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P.H. Allen

The regulatory environment for dams in Queensland will change when the new provisions of the Water Act 2000 are proclaimed in late 2001 or early 2002. The definition of a ‘referable dam’ has shifted from a simple height and storage criteria to one that requires a population at risk (PAR) before dams are considered referable. Additionally hazardous waste dams such as tailings dams will no longer be considered as referable dams and under the Act regulatory control will be transferred to the Environmental Protection Agency.

Referable water dams will be assigned a Failure Impact Category of 2 if they have a PAR greater than 100 and a Category of I if they have a PAR greater than or equal to 2 and less than 100. This has required the development of guidelines for the assessment of ‘population at risk’. These guidelines have been written to suit a wide variety of dam impact situations and a range of dam owner resources. The guidelines require certification of the failure impact assessment by a Registered Professional Engineer in the state of Queensland.

The Queensland Dam Safety Management Guidelines have also been re-written to make them more amenable for reference in dam safety conditions.

New dams will require development permits to be issued under the Integrated Planning Act and will have development permit conditions applied in accordance with their Failure Impact Category. There is a range of transitional provisions for existing dams.

This paper covers all of the above issues as well as providing an indication as to how these statutory guidelines relate to the various ANCOLD guidelines.

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2001 Papers

2001 – A New Regulatory Environment for Dams in Queensland
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P.H. Allen

The regulatory environment for dams in Queensland will change when the new provisions of the Water Act 2000 are proclaimed in late 2001 or early 2002. The definition of a ‘referable dam’ has shifted from a simple height and storage criteria to one that requires a population at risk (PAR) before dams are considered referable. Additionally hazardous waste dams such as tailings dams will no longer be considered as referable dams and under the Act regulatory control will be transferred to the Environmental Protection Agency.

Referable water dams will be assigned a Failure Impact Category of 2 if they have a PAR greater than 100 and a Category of I if they have a PAR greater than or equal to 2 and less than 100. This has required the development of guidelines for the assessment of ‘population at risk’. These guidelines have been written to suit a wide variety of dam impact situations and a range of dam owner resources. The guidelines require certification of the failure impact assessment by a Registered Professional Engineer in the state of Queensland.

The Queensland Dam Safety Management Guidelines have also been re-written to make them more amenable for reference in dam safety conditions.

New dams will require development permits to be issued under the Integrated Planning Act and will have development permit conditions applied in accordance with their Failure Impact Category. There is a range of transitional provisions for existing dams.

This paper covers all of the above issues as well as providing an indication as to how these statutory guidelines relate to the various ANCOLD guidelines.
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2005 Papers

2005 – Prioritising Spillway Upgrades – A Queensland Way
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Keith Ehm

SunWater has completed a portfolio risk assessment(PRA) on its 25 major dams and has identified a number of dams that do not currently satisfy the ANCOLD fallback position on spillway capacity. It has taken an initiative to target these dams for spillway upgrades to ultimately achieve the ANCOLD fallback standard and has prioritised these upgrades in a preliminary program for action in the short to medium term.

As background to this PRA, SunWater has developed and implemented a dam safety program which has successfully updated all necessary flood hydrology and dam break analyses and reassessed the consequences and hazards associated with dam failures. It has also completed within the last eight years, dam safety reviews on all its dams in preparation for a comprehensive risk assessment process which is now well in-hand. This process will identify and evaluate all other risks, in addition to floods,that should be addressed or at least considered in the planning and design of these spillway capacity upgrades.

This paper describes SunWater’s experience and approach to PRA and discusses the controlling factors considered in prioritisation. It shows the results and trends of a number of risk ranking methods, provides details of the current level of societal risks in respect of the ANCOLD tolerability limits and outlines SunWater’s current strategy for the timing and staging of spillway upgrades to achieve compliance and an optimum level of risk reduction.
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2006 Papers

2006 – The Requirement for Dam Instrumentation from a Queensland Regulatory Perspective
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Peter Allen

The Requirement for Dam Instrumentation from a Queensland Regulatory Perspective ANCOLD 2006 Conference – Instrumentation and Survey Seminar Page 1 THE REQUIREMENT FOR DAM INSTRUMENTATION FROM A QUEENSLAND REGULATORY PERSPECTIVE Peter Allen, Director Dam Safety (Water Supply) Department of Natural Resources and Water ABSTRACT This paper presents the Queensland dam safety regulator’s views on issues to be considered when designing and implementing instrumentation for referable dams in Queensland. It also summarises the general requirements for dam instrumentation contained in the Queensland Dam Safety Management Guidelines and gives some thoughts on what should be contained in any ANCOLD Instrumentation Guideline.
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2021 Papers

2021 – Poster Paper – Aspects considered in the selection of individual risk tolerability threshold for referable dams in Queensland
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Chris Nielsen, Irene Buckman

As individuals, we are concerned about how a risk affects us and the things we value
personally. We may be willing to live with a risk if it secures us certain benefits and if the
risk is kept low and clearly controlled. We are less tolerant of risks over which we have little
control.

ANCOLD’s risk assessment guideline (2003) identifies an individual risk threshold as being
one where “the dam safety risk to an individual should be close to the average background
risk of the population”. This is a principle of equity, where “all individuals have
unconditional rights to certain levels of protection” (HSE, 2001). The definition of
population at risk applied to Queensland’s referable dams (DNRME, 2018), being
individuals within a residence or workplace and typically not participating in any risky
activities such as driving a vehicle or walking through flooded waters, provides further
justification of this right.

In practice addressing societal risk tolerances and duty of care considerations may result in
individual risks being substantially lower than the thresholds. This may not always be the
case and, irrespective, should not distort the purpose of the individual risk tolerance test;
the principle of equity that drives individual risk tolerability has foundations in our societal
values and is easily and widely understood as a core value. This should be succinctly
described when justifying expenditure on risky infrastructure such as dams.
This poster describes aspects to consider when selecting a threshold individual risk
tolerance. Subject to site-specific considerations of the particular age group of individuals
most at risk, the wider benefit of the dam to society and ALARP, a single threshold
individual risk tolerance of less than 10-5 per annum (or 1 in 100,000 years) would appear
reasonable.

The aspects described are elaborated in the revised Guidelines on Safety Standards for
Referable Dams, soon to be published on the Queensland Government website (RDMW,
2021).
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2007 Papers

2007 – Planning to secure South East Queensland’s future water infrastructure
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Russell Paton and David Murray

The South-East Queensland Regional Water Supply Strategy is securing future water supplies, which includes a regional water grid and new water storages. The Queensland Government’s contribution to future water supplies includes Traveston Crossing Dam on the Mary River, Wyaralong Dam on the Teviot Brook, and Bromelton Offstream Storage and Cedar Grove Weir on the Logan River.

Queensland Water Infrastructure (QWI) was established by the Queensland Government in June 2006 to progress feasibility studies, design and construction of this new water infrastructure. QWI commissioned SunWater to investigate much of this infrastructure to preliminary design level for the impact assessment process and as supporting information for potential alliance partners for the delivery of the projects. The work undertaken included extensive geotechnical investigations, hydraulic modelling, hydrologic modelling and design activities. This paper outlines the investigations associated with the preliminary design of this infrastructure and process of risk and opportunity identification to establish the program and budgets for these projects.

Stage 1 of Traveston Crossing Dam is to be constructed by the end of 2011, with a storage capacity of 153,000 ML providing a yield of 70,000 ML each year. The design adopted for the dam consists of a roller compacted concrete structure across the valley floor with an earth embankment section on the left abutment. In order to limit inundation upstream and mitigate flooding in Gympie, a gated spillway on the right abutment has been adopted. The Traveston Crossing Dam has an estimated project cost of $1,700 million.

The design developed for the Wyaralong damsite provides a reservoir with storage capacity of 103,000 ML and a yield of 21,000 ML each year when operated in conjunction with Cedar Grove Weir. Preliminary designs have been prepared for three types of dam, which are all considered technically feasible for the site. They are a roller compacted concrete dam, an earth and rockfill dam and a concrete faced rockfill dam. The Wyaralong Dam has an estimated project cost of $500 million.

The Bromelton Offstream Storage, of earthfill construction, provides a storage capacity of 8,000 ML and Cedar Grove Weir, a sheet pile structure, provides a storage capacity of 1,000 ML and both are to be constructed by the end of 2007.

Keywords: Planning, Traveston Crossing Dam, Wyaralong Dam, Bromelton Offstream Storage, Cedar Grove Weir, Queensland, risk.
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2008 Papers

2008 – Securing water for growth in regional Queensland
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Tim Donaghy

Abstract: Queensland’s regions need additional water supply infrastructure to underpin the future economic growth of the state, and secure the water supplies of existing communities in light of climate variability.

Queensland’s economy has consistently been the fastest growing of all the States for the last decade. The major component of Queensland’s growth is underpinned by resources and industry, in regional areas of the State. If the enabling infrastructure is absent, or if timeframes for development do not align with the needs of the industry, this growth will be constrained, or will go elsewhere. Future investments that support growth cannot and will not occur without certainty around the availability of future water supply.

Queensland’s regions are emerging from the worst drought in recorded history, this has revealed serious deficiencies in the resilience of our regional water supplies. For the first time in living memory, major regional centres have been forced to face the prospect of running out of water.
The Queensland Government has been proactive in identifying these issues and has responded resolutely through the release of Statewide Water Policy which supports a $451 million investment in regional water infrastructure, which aims to meet the needs of urban and rural users.

As part of this policy SunWater has been named proponent for a range of projects considered essential for Queensland’s future economic sustainability which include the Nathan Dam on the Dawson River, Water for Bowen & Proserpine Pipeline Projects, Rookwood Weir & Eden Bann Weir Raising (with RRC & GAWB), Connors River Dam & Pipelines, Nullinga Dam and Kinchant Dam Raising. SunWater is also investigating the raising of Queensland’s largest dam, Burdekin Dam. This paper will outline the need for water supply infrastructure within regional Queensland, and the challenges faced by the projects being progressed by SunWater including the technical issues, environmental sustainability and approvals, and commercial development challenges.

Keywords: Queensland, Water Supply Infrastructure, Dams
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2008 Papers

2008 – Design considerations for upgrading SunWater’s dams for acceptable flood capacity
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Brendan Trebilco

Abstract: A number of SunWater’s dams are in the process of being upgraded to the acceptable flood capacity (AFC) to ensure the highest level of safety. The Fred Haigh Dam upgrade was completed in September 2006 and the Bjelke Petersen Dam upgrade was completed in October 2007. Borumba Dam is the latest upgrade being undertaken with construction commencing in April 2008 and is expected to be completed by December 2008. Each dam underwent a comprehensive risk assessment to identify and evaluate all risks with respect to the ANCOLD tolerability limits to ensure risks satisfied ALARP. The assessment identified the most cost effective upgrade solutions for detailed design.

The upgrade at Fred Haigh, Bjelke Petersen and Borumba Dams will enable them to pass an extreme flood equivalent to 50% of the Acceptable Flood Capacity (AFC). This is Stage 1 of a two stage upgrade to ultimately achieve 100% of the ANCOLD “Fallback” AFC which is the standard SunWater has adopted for its major dams. SunWater has prioritised spillway capacity upgrades to achieve a minimum dam portfolio standard of passing 50% Acceptable Flood Capacity inflow by 2015 and full Acceptable Flood Capacity inflow by 2025.

The most economic Stage 1 upgrade option for Fred Haigh, Bjelke Petersen and Borumba Dams was to maintain the existing spillway width and to raise the dam crest with a concrete parapet wall. For the Bjelke Petersen and Borumba Dams the spillway training wall heights were raised to allow for increased flow though the spillway. From the hydraulic model studies and flood routing a height of each different dam crest wall was obtained.

This paper will describe the different methods and considerations used for upgrading Fred Haigh, Bjelke Petersen and Borumba Dams to the 50% AFC.

Keywords: dam safety, spillway, Fred Haigh Dam, Bjelke Petersen Dam, Borumba Dam, SunWater, Queensland.
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2008 Papers

2008 – Fairbairn Dam – performance during flood of record
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Rob Ayre, Terry Malone

Abstract: Fairbairn Dam with a storage capacity of 1,301,100 ML is the second largest dam in Queensland in terms of water supply capacity. The dam forms the head works of the Nogoa – Mackenzie Water Supply Scheme operated by SunWater in Central Queensland. Completed in 1972, it consists of a zoned earth-fill embankment 49 m high and 823 m in length. The dam has an un-gated ogee spillway crest that is 4.2 m high and 165 m long, with an original design capacity of 15,600 m3/s.

In January 2008, Central Queensland experienced significant flood producing rains which were generated from low pressure systems associated with monsoonal activity across northern Australia. Rainfall totals over the 16,000 km2 catchment area of Fairbairn Dam varied in depth from around 200 mm to nearly 700 mm during a five day period to 20 January 2008. This resulted in the largest outflow from the dam since its construction and the first spill event from the dam since April 1990. While the dam had a significant mitigating impact, there was still major flooding of the township of Emerald, some 19 kilometres downstream.

This paper describes the performance of the dam during the event. Details of the data collected during and after the event, including assessments of spillway performance, dam safety surveillance and the implementation of the Emergency Action Plan will be presented. In particular, the paper focuses on the flood response concerning downstream communities and the resultant flood effects on Emerald and major infrastructure located in the downstream flood plain. It highlights the need for dam owners to have the capability of forecasting inflows and outflows to their structures and how this information contributes to the overall flood response system.

Keywords: dam safety, spillway, flooding, Fairbairn Dam, Emerald, SunWater, Queensland.
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2008 Papers

2008 – Design Rainfall Issues in South East Queensland
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Terry Malone

Abstract: Recent studies in SE Queensland for existing and proposed dams and other flood studies have highlighted a number of issues with respect to the design event approach in deriving and applying design rainfalls to calibrated runoff routing models.

The estimation of design rainfall depths for frequent to large events is usually done by the intensity-frequent-durations (IFD) methods outlined in Australian Rainfall and Runoff (AR&R) or CRC-Forge.

The design temporal patterns applied to these rainfall depths are critical in the estimation of design floods as are the adopted loss rates.

This paper describes the methods used to derive the design rainfall and some of the issues which arose in their application in the design event approach to assessing design floods. It uses examples at several locations in studies undertaken by SunWater and refers to similar issues encountered in other studies.

Implications for flood studies are outlined.

Keywords: design rainfall, design floods, CRC-FORGE, IFD, temporal patterns, SunWater, Queensland.
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2009 Papers

2009 – Ross River Dam Upgrade – Flood Commissioning Experience
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Rob Ayre, Simone Gillespie, Peter Richardson, Mark Harvey

In November 2007, NQWater (now Townsville City Council) completed the upgrade of Ross River Dam near Townsville. This upgrade included the installation of a Program Logic Control (PLC) operated radial gate structure in the existing spillway. The purpose of the upgrade was threefold; to meet current design standards regarding dam safety and flood capacity; increase the town water supply to Townsville and Thuringowa; and to maintain the flood mitigation benefit of the dam during flood events in the Ross River catchment.

The designers of the dam upgrade completed a risk assessment at the commencement of the design phase and concluded that a PLC operated gated dam posed less risk than an approach that relied purely on dam operators. This is seen as the “new way forward” in gate operated dams by many designers. The regulator of dam safety in Queensland has indicated a preference for an operator to remain on site full time whilst the PLC system is ‘proved’. As a consequence a flood operations team was engaged to monitor the dam during times of flood through the commissioning period of the upgrade.

This paper discusses the lessons learnt from the experiences of the Ross River Dam during its first few flood events and issues associated with the adopted design approach.

Keywords: Dam Safety, Gated Spillway, Flood Operations, Ross River Dam, NQWater, Townsville City Council, SunWater, Queensland.
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2009 Papers

2009 – Dam Safety Regulation of Large Farm Dams in Queensland
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Robert Fowden, Peter Allen, John McKenna

The Large Referable Farm Dam Assessment Program commenced in early 2006 after inspections identified a significant number of Queensland dams that were unknown to the Department of Environment and Resource Management (DERM) and could potentially threaten life if they were to fail. The program is unique given the number of structures under consideration and is understood to be the first widespread, systematic search for dams with a population at risk in the world. The Dam Safety (Farm Dams) team has developed many original solutions to allow the majority of investigations to be undertaken in-house, thus minimising the potentially higher cost and timeframe issues associated with obtaining external engineering and surveying support.

Keywords: Queensland, dam safety, dam failure, regulation, farm dams, surveying, modelling
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