Capturing the Potential of Stormwater

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"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)

Water Cycle

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.

Water cycle includes all forms of water:

• Recycled water
• Rainwater
• Stormwater
• Wastewater
• Groundwater
• Potable water
• 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) has become an accepted fact and common practice amongst stormwater harvesting experts (among many other stormwaterwater consultants), within the various levels of Government and general public.

Living in a dry country we need to value and use the rain that falls on our land and the stormwater run-off 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 run-off quality control approach. It is now progressing towards the harvesting and reuse concept whilst retaining the previous two targets.

Urban Stormwater Harvesting is one of essential components of Integrated Water Cycle Management 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 stormwater harvesting projects have been implemented in Australia to date and the number of stormwater harvesting schemes is expected to grow with wider uptake of Integrated Water Cycle Management encouraged by State and Federal Government.

In this paper the author presents key observations gained through his involvement in planning, design, construction and operation of 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.

Planning, Design, Construction and Operational Considerations

Based on practical experience, a few comments should prove useful for stakeholders contemplating investing in 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:

• Environmental Considerations
• Flora and Fauna
• Heritage and Cultural
• Land Capability Assessment
• Environmental Risks Assessment
• Planning/Approvals
• Statutory & Land Acquisition, Planning Zone, Dam Permit
• Diversion and Water Use Licenses From Water Authorities
• Utilities (e.g. electricity, communication)
• Public Consultation
• Site Investigations
• Geotechnical
• Services and Surveying
• Water quality sampling and flow monitoring
• Detail Design of Stormwater Harvesting Scheme
• Typical Components:
• Diversion works including 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)
• Landscape Architecture (some projects)
• Irrigation design (some projects)
• Estimation of Construction Costs/Quantity Surveying
• Project management, reporting and Quality Assurance
• Construction Management
• Commissioning and Scheme Validation
• Post Commissioning Scheme Performance Assessment, Audit and Reporting
• 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 (Water Sensitive Urban Design). A number of leading Australian stormwater expert consultants 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 stormwater harvesting particularly by Local Government is the absence of comprehensive Stormwater Harvesting 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 stormwater harvesting schemes in Australia as part of an Integrated Water Cycle Management approach, based on current legislation, best available engineering science and practical lessons learnt during planning, design, construction and operation of existing stormwater harvesting schemes.

Stormwater Harvesting Guidelines will provide the clear path for implementation of the best practice stormwater management related to Stormwater Harvesting Guidelines 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
• 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 stormwater harvesting projects the Guidelines will set the bench-mark for best practice stormwater harvesting and provide the know-how to achieve it, overcoming many concerns and lack of knowledge currently associated with stormwater harvesting. The stormwater harvesting guidelines will also assist in de-mystifying operational concerns and build confidence in managing "Harvesting Stormwater".

The development of Stormwater Harvesting 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 pillars:

• Current regulation & legislation
• Best engineering practice
• Consideration of operation & maintenance issues
• Case studies and practical examples

Stormwater Harvesting Guidelines Detailed Components

Stormwater Harvesting Guidelines indictive table of contents:

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 Stormwater Harvesting Guidelines 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 Integrated Water Cycle Management and Water Sensitive Urban Design 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 expert consultants 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 approach in Australian towns and cities via the:

• Increased certainty in the performance of stormwater treatment devices and resultant water quality delivered by Integrated Water Cycle Management 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 project
• 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 and Stormwater Australia and their respective work in this area that resulted in two reports produced and now displayed for public consultation via the Stormwater Australia website, namely:

• Independent Verification Scheme for Stormwater Treatment Devices – Road Map Discussion Paper
• Literature Review on Performance Testing Approaches of Gross Pollutant Traps

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 waste water market including treatment standards, roles and responsibilities of various stakeholders and approval processes
• 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 Water Sensitive Urban Design – 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 that, among other things, requires a 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

• Melbourne Water Corporation
• Stormwater Australia
• CSIRO Land and Water
• Institute of Public Works Engineering Victoria
• 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 (abolished in 2014), 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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