Peter 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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David S. Bowles, Loren R. Anderson, Joseph B. Evelyn, Terry F. Glover and David M. Van Dorpe
A demonstration risk assessment was conducted on the 283-foot high rolled-earthfill Alamo Dam as part of a U.S. Army Corps of Engineers (USACE) Research and Development program. The existing dam and 19 structural risk reduction alternatives were evaluated for flood, earthquake and normal operating conditions. The paper summarizes the risk assessment process, results, findings and recommendations. It also provides an evaluation of the risk assessment process and recommendations for better positioning the USACE to use risk assessment for dam safety evaluation and decision support.
The role of judgement in risk assessments as applied in dam safety management has been the source of considerable debate in recent years. With regard to risk analysis of dams, and while there is general agreement that judgement is an essential element of the process, essentially two schools of thought have emerged. One view holds that, in the assignment of probabilities, reliance can be based on collective engineering judgement that is anchored to a knowledge base. The second view holds that judgement should be based on the knowledge that is revealed by an appropriate amount of analysis. The paper, written from the perspective of the latter view, explores some of the underlying issues in this debate.
The role of judgement in risk evaluation, the process of judging the significance of risk, is considered to be equally important. However, the process of making value judgements and statements of principles is complex and often beyond the sphere of engineering. The third issue addressed in the paper concerns the search for answers to the question, “How good is the assessment?”
Garry Meinck, Chris Elliott and Tony Moulds
This paper describes the experiences of a former state statutory authority in the almost four years since it became corporatised to form a water utility with a fully commercial orientation and with a new board of management with a clear awareness of the responsibilities of corporate governance.
The need to commit to major remedial work at one of the principal dams focussed the Board’s attention on the safety status of all of the Corporation’s 56 referable dams.
In the absence of external dam safety regulation the Corporation has moved to satisfy its corporate governance responsibilities by adopting current best practice in dam safety. Key elements in this process were:
Dr Judy Henderson
Against a background of several decades of increasingly polarised and acrimonious debate, the World Commission on Dams (WCD) was established in 1998 with a two year mandate to review the development effectiveness of dams, assess alternatives for water resources and energy development and develop internationally acceptable criteria and guidelines for future decision- making. This report discusses the role of large dams in development and the challenges of water resource management in the future. T the work program of the WCD is outlined and progress to date on fulfilling its mandate.
Ungated spillways offer the safest form of spillway but they are more costly than gated spillways for the volume of water stored. Gated spillways offer a more cost-effective use of water by maximizing the storage capabilities of the dam. Gated spillways also lead to more cost effective new dams as well as increasing storage of existing dams. They can therefore offer considerable advantages but must not jeopardize dam safety. Most commonly used spillway gates are mechanically driven by electric or hydraulic systems reliant on external power supply and instrumentation, and usually require operators to control the systems. Unfortunately there is already a substantial record of these types of gates not operating when required, thereby placing the dam’s safety in jeopardy. The ideal is to have automatic gates which do not suffer the problems associated with mechanically-driven gates.
A number of automatic gates exist, some with differing degrees of success but most are not truly automatic in operation and suffer some limitations. A range of fully automatic water control equipment has been developed and has operated for more than 20 years in South Africa. Out of experience gained from this equipment, a new generation of spillway gates has been developed which meets nearly all the requirements of an ideal spillway gate.
This paper introduces the gates and examines their features and safety devices. Other benefits are also mentioned.