Capturing the Potential of Stormwater
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http://ivwater.com.au/stormwaternews/stormwater-article-awmr-2014.pdf
“Capturing the potential of stormwater by resolving the responsibilities and accountabilities of government agencies, water utilities and local government for stormwater is essential “
(Water Services Association of Australia, Vision and Outcomes to 2030)
Management of the urban water cycle in Australia has
changed significantly over the past few decades. As we lived through a series of droughts and
floods, we adapted our water systems to cope with our ever changing
environment. Australia’s variable
climate means that droughts and floods are inevitable – we just don’t know when
they will next occur, or how severe they will be. Today, we know much more about our water
cycle than ever before and we have markedly improved our knowledge about water
system management.
The water cycle includes all forms of water -
recycled water, rainwater, stormwater, wastewater, groundwater, potable water
and water contained in our rivers and bays. The notion of the
whole-of-water-cycle management and planning (also known as Integrated Water
Cycle Management IWCM) has become an
accepted fact and the common practice amongst water experts and within the
various levels of government and general public.
Living in the dry country we need to value and use
the rain that falls on our land and the stormwater runoff generated by that
rainfall.
Stormwater
management philosophy in most developed countries has evolved over the last
decades from the conventional, but still important, flood mitigation paradigm,
to the current runoff quality control approach.
It is now progressing towards the harvesting and reuse
concept whilst retaining the previous two targets.
Urban Stormwater Harvesting (SWH) is one of
the essential components of Integrated Water Cycle Management (IWCM) that offers
multiple solutions to urban water systems such as mains water demand
reduction, water quality
improvement and in many cases
creek ecosystem health protection. A number of SWH projects have
been implemented in Australia to date and the number of SWH schemes is expected
to grow with wider uptake of the IWCM encouraged by the State’s and Federal
Government.
In this paper the author presents the key observations
gained through his involvement in the planning, design, construction and operation
of the stormwater harvesting schemes and the practitioner’s view on some of the
key issues that need to be addressed.
Urban Stormwater Harvesting and its Major Components
Urban Stormwater Harvesting can be defined
as the collection, treatment, storage and use of stormwater run-off from urban
areas.
Stormwater harvesting requires a number of
physical facilities. These include infrastructure for
capture, storage, appropriate
treatment, maintenance and
supply to end users
in cost effective
ways. Sufficient runoff
must be available
and sufficient space be
available to permit
storage or retention,
depending on whether
the aim is water
supply or to
manage stormwater quantity
and quality.
Typical urban stormwater harvesting schemes
include all or a combination of the following components (Figure 1):
- Catchment providing the run off volume
- Diversion structure (DS)
- Primary screening device
- Buffer storage
- Transfer facilities from buffer storage (e.g. pump and rising main)
- Treatment facilities
- Transfer facilities to the clear water storage
- Clear water storage
- Distribution pumps
- Disinfection and supply rising main
- End use
Typical mode of operation for stormwater harvesting scheme (Figure 1):
a. Designated volume of run off from the catchment (1) is diverted by the diversion structure (2) installed on the existing drainage system
b. The diverted run off is screened to remove gross pollutants and coarse sediment (3)c. Screened run off gravitates into the buffer storage (4); the aim of the buffer storage is to level out the variance in the incoming flows and optimize the operational parameters of the pump that supplies water to the treatment componentd. Water from the buffer tank is transferred/pumped (5) into the treatment component e.g. wetland/bio retention (6) were the required quality of product water is achievede. Treated water is transferred to the clear water storage typically via a pump (7)f. The treated water is stored in the Clear Water storage (8) for intended use; in many of the schemes involving irrigational use of product water a relatively large storage is required due to the temporal difference between the rainfall (collection) and irrigation (usage)g. Product water is distributed to the end users via a system of pump(s) and lilac pipes (9)h. Distribution process typically includes the disinfection of product water (10) e.g. with the on line UV systemi. Fit for purpose water is delivered to the end users (11)
(Note: IVWater is formerly known as IourivWater Solutions)
Planning, Design, Construction and Operational Considerations
While it is beyond the scope of this article to discuss the particular detail of stormwater harvesting schemes, a few general comments based on practical experience should prove useful for stakeholders contemplating a stormwater harvesting scheme.
The tasks/disciplines required for the successful delivery of a stormwater harvesting scheme are diverse and would typically include the following:
1.0 Environmental Considerations
- Flora & Fauna
- Heritage & Cultural
- LCA (Land Capability assessment)
- Environmental Risks Assessment
2.0 Planning/Approvals
- Statutory & land acquisition, planning zone, dam permit
- Diversion and water use licenses from water authorities
- Other utilities (e.g. electricity, communication )
3.0 Public Consultation
4.0 Site Investigations
5.0 Detail Design of Stormwater harvesting scheme
Typical Components:
Tasks/Disciplines involved:
6.0 Landscape architecture (some projects)
7.0 Irrigation design (some projects)
8.0 Estimation of Construction Costs/QS
9.0 Project management, reporting and QA
10.0 Construction Management
11.0 Commissioning and scheme validation
12.0 Post Commissioning scheme performance assessment, audit and reporting
13.0 Operation & Maintenance
- Geotechnical
- Services and Surveying
- Water quality sampling and flow monitoring
- Others
5.0 Detail Design of Stormwater harvesting scheme
Typical Components:
- Diversion works incl. primary screens
- Raw water transfer infrastructure
- In line detention
- Raw water storage (open dam or underground tanks)
- Water treatment
- Clear water storage
- Distribution infrastructure
Tasks/Disciplines involved:
- Hydraulics design (diversion rates, detention and storage volumes, intake/outlet structures, pipes, pumps)
- Mechanical (pipes, pumps, tanks)
- Structural engineering (soil mechanics/retaining structures, dams, concrete structures, pits, pump stations)
- Civil structures (open storages, access roads, drainage, waste disposal)
- Electrical engineering (extension of services, switchboards)
- Process treatment part 1 – natural systems (e.g. wetlands, bio filtration)
- Process treatment part 2 - conventional (e.g. media filtration, UV)
- Instrumentation & Controls (e.g. SCADA)
6.0 Landscape architecture (some projects)
7.0 Irrigation design (some projects)
8.0 Estimation of Construction Costs/QS
9.0 Project management, reporting and QA
10.0 Construction Management
11.0 Commissioning and scheme validation
12.0 Post Commissioning scheme performance assessment, audit and reporting
13.0 Operation & Maintenance
Development of Stormwater Harvesting Practice
The robust engineering basis for the planning, design, construction, operation and maintenance of urban stormwater harvesting is yet to be developed. This is because it is a relatively new engineering concept, despite being used in some form or another in various places around the world for centuries.
In the absence of the established design basis for stormwater harvesting – designers of these schemes frequently resort to the approaches borrowed from the more traditional disciplines such as municipal drainage and water sensitive urban design (WSUD). A number of leading Australian stormwater professional have commented on this issue e.g. Hatt, Deletic, Fletcher wrote in their article ‘Integrated treatment and recycling of stormwater: a review of Australian practice’ Journal of Environmental Management, vol.79, issue 1, April 2006:
“Existing stormwater recycling practice is far ahead of research, in that there are no technologies designed specifically for stormwater recycling. Instead, technologies designed for general stormwater pollution control are frequently utilized, which do not guarantee the necessary reliability of treatment. Performance modelling for evaluation purposes also needs further research, so that industry can objectively assess alternative approaches. “
However, as the practice of stormwater harvesting is continued and more projects are commissioned in the years to come, the design paradigm for stormwater harvesting should be further developed and validated.
Stormwater Harvesting Guidelines
One of the major barriers to the wider uptake of SWH particularly by Local Government is the absence of comprehensive SWH guidelines. Such a guideline would allow the proponents of the schemes (Councils, regulators, consultants, contractors and other stakeholders’ groups) to have a uniform reference document outlining current best practice including legislative framework, design / functionality, construction, operation and maintenance.
This document, once developed could offer comprehensive guidelines for implementation of storm water harvesting schemes in Australia as part of an Integrated Water Cycle Management (IWCM) approach, based on current legislation, best available engineering science and practical lessons learnt during planning, design, construction and operation of existing SWH schemes.
The SWH Guidelines will provide the clear path for implementation of the best practice stormwater management related to SWH and re-use in Australia, contributing to:
- better management of stormwater (balancing the harvesting to maximum aquatic and terrestrial benefits)
- improved water quantity and quality management
- reduced local flooding
- maximising the sustainable utilization of stormwater as a resource
- greater uptake of stormwater harvesting
- improved green space in urban areas contributing to livability
- improve allocation and harvesting of stormwater and integration with water sensitive urban design
- better landscapes and parkland managed with available stormwater
- informed strategic directions and policies for stormwater management and integrated water management across communities, councils and catchments
By providing the knowledge and confidence to implement sustainable well designed SWH projects the Guidelines will set the bench-mark for best practice SWH and provide the know-how to achieve it, overcoming many concerns and lack of knowledge currently associated with stormwater harvesting. The SWH guidelines will also assist in de-mystifying operational concerns and build confidence in managing "Harvesting Stormwater".
The development of SWH Guidelines is a complex and multidiscipline project requiring good coordination, adequate resources, extensive stakeholder’s consultation and sufficient time and funding.
The resultant document should be based on “four pillar” (Figure 2):
- Current regulation & legislation
- Best engineering practice
- Consideration of operation & maintenance issues
- Case studies and practical examples
Stormwater Harvesting Guidelines Development – Major Components (Figure 2)
More detail flowchart on topics and structure of the guidelines is presented in Figure 3:
Stormwater Harvesting Guidelines – Detailed Components (Figure 3)
SWH GUIDELINES - INDICATIVE TOC
|
|
1.
|
Overview
|
1.1
|
Purpose
and aim of guideline
|
1.2
|
Overview
structure/outline
|
1.3
|
Integration with other relevant guidelines
|
2.
|
Planning your SWH project
|
2.1
|
Planning and Regulations
|
2.1.1
|
Relevant
legislation
|
2.1.2
|
Approvals and Licencing
|
2.2
|
Drivers & objectives
|
2.3
|
Risk based analysis of SWH project
|
2.3.1
|
Assessment
framework (AGWR)
|
2.3.2
|
Assessment
tools
|
2.3.3
|
Risk
Management Plan (RMP)
|
2.4
|
Demands, Supplies and Water balance
|
2.4.1
|
Water balance approach & major
principles
|
2.4.2
|
Water balance tools & software
|
2.5
|
Selection
of sites
|
2.5.1
|
Locating and ranking suitable SWH sites in
urban area
|
2.5.2
|
Assessment tools (GIS based etc.)
|
2.6
|
Options Assessment
|
3.
|
Design of SWH project
|
3.1
|
Design
basis & functionality
|
3.2
|
Major
components and functions
|
3.3
|
Rainfall
and stormwater flow modelling
|
3.3.1
|
Selection
of Rainfall years for modelling
|
3.3.2
|
Modelling
tools
|
3.3.3
|
Balancing
Demands and Supplies
|
3.3.4
|
Downstream
impacts from harvesting
|
3.4
|
Diversions
|
3.5
|
Treatment
train for SWH
|
3.5.1
|
Water
quality objectives
|
3.5.2
|
GPT
and pre- screening
|
3.5.3
|
Secondary
Treatment
|
3.5.3.1
|
Bio - filtration & wetlands
|
3.5.3.2
|
Engineered solutions (media filtration etc.)
|
3.5.3.3
|
Disinfection
|
3.6
|
Storage
of water
|
3.6.1
|
Balance
storage or raw water storage
|
3.6.2
|
Product
water storage
|
3.6.3
|
Wetlands
|
3.6.4
|
Aquifer
Storage and Recovery
|
3.6.5
|
Other
(tanks etc.)
|
3.7
|
Distribution
to end users
|
3.8
|
Associated
Infrastructure
|
3.8.1
|
Pumps
|
3.8.2
|
Gravity
pipework
|
3.8.3
|
Rising
mains
|
3.9
|
Controls
& Electrical Equipment
|
3.10
|
Documentation
of the Design solution
|
4.
|
Construction
of SWH project
|
4.1
|
Selection
of project delivery mechanism
|
4.1.1
|
Principle
contractor (traditional)
|
4.1.2
|
Design
& Construct
|
4.1.3
|
Design,
Construct & Operate
|
4.2
|
Performance
guarantee & liabilities
|
4.3
|
Assets
ownership
|
4.4
|
Planning
and timelines
|
4.5
|
On-site
work
|
4.6
|
Commissioning
and proof of performance
|
5.
|
Operations & Maintenance
|
5.1
|
Assets
life
|
5.2
|
Maintenance
requirements
|
5.3
|
Monitoring
requirements
|
5.4
|
Risk
Management Plan Audit and Review
|
6.
|
Economics of
SWH project
|
6.1
|
General
principles
|
6.2
|
Estimation
of costs for capital works
|
6.3
|
Estimation
of running costs
|
6.4
|
Life
expectancy & Net Present Value of assets
|
6.5
|
Non
tangible values (e.g. green infrastructure)
|
6.6
|
TBL
analyses
|
6.6.1
|
Life
cycle costs
|
6.6.2
|
Carbon
sensitivity
|
6.6.3
|
Environmental
impacts
|
7.
|
Appendices
|
7.1
|
Design
Tables & References
|
7.2
|
Decision
Support Tools
|
8.
|
Case Studies
|
Indicative Table of Contents for
Stormwater Harvesting Guidelines document (Table 1)
Performance Assessment for Stormwater Treatment Devices
Selecting the right treatment train to meet the water quality objectives is essential for the successful and sustainable operation of SWH systems.]
At present, there are no standard methods or guidelines for the testing, validation and performance assessment of stormwater treatment devices in Australia. The wider uptake of IWCM and WSUD and growing number of stormwater treatment devices pose a need for the consistent and verifiable performance database to inform the fair and technically robust assessment and selection processes for treatment of stormwater. As the market for stormwater treatment devices’ expands - the lack of published data on their performance becomes more apparent (Victorian Stormwater Committee 1999), while detailed field monitoring is also very scarce (Wong et al. 2000). The combination of a large number of devices, a lack of reporting protocols and standard methods and only a small number of detailed monitoring studies has resulted in a large uncertainty in stormwater treatment devices selection. Local government, which is largely responsible for the implementation and management of stormwater infrastructure in Australia, is dependent on in-house expertise and manufacturer’s advice in selecting appropriate stormwater treatment strategies.
Independent discussions with local government, water authorities and stormwater industry professionals have revealed interest in the documentation and development of guidelines and frameworks to assist in the system design, product selection and evaluation to ensure adequate stormwater treatment and management.
Development of the protocols on the performance assessment for stormwater treatment devices will greatly
assist in the adoption and utilization of Integrated Water Cycle Management (IWCM) approach in Australian towns and cities via the:
- Increased certainty in the performance of stormwater treatment devices and resultant water quality delivered by IWCM projects
- Consistent and structured approach to the selection of stormwater treatment devices with the direct benefit to the proponents (e.g. councils/developers), designers, asset owners and other stakeholders of a stormwater projects
- Sharing the legacy of knowledge in stormwater treatment with the industry
In recognition of this industry need a number of research projects have been commissioned by various organizations with a view to assess the options available for independent verification of stormwater treatment devices in Australia, both at the state and federal level.
In this article I’d like to acknowledge the initiatives and support of Melbourne Water Corporation (MWC) and Stormwater Australia (SIA) and their respective work in this area that resulted in two reports produced and now displayed for public consultation via the SIA website, namely:
Practitioner View
Practicing in the area of integrated water cycle management and seeing through the delivery of both waste water and stormwater projects I have noticed some significant differences between those two groups affecting the choice of its delivery mechanism, namely:
- Stricter and more defined regulations in the wastewater market including treatment standards, roles and responsibilities of various stakeholders, approval processes etc.
- Wider adoption of the Design and Construct and Design, Built and Operate contract types as a waste water project delivery mechanism, generally with the Performance Guarantee provided by the Contractor
- Established practice of performance validation and verification in the waste water market
Given the current interest in the uptake of stormwater as a resource (stormwater harvesting) and the on-going commitment to control and treat the run off prior to its discharge into the natural environment by application of WSUD – the Australian stormwater market is likely to grow in the years to come.
The pace that the stormwater market in Australia grows will, to a large degree, depend on the certainty that it can offer to the public, the clients and the government in delivering the stated objectives. Which requires, amongst other things, the clear path on how to achieve the stated objectives (i.e. Stormwater Harvesting Guidelines) and the means to verify that it actually works (i.e. validation and verification protocols).
The increased certainty in the requirements for and the performance of the stormwater treatment components delivered by these guidelines and protocols should allow the market to offer/request a guarantee of performance. This guarantee should open more opportunities for funding, delivery, operation and maintenance of stormwater projects, leading to the greater uptake of stormwater treatment and utilization as a resource.
Acknowledgements
Stormwater Australia (SIA)
CSIRO Land and Water
Institute of Public Works Engineering (IPWEA) VIC
Claudio Cullino, MECC Consulting Pty Ltd
Dr Daryl Stevens, Atura Pty Ltd
References
Michelle Philp, Joseph McMahon, Sonja Heyenga, Oswald Marinoni, Graham Jenkins, Shiroma Maheepala, Margaret Greenway – “Review of Stormwater Harvesting Practices” CSIRO Publishing, 2008
Hatt B.E., Deletic A., Fletcher T.D. - ‘Integrated treatment and recycling of stormwater: a review of Australian practice’ article published in the Journal of Environmental Management, vol.79, issue 1, April 2006”
“ Institutional and Regulatory Models for Integrated Urban Water Cycle Management - Issues and Scoping Paper” Australian Government, National Water Commission, February 2007
I.Brodie “Stormwater Harvesting and Water Sensitive Urban Design Detention: A Compatibility Analysis” 12nd International Conference on Urban Drainage, Porto Alegre/Brazil, 10-15 September 2011
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