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1999 Papers
1999 – Dam Safety Management using the Asset Safety Evaluation Tool in the Hydro Electric Corporation Tasmania
Learn morePeter Quinlan and Sergio Giudici
The Hydro Electric Corporation (HEC) owns and manages 54 large and referable dams across Tasmania. Monitoring, data storage and data utilisation techniques have evolved significantly over the years as the dams have aged and as instrumentation, communication and data management technologies have advanced. This paper describes the development of the HEC’s ‘Asset Safety Evaluation Tool’ (ASET) for acquisition, management and interpretation of data relating to dam safety management. The paper also provides examples of how ASET has been applied within the HEC to demonstrate how the primary functional development goals of robustness and practicality have been achieved.
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1999 Papers
1999 – Working with Safe Dams
Learn moreNorm Robins
A strategy designed to ensure that an existing dam continues to perform effectively will include:
- a set of operating instructions.
- maintenance of the reservoir components.
- an ongoing review of structural performance.
- a system to indicate the appropriate application of resources.
- the ability to respond to an incident.
This paper will explore each of these issues and how they may be applied to dams in a variety of situations. These situations include water supply reservoirs, flood retarding basins, levees and wastewater lagoons. While each situation is different, the underlying principles will remain consistent. The range of situations encountered by Victorian Water Authorities provides the inspiration for the development of an efficient approach to the management of the safety of dams.
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2000 Papers
2000 – Development in Non-Linear Finite Element Analysis for Dam Safety Management
Learn moreA.J. Crichton, A.W. Ford, and J.T. Williams
Developments in finite element analysis software are allowing more scope for their use in the stability review of Australia’s ageing dam population. Until recently, model simulation of structural discontinuities were outside the scope of routine dam safety assessment. Current state of the art finite element software puts complex joint modelling tools within the reach of the practicing dam engineer.
This paper describes the use of non-linear finite element techniques to assess the structural adequacy of the Julius Dam, a 26.5 m high multiple arch buttress dam in North-western Queensland. This structure impounds 127,000 ML behind its 399 m crest length for the Mt Isa water supply. The assessment of the structural adequacy included using non linear contact elements to model the sliding between adjacent arch barrels. Contact elements are able to simulate friction on an interface by allowing force transfer by friction under compression with no tensile strength. This tool is invaluable for assessing formed joints or defects within existing structures, as is demonstrated in the paper.
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2000 Papers
2000 – The Dam Safety Upgrade at Lake Eppalock
Learn moreRichard R. Davidson, Roger Vreugdenhil and Mark Foster
Significant cracking was observed on the crest of the main embankment at Lake Eppalock for many years, but in recent years increasing movement upstream during low reservoir levels indicated a progressively deteriorating stability situation. Investigations also revealed cohesive filter material that would allow a crack to propagate. A fast-tracked remedial works program was completed in 1999 to rebuild the highly vulnerable upper rockfill shells and filters, both upstream and downstream. To manage construction risk, the works were carried out directly by G- MW with innovations in removal, protection and replacement of the downstream shoulders, and placement of a new multi-zone filter.
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2001 Papers
2001 – Management of the TrustPower Ltd Dam Portfolio
Learn morePeter Lilley, Kelly Deighton, Don Tate, Craig Scott
In recent years TrustPower has undergone a rapid transition from a part owner of three dams in the Kaimai ranges south of Tauranga and the Hinemaiaia and Wheao schemes near Taupo in 1998, to the present ownership situation. Today TrustPower owns 22 dams comprising a range of structure types, including arch, earthfill, rockfill, concrete gravity and a number of embankment canal systems. The dam classifications for the dam portfolio vary from small to large and the NZSOLD potential impact ratings vary from very low to high. The portfolio includes some of the largest dams in New Zealand, for example Matahina Dam a 70m high central core rock fill, Patea Dam an 80m high earthfill dam and Mahinerangi Dam a 40 m high concrete arch dam with concrete gravity abutments.
The dam structures vary significantly in terms of age, potential impact and risk to TrustPower . The Dam Safety Management Procedures (including monitoring and surveillance systems, inspections and reviews) that existed for each dam also showed considerable variation in comparison.
The approach adopted for dam safety management is described, and the interrelationship with commercial objectives and commonly accepted standard practices.
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2002 Papers
2002 – Meeting Referable Dam and Water Management Requirements of the Queensland Water Act – A ‘How To’ Guide
Learn moreR.A. Ayre and T. L. McGrath
The regulatory environment of Queensland’s water resources has changed significantly within the last few years as a consequence of the passing of the Water Act 2000. SunWater, as the owner of referable dams and the operator of water infrastructure, is required to observe the provisions of the new Act.
SunWater has undertaken dam failure analyses of a number of its dams in accordance with the new guidelines prepared by the Department of Natural Resources and Mines. The results of these assessments are being used as part of a portfolio risk assessment of its assets to help prioritise refurbishment activities. Aspects within the guidelines relate to various ANCOLD publications, with a focus on the consequence of failure for determining incremental hazard categories and appropriate design standards for spillway adequacy.
SunWater also operates its schemes under the provisions of Interim Resource Operation Licenses (IROLs). As part of Government’s water planning process, SunWater is required to submit proposed water management arrangements for its schemes. SunWater develops these arrangements, which include operation, water trading, and monitoring rules, to meet its business objectives and the objectives of government. With government approval, these proposed arrangements will translate to the provisions of Resource Operation Licenses when the Resource Operation Planning (ROP) process is completed.
This paper describes SunWater’s experience and approach to meeting regulatory requirements in the above areas.
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2002 Papers
2002 – Risk-informed Dam Safety Decision-making
Learn moreD.S. Bowles and Loren R Anderson
Starting a quarrel is like breaching a dam; so drop the matter before a dispute breaks out. Proverbs 17:14 (NIV)
An approach is summarised for presenting the outcomes of traditional engineering assessments and risk assessments to inform non-technical decision makers. The decision justification approach can be adapted to any dam owner’s unique decision context. It includes rating systems for presenting the outcomes from engineering assessments and from applying tolerable risk criteria, including ALARP. Three decision types are addressed: setting tolerable risk goals for individual dams, identifying a risk reduction pathway for a portfolio of dams, and managing residual risk on an on-going basis
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2003 Papers
2003 – An Innovative Approach to Dam Safety Emergency Planning By An Owner of a Large Portfolio of Dams
Learn moreGregg Barker B.E. (Hons.) GradIEAust
Dam safety emergency plans (DSEPs) are typically produced for individual dams. For owners of a large portfolio of dams, this approach creates document control difficulties, requires excessive time and effort and can lead to confusion when a single emergency affects multiple dams having individual DSEPs. Hydro Tasmania has developed a single DSEP which is applicable to its portfolio of 54 referable dams. The DSEP contains generic emergency response procedures, is applicable to a whole range of generic dam safety incidents, uses a simple colour-coded flowchart-action list format, has a two-stage emergency response, retains all necessary dam-specific information and can be easily adapted to any organisational structure. This approach was found to have benefits in document control, flexibility in the management of the emergency response and short lead time in terms of having DSEPs which cover an entire portfolio of dams.
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2004 Papers
2004 – Dam Safety Emergency Exercises for Dartmouth Dam, Hume Dam and Yarrawonga Weir
Learn moreB Dyer, A Evans, J Titterton
Hume Dam is managed by State Water Corporation, NSW while Dartmouth Dam and Yarrawonga Weir are managed by Goulburn-Murray Water (G-MW),Victoria, all under direction from River Murray Water (RMW).
A series of dam safety emergency exercises commenced with an exercise involving the above agencies and has built up to a multi-agency exercise. The exercises have been designed to test the Dam Safety Emergency Plans, Emergency Action Plans and Flood Operations Plans for these dams under a variety of emergency situations.
These exercises have consisted of a tabletop exercise in 2002 involving the water agencies RMW, G-MW and State Water which presented terrorism and earthquake scenarios; a flood exercise in 2003 for Dartmouth Dam, Hume Dam and Yarrawonga Weir with six control rooms set up at dam sites and water agencies; and a multi agency tabletop flood exercise in 2004 for Hume Dam, involving RMW, G-MW, State Water, Police, SES and local government authorities from both NSW and Victoria.
The third exercise focused on communication and flow of information between agencies, not detailed tactical response.
Outcomes aimed for in these exercises have been improvement in the water agency emergency response plans and inter-agency communications, clarification of roles, responsibilities and capabilities, and to determine opportunities for improved cooperation between agencies.
The exercises highlighted areas which require improvement in the area of emergency response. Implementation of recommendations arising from each exercise is in progress.
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2005 Papers
2005 – Revised Extreme Floods in Tropical Regions
Learn moreR.A. Ayre and T. L. McGrath
SunWater as an owner of 25 major dams in Queensland has completed a programme to update the design flood hydrology of all of its referable structures in accordance with the latest methodology for estimating extreme design floods. This programme ensures the adequacy of existing spillways is included in an overall dam safety portfolio risk assessment in a consistent fashion.
This paper describes the methodology adopted in the re-assessment of the design flood hydrology of the storages. Principally this has meant the use of a design hydrograph approach utilising runoff-routing methods as described in Australian Rainfall and Runoff (1999). Design rainfall inputs have been based on generalised techniques derived by the Bureau of Meteorology such as the Revised Generalised Tropical Storm Method and the Generalised Short Duration Method for the estimation of Probable Maximum Precipitation. These estimates, coupled with the use of a regional design rainfall estimation technique known as CRC-Forge that is used for determining large to rare design rainfall estimates, have been used to derive a complete estimate of the inflow/outflow flood frequency curve for each dam.
The paper also provides an insight into the significant factors and relationships that are involved in the changes resulting from this process. Overall, there has been an increase in design rainfall depth estimates for the extreme events, and a general reduction to neutral change in the large to rare rainfall range. These changes plus the influence of temporal effects and the assignment of Annual Exceedance Probability (AEP) has led to substantial changes from previous estimates of design floods. The implication of these changes is profound for
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an organisation such as SunWater. -
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2006 Papers
2006 – ALARP Considerations for Dam Safety – Are We There Yet?
Learn morePeter Allen, Malcolm Barker, Shane McGrath and Chris Topham
Are we there Yet? The question we all ask in Tolerability of Risk. The answer is in the journey, which we are all on as owners, regulators or designers.
A number of authorities in Australia are applying risk assessment for the evaluation of dam safety upgrades in accordance with the October 2003 ANCOLD Guidelines on Risk Assessment. A fundamental requirement for the evaluation of risk below the limit of tolerability is the use of the As Low As Reasonably Practicable(ALARP) principle. In making a judgement as to whether an ALARP position may have been reached, ANCOLD suggest the evaluation of a Cost to Save a Statistical Life, good practice, level of existing risk, social concerns, affordability and duration of risk. ANCOLD also suggests consideration of the USBR Criteria for evaluating risk. Recent guidelines on the Acceptable Flood Capacity for Dams developed by the Queensland Dam Safety Regulator provide further insight into the application of ALARP.
The objective of the paper is to make dam owners, regulators and designers aware of some current practice regarding the evaluation of ALARP in Australia, highlight the challenges of applying this principle and to encourage further discussion.
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2006 Papers
2006 – An Overview of the U.S. Army Corps of Engineers’ Screening for Portfolio Risk Assessment for Dam Safety Program
Learn moreDavid M. Schaaf, P.E., Jeff Schaefer, Ph.D., P.E., P.G
The United States Army Corps of Engineers (USACE) has an inventory of over 600 dams. The main purpose of many of these dams is for flood control, but there are a significant number of dams primarily used for navigation. Additional benefits at many of these projects are provided through hydropower generation, recreation, and irrigation for farmers. Many of the dams are quite old and represent an aging infrastructure across the inventory. In addition, leaner budgets relative to the need for repairs across the aging system require that USACE invest wisely in order to efficiently use available funds to reduce the greatest risks across the inventory. Previously, individual projects with perceived deficiencies were evaluated separately by the responsible district. This evaluation was not compared in any programmatic way to other USACE dams being evaluated for deficiencies.
In order to improve the process of making risk-based decisions across the entire spectrum of USACE dams, the Screening for Portfolio Risk Assessment (SPRA) for the USACE Dam Safety Program was initiated during the summer of 2005. This effort represents the first level of a multiple phased effort to bring full scale risk assessment to the decision-making regarding making investment decisions associated with dam safety by linking engineering reliability with economic and life loss impacts on a relative scale. The SPRA effort involved the development of a tool for evaluating the relative life and economic risk of dam failures for a variety of deficiencies across the inventory of USACE dams. This paper will focus on the basic aspects of the evaluation tool as well as the process by which the screening was completed.
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2006 Papers
2006 – Corporate Governance For Dam Safety
Learn moreS. Frazer
Ensuring compliance with the Regulator’s requirements is a cornerstone consideration for any water corporation in planning its risk minimisation strategies against dam failure. With the increased focus on due diligence and corporate governance however, there are emerging themes that are of equal importance for a water corporation in planning protections against its core risks to dam safety. These considerations include:
- documenting and implementing plans and strategies to ensure corporate compliance with the Regulator’s requirements and updating these in line with legislative and policy changes;
- Documenting and implementing the corporation’s defences to the common law duty of care for public liability, including keeping up to date with the latest case law development locally and internationally in interpreting implications in respect of damage to property and injury and loss of life in relation to dam failure.
- Adopting behaviours and practices that bear out a compliance culture – is the current dam safety assessment and training “best practice” and is this enough to defend a claim? What is reasonable in economic and practical terms to ensure defensibility?
- ensuring the Board, Executive and other Officers are informed of operational decisions and incidents and their advice is implemented;
- arranging and maintaining appropriate insurances if available for public liability and property damage, as well as protections for directors and officers, both past and current.
- Developing and implementing a policy for disclosure, document management and retention that will support investigation for legal proceedings purposes; including providing privilege for relevant legal advices
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2006 Papers
2006 – Corporate Governance for Dam Safety
Learn moreS. Frazer
Ensuring compliance with the Regulator’s requirements is a cornerstone consideration for any water corporation in planning its risk minimisation strategies against dam failure. With the increased focus on due diligence and corporate governance however, there are emerging themes that are of equal importance for a water corporation in planning protections against its core risks to dam safety.
These considerations include:
- documenting and implementing plans and strategies to ensure corporate compliance with the Regulator’s requirements and updating these in line with legislative and policy changes;
- Documenting and implementing the corporation’s defences to the common law duty of care for public liability, including keeping up to date with the latest case law development locally and internationally in interpreting implications in respect of damage to property and injury and loss of life in relation to dam failure.
- Adopting behaviours and practices that bear out a compliance culture – is the current dam safety assessment and training “best practice” and is this enough to defend a claim? What is reasonable in economic and practical terms to ensure defensibility?
- ensuring the Board, Executive and other Officers are informed of operational decisions and incidents and their advice is implemented;
- arranging and maintaining appropriate insurances if available for public liability and property damage, as well as protections for directors and officers, both past and current. •
- Developing and implementing a policy for disclosure, document management and retention that will support investigation for legal proceedings purposes; including providing privilege for relevant legal advices.
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2006 Papers
2006 – Development and Application of a Risk Analysis and Prioritisation Tool (RAPT) for Dam Safety Management
Learn morePeter Hill, Rory Nathan, Phillip Jordan, Mark Pearse
This paper outlines the development and application of the Risk Analysis Prioritisation Tool (RAPT) which has been developed as an interactive tool to aid dam safety risk management. RAPT allows the risk profile and prioritisation of upgrades to be incrementally updated as inputs are refined. The paper outlines some of the requirements of a risk management tool and the resulting functionality of RAPT and the lessons learnt from its application to more than 75 dams.
Issues covered include:
- importance of understanding and tracking the reliability of the inputs;
- requirements for incorporating staged upgrades and non-structural risk reduction measures;
- impact of different approaches to prioritising risk reduction measures; and
- approaches for summarising and conveying risk results
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2006 Papers
2006 – Specialist Dam Safety Instrumentation for Identifying and Monitoring Earthquake Damage at Aviemore Dam, New Zealand
Learn moreP Amos, N Logan, and J Walker
There are a number of geological faults in close proximity to Aviemore Power Station in the South Island of New Zealand, including a fault in the foundation of the 48m high earth dam component of the power station. Possible movement of the Waitangi Fault in the earth dam foundation is of particular concern for dam safety, and the effects on the dam of a fault rupture has been the subject of detailed investigation by the dam’s owner Meridian Energy Ltd. These investigations have concluded that the dam will withstand the anticipated fault displacement related to the Safety Evaluation Earthquake without catastrophic release of the reservoir.
The identification of damage to the dam following an earthquake and monitoring of the dam to identify the development of potential failure mechanisms are important for determining the post-earthquake safety of the power station. The first stage of the post-earthquake response plan is the quick identification of any foundation fault rupture and damage to the dam to enable immediate post-earthquake mitigation measures to be initiated, such as reservoir drawdown. Following initial response, the next stage of the post-earthquake monitoring programme for the embankment dam is longer term monitoring to identify a changing seepage condition due to damage to the dam that might lead to a piping incident. Such an incident may not occur immediately after an earthquake, and it can be some time before the piping process becomes evident.
This paper presents some key instrumentation installed at Aviemore Dam and included in the emergency response plan for the post-earthquake monitoring of the embankment dam.
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