catchment to be treated) must be located within the first 20% of the
macrophyte zone.
MZ6
The macrophyte zone outlet must be located at the opposite end of the
Melbourne Water Constructed Wetlands Design Manual: Part B2
macrophyte zone to the inlet(s).
MZ7
The macrophyte zone must have a sequence and mix of submerged,
shallow and deep marsh zones arranged in a banded manner
perpendicular to the direction of flow. Refer Figure 2).
MZ8
Inlet and outlet pools must be ≤ 1.5 m
MZ9
Intermediate pools (between the inlet and outlet pool) must be ≤ 1.2 m
deep.
MZ10
Velocities in the macrophyte zone must be:
 less than 0.5 m/s for the peak 100 year ARI flow
 less than 0.05 m/s for the peak three month ARI
Compliance with the above criteria must be demonstrated using the
methods described in WSUD Engineering Procedures: Stormwater
(Melbourne Water, 2005) or using a hydraulic model such as HEC-RAS.
Refer to Part E of this Manual for guidance on undertaking velocity
checks.
MZ11
The macrophyte zone must provide a 90th percentile residence time of 72
hours (assuming plug flow between inlet and outlet through the EDD and
50% of the permanent pool volume).
MZ12
A minimum grade of 1:150 must be provided between marsh zones
(longitudinally through the macrophyte zone) to enable the wetland to
freely drain. Intermediate pools will generally be needed to transition
between marsh zones.
MZ13
A marker must be used to show wetland water level relative to NWL and
EDD. The marker must be able to be read from the bank and attached to
the wall of the submerged outlet pit.
Constructed Wetlands Design Manual: Part B2 Melbourne Water
5
Figure 2 Macrophyte zone planting bands
Bypass
BY1
The bypass route must be sized to convey the maximum overflow from the
sediment pond that will occur during the peak 100 year ARI event. Where a
sediment pond is within a retarding basin, the bypass must convey at least
the peak one year ARI flow.
Note: Refer to Part D of the Melbourne Water Waterways Manual for
channel design specifications when designing bypass routes.
Inlets and outlets
6
IO1
All pits, grilles and structures must conform to Melbourne Water’s
standards as shown in the Land Development Manual and Standard
Drawings. All covered pits must have approved lids and all uncovered
outlet structures must have approved grilles/grates.
IO2
Outlet structures must be easily identifiable and maintainable. They must
be accessible from the bank. The edge of the outlet structure closest to the
bank (maintenance access point) must be located in < 350 mm water
depth.
IO3
The controlled outlet (e.g. weir plate) must be visible from the surface (e.g.
Melbourne Water Constructed Wetlands Design Manual: Part B2
through a grate).
IO4
The connection between the sediment pond and macrophyte zone must be
sized such that:
 All flows ≤ the peak three month ARI event are transferred into the
macrophyte zone when the EDD in the macrophyte zone is at NWL
(refer Figure 4), AND
 70% of the peak 1 year ARI flow overflows from the sediment pond
into the bypass channel/pipe when the water level in the macrophyte
zone is at TED (and not enter the macrophyte zone) (refer Figure 5),
AND
 The velocity through the macrophyte zone is ≤ 0.5 m/s during the
peak 100 year ARI event:
i. Assuming the macrophyte zone is at TED if the
wetland is not within a retarding basin or flood plain
ii. Assuming the water level is at the peak five year ARI
water level if the wetland is within a retarding basin or
flood plain
IO5
The connection from the macrophyte zone to the pit containing the
controlled outlet must be submerged to minimise clogging from floating
debris (refer Standard Drawing WG020).
IO6
The macrophyte zone controlled outlet must be configured so that:
 The NWL can be drawn down by up to 150 mm during plant
establishment and maintenance.
 The NWL can be permanently adjusted up or down by 100 mm to
respond to changes in wetland hydrology due to potential future
climate conditions.
 The stage/discharge rate can be adjusted if required to achieve
suitable residence times and/or inundation patterns
IO7
Maintenance drawdown pipes, minimum 225 mm sewer class PVC, must be
placed between all open water zones (inlet, intermediate and outlet pools)
to enable water levels to be drawn down for maintenance or water level
management purposes (refer Figure 3).
The invert of maintenance
drawdown pipes must be at least 100 mm above the base of the
macrophyte zone to minimise the risk of clogging. Maintenance drawdown
pipes must be configured such that each of the open water areas can be
drawn down independently.
Constructed Wetlands Design Manual: Part B2 Melbourne Water
7
Figure 3 Maintenance drawdown pipes
8
Melbourne Water Constructed Wetlands Design Manual: Part B2
Figure 4 Connection between sediment pond and macrophyte zone – three month ARI
flow check
Figure 5 Connection between sediment pond and macrophyte zone – one year ARI flow
check
Vegetation
VG1
The macrophyte zone must contain a minimum 80% cover of emergent
macrophytes calculated at NWL comprising of shallow and deep marsh
Constructed Wetlands Design Manual: Part B2 Melbourne Water
9
zones. Open water areas (maximum 20% of the wetland area calculated at
NWL) must include submerged vegetation.
VG2
Any open water areas in excess of 20% of the macrophyte zone area (at
NWL) must be located as a separate water body. These separate water
bodies are not considered by Melbourne Water to be constructed wetlands
for the purpose of treating stormwater, and are therefore beyond the scope
of this document. MUSIC models to demonstrate the performance of the
proposed wetland should assume there is no reduction in pollutant loads
within these separate waterbodies.
VG3
Ephemeral batters (NWL to 200 mm above NWL) of the macrophyte zone
and sediment pond must be densely planted. 80% of the plants used in the
ephemeral batters must be in accordance with the species and densities
shown in Table 1.
VG4
The ephemeral batters must be planted with individual plants grown in
individual pots or tray cells that are at least 90 cm3 in volume (i.e. the
minimum acceptable pot/cell size is a hiko cell).
VG5
The shallow marsh (NWL to 150 mm below NWL) of the macrophyte zone
and sediment pond must be densely planted. 90% of the plants used in the
shallow marsh must be in accordance with the species and densities shown
in
Table 2. A minimum of three species must be specified for the shallow
marsh zone.
VG6
The deep marsh (150 to 350 mm below NWL) of the macrophyte zone must
be densely planted. 90% of the plants used in the deep marsh must be in
accordance with the species and densities shown in
Table 3. A minimum of three species must be specified for the deep marsh
zone.
VG7
The submerged marsh (350 to 700 mm below NWL) of the macrophyte
zone must be densely planted. 90% of the plants used in the submerged
marsh must be in accordance with the species and densities shown in Table
4.
VG8
Emergent and submerged macrophyte seedlings must be grown in
individual pots with a minimum volume of:
 200 cm3 (i.e. forestry tubes) or
 600 cm3
Note: Seedlings sourced from bare-root divisions from tub/tray grown stock
or stock harvested from existing wetlands will not be accepted.
VG9
Seedlings grown in 200 cm3 tubes must have:
 minimum stem height of 300 mm
 well developed, healthy root system that occupies the full pot
volume
Seedlings grown in 600 cm3 tubes must have:
10
Melbourne Water Constructed Wetlands Design Manual: Part B2



minimum stem height of 500 mm (except Triglochin procerum and
Eleocharis acuta – minimum stem height of 400 mm)
total stem area must cover at least 50% of the pot surface area
well developed, healthy root system that occupies the full pot volume
(i.e. the growing media must remain intact when the plant is
removed from the pot)
Note: The minimum stem height criteria specified for 200 cm3 and 600 cm3
pots does not apply to submerged macrophyte species.
VG10
The effective water depth (permanent pool depth plus EDD) must not
exceed half of the average plant height for more than 20% of the time.
This must be demonstrated using inundation frequency analysis assuming
the plants heights are in accordance with those shown in Table 2 to Table 4.
Refer to Part E of this Manual for guidance on how to undertake an
inundation frequency analysis.
VG11
Where stormwater is harvested from the permanent pool of a wetland, the
extraction must not occur if the water level is more than 100 mm below
NWL. Please note that a diversion licence is required to harvest water from
Melbourne Water assets.
Table 1 Ephemeral batter plant list
Botanical name
Common name
Minimum
density
(plants/m2)
Baumea
rubiginosa
Soft Twig-rush
4
Carex appressa
Tall Sedge
4
Carex
tereticaulis
Basket Sedge
4
Cyperus lucidus
Leafy Flat-sedge
4
Juncus amabilis
Hollow Rush
8
Juncus flavidus
Yellow Rush
8
Juncus krausii
Sea Rush
8
Juncus pallidus
Pale Rush
8
Poa labillardierei
Common Tussock
4
Lomandra
longifolia
Spiny-headed Mattrush
4
Table 2 Shallow marsh plant list
Botanical name
Common name
Minimum density
(plants/m2)
200cm3
600cm3
Average
plant
height
Constructed Wetlands Design Manual: Part B2 Melbourne Water
11
tube
tube
(m)
Baumea articulata
Jointed Club-rush
6
3
1.8
Bolboschoenus caldwellii
Sea Club-rush
6
3
1.0
Bolboschoenus fluviatilis
Tall Club-rush
6
3
1.8
Bolboschoenus medianus
Marsh Club-rush
6
3
1.5
Cladium procerum
Leafy Twig-rush
6
3
2.0
Eleocharis acuta
Common Spikerush
6
3
0.5
Schoenoplectus
tabernaemontani
River Club-rush
6
3
1.8
Triglochin procerum
Water Ribbons
6
3
1.0
Common name
Minimum density
(plants/m2)
Table 3 Deep marsh plant list
Botanical name
200cm3
tube
600cm3
tube
Average
plant
height
(m)
Baumea articulata
Jointed Club-rush
4
2
1.8
Bolboschoenus fluviatilis
Tall Club-rush
4
2
1.8
Bolboschoenus medianus
Marsh Club-rush
4
2
1.5
Cladium procerum
Leafy Twig-rush
4
2
2.0
Eleocharis sphacelata
Tall Spike-rush
4
2
1.5
Phragmites australis
Common reed
4
2
2.5
Schoenoplectus
tabernaemontani
River Club-rush
4
2
1.8
Triglochin procerum
Water Ribbons
4
2
1.0
Table 4 Submerged marsh plant list
Botanical name
Common name
Minimum density
(plants/m2)
200cm3
tube
600cm3
tube
Myriophyllum crispatum
Upright Watermilfoil
2
1
Potamogeton ochreatus
Blunt Pondweed
2
1
Vallisneria americana
Eel-grass
2
1
Liner and topsoil
LN1
12
The exfiltration rate from the base and the sides of the wetland must be
Melbourne Water Constructed Wetlands Design Manual: Part B2
accurately represented in the MUSIC analysis and associated water level
spells analysis.
Wetlands with a permanent pool generally have a
compacted clay liner made from site soils and/or imported material where
site soils are unsuitable. Where no liner is proposed, in-situ geotechnical
testing (at the depth of the wetland base) must be undertaken and used to
justify the selected exfiltration rate used in modelling.
LN2
Impermeable liners must be used where the groundwater table is likely to
interact with the wetland or where there are saline in-situ soils.
LN3
At least 200 mm topsoil must be provided in all areas of the wetland and in
sediment ponds to 350 mm below NWL.
LN4
Topsoils used within the wetland (in situ or imported) must comply with AS
4419 Soils for landscaping and garden use2. Testing must be carried out by
a NATA accredited laboratory. If required, amendments to the topsoil must
be undertaken to achieve compliance with AS 4419.
Landscape design structures
LDS1
All boardwalks, piers, bridges and/or structurally treated edges installed and
maintained by others are to have heights and/or railings in accordance with
relevant design codes and satisfy inundation and safety criteria.
LDS2
All boardwalks, bridges and formal pedestrian paths, must be at or above
the peak 10 year ARI water level.
LDS3
Boardwalks or viewing platforms are not permitted over sediment ponds.
Edge treatment
ET1
The edge of any deep open water should not be hidden or obscured by
embankments or terrestrial planting unless measures are taken to preclude
access. Public access to structures, the top of weirs, orifice pits and outlet
structures must be restricted by appropriate safety fences and other
barriers.
Permanent fencing is required adjacent to potentially unsafe
structures.
ET2
All wetland edges must have:
 Vegetated approach batters no steeper than 1:5, a 2.4 metre wide
vegetated safety bench at 1:8 between NWL and 350 mm below NWL
and a maximum 1:3 slope beyond 350 mm below NWL (refer Figure
6). OR

Batters no steeper than 1:4 between TED and 350 mm below NWL with dense
impenetrable planting that is a minimum of 2.5 metres wide and 1.2 metres
2
The AS 4419 requirement for % organic matter content does not apply. Topsoils used in wetlands
must have a minimum of 5% organic matter content.
Constructed Wetlands Design Manual: Part B2 Melbourne Water
13
high (refer Figure 7 and Figure 8).
Note: Wetlands without vegetated safety benches must be protected by temporary
fencing. The temporary fencing must be left in place until dense vegetation has been
established and approval is given by the Melbourne Water surveillance officer that the
fencing can be removed.
Wetlands with batters steeper than 1:4 between TED and 350 mm below NWL must
have permanent fencing. Permanent fencing must be compliant with Australian
Standard AS 1926.1– 1993 Fencing for Swimming Pools. Wetland batters with
permanent fencing must make up no more than 10% of the wetland perimeter.
14
ET3
Maintenance access areas from which safety standards are not met, must be
signed, fenced and gated to discourage access.
ET4
A minimum offset of 15 metres must be provided from the edge of the water
at NWL to any allotment or road reserve. A safety design audit is required
for any proposal that does not achieve this condition.
Melbourne Water Constructed Wetlands Design Manual: Part B2
Figure 6 Indicative section of vegetated wetland edge with safety bench
Figure 7 Indicative section of vegetated wetland edge with impenetrable planting
Figure 8
planting
Photos showing examples of wetland edges with dense impenetrable
Constructed Wetlands Design Manual: Part B2 Melbourne Water
15
Constructed Wetlands
Design Manual
Part C: Design acceptance process
Table of contents
Introduction
1 Two submission/acceptance pathways
2 Deemed to Comply.................................................................................3 Alternative approach ..............................................................................3 Working with Melbourne Water
4 Concept design stage
5 Concept design steps ..............................................................................6 Functional design stage
12 Functional design steps ......................................................................... 12 Detailed design stage
19 Detailed design steps ........................................................................... 19 Pre-construction stage
22 Pre-construction steps .......................................................................... 22 As-constructed and establishment stage
25 As-constructed steps ............................................................................ 25 Constructed Wetlands Design Manual: Part C Melbourne Water
i
Part C: Design acceptance process
Introduction
Melbourne Water is the ultimate client for almost all constructed wetlands in the
growth areas of Melbourne. Once constructed, these wetlands become either the
responsibility of Melbourne Water or the local Council to own and maintain.
Designers must ensure they meet the design process requirements of Melbourne
Water, and sometimes Council, in the same way they meet the requirements of the
Developer for the subdivision/development adjacent to the constructed wetland.
Wetland designers therefore play a pivotal role in ensuring that the constructed
wetland design interfaces with the surrounding development and environment to the
satisfaction of all parties.
Melbourne Water has a design acceptance process that the designer must follow for
the delivery of stormwater assets including pipelines, wetlands and waterways. The
process has a series of steps, which are detailed in this part of the manual, and are
specific to constructed wetland designs.
Under Melbourne Water’s Quality Management system, developers, engineering
consultants and contractors have defined roles and responsibilities with respect to the
delivery of Melbourne Water assets, such as constructed wetlands and waterways.
Further information about this can be found on the Planning and Building pages of
Melbourne Water’s website.
The following flow chart (Figure 1) outlines the interactions between the design
approach undertaken by the designer, and the steps of the design acceptance
process. The design acceptance process steps and the information required by
Melbourne Water at each acceptance milestone or hold-point are detailed in this part
of the manual. The wetland designer is required to work through key design stages:
concept, functional and detailed, and should also be heavily involved during the
construction and establishment of the asset.
Constructed Wetlands Design Manual: Part C Melbourne Water
1
Design acceptance process
Concept design package submission
Request for Scheme Servicing Advice
Application for conditions
Functional design package submission
Detailed design package submission
Works offer acceptance
Functional Design Stage
Concept Design Stage
Concept design acceptance
Design criteria / information
Design certification statement
Detailed Design Stage
Works offer
Functional design acceptance Design acceptance
‐ Melbourne Water Developer Works Team ‐ Designer / developer
‐ Melbourne Water Developer Projects Works Team
‐ Melbourne Water Corporation
Construction acceptance process
Submit SEMP
Tender process
Permits and pre‐
qualifications
Pre‐construction certification statement
Pre – construction Stage
Reimbursement calculated
Superintendent Construction certification statement
Construction
Stage
Surveillance
As constructed plans submitted & Survey certification statement
Defects Liability Stage
Certificate of practical completion
End of defects certification
Project Finalisation Stage
Reimbursements paid
Statement of compliance for subdivision
Certificate of completion
Maintenance agreement signed
Figure 1 Overview of design acceptance process
The following forms are key administrative parts of the design acceptance process
under Melbourne Water’s Quality Assurance program for developer constructed assets,
including constructed wetlands:

Request for Scheme Servicing Advice

Deemed to Comply Checklist

Application for Conditions

Acceptance of Conditions

Design Certification Statement

Construction Certification Statement

As-Constructed Certification Checklist
Two submission/acceptance pathways
Melbourne Water has adopted two review/acceptance pathways. These pathway
options are:
2
Melbourne Water Constructed Wetlands Design Manual: Part C
1. Deemed to comply
2. Alternative approach
Deemed to Comply
The Deemed to Comply pathway requires designers to demonstrate compliance with a
prescriptive set of design criteria (see Part B2). The review and acceptance process
for the Deemed to Comply process is quick (estimated timeframe around 2-4 weeks),
and designers have a high level of confidence that their designs will be accepted by
Melbourne Water. The Deemed to Comply conditions are included in the design
checklists, provided in Part F.
Alternative approach
The Alternative approach pathway provides designers with the option of submitting an
approach that differs from the Deemed to Comply prescriptive approach (outlined in
Part B2), but still delivers the required core outcomes and design objectives for
constructed wetlands (outlined in Part B1).
The designer is responsible for providing Melbourne Water with evidence that the
Alternative Approach achieves equivalent or better performance than the Deemed to
Comply approach for core outcomes and design objectives.
The review and design acceptance process for the Alternative approach will take
longer and designers will be made aware that there is no certainty that their design
will be accepted by Melbourne Water. This provides the opportunity for developers
and their designers with tight time constraints and/or those that are risk adverse to
pursue the Deemed to Comply pathway.
The review and design acceptance process for the Alternative approach pathway will
be same as the Deemed to Comply pathway, with a concept, functional and detailed
design package required for each stage of the process. This ensures a transparent and
consistent process for internal and external stakeholders. When an Alternative
approach design is submitted, Melbourne Water involves input from various internal
departments and expertise in wetland design and operation, including hydrology,
hydraulics, ecology, constructability and maintenance.
For unusual design applications, or where internal resources are not available,
Melbourne Water may choose to seek expert opinion from independent peer reviewers
about whether the information submitted demonstrates that Melbourne Water’s core
outcomes and design objectives will be achieved.
Constructed Wetlands Design Manual: Part C Melbourne Water
3
Working with Melbourne Water
Melbourne Water’s Development Planning team, within the Waterways and Land
Group, is the principle point of contact for all customers undertaking land
development within areas that are covered by a Development Services Scheme or for
projects where a Melbourne Water wetland is proposed.
To find out if your development is located within a Development Services Scheme,
and for more information on working with Melbourne Water, please visit Melbourne
Water’s Planning and Building website:
www.melbournewater.com.au/Planning-and-building/Pages/planning-and-building
The following diagram represents the structure of the Development Planning team as
it relates to the planning and delivery of key assets in Development Services
Schemes, such as constructed wetlands.
4
Melbourne Water Constructed Wetlands Design Manual: Part C
Strategy development
• Developer Strategies Team
• Implementation of Development Services Schemes; review of Precinct Structure Plans; assessment of catchment models including RORB, hydraulc models and MUSIC in greenfield areas
• Developer WorksTeam
• Scheme Servicing or Feasibility advice; review and assessment of Greenfield planning permit applications and subdivision applications; review of surface water management strategies; review of concept design package; confirmation of wetland location and indicative footprint; review of core outcomes associated with wetland proposal
Concept Design
Functional Design
Detailed Design
• Developer Works Team
• Review and assessment of functional design package; preparation of internal business cases for the delivery (timing and funding)
of projects; preparation of Non‐Works and Works Offers; review of MUSIC and flood models;and review of Certification of Plan of Subdivision and consent to the issue of a Statement of Compliance
• Developer Project Works Team
• Assessment of detailed design packages; issue design certification; contractor assessment; calculation of reimbursements for scheme works; preparation of maintenance agreements
• Developer Project Works Team
• Pre‐commencement meeting onsite; issue of permit to work; surveillance of on‐ground works; issue certificate of practical Pre‐Construction completion
& Construction
• Developer Project Works Team
• Full reimbursements paid; maintenance agreements signed; issue certificate of completion
As‐Constructed
Concept design stage
The concept design stage provides a chance to consider the opportunities and
constraints of the subject site in relation to wetland design and construction, and to
understand Melbourne Water’s requirements and aspirations for the wetland that any
design must address.
Before design work commences, the criteria and objectives for the design should be
determined. Melbourne Water will provide broad design objectives and criteria for the
constructed wetland to inform the concept design. The wetland must be designed to
achieve the required core outcomes for constructed wetlands, including:

Effective pollutant removal

Community Safety
Constructed Wetlands Design Manual: Part C Melbourne Water
5

Maintenance and operational staff safety

Cost effective asset management
The land developer and the local government authority may also have design
specifications for the wetland and surrounding open space. The designer is tasked
with the job of preparing a concept that meets each of these combined design
objectives.
In summary, the concept design phase in this manual is concerned with the process of
synthesising and identifying various options that could potentially meet the design
objectives for the constructed wetland. It is at the functional design stage where these
options and ideas are tested to determine their feasibility and arrive at an end
product, being the preferred design scenario. This underlines the importance of
iteration during the evolution of the concept and functional design as different options
are explored and refined.
Important note: It is not recommended to combine both the concept and functional
design stage in the design acceptance process as this will often lead to problems and
longer time delays, and there is no certainty that this will speed-up the acceptance
process.
Concept design steps
The concept design stage consists of six steps (see Figure 2).
Concept design stage
Step 1. Submit request for Scheme Servicing Advice
Step 4. Meet with Melbourne Water
Step 2. Design criteria / information –
Scheme servicing advice
Step 5. Submit final concept design
Step 3. Prepare initial concept design package
Step 6. Concept design acceptance
Designer
Melbourne
Water
Figure 2 Concept design stage steps
Step 1 – Submit request for Scheme Servicing Advice
The consultant must submit the relevant form to Melbourne Water requesting Scheme
Servicing Advice. The form should include the following information:
6

A catchment plan clearly defining the property boundaries

An overall estate plan (if available)
Melbourne Water Constructed Wetlands Design Manual: Part C

Any baseline due diligence reports and topographical survey information
It should be noted that this is not an application for Conditions (i.e. the Works Offer),
but a request for Scheme Servicing Advice.
Scheme Servicing Advice / Feasibility website
Step 2 – Design criteria / information – Scheme Servicing Advice
Melbourne Water will provide the designer with advice regarding the scheme
objectives and intent. This advice includes highlighting component size requirements,
open space and waterway corridor requirements (if applicable), design flows, relevant
plans and strategies, Development Services Scheme infrastructure (such as indicative
sizes of pipelines and outfall locations) and any available background studies (flora,
fauna, cultural heritage, etc.).
Step 3 – Prepare initial concept design package
A concept design package must be submitted to Melbourne Water’s Developer Works
Team. The purpose of the concept design package is to demonstrate that the wetland
site is appropriate and that the draft plan of subdivision provides adequate space for
the wetland footprint.
The initial concept design package is prepared by the wetland designer, in close
consultation with the design team, which should include a landscape architect.
The concept design package must contain:
1. A statement listing any aspects of the package that do not conform with the
“Deemed to Comply” requirements outlined in this manual (Part B2) and
justification as to how the proposed alternative approach achieves equivalent or
better than the deemed to comply approach, in relation to:
a. pollutant reductions
b. safety outcomes
c. maintenance
d. sustainability/robustness (i.e. ≥ 25 year life)
2. A Concept Design Package Report that:
a. Identifies the developer and development location
b. Describes the overall stormwater management strategy (including all
treatment systems) for the site, including whether treatment systems
will be:
Constructed Wetlands Design Manual: Part C Melbourne Water
7
i. integrated within retarding ponds and/or
ii. form part of a stormwater harvesting system
c. Identifies how gross pollutants in the catchment will be managed
d. Identifies whether wetlands are intended to be ephemeral or contain a
permanent pool of water
e. Summarises MUSIC modelling, including:
i. version of MUSIC
ii. meteorological data used
iii. catchment areas with impervious percentage
iv. any routing used
v. treatment node parameters
vi. any modelling parameters that are not in accordance with
Melbourne Water’s MUSIC Modelling Guidelines
vii. pollutant removal results
f.
A summary of site characteristics and constraints, including:
i. results from a site Flora and Fauna survey, including identification
of any species of significance listed under the Flora and Fauna
Guarantee Act and Environmental Protection and Biodiversity
Conservation Act (the full Flora and Fauna survey must be
included as an appendix to the report)
ii. applicable geology and soils at the site
iii. whether the wetland is likely to be inundated by flows from a
catchment other than the one it is treating (e.g. overflow from
adjacent waterway) and, if so, how often this inundation is likely
to occur
iv. If applicable, results from a Cultural Heritage Management Plan
that is relevant to the wetland footprint (the full Cultural Heritage
report must be included as an appendix to the report)
v. information on existing or proposed services or assets
g. Is technically reviewed and undersigned by the wetland designer
3. A plan showing catchment boundaries for each treatment system and location
of receiving waterways
8
Melbourne Water Constructed Wetlands Design Manual: Part C
4. A draft Plan of Subdivision and draft Development Plan for the development
site. The Plan of Subdivision must show the boundary of the reserve the
wetland will sit within. The Development Plan must show the whole
development area including subdivision stages and all reserves
5. A plan showing the location and indicative footprint of all existing and planned
treatment systems, waterways (constructed and/or natural) and retarding
ponds that will be located within and/or service the land shown on the draft
Plan of Subdivision
6. A plan of each proposed wetland showing indicative footprint (allowing for
batter slopes of sediment pond, high flow bypass, macrophyte zone,
maintenance access routes, location of any pipe connections and sediment
dewatering areas. The plan must show these items overlayed on site survey
and constraints (with labelled contours) or a recent aerial photograph. The plan
must show:
a. flow direction, inlet and outlet locations
b. the boundary of the reserve that the constructed wetland will sit within;
note that the reserve boundary should be at least 20% larger than the
maximum extent of all parts of the wetland footprint, as above, to
accommodate any changes to the footprint during later design phases.
This plan must show existing waterways and/or pipe networks within or
adjacent to the reserve
c. details on which assets the developer is proposing will be transferred to
Melbourne Water and who the proposed owner/operator is for other
adjacent assets
d. the location of sediment pond inlet(s) and high flow bypass and
macrophyte zone outlets
e. the alignment of existing or proposed services determined from a
desktop study (e.g. sewer, gas, mains water underground electrical
cables and overhead power lines)
f.
the levels (m AHD) of land surrounding the wetland
g. the location of any existing vegetation that is to be retained
h. the location of any cultural/historical features to be retained
i.
the boundary of any planning overlays
j.
any existing or proposed community facilities adjacent to the wetland
location (e.g. playgrounds, buildings and/or walking paths)
7. An indicative long section for each wetland showing:
Constructed Wetlands Design Manual: Part C Melbourne Water
9
a. existing surface level
b. NWL (m AHD)
c. EDD
d. the base of permanent pool
e. planting zones
f.
invert of inlet pipe/channel(s)
g. invert of outlet pipe and how this relates to the receiving waterway/drain
h. weir crest levels
8. An indicative cross section showing batter slopes
The concept design package is to be submitted in the following file formats (Table 1).
Table 1 Accepted file formats for the concept design packages
Item
Format
Statement
Pdf
Report
Pdf
Plans and sections
Pdf or jpeg
Step 4: Meet with Melbourne Water
The wetland designer and consultant project team should meet with Melbourne Water
and the other relevant stakeholders and approval authorities to discuss the initial
concept design. The aim of this step is to seek feedback that the concept is generally
to the satisfaction of Melbourne Water and the other stakeholders, and to give
direction to the designer to ensure they are on the right track for approval of the
asset. Information associated with the concept design should be submitted to
Melbourne Water at least one week prior to this meeting.
Step 5: Submit final concept design
Collate the feedback from Melbourne Water, relevant stakeholders and approval
authorities, and incorporate this into an iteration of the concept design. If any
changes to the concept are required, you’ll need to re-submit an updated concept
design package for further review/comment to check that the iteration correlates with
the feedback provided. This submission should:
10

Highlight any conflicts that arose from undertaking the iteration in attempting
to address all parties’ comments.

Highlight any significant changes from the original concept that may not
otherwise be obvious to the reviewers.
Melbourne Water Constructed Wetlands Design Manual: Part C
Finalise the concept design as per the feedback from this Step, then update the
concept design package for submission to Melbourne Water for formal acceptance.
Step 6: Concept design acceptance
Melbourne Water is to provide confirmation of concept design acceptance within 21
days of receipt of the complete package, if the acceptance pathway is the Deemed to
Comply approach, or within 42 days if the acceptance pathway is the Alternative
approach.

If the package is incomplete or not to Melbourne Water’s satisfaction, there is
no guarantee that the above review timeframes will be met.

Melbourne Water does not accept any liability for delays caused by incomplete
or inaccurate information submitted for review.
Melbourne Water’s concept design acceptance will take the form of an ‘in-principle
acceptance subject to’, with the ‘subject to’ being further feasibility analysis that
needs to be undertaken through the functional design phase.
At the end of the concept design phase, the three key parameters that should
generally have been agreed upon (subject to functional design) are:
1. The design objectives
2. The indicative wetland footprint
3. The general location of the constructed wetland
There is an understanding, at this stage, between Melbourne Water and the land
developer that nothing is ‘locked-in’ and that some changes to size and location of the
constructed wetland, and possibly some of the objectives, may need to be made
according to the results of the analysis undertaken during the functional design.
Further to completing a concept design to Melbourne Water’s satisfaction, and to help
inform a planning permit application, a land developer and their consultant team
should consider working with Melbourne Water to arrive at a concept and functional
design that meets Melbourne Water’s requirements before seeking Melbourne Water’s
consent to a Planning Permit and Certification of a Plan of Subdivision.
Constructed Wetlands Design Manual: Part C Melbourne Water
11
A concept design is a great communication tool that will assist in explaining the intent
of the design response to Melbourne Water, Councils and other interested parties.
Melbourne Water’s Development Planning Team will not accept a functional design
package for a wetland until they have reviewed and accepted the concept design
package.
Functional design stage
Melbourne Water defines a functional design as:

Demonstrating the optimal solution to achieve our design objectives and criteria
for that asset (see Part B1 and Part B2);

Providing confidence that the asset, if constructed according to the design, will
function according to our requirements;

Confirming the physical area (accounting for all requirements) needed to
accommodate the asset within the landscape of the proposed development;

Being prepared in conjunction with rigorous analysis performed using available
modelling software and calculation methods relevant to the type of asset being
designed; and

Enabling a preliminary construction cost-estimate for the asset to be prepared.
Most constructed wetlands are subject to land reimbursements from Melbourne Water.
Functional designs are a critical part of determining the land area required for these
assets as part of the land reimbursement process.
Functional design steps
The functional design phase consists of seven steps (see Figure 3).
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Melbourne Water Constructed Wetlands Design Manual: Part C
Figure 3 Steps in the functional design phase
Step 1 – Prepare and submit functional design package
A functional design package must be submitted to Melbourne Water’s Developer
Works Team. The purpose of the functional design package is to demonstrate that the
wetland configuration allows the required pollutant reductions to be achieved, the
safety requirements to be met and for cost effective maintenance. The functional
design package is prepared by the consultant for the project. The package must
contain:
1. A statement listing any aspects of the package that do not conform with the
“Deemed to Comply” requirements outlined in this manual (Part B2) and
justification for how the proposed alternative approach achieves equivalent or
better than the deemed to comply approach, in relation to:
a. pollutant reductions
b. safety outcomes
c. maintenance
d. sustainability/robustness (i.e. ≥ 25 year life).
2. A report that describes:
a. The overall operation of the system, including
assumptions made during the concept design phase
any
changes
to
b. A summary of any consultation with other approval authorities (e.g.
Council)
c. The design flow rates, and the method and assumptions used to
estimate them
d. The peak water levels above wetland and in surrounding reserve for 5,
10 and 100 year ARI events, and the method and assumptions used to
estimate them
e. how gross pollutants will be managed
f.
the inlet function
g. The calculations used to size the sediment pond/s
h. The calculations used to size the high flow bypass channel
i.
The calculations used to size the connection between the sediment pond
and macrophyte zone
j.
The calculations used to size the connection between the sediment pond
and high flow bypass (i.e. sediment pond overflow outlet)
Constructed Wetlands Design Manual: Part C Melbourne Water
13
k. The calculations used to size the macrophyte zone extended detention
controlled outlet
l.
The calculations used to size the macrophyte zone overflow outlet
m. The maximum flow velocities through sediment pond and macrophyte
zone
n. The plant species and densities that will be used in each zone
o. A description of how sediment ponds can be dewatered during
maintenance (without dewatering macrophyte zone)
p. The calculations used to size the sediment dewatering area
q. A summary of findings of geotechnical testing (full geotechnical report to
be included as an appendix to the functional design report). This
summary must address:
i. Whether maximum groundwater level is within 0.5 m of the
wetland base
ii. Dispersiveness of soils
iii. Whether wetland earthworks involve contaminated material and,
if so, the required soil management approach and costs
iv. Suitability of site soils to form an impervious wetland liner, for
wetlands with a permanent pool
v. The likely infiltration rate from base of wetland, for ephemeral
wetlands
r.
The peak 5, 10 and 100 year water levels in the sediment pond and
macrophyte zone
s. A description of the updated MUSIC model, including matching:
i. the inlet pond volume in MUSIC to the sediment pond volume
shown on plans (excluding the sediment accumulation volume)
ii.
the permanent pool volume to the proposed bathymetry (using
the user defined stage-storage relationship)
iii. the high flow bypass configuration to the design
iv. the extended detention controlled outlet configuration to the
design (using the user defined stage-storage relationship)
t.
A Spells analysis of water level patterns in macrophyte zone
u. The 90th percentile residence time in the macrophyte zone
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Melbourne Water Constructed Wetlands Design Manual: Part C
v. A report from MUSIC auditor tool (if available)
w. A table showing percentage of macrophyte zone (at NWL) that is in the
following depth zones:
i. 0 to 150 mm below NWL
ii. 150 to 350 mm below NWL
iii. Greater than 350 mm below NWL
x. How the surrounding environment will be protected during construction
(e.g. protection of significant existing vegetation and preventing
contaminated runoff leaving the site).
3. Scale plan(s) showing proposed surface levels (in m AHD) within and
surrounding the wetlands (e.g. produced from earthworks model). The plan(s)
must show lines indicating TED, NWL, the edge of each planting zone,
maintenance access tracks and sediment dewatering areas, any existing or
proposed services within the wetland reserve and locations of any edges that do
not contain safety benches and will therefore be fenced. Note that presence,
alignment and estimate depth of underground services must be based on
physical site proving (unobtrusive testing using a detector is acceptable).
4. Plan showing maintenance responsibility boundaries (i.e. which parts Melbourne
Water will be responsible for maintaining and which parts will be maintained by
others - Council).
5. Letters from other parties agreeing to be responsible for maintaining areas of
assets adjacent to the wetland.
6. Indicative long section of sediment pond(s) and macrophyte zone(s) showing
planting zones, topsoil, liner, peak 5,10 and 100 year ARI water level and the
location and depth of any underground services.
7. Indicative long section of the high flow bypass.
8. Schematic dimensioned drawings with levels to “m AHD” of:
a. Inlet to sediment pond
b. Connection between the sediment pond and macrophyte zone
c. Connection between the sediment pond and high flow bypass
d. Sediment pond maintenance draw down outlet
e. Macrophyte zone extended detention controlled outlet (including facility
to temporarily lower the NWL by 150 mm)
f.
Macrophtye zone overflow outlet
Constructed Wetlands Design Manual: Part C Melbourne Water
15
g. Connection of wetland outlet(s) to downstream drain/waterway including
the peak 1 year ARI water level in the downstream drain/waterway and
the maximum high tide level (accounting for anticipated sea level rise)
9. Geo-referenced GIS (MapInfo) layers showing catchment boundary for each
sediment pond
10. Landscape concept plans for surrounding areas
11. Works cost estimate with clearly itemised items to be funded by Melbourne
Water.
12. Copy of supporting hydrologic, hydraulic and water quality models (e.g. MUSIC,
RORB and HEC-RAS)
File formats and supplementary information on the required elements of the functional
design package are presented in Table 2:
Table 2 Accepted file formats for the functional design packages
Item
Format
Statement
Pdf
Report
Pdf
Plans, sections, schematic drawings
Pdf
Letters
Pdf
Catchment boundary
Geo-referenced MapInfo layers
Modelling files
MUSIC, RORB and/or HEC-RAS files
Step 2 – Application for Conditions
The Developer must submit the following items to Melbourne Water:

A completed Melbourne Water Application for Conditions (Form A) signed by the
Developer; and

All plans and information specified on the Application for Conditions form.
The date of the application is the date upon which all required plans and information
have been received by Melbourne Water (i.e. not necessarily the date on the
application form). All applicable fees, charges or contributions are based on the rates
current at this date. It is therefore in the Developer’s best interest to ensure a
complete and correct application is submitted.
Subsequent to the Application for Conditions being made, if there are changes to the
Plan of Subdivision that affect the extent of Works and/or contributions payable, the
Developer must submit a new application. A new application is not required for minor
Plan of Subdivision changes such as minor easement creations or relocations.
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Melbourne Water Constructed Wetlands Design Manual: Part C
All fees, charges, contributions and conditions for a new application would be those
current at the new application date.
Step 3 – Meet with Melbourne Water
The designer and consultant project team must meet with Melbourne Water and the
other relevant stakeholders and approval authorities to discuss the functional design.
The aim of this step is to confirm that the functional design is generally in accordance
with the expectations of Melbourne Water and the stakeholders, and to give direction
to the designer so that they continue on the right track. Information associated with
the functional design should be submitted to Melbourne Water at least one week prior
to this meeting.
Step 4 – Submit final functional design package
The wetland designer must collate all relevant information and feedback from
Melbourne Water, relevant stakeholders and approval authorities, and incorporate this
into a final functional design package.
If any changes are required, you’ll need to re-submit the functional design package
for further review/comment to check that your iteration correlates with the feedback
provided. This submission should:

Highlight any conflicts that arose from attempting to address all interested
parties’ comments; and

Highlight any significant changes from previous design submissions that may
not otherwise be obvious to the reviewers.
Step 5 – Functional design acceptance
Melbourne Water is to provide confirmation in writing of the functional design
acceptance within 21 days of receipt of the complete package if the acceptance
pathway is the Deemed to Comply approach or within 42 days if the acceptance
pathway is the Alternative approach.

If the functional design package is incomplete or not Melbourne Water’s
satisfaction, there is no guarantee that the above review timeframes will be
met.

Melbourne Water does not accept liability for delays caused by incomplete or
inaccurate information submitted for our review.
Step 6 – Works offer
Once Melbourne Water has received the Developer’s ‘Application for Conditions’ form
(Form A) and the functional design package, Melbourne Water will prepare a business
Constructed Wetlands Design Manual: Part C Melbourne Water
17
case for internal management approval and forward an Offer of Conditions of
Agreement (the Works Offer) to the Developer. The Works Offer sets out conditions
under which waterway, flood protection and drainage services will be provided to the
development. The Works Offer will include details of any special conditions and
financial arrangements relating to the delivery of scheme infrastructure and the
adjacent development.
Melbourne Water will respond to the Works Offer application within 60 calendar days
from the date of application. The timeframe may be extended beyond 60 calendar
days where insufficient information is submitted,(to enable proper assessment of the
application) or where Melbourne Water requires additional information from the
Developer/consultant during the application review process.
The written Works Offer will:

identify significant environmental issues that need to be considered in the
design or the need for further survey work to be undertaken;

identify significant cultural issues that need to be considered in the design, or
the need for further survey work to be undertaken;

include details about how the reimbursement will be determined;

include details on the defects liability period; and

include comments about the design plans (including maintenance comments)
from our Developer Works Team.
Step 7 – Works offer acceptance
The Developer is considered by Melbourne Water to have accepted the Works Offer
when the following items have been lodged with Melbourne Water to its satisfaction
before the Offer expiry date (which is three months from the date of issue-the letter
date):

The final functional design package and functional design acceptance;

A completed Melbourne Water Offer of Acceptance Form signed by the
Developer and the Consultant; and

Any other required information and statements for Quality Assurance purposes.
If the acceptance does not meet Melbourne Water’s requirements, the Developer will
be notified by Melbourne Water within 5 working days of receiving the acceptance.
Any changes or additional information needed to satisfy Melbourne Water must be
lodged before the Works Offer expiry date.
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Melbourne Water Constructed Wetlands Design Manual: Part C
If a Works Offer is not accepted within three months of the date of issue, then the
Works Offer will expire. After this point, a new Application for Conditions will have to
be made by the Developer. The maximum 60 day timeframe will apply from the new
application date.
Important note: If you choose to commence work before accepting the Works Offer
or without a Works Offer, you accept to carry the risks associated with:
1. Lack of clarity on the basis for reimbursement
2. Impact on flora, fauna and cultural heritage issues
3. Land disturbance and environmental pollution
4. Community related issues
5. An asset that is not transferrable over to an Authority
6. Retrofitting costs to meet Melbourne Water’s standards
Detailed design stage
A detailed design package must be submitted to Melbourne Water’s Developer Project
Works team. The aim of the detailed design stage is to confirm the way the wetland
will be constructed, established and maintained. Key steps in this stage are gaining
final design acceptance from Melbourne Water and the lodgement of design
certification paperwork to Melbourne Water, including the addition of set-out
information to the drawing set.
Detailed design steps
The detailed design stage consists of four steps (see Figure 4):
Detailed design stage
Step 1. Prepare detailed design package
Step 2. Submit detailed design package
Step 3. Prepare the design certification statement
Designer
Step 4. Detailed design acceptance
Melbourne
Water
Figure 4 Steps in the detailed design phase
Step 1 – Prepare detailed design package
The detailed design package is prepared by the designer. Tasks carried out to prepare
all of the information required as part of the package include to:
Constructed Wetlands Design Manual: Part C Melbourne Water
19

Incorporate comments from the previous Stage in the design acceptance
process;

Prepare detailed design drawings suitable for public tender;

Finalise the maintenance plan, schedule and budget;

Finalise the cost estimate and submit tenders.
Important note: Consultation with the Melbourne Water Project Initiator in the
Developer Project Works Team will be required for any design changes that may be
proposed/required during the preparation and review of the detailed design if those
changes are considered likely to have an impact on the function of the constructed
wetland.
File formats and supplementary information on the elements of the detailed design
package are presented below:
Table 3 Accepted file formats for the detailed design package
Item
Format
Statement
Pdf
Reports
Pdf
Models
MUSIC, RORB, HEC-RAS files
Plans
Pdf and dwg
Specifications
Pdf
Step 2 – Submit detailed design package
A detailed design package must be submitted to Melbourne Water’s Developer Project
Works team. The aim of the detailed design stage is to document the design for
construction. Key steps in this stage are gaining final design acceptance from
Melbourne Water and the lodgement of design certification paperwork to Melbourne
Water. The detailed design package must include:
1. A statement listing any aspects of the package that do not conform with the
“Deemed to Comply” requirements outlined in this manual, and justification for
how the proposed alternative approach achieves equivalent or better than the
deemed to comply approach, in relation to:
a. pollutant reductions
b. safety outcomes
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Melbourne Water Constructed Wetlands Design Manual: Part C
c. maintenance costs
d. sustainability/robustness (i.e. ≥ 25 year life).
2. An updated design report with a summary of any design changes that have
been made since the functional design was accepted by Melbourne Water. In
addition to the items that must be included in the functional design package
design report, the final design report must include calculations and assumptions
used to specify all scour protection and energy dissipation works.
3. Copies of final hydrologic, hydraulic and water quality models
4. Civil and landscape construction drawings covering all aspects of the wetland
and showing all the required items listed in the functional design package, plus:
a. Scour protection
b. Method for identifying base of sediment pond
c. Material for maintenance access tracks
d. Topsoil properties
e. Dimensions and details for all hydraulic structures including pits, pipes,
headwalls and weirs
f.
Details of any fencing and signage
5. Civil and landscape specifications in accordance with AS2124, with the sections
that relate to the wetland highlighted.
6. Contact details for the Superintendent for the construction contract and an
outline of their relevant qualifications and experience (including records of
Green Card training).
7. An asset operation plan and maintenance agreement.
8. Details of establishment/maintenance to be undertaken in the first 24 months
following construction (i.e. before the asset is transferred to Melbourne Water).
9. Written approval from service authorities for any service alterations/relocations.
10. A summary of requirements of any Cultural Heritage Management Plan that
relate to the wetland construction.
11. A draft site environmental management plan.
Melbourne Water will review and provide comment on the detail design. Some
amendments may be required prior to lodgement of design certification.
Constructed Wetlands Design Manual: Part C Melbourne Water
21
Step 3 – Prepare the design certification statement
Once the design has been amended, as per comments from Step 2, and the designer
is confident that their design is acceptable, the Developer must submit The Design
Certification Statement to Melbourne Water:

The Design Certification Statement
Step 4 – Detailed design acceptance
Melbourne Water will provide confirmation of detailed design acceptance within 28
days of receipt of the completed package.

If the detailed design package is incomplete or not to Melbourne Water’s
satisfaction, there is no guarantee that this 28 days review timeframe will be
met.

Melbourne Water does not accept liability for delays caused by incomplete or
inaccurate information submitted for our review.
Pre-construction stage
The objective of the pre-construction phase is to ensure that all stakeholders
associated with the project are aware of their responsibilities, and that the contractor
has all of the information relevant to the construction works. The pre-construction
stage incorporates the tender process and the lodgement of pre-construction
certification paperwork to Melbourne Water.
Pre-construction steps
The pre-construction stage consists of six steps (Figure 5):
Pre Construction
Step 1. Tender process
Step 2. Submit SEMP
Step 4. Permits and pre‐
qualifications
Step 5. Prepare pre‐
construction certificate statement
Step 3. Reimbursement calculated
Step 6. Organise pre construction meeting
Designer
Melbourne
Water
Figure 5 Steps in the pre-construction phase
Step 1 – Tender process
The tender interview process should include design related questions so that the
contractor’s understanding of the project can be determined. It is recommended that
the process include a site walk where the designer can communicate the design intent
to the contractor and the field staff. The tender review process is to be conducted by
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Melbourne Water Constructed Wetlands Design Manual: Part C
the Developer or their representative. Melbourne Water is not generally involved in
the tender review process.
Step 2 – Prepare and submit Site Environmental Management Plan
The contractor, in consultation with the consultant, must prepare and submit the Site
Environmental Management Plan (SEMP) to Melbourne Water, for our records.
Step 3 – Reimbursement calculated
The actual reimbursement amount will be calculated and Melbourne Water will advise
the Developer of the proposed reimbursement.
Step 4 – Permits and pre-qualifications
Before works commence, the contactor is to obtain all permits and complete all prequalification processes:

The contractor must obtain a Permit to Work for any projects that involve
connections to an existing Melbourne Water pipeline or outlets to a waterway.
The Permit to Work will be issued by the Project Surveillance Office at the Precommencement meeting. The contractor must have completed a Permit
recipient training course in order to obtain a Permit to Work.

While civil works are being carried out, the contractor must have someone on
site that has obtained a Melbourne Water green card (i.e. attended the Site
Environmental Awareness Training course)
Step 5 - Prepare pre-construction certification statement
Before commencing construction, the Developer must submit the following documents
to Melbourne Water:

The Pre-Construction Certificate List in the Construction Specifications section of
Melbourne Water’s website in accordance with Commencement of Works.

Evidence that insurance requirements set out in the Insurance Conditions
section of Melbourne Water’s website have been complied with.
Melbourne Water must have at least two weeks’ notice of intention to start
construction by submission of a Pre-Construction Certification Statement and
Checklist.
Important Note: You must give Melbourne Water at least two working days’ notice
from the start date if construction is going to be delayed. Melbourne Water also needs
to know your new start date at least two working days before you begin.
Constructed Wetlands Design Manual: Part C Melbourne Water
23
Step 6 – Organise a pre-construction meeting
Once you have completed all the necessary pre-construction activities, you must
organise a project pre-construction meeting with Melbourne Water to review your
plan.
By this stage you should have:

lodged your pre-construction certification checklist and statement;

lodged your site environmental management plan;

had your reimbursement calculated;

selected a contractor; and

paid or lodged the necessary bonds if there is no reimbursement associated
with the works
Important note: Consultation with the Melbourne Water Project Officer in the
Developer Project Works Team will be required for any design changes during
construction that are considered likely to have an impact on the function of the
constructed wetland. Works must match the accepted design, unless Melbourne Water
provides permission for any changes. If the contractor’s works do not match the
design or meet Melbourne Water’s construction standards, the principal/developer
may be asked to rectify them at their own cost.
View our construction of works website for guidelines and details on construction.

Construction website
During construction, Melbourne Water’s Developer Project Works Team will:

visit your site to make sure the work complies with our standards; and

monitor your Site Environmental Management Plan, and amend the plan where
necessary.
If unforeseen issues occur during construction that impact on and/or require a
variation to the accepted design, it may be necessary to resubmit the new design to
Melbourne Water for formal review and acceptance.
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Melbourne Water Constructed Wetlands Design Manual: Part C
Important note: Make the most of Melbourne Water’s expertise when staff are on
site. For more complex or unfamiliar work, you should consider building a small
sample section of work and have it assessed by your Project Surveillance Officer. You
can then proceed based on an agreement solution and favourable review.
As-constructed and establishment stage
Documentation of what has been constructed is a crucial part in demonstrating that
the construction process has met the intent of the design, that Melbourne Water’s
objectives for the constructed wetland have been met, and that our desired outcomes
are likely to be realised over time as the constructed wetland is established.
As-constructed steps
The as-constructed phase consists of seven steps (see Figure 6):
As constructed and establishment phase
Step 1. Construction certification
Step 2. As‐constructed documentation
Step 5. Submit your End of Defects Liability Period Statement
Step 3. Certificate of practical completion
Step 6. Final reimbursement
Step 4. Works Warranty Bond
Step 7. Certification of Completion
Designer
Melbourne
Water
Figure 6 Steps in the as-constructed and establishment phase
Step 1 – Construction certification
At the end of construction, the designer must submit a Construction Certification
Statement. Melbourne Water will consider the Works as completed when they have
reviewed and accepted the Construction Certification Statement.
Check that you are ready to lodge your Construction Certification Statement by using
our Construction Certification Checklist. See Melbourne Water’s website for more
details.
Be sure to review all conditions in the Works Offer before submitting the Construction
Certification Statement.
Constructed Wetlands Design Manual: Part C Melbourne Water
25
If the works are not completed to Melbourne Water’s satisfaction by the due date
(eighteen (18) months from the date of issue of the Works Offer):

The agreement may be terminated at the discretion of Melbourne Water;

The developer must pay any reasonable additional costs incurred by Melbourne
Water.
If the Agreement terminates, money paid by the Developer under the Agreement will
be forfeited or refunded at the discretion of Melbourne Water. Melbourne Water will
deduct any reasonable costs incurred, before determining any refund amount.
Melbourne Water will not accept the Construction Certification Statement if there is
reason to believe there are discrepancies between the condition of the works as
certified and as-constructed. As-constructed feature surveys should be undertaken
and/or thoroughly reviewed by the consultant/developer to validate the
construction/design process.
Step 2 – As-constructed documentation
Use the As-constructed Survey Certification Checklist to check that the plans you are
submitting contain all the necessary detail.
When the documentation is ready, submit the ‘as-constructed’ plans and complete the
following forms:

As-constructed Survey Certification Checklist

Submission of digital data
Step 3 – Certificate of Practical Completion
Following receipt of the Construction Certification Statement and supporting
information, and providing there are no discrepancies between the condition of the
works as certified and as constructed, Melbourne Water will:

issue you the Certificate of Practical Completion;

provide you with a Letter of Release for the subdivision (if one has been
requested); and

pay the reimbursement, less the amount held until the defects liability period
finishes.
Step 4 - Works Warranty Bond
The Developer must lodge the Works Warranty Bond to be eligible to receive the
Certificate of Completion. For more information on the Works Warranty Bond, visit
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Melbourne Water Constructed Wetlands Design Manual: Part C
Melbourne Water’s Indemnity and insurance conditions page on the Melbourne Water
website:

Indemnity and insurance conditions
Step 5 – Submit your End of Defects Liability Period Statement
The defects liability period starts on the date of the Certificate of Practical Completion.
The Developer must submit an End of Defects Liability Period Certification Statement
at the end of the defects liability period.
The defects liability period differs depending on the asset. The following periods apply
and take effect from when the Certificate of Practical Completion is issued:

pipes and structures – three months

earthwork and rockwork – 12 months

plantings – 3 month establishment period and two years maintenance period
The Developer is responsible for all reasonable costs incurred by Melbourne Water
during the defects liability period. These costs will be included when the account is
finalised. Melbourne Water reserves the right to extend the defect liability period.
Such extended period will be specified in the special conditions of the agreement.
The Developer's nominated representative must certify that all works still comply with
the Construction Certification Statement and that the construction of the
development's roads and other services is complete.
Use the End of Defects Liability Period Certification Checklist to make sure that all the
necessary steps are completed, then submit the End of Defects Liability Period
Certification Statement.

End of Defects Liability Period Certification Checklist

End of Defects liability Period Certification Statement
Once Melbourne Water has accepted your End of Defects Liability Period Certification
Statement and a Works Warranty Bond has been lodged, Melbourne Water will
organise for the remainder of the reimbursement to be paid and provide a Certificate
of Completion.
Melbourne Water will not accept the End of Defects Liability Period Certification
Statement if it has reason to believe that there are discrepancies between the
condition of the Works as certified and as existing.
Constructed Wetlands Design Manual: Part C Melbourne Water
27
Step 6 – Final reimbursement
Melbourne Water reimburses for works after the issue of a Certificate of Practical
Completion and a Certificate of Completion as per the schedule outlined in Melbourne
Water’s Land Development Manual website:

Reimbursements – Land Development Manual
Step 7 – Certificate of Completion
A Certificate of Completion will be issued by Melbourne Water when all the
requirements of the agreement have been satisfied. The requirements (if applicable),
include:
1. The Certificate of Practical Completion issued by Melbourne Water
2. All contributions have been paid
3. All other money required by Melbourne Water has been paid
4. Downstream outfall works have been certified complete or the Developer has
made alternative arrangements which are acceptable to Melbourne Water
5. A copy of the amended plan of subdivision, certified by the council and
indicating the easements and/or reserves required to cover all Works, has been
received by Melbourne Water
6. Any other information, notices or documents required by Melbourne Water have
been provided
7. The defects liability period has ended to the satisfaction of Melbourne Water
8. A maintenance agreement is in place (if required).
Important note: The applicable Works Warranty Bond must be lodged with
Melbourne Water prior to the Certificate of Completion and final payment being made.
Important note: Complete the works to Melbourne Water standards and submit the
required documentation to obtain a Certificate of Practical Completion, Letter of
Release (if required) and any outstanding reimbursements.
28
Melbourne Water Constructed Wetlands Design Manual: Part C
Constructed Wetlands
Design Manual
Part D: Technical design, construction and establishment
approach
Table of contents
Introduction
1 Concept design
2 MUSIC Modelling ....................................................................................2 Hydrologic and hydraulic modelling ...........................................................3 Functional design
3 Detailed design
4 Pre-construction
4 Construction and establishment
4 Constructed Wetlands Design Manual: Part D Melbourne Water
i
Part D: Technical design, construction and
establishment approach
Introduction
The design approach for constructed wetlands is presented in this Part of the manual.
The design approach reflects the design acceptance process set out in Part C, and
follows the same linear sequence from concept design at the commencement of the
project to completion of the detailed design stage and finally through to construction,
establishment and maintenance.
This document describes the analytical and design tools, and technical resources
required by the designer. A description of the technical details of these tools and
resources is provided in Part E on the manual.
This section includes:





Concept design
Functional design
Detailed design
Pre-construction
Construction and establishment
Part D is structured as a series of steps that take the designer on a linear path
through the design process. There are often design iterations required during the
design process. This requires the designer to retrace their steps and repeat some
steps until the design meets the required criteria.
The design approach presented in this Part of the manual assumes a sound
understanding of the fundamentals of wetland function (Part A), the design objectives
and Deemed to Comply design criteria (Part B), and the design acceptance process
(Part C).
This section should be read in conjunction with the current versions of the following
documents:
•
•
Melbourne Water’s Planning and Building website [quick link]
Urban Stormwater: Best Practice Environmental Management Guidelines
(Victorian Stormwater Committee, 1999) [quick link]
•
WSUD Engineering Procedures: Stormwater (MWC, 2005) [quick link]
Any variations between this document and those listed above are superseded by this
manual.
Constructed Wetlands Design Manual: Part D Melbourne Water
1
Concept design
The concept design phase is likely to include:








Authority consultation
Site visit
Catchment analysis
Collaboration between members of design team (e.g. engineering, ecology,
landscape)
MUSIC modelling to estimate performance
Preliminary estimates of design flow rates to size high flow bypass route width
Analysis of feature survey or other information to estimate wetland levels and
spatial constrains (e.g. existing trees)
Analysis of flora and fauna survey, geotechnical testing and other relevant site
investigations
MUSIC Modelling
MUSIC modelling must be undertaken using the most recent version of the software
and should be in accordance with Melbourne Water’s MUSIC Modelling Guidelines.
Where the modelling approach is not in accordance with Melbourne Water’s
Guidelines, a full justification for the alternative approach must be provided.
The sediment pond will be sized accurately during the functional design stage. For the
concept design stage, the sediment pond can be assumed to be 10% of the
macrophyte zone area and have an average depth of 1.5 meters.
Where the sediment pond and macrophyte zones have a common Top of Extended
Detention (TED), a single “wetland” node should be used to represent the system in
MUSIC. The Inlet Pond Volume should represent the volume of the sediment pond’s
permanent pool above the sediment accumulation zone.
Where the sediment pond’s TED is higher than the macrophyte zone’s TED, the
sediment pond and macrophyte zone should be modelled using separate nodes in
MUSIC (i.e. a “sedimentation basin” node and a “wetland node”). When separate
nodes are used, the wetland node’s “inlet pond volume” should be set to zero. The
sedimentation basin’s equivalent pipe diameter or Custom Outflow Relationship must
reflect the hydraulic control between the sediment pond and macrophyte zone.
For the purpose of the concept design phase, it is recommended that the surface
areas used in the MUSIC node(s) are assumed to be the area at the bottom of the
Extended Detention Depth (EDD). Alternatively, the Custom Storage Relationship can
be used to define the storage volume at a range of depths (although this level of
detail is usually not available at the concept design stage).
2
Melbourne Water Constructed Wetlands Design Manual: Part D




MUSIC tool guidelines (PDF, 1.18 MB)
MUSIC rainfall templates (ZIP, 48.07 KB)
Rainfall distribution map - Melbourne (JPG, 3.29 MB)
MUSIC Auditor
Hydrologic and hydraulic modelling
During the concept design phase, peak design flows are estimated (generally using
the Rational Method) to size the high flow bypass channel. The indicative channel
dimensions can be estimated using Manning’s Equation. Refer to Part E of this
manual for advice on hydrologic modelling and hydraulic analysis.
Functional design
The functional design phase is likely to include:










Authority consultation to confirm design requirements and maintenance
commitments
Collaboration between members of the design team (e.g. engineering, ecology,
landscape)
Confirmation of sediment basin and sediment dewatering area configuration
Refined MUSIC modelling to confirm performance and ensure adequate
residence time and inundation patterns
Confirmation of design flow rates to size hydraulic structures and high flow
bypass route
Three dimensional representation of wetland form to confirm wetland levels and
extent relative to any site constraints
Analysis of water levels and flow velocities relevant to wetland function
Confirmation of wetland bathymetry and planting design
A record of design approach and outcomes in a report format
An estimate of capital costs of proposed works
WSUD Engineering Procedures: Stormwater (Melbourne Water, 2005) should be the
primary reference for the functional design methods. The advice in Part E of this
manual supersedes the advice in the Engineering Procedures document. In particular:

The controlled outlet must be sized using the method described in Part E rather
than the method in the Engineering Procedures

The velocities must be checked using the method described in Part E rather
than the method in the Engineering Procedures.
Constructed Wetlands Design Manual: Part D Melbourne Water
3
The
functional
design
stage
MUSIC
model
must
reflect
the
actual
stage/storage/discharge relationship of the wetland’s extended detention. Where the
wetland is within a retarding basin, the MUSIC model must also reflect the
stage/storage/discharge relationship of the retarding basin (i.e. when the water level
exceeds TED). The actual stage/storage/discharge relationships must be represented
using MUSIC’s Custom Outflow and Storage Relationship function.
Detailed design
The primary reference for the detailed design phase is the standard drawings on
Melbourne Water’s Planning and Building website:



Planning and Building website
Design of works
Standard drawings
Pre-construction
The primary reference for the pre-construction phase is Melbourne Water’s Planning
and Building website:




Planning and Building website
Permit to Work
Tendering of works
Construction of works
Construction and establishment
The primary reference for the construction and establishment phase is Melbourne
Water’s Planning and Building website:







Planning and Building website
Construction of works
Provision of notice
Working on live assets
Indemnity and insurance
Certification at the end of construction
Certificate of completion
The Construction and Establishment Guidelines: Swales, Bioretention Systems and
Wetlands (Water by Design, 2010) is a recommended references for the Construction
and Establishment phase stage for a constructed wetland.
4
Melbourne Water Constructed Wetlands Design Manual: Part D
Constructed Wetlands
Design Manual
Part E: Design tools, resources and glossary
Table of contents
Introduction
1 Design tools
1 Hydrological modelling ............................................................................1 Continuous simulation modelling ..............................................................6 Hydraulic analysis of flow velocities ........................................................ 10 Resources
16 Planning ............................................................................................. 16 Design ............................................................................................... 16 Maintenance........................................................................................ 17 Construction and establishment ...............................................................5 Glossary
6 Constructed Wetlands Design Manual: Part E Melbourne Water
i
Part E: Design tools, resources and
glossary
Introduction
This section provides some of the necessary tools required for constructed wetland
design. The information supports Part D of the manual and should be consulted in
tandem with the design procedures outlined.
Design tools
The wetland design process uses software that is available and frequently used by the
Melbourne Water and land development industries. This section presents guidance
regarding:
1. Hydrological event modelling
2. Continuous simulation (water quality, residence time and water level analysis)
3. Hydraulic analysis of flow velocities
Where the wetland designer is using hydrologic event modelling and one-dimensional
hydraulic modelling, Melbourne Water requires the wetland designer to use RORB and
HEC-RAS software.
The continuous simulation modelling must be undertaken using the Model for Urban
Stormwater Improvement Conceptualisation (MUSIC).
Various terrain modelling packages are used across the industry and are acceptable to
Melbourne Water. Melbourne Water’s preference is that a software package such as
12D is used.
Hydrological modelling
The catchment hydrology can be estimated using a combination of the Rational Method
and RORB runoff routing software.
The Rational Method
The Rational Method provides a simple estimation of the design peak flow rate. The
Rational Method is recommended for use to:


Calculate the design flow rate for small, simple catchments (less than 400 ha)
Calibrate a RORB model
Constructed Wetlands Design Manual: Part E Melbourne Water
1
The Rational Method does not provide runoff volume or hydrograph shape and so
cannot be used to size volume based assets such as retention basins. The Rational
Method is generally not suitable for catchments of unusual shape, with significant
isolated areas of different hydrologic characteristics, with significant on-line or off-line
storage, with a time of concentration greater than 30 minutes (where a high degree of
reliability is required), and urban catchments greater than 400 ha in size.
Important note: For catchments less than 100 ha, Melbourne Water may accept the
use of the Rational Method for sizing retarding basin storage volumes and designing
other assets. However, project specific written consent from Melbourne Water must be
obtained to confirm if this approach is acceptable.
The Rational Method procedure is described in Book 4 of Australian Rainfall and Runoff
(1998). Book 8 provides information specific to urban stormwater management.
Melbourne Water’s Land Development Manual outlines the Rational Method procedure
including all input parameters and/or sources in Section 5.3.2 Design of Stormwater
Conveyance – Hydrologic and Hydraulic Design (available online):
http://www.melbournewater.com.au/Planning-and-building/Standards-andspecifications/Design-general/Pages/Hydrologic-and-hydraulic-design.aspx
RORB
The Melbourne Water recommended RORB modelling procedure includes:
1. Set-up of a preliminary RORB model of the catchment without any diversions or
detention storages.
2. Calibration of the preliminary RORB model using the Rational Method
3. Use of the calibrated preliminary RORB model as basis for modelling future
scenario/s with proposed diversions and/or detention storages.
Modelling scenarios
Modelling of the existing condition is to be based on the current planning zones (or
historical if current zone is Urban Growth) and should only consider existing
topography and infrastructure. Modelling of future conditions is to be based on the
proposed planning zone and include all infrastructure (drainage, storage, etc.) and
any changes to topography.
18
Melbourne Water Constructed Wetlands Design Manual: Part E
The full suite of design events required for the design of constructed wetlands must be
modelled. Generally, this includes (but is not limited to): Q1, Q2, Q5, Q10, and Q100.
For all events, the full range of storm durations from 10 minutes to 72 hours must be
run to identify the critical duration.
Important note: Generally, RORB underestimates flows for less than 10 year ARIs.
Therefore, the designer needs to check and adjust if necessary RORB flow estimates
for less than 10 year events using the Theoretical relationship between average
recurrence intervals of annual and partial series floods in Australian Rainfall and
Runoff.
Delineation of RORB catchment and sub-catchment boundaries, nodes and
reach alignments
The following requirements apply to the delineation (or review) of RORB subcatchment areas, nodes and reach alignments:





A catchment boundary must match adjoining catchment boundaries that have
been provided by Melbourne Water.
Sub-catchments must be delineated as is most appropriate for the 1 in 100 year
ARI event.
Sub-catchments, nodes and reaches must be named/numbered as
recommended by Melbourne Water.
Nodes must be located within and at the downstream end of each subcatchment.
Where relevant, the local Council drainage systems should be considered when
delineating sub-catchments.
Fraction impervious methodology
The fraction impervious must be determined using the existing planning zones (as per
the Planning Schemes Zones MapInfo table provided by Melbourne Water) as a starting
point. The Developer must then assess the fraction impervious for each zone in a subcatchment.
The fraction impervious must be reported in table format, detailing the fraction
impervious for each zone within a sub-catchment as well as the overall fraction
impervious for the sub-catchment. This must be reported as part of submissions made
to Melbourne Water.
Constructed Wetlands Design Manual: Part E Melbourne Water
1
RORB model calibration and model parameters
The preliminary RORB model must be reconciled to a Rational Method estimated flow,
unless it is specifically agreed with Melbourne Water that sufficient data is available to
warrant a calibration to historic data.
The preliminary RORB model must have:



no special storages;
no diversions to separately route multiple flow paths (i.e. overland and
underground flows); and
a structure and reach types consistent with the assumptions of the Rational
Method and the way in which the time of concentration is estimated.
Calibration at multiple locations within the catchment will be required when:




the topography varies significantly across the catchment; and/or
the land use varies (i.e. urban vs rural) across different parts of the catchment;
and/or
the size of the catchment is larger than 20 km2 and/or
the Developer considers it necessary.
As a minimum, the calibration checks must occur at the upstream end of the
Melbourne Water drainage system. Some projects may require calibration at the
upstream end of the modelled council drainage system, the catchment outlet and/or
at confluences of drainage networks.
Important note: the designer must discuss calibration points and obtain approval
from Melbourne Water prior to proceeding. The calibration must be to a 1 in 100 year
and 1 in 10 year Rational Method Flow estimate, calculated in accordance with AR&R
and taking into account time of concentration calculation requirements outlined in this
document.
All reach alignments should be consistent with the assumptions for calculating the
Rational Method flow for the catchment. Similarly, the fraction impervious should
also be consistent between the preliminary RORB model and the fraction impervious
used to estimate the Rational Method Coefficient of Runoff. The correlation between
runoff coefficient and catchment fraction impervious is described in AR&R.
18
Melbourne Water Constructed Wetlands Design Manual: Part E
A value of 0.8 must be assigned to the exponent m unless the Developer believes this
is inappropriate, in which case the recommended value is to be discussed with
Melbourne Water prior to proceeding with this part of the work.
The parameter kc must be adjusted so the flow from the preliminary RORB model
matches the Rational Method estimated flow.
AR&R method (Section 1.7 of Book II) must be used for the Areal Reduction Factor
(ARF). ARFs need only be used for catchment areas greater than 400 hectares.
Suitable initial loss values must be determined by the developer. As a guide, the
following values may be appropriate in the absence of better information:


For urban catchments: Initial loss of 10 mm
For rural catchments: Initial loss between 10 mm – 25 mm
Temporal patterns must be fully filtered.
Suitable runoff coefficients must be determined by the developer. As a guide, a
value of 0.6 is often found to be suitable for an urban catchment for the 100 year ARI
event. If the Developer proposes to use another value, the rationale for adopting that
value must be discussed and agreed with Melbourne Water prior to undertaking this
part of the work. For rural catchments, the Developer is to propose an approach to be
used regarding the use of a Runoff Coefficient versus Initial loss/Continuous loss.
Calculating time of concentration
The method for calculating the time of concentration for the Rational Method is
outlined in Melbourne Water’s Land Development Manual Section 5.3.2 Design of
Stormwater Conveyance – Hydrologic and Hydraulic Design (available online):
http://www.melbournewater.com.au/Planning-and-building/Standards-andspecifications/Design-general/Pages/Hydrologic-and-hydraulic-design.aspx
RORB model data
The .catg files of all scenario modelling, along with parameter files and IFD parameters
and catchment plan/s in CAD or MapInfo format (with GDA 94 coordinate system),
must be provided to Melbourne Water as part of carrying out the project.
All RORB reach alignments, node locations, sub-catchment and catchment boundaries
are to be populated with appropriate descriptions, slopes, lengths to correspond with
the RORB model code.
Constructed Wetlands Design Manual: Part E Melbourne Water
1
Continuous simulation modelling
MUSIC Guidelines
Melbourne Water has created the MUSIC Guidelines (2010) which recommend input
parameters and modelling approaches for MUSIC users. The objectives of the MUSIC
tool guidelines are to:



Ensure a consistent scientifically based approach is applied to MUSIC models
Provide guidance on methods specific to the Melbourne region without inhibiting
innovative modelling approaches
Reduce the time taken by Melbourne Water in assessing models.
The Melbourne Water Guidelines should be read in conjunction with the MUSIC User’s
Manual (eWater). Users of this Wetland Manual are expected to be sufficiently trained
in the use of MUSIC software and know how to use it appropriately.
MUSIC Auditor
The MUSIC auditor is a tool that has been developed for checking the parameter
inputs to MUSIC models to ensure they comply with relevant guidelines and are within
expected or reasonable ranges. The MUSIC Auditor is intended for use by suitably
experienced professionals with an understanding of water sensitive urban design and
MUSIC software.
The MUSIC Auditor is free for anyone to use within Melbourne Water's area of
responsibility and can be accessed using the following website:
http://www.musicauditor.com.au/
The MUSIC Auditor was developed by Microburst Software with the support of
Melbourne Water and in collaboration with E2Designlab.
How to determine residence time using continuous simulation
The wetland residence time is defined as the time a particle of water spends in the
wetland. The residence time is predicted assuming plug flow between the wetland
inlet and outlet. The residence time for a particle of water entering the wetland can be
determined by counting the number of time-steps it takes for the water “in front” of
that particle of water to be displaced from the wetland (refer Figure 1). This
calculation can be done using wetland flux files generated in MUSIC.
18
Melbourne Water Constructed Wetlands Design Manual: Part E
Water particle “X” that enters wetland at timestep “Y”
Wetland inlet
Flow direction
Wetland outlet
Volume of water that must be displaced before water particle “X” will exit wetland
Figure 1 Residence time for a particle of water entering a wetland
The plug flow of water through the wetland is assumed to involve 100% of the
extended detention volume and the upper parts of the permanent pool volume.
Melbourne Water will accept calculation methods where up to 50% of the permanent
pool volume is assumed to be involved in plug flow.
An iterative process is needed to identify a wetland configuration that achieves a 10th
percentile residence time of at least 72 hours. A 10th percentile residence time of 72
hours means that the residence time will be 72 hours or more 90% of the time. The
recommended method for predicting the 10th percentile residence time for a particular
wetland configuration is described below. Melbourne Water has created an online tool
to assist practitioners predict wetland residence time (refer WEBSITE X). Note that the
first two steps are needed even if the online residence time tool is used.
1. Create a six minute MUSIC model of the system that is in accordance with
Melbourne Water’s MUSIC Guidelines. Ensure the wetland node has an accurate
stage-discharge and stage-storage relationship. This will require the use of the
“Custom Outflow and Storage Relationship” option in MUSIC (refer Error!
Reference source not found.), unless the wetland has vertical sides and a
single horizontal circular orifice outlet which is not in accordance with the
Deemed to Comply criteria.
Constructed Wetlands Design Manual: Part E Melbourne Water
1
Figure 2 Custom Outflow and Storage Relationship option in MUSIC wetland nodes
2. Export a flux file from the wetland node. Use an online tool or steps below to
analyse the flux file.
3. Delete all columns except for “outflows” and “storage”. Use a pivot table in
excel, or another data processing method, to determine the:
a. Total inflow volume for each day
b. Total outflow volume from the controlled outlet for each day (exclude
overflows)
c. Average storage volume for each day
18
Melbourne Water Constructed Wetlands Design Manual: Part E
Important note: Your MUSIC model should run at a six minute time-step and post
processing of the flux file should be used to determine these daily metrics rather than
running the model at a daily time-step.
4. Determine the average “plug flow volume” for each day in the time-series by
subtracting 50% of the permanent pool volume from the average storage
volume calculated from the flux file.
5. For each day in the time-series, count the minimum number of proceeding days
until the cumulative outflow volume equals the plug flow volume. Use this
method to create a daily time-series of residence times.
6. Modify the residence time time-series so that it only includes values
corresponding to days where the inflow is > 0 (this avoids double counting of
parcels of water at the front end of the wetland).
7. Determine the 10th percentile value of the daily time-series of residence times.
If this 10th percentile value is three days or more, the wetland configuration
provides an acceptable residence time.
How to undertake inundation frequency and duration analysis
Plant inundation (submergence) is a major constraint on the growth and species
distribution of emergent macrophytes. Despite having a wide range of biochemical,
molecular and morphological adaptations to inundation, emergent macrophytes are
often highly sensitive to inundation, particularly in stormwater treatment wetlands
where high turbidity can severely restrict photosynthesis.
An inundation frequency analysis is required to ensure that the plant species proposed
for the wetland are able to cope with the expected wetland hydrology. Melbourne
Water has created an online tool to assist practitioners undertake inundation
frequency analysis (refer WEBSITE X).
1. Use the plant height information in the tables within Part B2 of this manual to
determine the emergent macrophyte species (excluding ephemeral batter
species) that, when mature, will be the shortest relative to NWL for both
shallow and deep marsh zones. Note that the planting depth relative to NWL
must be taken into account. For example, if a plant will be 500 mm high when
mature, and will be planted at a depth of 200 mm, the height relative to NWL
will be 300 mm.
Constructed Wetlands Design Manual: Part E Melbourne Water
1
Figure 3 Plant height characteristics for inundation frequency analysis.
2. Create a six minute MUSIC model of the system in accordance with Melbourne
Water’s MUSIC Guidelines. Ensure the wetland node has an accurate stagedischarge and stage-storage relationship. These relationships should include
any detention storage above wetland (e.g. retarding basin). This will require the
use of the “Custom Outflow and Storage Relationship” option in MUSIC (refer
Error! Reference source not found.), unless the wetland has vertical sides
and a single horizontal circular orifice outlet which is not in accordance with the
Deemed to Comply criteria.
3. Export a flux file from the wetland node. Use an online tool or steps below to
analyse the flux file.
4. Determine the 20% percentile of the water level time-series using Excel or
another data analysis method.
5. Ensure that the effective water depth (permanent pool depth plus extended
detention depth) does not exceed half the average plant height for more than
20% of the time.
Hydraulic analysis of flow velocities
An initial check of maximum wetland velocities (sediment pond and macrophyte zone)
can be undertaken using a simple calculation (maximum flow rate divided by smallest
cross sectional flow area). This will produce a conservative estimate of the maximum
18
Melbourne Water Constructed Wetlands Design Manual: Part E
velocity. If the velocities estimated by this preliminary calculation are less than the
prescribed limits, no further flow velocity analysis is required. If the prescribed limits
are exceeded, a HEC-RAS model is required to obtain a more accurate estimate of flow
velocities.
Manual calculation
The manual velocity calculation involves the following steps:
1. Identify the following peak design flow rates:
a. Peak flow rate through the sediment pond during the critical:
i. 10 year ARI event
ii. 100 year ARI event
b. Peak flow rate through the macrophyte zone during the critical:
i. three month ARI event
ii. 10 year ARI event
iii. 100 year ARI event
2. Determine the peak water level in the sediment pond during the critical 10
year ARI event1 (e.g. if the sediment pond is not within a retarding basin and
overflow outlet is a weir, use the weir equation to determine the head of water
needed to pass the peak 10 year ARI flow over the weir). If the sediment pond
is within a retarding basin use RORB to determine the peak 10 year ARI water
level.
3. Determine the narrowest part of the sediment pond in the direction of flow
between the inlet and overflow outlet. Determine the width between the batters
at the location at:
a. NWL; and
b. the peak 10 year ARI water level.
4. Determine the cross section flow area at the narrowest point of the sediment
pond by multiplying the distance between NWL and the peak 10 year water
level by the average of the two widths determined in Step 3.
5. Estimate the 100 year ARI flow velocity at the narrowest point of the sediment
pond by dividing the peak 100 year ARI flow rate by the cross sectional area
determined in Step 4. Ensure the 100 year flow velocity does not exceed 0.5
m/s (in accordance with Deemed to Comply Condition SP3).
1
Note this method assumes the peak 100 year ARI flow occurs when the water level in
the sediment pond is equal to the peak 10 year ARI water level.
Constructed Wetlands Design Manual: Part E Melbourne Water
1
6. Determine the peak water level in the macrophyte zone during the critical 10
year ARI event2 (e.g. if the macrophyte zone is not within a retarding basin and
the overflow outlet is a weir, use the weir equation to determine the head of
water needed to pass the peak 10 year ARI flow over the weir). If the
macrophyte zone is within a retarding basin, use RORB to determine the peak
10 year ARI water level.
7. Determine the narrowest part of the macrophyte zone in the direction of flow
between the inlet and outlet. Determine the width between the batters at the
location at:
a. NWL;
b. TED; and
c. the peak 10 year ARI water level.
8. Determine the cross section flow area at the narrowest point of the
macrophyte zone:
a. For the three month ARI event, multiply the EDD by the average of the
NWL and TED widths determined in Step 7.
b. For the 100 year ARI event, multiply the distance between the NWL and
the peak 10 year ARI water level by the average of the NWL width (7a)
and the peak 10 year ARI water level width (7c).
9. Estimate the three month ARI flow velocity at the narrowest point of the
macrophyte zone by dividing the peak three month ARI flow rate by the cross
sectional area determined in Step 8a. Ensure the three month flow velocity does
not exceed 0.05 m/s (in accordance with Deemed to Comply Condition MZ9).
10. Estimate the 100 year ARI flow velocity at the narrowest point of the
macrophyte zone by dividing the peak 100 year ARI flow rate by the cross
sectional area determined in Step 8b. Ensure the 100 year flow velocity does
not exceed 0.5 m/s (in accordance with Deemed to Comply Condition MZ9).
HEC-RAS
The Hydrologic Engineering Centre of the US Army Corps of Engineers developed the
River Analysis System (HEC-RAS) software. The software allows the user to perform
one-dimensional steady and unsteady river calculations (US Army Corps HEC RAS
manual) through interaction with the graphical user interface.
2
Note this method assumes the peak 100 year ARI flow occurs when the water level in
the macrophyte zone is equal to the peak 10 year ARI water level.
18
Melbourne Water Constructed Wetlands Design Manual: Part E
HEC-RAS comprises four river analysis components: (i) steady flow water surface
profiles, (ii) unsteady flow simulation, (iii) sediment transport/movable boundary
computations, and (iv) water quality analysis. The steady flow water surface profile
component can be used to estimate wetland flow velocities.
Getting started
The HEC-RAS software and supporting resources (user’s manual, applications guide
and the hydraulic reference manual) is freely available at:
http://www.hec.usace.army.mil/software/hec-ras/downloads.aspx
This manual assumes that the user is familiar with the steps required to set-up a basic
steady flow simulation project in HEC-RAS.
The HEC-RAS user’s manual provides an overview of installation, getting started,
entering and editing geometric and flow input data, modelling components and
processes, and using the output results. The user’s manual also contains simple
example applications.
The hydraulic reference manual provides the background
assumptions, and modelling approaches) to HEC-RAS.
theory
(equations,
The applications guide contains a series of examples to demonstrate the various
modelling aspects (data requirements and modelling approach) with supporting
illustrations.
The geometry file
This file is used to:

Define geometric data (e.g. geometry exported from terrain modelling package)

Specify the hydraulic roughness (Manning’s n)

Where applicable, specify bridge/culvert, inline and lateral structure information
HEC-RAS can import geometric data in several different formats (GIS, HEC-RAS, and
others). The HEC-RAS format may be used when importing geometric data from 12d
Model.
 Geometric data created in 12d Model is imported to HEC-RAS in HEC-RAS
format by selecting File | Import geometry Data | HEC-RAS Format from within
the geometric data editor window. The HEC-RAS user’s manual (pp. 6-131 to 6137) provides supporting information for the process.
Constructed Wetlands Design Manual: Part E Melbourne Water
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The wetland geometry file should be created using the following steps:
1. Determine a “design line” or centreline of flow as it passes through the system
(typically the longest route through the deepest parts of the wetland. Note that
the design line may be different for the three month and 10 to 100 year events,
in which case two geometry files will be required.
2. Define suitably spaced cross sections along the design line (typically 20 to 50 m
spacing depending on wetland size). The top of the ephemeral batters should
generally be used as the left and right bank station.
3. Mark the cross section locations on a scale plan and measure the downstream
reach lengths for left over bank (LOB), right over bank (ROB) and channel flow.
4. Determine suitable Manning’s roughness coefficients for different sections of the
wetland geometry. Note that variable Manning’s n values can be defined by
selecting “Options – Horizontal Variation in n values” in the cross section
geometry editor. The HEC-RAS user’s manual recommends Mannings n values
for common waterway types (Table 3-1 from pp 3-14 to 3-16 in the HEC-RAS
User’s Manual).
Typical Manning’s n values are:
Low flows
0.08 (normal) relating to channels not maintained, weeds and
brush uncut, dense weeds as high as flow depth
High flows
0.03 to 0.05 -> adopt 0.035 (normal) relating to flood plains,
pasture no brush, high grass
Note: the Manning’s n value for low flows is not listed in the HEC-RAS Manual,
but has been sourced from Chow (1959)3, which is referenced in the HEC-RAS
Manual.
Check steady flow velocities
The steady flow velocities should be checked using the following steps:
1. Enter the peak three month and 100 year flow rates into the HEC-RAS model as
steady flow data.
2. Adopt the NWL for the downstream boundary condition for the peak three
month flow.
3
18
Chow, V.T. (1959) Open-channel hydraulics. McGraw- Hill Book Co., New York, 680 p.
Melbourne Water Constructed Wetlands Design Manual: Part E
3. Adopt the peak 10 year water level (determined as part of the manual
calculations described in the previous section) as the downstream boundary
condition for the peak 100 year ARI flow.
4. Run the model using the steady flow option.
5. View the Profile Output Summary table in HEC-RAS and check that:
a. For all cross sections in the sediment pond and macrophyte zone the
peak 100 year ARI flow velocities are less than 0.5 m/s
b. For all cross sections in the macrophyte zone, the peak three month ARI
flow velocities are less than 0.05 m/s.
If the peak 100 year ARI steady flow velocities exceed the Deemed to Comply
thresholds, modify the wetland configuration. If the peak 100 year ARI steady flow
velocities complies with the thresholds but the peak three month ARI velocity in the
wetland does not, either proceed with checking the unsteady three month velocities or
modify the wetland configuration.
Check unsteady three month flow velocities
The unsteady three month flow velocities should be checked using the following steps:
1. Determine the flow duration for the critical three month ARI event and
construct an approximate flow hydrograph for this event (using RORB output
data).
2. Determine volume of water in the critical three month ARI event (area below
hydrograph).
3. Estimate the wetland outflow hydrograph by assuming:
a. The volume of water in the inflow hydrograph is equal to the volume of
water in the outflow hydrograph
b. The outflow hydrograph is a triangular shape
c. The outflow hydrograph peaks after 36 hours and finishes at 72 hours.
4. In HEC-RAS:
a. set the upstream boundary condition to be the critical three month ARI
hydrograph (from Step 1)
b. set the downstream boundary condition to be the outflow hydrograph
(from Step 3)
c. set the Initial Stage for the downstream boundary condition to the
wetland NWL.
Constructed Wetlands Design Manual: Part E Melbourne Water
1
Resources
Planning
The following key strategies and plans detail how Melbourne Water manages its water
assets:
 Waterways and Drainage Strategy
Formally known as the Waterways Operating Charter, the strategy outlines our
responsibilities, goals, services and work programs in managing waterways, drainage
and floodplains.
 Flood Management and Drainage Strategy
This strategy aims to minimise flood risks to public health and safety, property and
infrastructure. It defines five flood management objectives, and outlines actions to
achieve these and guide our priorities and expenditure.
 Healthy Waterways Strategy
This strategy outlines our role in managing rivers, estuaries and wetlands in the Port
Phillip and Westernport region. The strategy set priorities, actions and targets for
improving waterway health 2013/14 to 2017/18.
 Stormwater Strategy
The Stormwater Strategy is closely linked to the Healthy Waterways Strategy and
covers the same five-year period. It focuses on managing stormwater to protect and
improve the ecosystem health of waterways and bays.
 Better bays and waterways
Better Bays and Waterways defines our economic, social, and environmental values,
the threats to these values, and our commitments through an adaptive management
approach to improve the water quality of our rivers, creeks and marine environments
for a more sustainable future.
Design
Melbourne Water has produced the following range of guidelines which may be of use
or further interest to the wetland designer.
18

MUSIC Guidelines

WSUD Engineering Procedures – Stormwater (CSIRO, 2005)
Melbourne Water Constructed Wetlands Design Manual: Part E

Waterway Corridors Greenfield Development Guidelines

Flood retarding basins design and assessment guidelines

Waterway Crossings Guidelines

Stormwater connections

Constructed Waterways in Urban Developments Guidelines

Shared Path Guidelines

Jetties Guidelines

Guidelines for development in flood prone areas

Building in flood prone areas

Land Development Manual

Australian Rainfall and Runoff)

Constructed Shallow Lake Systems – Design Guidelines for Developers

Urban Stormwater: Best Practice Environmental Management Guidelines
Maintenance
A maintenance agreement must be provided to Melbourne Water as part of the
detailed design package. The maintenance agreement outlines all of the activities
associated with maintaining the treatment wetland, and provides for the separation of
maintenance tasks in situations where a wetland may be jointly managed by a Council
and Melbourne Water.
The maintenance agreement comprises of up to four components:




Schedule 2 – Council maintenance works
Schedule 3 – Melbourne Water maintenance works
Plan of assets
Priority weeds list
Constructed Wetlands Design Manual: Part E Melbourne Water
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The maintenance agreement package should also include an Asset Operation Plan
which provides a brief description of the wetland operation, including all of the key
functional components (which must be clearly labelled on the plan of the asset), any
site access issues (site entry, pit access keys) and any other associated management
information.
Copies of the Melbourne Water maintenance agreement template (including a
completed Maintenance Agreement Schedule example) can be downloaded from the
Land Development Manual website - http://www.melbournewater.com.au/Planningand-building/Forms-guidelines-and-standard-drawings/Documents/MaintenanceAgreement-Package.zip
A schedule of wetland inspection and maintenance requirements is provided in
18
Melbourne Water Constructed Wetlands Design Manual: Part E
Table 1 Schedule of wetland maintenance requirements
Item
What to check for
Action
Frequency
Civil components
Inlet
No erosion, blockage or damage
Clear inlet of accumulated sediment or debris.
Storm events
Eroded areas should be locally re-profiled or reinforced, and re-planted if
3 months
necessary.
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
Assets if the erosion is either recurring or severe.
Outlet
No erosion, blockage, damage or
Clear outlet of accumulated sediment or debris.
Storm events
standing water
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
3 months
Outlet freely draining.
Assets if standing (backwatering into the raingarden) is present.
Other
No erosion and damage to other
Repair minor damage to structures.
structures
structures, e.g. pits, pipes, access
Eroded areas should be repaired (reinforced). This may involve minor re-profiling or
ramps, walls and rock protection.
re-planting works.
3 months
For severe damage, i.e. where flows have scoured down the side of a structure
refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
Assets.
Batters and
No erosion.
Eroded areas should be locally re-profiled or reinforced, and re-planted if
Sediment
Accumulated sediment no less than
Clean out accumulated sediment from the sediment pond.
accumulation
0.5 m below NWL.
Accumulated sediment to be removed from the macrophyte zone and the system
No major sediment accumulation on
replanted as required.
bunds
Annually
necessary.
Annually
macrophyte zone topsoil.
Topsoil
No surface scour or depressions.
surface
Algal growth
Topsoil surface to be repaired. This may involve evening out the surface, importing
3 months
additional soil and replanting.
No major algal growth (less than 10%
If significant patches of algal growth persist across the macrophyte zone (i.e.
of macrophyte zone is permissible).
greater than 10% of the surface) then refer to Water by Design (2012) Rectifying
3 months
Vegetated Stormwater Treatment Assets.
Harvesting
No blockages and equipment is
infrastructure
functioning as designed.
Refer to manufacturer’s instructions.
Annually
(if relevant)
Constructed Wetlands Design Manual: Part E Melbourne Water
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Landscape components
Vegetation
Greater than 90% vegetation cover in
Remove any dead or diseased vegetation.
cover
designated marsh areas of the
Replant individual bare patches (greater than 5% of the area) using either new
-
macrophyte zone.
plants or by dividing and translocating existing plants.
macrophytes
Plants healthy, free from disease and
If bare areas represent greater than 30% of the macrophyte zone area, refer to
vigorously growing.
Water by Design (2012) Rectifying Vegetated Stormwater Treatment Assets.
Vegetation
Continuous vegetation cover along the
cover
lower batter.
- ephemeral
Greater than 90% vegetation cover.
/terrestrial
Plants healthy, free from disease and
batters
vigorously growing.
High flow
Greater than 90% vegetation or other
Surface to be repaired. This may involve evening out the surface, importing
bypass
scour protection (e.g. rock beaching).
additional soil and replanting.
No surface scour or depressions.
Remove any dead or diseased vegetation and replant bare patches
Less than 10% of the macrophyte zone
Physically remove weeds from filter media surface and batters.
area and batters covered in weeds
Do not use herbicides as these may harm the desirable wetland vegetation and
Weeds
3 months
Annually
3 months
contaminate wetland outflows.
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
Assets if weed ingress is a persistent problem (i.e. weed coverage is persistently
greater than 30%).
Litter
Macrophyte zone and batters free of
Remove all litter and excessive debris
3 months
No damage by pest animals and
Seek specialist advice if persistent insect damage is observed.
3 months
insects.
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
litter (i.e. less than 1 piece litter per 4
m2).
Pests
Assets if there is evidence of pest animal damage.
Constructed Wetlands Design Manual: Part E Melbourne Water
2
to assist with the preparation of the maintenance agreement (Schedules 2 & 3). A
wetland inspection and maintenance checklist is provided in Error! Reference
source not found.. The checklist should be used during inspection and maintenance,
as it provides a list of the key inspection elements, and is a permanent record of the
maintenance activities undertaken.
Safety in Design
As part of our ‘Zero Harm’ culture, ‘Safety in Design’ is a paramount consideration.
We ensure our designs are safe for the contractors to build, safe for people to use,
and safe for people to maintain in the future. Included in our management of risks
and hazards is eliminating, through design, as many risks as possible that could be
encountered during construction, maintenance or demolition.
Constructed Wetlands Design Manual: Part E Melbourne Water
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Table 1 Schedule of wetland maintenance requirements
Item
What to check for
Action
Frequency
Civil components
Inlet
No erosion, blockage or damage
Clear inlet of accumulated sediment or debris.
Storm events
Eroded areas should be locally re-profiled or reinforced, and re-planted if
3 months
necessary.
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
Assets if the erosion is either recurring or severe.
Outlet
No erosion, blockage, damage or
Clear outlet of accumulated sediment or debris.
Storm events
standing water
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
3 months
Outlet freely draining.
Assets if standing (backwatering into the raingarden) is present.
Other
No erosion and damage to other
Repair minor damage to structures.
structures
structures, e.g. pits, pipes, access
Eroded areas should be repaired (reinforced). This may involve minor re-profiling or
ramps, walls and rock protection.
re-planting works.
3 months
For severe damage, i.e. where flows have scoured down the side of a structure
refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
Assets.
Batters and
No erosion.
Eroded areas should be locally re-profiled or reinforced, and re-planted if
Sediment
Accumulated sediment no less than
Clean out accumulated sediment from the sediment pond.
accumulation
0.5 m below NWL.
Accumulated sediment to be removed from the macrophyte zone and the system
No major sediment accumulation on
replanted as required.
bunds
Annually
necessary.
Annually
macrophyte zone topsoil.
Topsoil
No surface scour or depressions.
surface
Algal growth
Topsoil surface to be repaired. This may involve evening out the surface, importing
3 months
additional soil and replanting.
No major algal growth (less than 10%
If significant patches of algal growth persist across the macrophyte zone (i.e.
of macrophyte zone is permissible).
greater than 10% of the surface) then refer to Water by Design (2012) Rectifying
3 months
Vegetated Stormwater Treatment Assets.
Harvesting
No blockages and equipment is
infrastructure
functioning as designed.
Refer to manufacturer’s instructions.
Annually
(if relevant)
Constructed Wetlands Design Manual: Part E Melbourne Water
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Landscape components
Vegetation
Greater than 90% vegetation cover in
Remove any dead or diseased vegetation.
cover
designated marsh areas of the
Replant individual bare patches (greater than 5% of the area) using either new
-
macrophyte zone.
plants or by dividing and translocating existing plants.
macrophytes
Plants healthy, free from disease and
If bare areas represent greater than 30% of the macrophyte zone area, refer to
vigorously growing.
Water by Design (2012) Rectifying Vegetated Stormwater Treatment Assets.
Vegetation
Continuous vegetation cover along the
cover
lower batter.
- ephemeral
Greater than 90% vegetation cover.
/terrestrial
Plants healthy, free from disease and
batters
vigorously growing.
High flow
Greater than 90% vegetation or other
Surface to be repaired. This may involve evening out the surface, importing
bypass
scour protection (e.g. rock beaching).
additional soil and replanting.
No surface scour or depressions.
Remove any dead or diseased vegetation and replant bare patches
Less than 10% of the macrophyte zone
Physically remove weeds from filter media surface and batters.
area and batters covered in weeds
Do not use herbicides as these may harm the desirable wetland vegetation and
Weeds
3 months
Annually
3 months
contaminate wetland outflows.
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
Assets if weed ingress is a persistent problem (i.e. weed coverage is persistently
greater than 30%).
Litter
Macrophyte zone and batters free of
Remove all litter and excessive debris
3 months
No damage by pest animals and
Seek specialist advice if persistent insect damage is observed.
3 months
insects.
Refer to Water by Design (2012) Rectifying Vegetated Stormwater Treatment
litter (i.e. less than 1 piece litter per 4
m2).
Pests
Assets if there is evidence of pest animal damage.
Constructed Wetlands Design Manual: Part E Melbourne Water
3
Table 2 Example wetland inspection and maintenance checklist
Wetland inspection and maintenance form
Asset ID
Location
Inspection officer’s
name
Date
Date of last
rainfall
Photos of site (explanatory notes)
1.
2.
3.
4.
5.
General comments, sketches, description of maintenance
undertaken
Item
What to check for
Inspected
Maintenance
Further
undertaken
action
required or
comment
Civil components
Inlet
No erosion, blockage or damage.
Outlet
No erosion, blockage, damage or standing
water
Outlet freely draining.
Other
No erosion and damage to other
structures
structures, e.g. pits, pipes, access ramps,
walls and rock protection.
Batters and
No erosion.
bunds
4
Sediment
Accumulated sediment no less than 0.5 m
accumulation
below NWL.
Melbourne Water Constructed Wetlands Design Manual: Part E
No major sediment accumulation on
macrophyte zone topsoil.
Topsoil
No surface scour, depressions.
surface
Algal growth
No major algal growth (less than 10% of
macrophyte zone is permissible).
Harvesting
No blockages and equipment is
infrastructure
functioning as designed.
(if relevant)
Landscape components
Vegetation
Greater than 90% vegetation cover in the
cover
designated marsh areas of the
- macrophyte
macrophyte zone.
zone
Plants healthy, free from disease and
vigorously growing.
Vegetation
Continuous vegetation cover along the
cover
lower batter.
- ephemeral/
Greater than 90% vegetation cover.
terrestrial
Plants healthy, free from disease and
batters
vigorously growing.
Greater than 90% vegetation cover.
Plants healthy, free from disease and
vigorously growing.
Weeds
Less than 10% of the macrophyte zone
and batters covered in weeds
Litter
Macrophyte zone and batters free of litter
(i.e. less than 1 piece litter per 4 m2).
Pests
No damage by pest animals and insects.
Construction and establishment
The Construction and Establishment Guidelines: Swales, Bioretention Systems and
Wetlands (Water by Design, 2010) provides information and resources to inform best
practice wetland construction and establishment. The guidelines provide civil and
landscape specifications, step by step procedures, checklists and sign off forms for
certification and compliance. The document can be downloaded from:
http://waterbydesign.com.au/guidelines/
Constructed Wetlands Design Manual: Part E Melbourne Water
5
Glossary
6
Term
Definition
Adhere
To stick (e.g. suspended sediment sticking onto a biofilm coating
the stem of a macrophyte stem).
Algae
Simple photosynthetic plants that live in water or moist places
(Source: Melbourne Water).
Algal bloom
A rapid increase in the mass of one or more algae, usually caused
by a change in the flow, light, temperature or nutrient levels of the
water in which it lives.
Amenity
Attractiveness or community value.
Aquatic
ecosystem
The community of organisms living within or immediately adjacent
to water (including riparian and foreshore zones).
Australian
Height Datum
(AHD)
A measure of height above mean sea level.
Average
Recurrence
Interval (ARI)
A statistical estimate of the average period in years between a
flood occurrence of a given magnitude. The ARI of a flood event
gives no indication of when a flood of that size will occur next.
Bathymetry
Topography or the configuration of the underwater land surface.
Batter slopes
An edge that slopes backwards from perpendicular.
Best practice
The best combination of techniques, methods, processes or
technology used in an industry sector or activity that demonstrably
minimises the environmental impact of that industry sector or
activity.
Biofilm
A gelatinous sheath of algae and micro-organisms, including
benthic algae and bacteria, formed on gravel and sediment
surfaces and surfaces of macrophytes.
Biological
treatment
Using natural processes to breakdown high nutrient and organic
loading in water.
Biological uptake
The transfer of a substance (typically nutrients) from water or soil
to a living organism such as plants or micro-organisms (a biofilm).
Bypass route
A channel or pipe conveying overflows from the sediment pond
around the macrophyte zone.
Catchment
All land which drains to a specific location such as a constructed
wetland.
Constructed
wetland
An artificially created water system for the purpose of removing
pollutants from stormwater containing pond, marsh and swamp
features.
Melbourne Water Constructed Wetlands Design Manual: Part E
Controlled outlet
An outlet that controls the discharge rate when the water level is
between normal water level (NWL) and top of extended detention
(TED). The controlled outlet is configured to provide the required
residence time and water level regimes for the plants.
Deemed to
Comply
Set of wetland design conditions that are satisfactory to Melbourne
Water. If a wetland design does not comply with one or more of
the Deemed to Comply conditions it may not be accepted by
Melbourne Water.
Deep marsh
Underwater vegetated parts of the wetland that are between 150
and 350 mm below normal water level (NWL).
Denitrification
The biological conversion of nitrate to nitrogen gas, nitric oxide or
nitrous oxide.
Design Flow
Calculated flow used to size engineering structures to a defined
standard.
Discharge
The volume of flow passing a predetermined section in a unit of
time.
Ephemeral
Temporary or intermittent (e.g. a wetland that dries up
periodically)
Ephemeral
batter
Land around the perimeter of a wetland that slopes towards the
wetland and is above the normal water level (NWL) and below the
top of extended detention (TED).
Epiphyte
A plant that grows on another plant for physical support but is not
parasitic.
Extended
detention depth
(EDD)
Distance between normal water level (NWL) and the overflow weir
crest.
Gross pollutant
trap (GPT)
A structure used to trap large pieces of debris (>5 mm)
transported through the stormwater system.
HEC-RAS
A computer program that models the hydraulics of water flow
through channels. The program is one-dimensional and was
developed by the US Department of Defense, Army Corps of
Engineers in 1995.
Inlet pipe
Pipe(s) conveying water into the sediment pond.
Inlet pool
Open water at the most upstream end of a macrophyte zone.
Inlet zone
See Sediment pond.
Intermediate
pool
An open water section within the macrophyte zone located between
the inlet and outlet pools. Not all wetlands have intermediate
pools.
Lake
Lakes, like ponds, are artificial bodies of open water usually formed
by a simple dam wall with a weir outlet structure. A lake is usually
Constructed Wetlands Design Manual: Part E Melbourne Water
7
created for amenity and landscaping purposes.
8
Lined channel
Constructed open drain that is designed to convey stormwater to a
downstream waterway.
Macrophyte
A type of vegetation, such as reeds, used in constructed wetlands.
They are plants that grow in waterlogged conditions.
Macrophyte zone
Vegetated section of a wetland.
MUSIC
The acronym used for the Model for Urban Stormwater
Improvement Conceptualisation software developed by the
Cooperative Research Centre for Catchment Hydrology to model
urban stormwater management schemes.
Normal water
level (NWL)
The top of the permanent pool. Above this level water will be
discharged from the macrophyte zone via the controlled outlet.
Nitrification
The process by which ammonia is converted to nitrites and then
nitrates.
Nutrients
Organic substances such as nitrogen or phosphorous in a water.
Permanent pool
The level of water retained within a basin below the invert of the
lowest outlet structure
Plan of
Subdivision
Lodged under Section 22 of the Subdivision Act 1988, when a
single title is divided into two or more new parcels of land. The
Plan of Subdivision will show the reserve that a constructed
wetland will sit within.
Pond
Ponds, like lakes, are artificial bodies of open water usually formed
by a simple dam wall with a weir outlet structure. Typically the
water depth is greater than 1.5m.
Open water
Unvegetated parts of a constructed wetland.
Outlet pool
Open water at the most downstream end of a macrophyte zone.
Overflow
Outlet (e.g. pit or weir) that conveys flows when the water level
exceeds the top of extended detention (TED).
Referral
Authority
An authority nominated in Section 55 of the Planning and
Environment Act 1987 that has statutory powers to provide
conditions or object to a planning permit application.
Residence time
The time it takes for water to flow from the inlet to the outlet.
Retarding basin
A temporary flood storage system used to reduce flood peaks. A
basin designed to temporarily detain storm or flood waters, to
attenuate peak flows downstream to acceptable levels. Also known
as a retention basin.
RORB
RORB is a computer program that is used to calculate flood
hydrographs from rainfall and other channel inputs. It can be used
to design retarding basins and to route floods through channel
Melbourne Water Constructed Wetlands Design Manual: Part E
networks.
Safety bench
An upper submerged batter that has a mild slope to minimise
aquatic safety risks for those who inadvertently enter constructed
wetlands.
Sedimentation
A primary treatment process that removes pollutants through
gravity settling. Sedimentation occurs at reduced flow velocities
and thereby causes particles to settle.
Sediment
accumulation
zone
Lower part of a sediment pond’s permanent pool that is intended to
collect sediment for subsequent removal.
Sediment
dewatering area
Space close to sediment pond for dewatering material excavated
from the sediment pond prior to removing from site.
Sediment pond
Used to retain coarse sediments from runoff. They are typically
incorporated into pond or wetland designs. Also known as an inlet
zone or sedimentation basin.
Shallow marsh
Underwater vegetated parts of the wetland that are between 0 and
150 mm below normal water level (NWL).
Spells analysis
Using results of continuous flow simulation to determine the
frequency and duration of consecutive wet and dry conditions.
Stormwater
Rainfall runoff from all urban surfaces.
Stormwater
harvesting
The collection and storage of rainfall that runs off impervious
surfaces for subsequent use.
Submerged
batter
Underwater edge of wetland that slopes down from normal water
level (NWL).
Submerged
marsh
Underwater vegetated parts of the wetland that are between 350
and 700 mm below normal water level (NWL).
Suspended
solids
Small solid particles which remain in suspension in water as a
colloid or due to the motion of the water. It is used as one
indicator of water quality.
Suspension
A mixture of small solid particles dispersed in a liquid. The solid
particles are large enough to settle out of the liquid if left
undisturbed.
Terrestrial plant
A plant that grows on or in land (i.e. not in water).
Terrestrial batter
Land around the perimeter of a wetland that slopes towards the
wetland and is above the top of extended detention (TED).
Top of extended
detention (TED)
The height at which an overflow outlet (e.g. weir) is engaged.
Below this level, wetland outflow rates are determined by the
controlled outlet.
Transfer
pipe/weir
Connection to allow stormwater to flow from a sediment pond into
a macrophyte zone.
Constructed Wetlands Design Manual: Part E Melbourne Water
9
10
Treatment train
A series of treatment measures to provide an overall approach to
the removal of pollutants from catchment runoff.
Velocity
The rate of movement of an object (e.g. a water particle).
Water quality
The physical, chemical and biological characteristics of water in
relation to a set of standards.
Water sensitive
urban design
(WSUD)
WSUD embraces a range of measures that are designed to avoid,
or at least minimise, the environmental impacts of urbanisation.
WSUD recognises all water streams in the urban water cycle as a
resource.
Waterway
A defined watercourse with identifiable flow. A waterway’s
catchment is typically greater than 60 hectares.
Melbourne Water Constructed Wetlands Design Manual: Part E
Constructed Wetlands
Design Manual
Part F: Forms, templates and example plans
Table of contents
Introduction
1 Design acceptance process – Forms, templates and checklists
1 Example design plans .............................................................................2 Example as-constructed plans ..................................................................2 Example maintenance agreement and plan ................................................ 2 Example operational plan ........................................................................2 Standard drawings .................................................................................2 Constructed Wetlands Design Manual: Part F Melbourne Water
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Part F: Forms, templates and example
plans
Introduction
The following forms and certification statements are required as part of the land
development process.
Design package templates have been provided for each stage of the design acceptance
process. It is expected that all design submissions to Melbourne Water will adhere to
the structure of the templates, as this will enable efficient processing of applications.
Design packages must be complete and the declaration at the front of each design
package signed prior to submitting the package to Melbourne Water. Additional project
specific information may be added to the design package, as necessary.
Melbourne Water must be advised in writing of any variations from the requirements
set out in the Agreement and the Land Development Manual (with supporting
explanations) when the Certification Statements are forwarded to us.
Design acceptance process – Forms, templates and checklists
Concept design stage
 Concept design package template
 Concept design calculation summary table
 Deemed to comply checklist
Functional design stage
 Functional design package template
 Functional design calculation summary table
 Deemed to comply checklist
 Application for Offer of Conditions of Agreement for the Provision of Stormwater
Facilities
 Land Development – Acceptance of Offer of Conditions of Agreement for the
provision of Drainage Facilities
Detailed design stage
 Detailed design package template
 Deemed to comply checklist
 Consultant’s Design Certification Checklist
 Consultant’s Design Certification Statement
 Template for Site Environmental Management Plan
 Template for Maintenance Agreement / Plan
 Template for Operational Plan
Pre-construction stage
 Consultant’s Pre-Construction Certification Checklist
 Consultant’s Pre-Construction Certification Statement
 Permit to Work
Constructed Wetlands Design Manual: Part F Melbourne Water
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As-constructed and establishment stage
 Consultant’s Construction Certification Checklist
 Consultant’s Construction Certification Statement
 Consultant’s ‘As Constructed’ Survey Certification Checklist
 Consultant’s ‘As Constructed’ Survey Certification Statement
 Consultant’s Submission of Digital Data
 End of Defects Liability Period Certification Checklist
 End of Defects Liability Period Certification Statement
 Wetland inspection and maintenance checklist (see Part E)
Example design plans
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Concept design plan example
Functional design plan example
Detailed design plan example
Design of works
Generic plan contents
Sample notes for design plans
Standards for plans and design drawings
Example site plan
Example detail plan
Example longitudinal section
Example as-constructed plans
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As constructed plan example
Connection to title boundaries
As constructed requirements for digital format
Media and file naming conventions
Example maintenance agreement and plan
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Maintenance agreement template (ZIP, 1.63 MB)
Example operational plan
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Currently being prepared.
Standard drawings
The following are our standard drawings, which are specific to constructed wetlands:
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Drawing-No-3159_D0010_A_WIP-WG010_Pit and pipe connection between
sediment pond and macrophyte zone (PDF, 287 KB)
Drawing-No-3159_D0020_A_WIP-WG020_Typical wetland outlet configurations
(PDF, 221 KB)
Drawing-No-3159_D0030_A_WIP-WG030_Wetland outlet pit (integrated outlet
and overflow) (PDF, 138 KB)
Drawing-No-3159_D0031_A_WIP-WG031_Submerged offtake pit (PDF, 105 KB)
Melbourne Water Constructed Wetlands Design Manual: Part F
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Drawing-No-3159_D0040_A_WIP-WG040_Wetland outlet pit (integrated outlet
and overflow) (PDF, 132 KB)
Drawing-No-3159_D0050_A_WIP-WG050_Wetland overflow pit (PDF, 103 KB)
Drawing-No-3159_D0060_A_WIP-WG060_Typical overflow weir (PDF, 153 KB)
Drawing-No-3159_D0070_A_WIP-WG070_Wetland edge with submerged safety
barrier (PDF, 128 KB)
Drawing-No-3159_D0080_A_WIP-WG080_Wetland level gauge (PDF, 290 KB)
Drawing-No-3159_D0090_A_WIP-WG090_Sediment pond base profiles (PDF,
94 KB)
Drawing-No-3159_D0100_A_WIP-WG100_Macrophyte zone clay liner and
topsoil profile (PDF, 91 KB)
Drawing-No-3159_D0110_A_WIP-WG110_Access path and sediment pond
maintenance access ramp (PDF, 134 KB)
All of our standard drawings and concept drawings are located on our website:
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Standard drawings
Constructed Wetlands Design Manual: Part F Melbourne Water
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