ANCOLD Bulletin No.110 (December 1998)
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Papers 1998
1998 – A Risk Based Approach for Optimising Dam Monitoring
Learn moreAndrew Pattle and Bram Knoop
This paper provides an outline of a process that can be used to optimise regular dam surveillance and monitoring activities. The process is applicable for a wide range of dam types that an owner/operator may be responsible for. Basic assessments are made of inherent reliability and potential consequences of failure using key factors such as construction features, foundation conditions and observed performance. The key factors are combined to give a relative risk ranking for each dam. These rankings are used to determine specific dam monitoring schedules. The process focuses the monitoring effort on those dams that are perceived to constitute the greatest portion of the overall risk. The methodology is simple and provides a cost-effective framework for setting appropriate resourcing levels for dam monitoring.
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Papers 1998
1998 – Repair of Two Dams Suffering Leakage – Two Case Studies
Learn moreNikifor Petrovic
One of the most important issues during design and construction of an earthfill dam is how to secure a dam against unwanted events which may occur as a result of water flow (uncontrolled seepage, leakage & piping) through the dam.
Although earthfill dams are the largest by volume compared with other types of dams and they are designed to cope with seepage, their integrity is most sensitive to the effects which may be caused by it. The reason being that the earthfill materials are generally extremely heterogeneous and only one “unwanted” pocket is enough to create problems.
Another critical area is the foundation. In many situations it is not possible to avoid the complex geology which includes faults and joints as part of the foundation. An additional complication may be the presence of dispersive clay in the foundation.
In the area of tailings dams, the problems with seepage are slightly reduced as in most cases, tailings provide a degree of sealing. Tailings dams are very often designed as leaky dams. However, there is a hidden danger in approaching the design this way as at any stage of their lives they can retain water.
This paper presents two case histories of repairs carried out to tailings dams suffering leakage. One case describes leakage through the embankment wall while the other describes seepage through the foundation which contains dispersive soil.
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Papers 1998
1998 – Portfolio Risk Assessment of SA Water’s Large Dams
Learn moreDavid S. Bowles, Andrew M. Parsons, Loren R. Anderson and Terry F. Glover
This paper summarises the Portfolio Risk Assessment (PRA) process that was implemented for SA Water’s 17 large dams, the information obtained from the PRA, and its use by SA Water. The PRA was designed to provide a baseline assessment of the existing dams and an initial prioritisation of future investigations and possible risk reduction measures. The PRA comprised a reconnaissance-level engineering assessment and risk assessment. These assessments were performed for floods, earthquakes, and static loading. Various structural and non-structural risk reduction measures were developed and evaluated. Information from the PRA can be used to provide inputs to capital budgeting, due diligence and liability evaluations, contingency planning and business criticality assessment, evaluation of loss financing and insurance programs, and a firm basis for monitoring and surveillance, operations and maintenance, and emergency preparedness planning.
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Papers 1998
1998 – Heritage Planning for Dams
Learn moreTony Moulds
A dam owner is often surprised to learn that his dam has been listed on a heritage register. This is often the first indication that the dam has heritage significance.
This paper discusses the different types of heritage listing and what the implications are for an owner. It suggests that a prudent owner will find out whether he needs a heritage conservation plan, particularly where redevelopment or remedial work at the dam is contemplated. The paper describes the content of a typical conservation plan for a large dam and how it is implemented.
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Papers 1998
1998 – Risk Assessment of Dams – Future Directions for Victoria
Learn moreDavid Watson and John Adem
For several years risk management has been promoted by the Victorian Department of Natural Resources and Environment – Water Agencies as the key mechanism for the effective and efficient business management of dams. As part of an extensive water reform program, the Victorian Government announced in October 1997, a financial assistance package for the water industry which included funding for dam improvements covering a majority of large dam owners in the State. One of the conditions for receipt of these improvement funds was the need for each water authority to undertake a Business Risk Assessment of all significant and high hazard dams under its responsibility.
This paper discusses the Business Risk Assessment document based on a framework developed by Water Agencies after consultation with the industry and expands on the following reasons why the document was produced:
- To stress the importance and value of risk assessment in managing dams and the major role it plays in business planning and understanding dam performance. Risk assessment is not an alternative to the traditional engineering or deterministic approach but an enhancement,
- To identify the minimum assessment required and examples of different approaches such as portfolio risk assessments,
- To provide preliminary reference risk criteria to assist water authorities to determine appropriate business performance requirements. This preliminary criteria was developed from considering likely (although subject to change) outcomes of the current revision of Australian National Committee on Large Dams (ANCOLD) 1994 Risk Assessment Guidelines and other guidelines involving risk aspects recently or being prepared,
- To indicate future reporting and actions expected over the five year duration of the package including project evaluations and further risk assessments,
- To assist with inputs into ANCOLD’s continuing development and revision of guidelines, and
- To provide a platform for development over the next 18 months of an appropriate regulatory framework for covering all referable dams in the State. Key considerations will included performance based requirements encompassing risk management concepts, appropriate drivers which promote duty of care and associated legal issues and liabilities.