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:
Legal and moral requirements necessitate an “equivalent to industry standard” approach to dam management by all dam owners. As an urban authority Central Highlands Water has a portfolio of dams with a broad range of classification and risk. ANCOLD Guidelines form the basis of our approach to dam management. Thus any guidelines developed can have significant affect on our budget and operation. Guidelines with requirements targeted at extreme and high hazard dams managed by large authorities with “deep pockets” may not be reasonable to impose upon low risk structures managed by lesser authorities. This does not mean smaller authorities want to do it on the “cheap” but budgets for such infrastructure can be hard to sustain. Consequently when guidelines are considered so too should the flow on affect to those who must implement them.
Lawrie Schmitt and Angus Paton
As the owner of most of the large dams in South Australia the South Australian Water Corporation (SA Water) is responsible for the safety of these structures and their designed function of water supply and flood control. In order to meet these responsibilities SA Water monitors the performance of the structures using engineering deformation surveys and various forms of instrumentation. This paper outlines the instrumentation and survey monitoring undertaken at SA Water large dams and discusses the issues arising.
D.N.D. Hartford and P. A. Zielinski
With the notable exceptions of dyke safety in the Netherlands and dam safety in Australia, explicit consideration of the equity versus efficiency dilemma associated with dam safety decision-making has been virtually ignored in the past debates related to safety of dams thus leading to inconsistent judgments in the development of dam safety policies. The equity-efficiency dilemma is now being debated in Canada as part of the process of revising the Canadian Dam Safety Guidelines. This paper explains how the argument in favour of formulating the new Canadian Dam Safety Guidelines within the formal risk assessment and risk management framework is being presented. The paper then focuses on the difficulties involved in aligning the well tried and tested and generally successful traditional approach to dam safety with the relatively untried and untested risk assessment approach. While the paper does not provide a significantly different perspective (a made in Canada approach) to the role of risk assessment in dam safety management as established in Australia and as presented in ICOLD Bulletin 130 (ICOLD, 2005), it does challenge some aspects of the ways dams are classified in the emerging risk assessment frameworks for dam safety management.
The paper describes the methodology, operative techniques and organizational aspects that are used for dam safety assessment procedures. Kelag owns 15 larger dams with wall heights up to 110 m. It is necessary to monitor the aging of the structures and to check all safety equipment regularly. The manned control centre is situated at the KELAG Headquarter in Klagenfurt, which is the capital of Austria’s southern-most Province, Carinthia. KELAG is the principal electricity supplier in Carinthia, and owns several reservoirs in the Austrian Alps. The whole hydropower system has a capacity of 434 MW with an annual production of 1000 GWh. During the last century KELAG employees designed, supervised and constructed most of the structures in cooperation with the authorities. Most of the rock-fill dams have a bituminous concrete sealing on the upstream face. KELAG owns one concrete arch dam with a height of 30 m. A pendulum monitors the movement of the dam crest. This information is transmitted to both the power house and the manned control centre in Klagenfurt. Seepage is monitored at all rock-fill dams. In case of an alarm a skilled engineer has to be informed by the staff of the manned control centre. This dam safety engineer starts to check the reasons on site and manages the emergency action plan. Data has been collected since 1998 and special software is used to handle this information, carry out interpretation and safety assessments. One aim of data collection is to develop a decision support system performing online evaluation, explanation and interpretation of dam behaviour. Normally, once a year geodetic measurements are carried out at all dams.
KELAG’s experience gained in the use of automatic monitoring and risk assessment of dams is covered in this paper. The monitoring systems show the state of the structures and those showing anomalous situations requiring human intervention can be identified as soon as possible. Although the repercussions of the free market system have led to substantial staff reductions, the quality of dam surveillance has had to remain unaffected. Dam safety is guaranteed by new types of instrumentation, data transmission and data assessment. A special software has to be updated constantly.
In Austria, special procedures for ensuring dam safety apply to dams higher than 15 m or reservoirs with a capacity of more than 500,000 m³. There are at present about 90 dams which belong to this category. The largest one is the 200 m high Kölnbrein arch dam.
In general, it is the task of the dam owner to provide for the safety of a dam. For that, he has to appoint qualified engineers, the “Dam Safety Engineers”, which are in charge of dam surveillance and maintenance. The Water Authority verifies that the owner makes the necessary provisions for dam safety. Water Authorities are the Provincial Governor and the Federal Minister of Agriculture and Forestry. The Water Authorities are supported by a governmental advisory board, the “Austrian Commission on Dams”.
Projects for new dams or for reconstruction of existing dams are examined by the Austrian Commission on Dams. Approval by the Water Authority is based on the findings of this commission. A group of a few experts of the commission accompanies the project during construction, first impounding and the final acceptance procedure. In normal operation, dam attendants carry out visual inspections and measurements. The most important instruments are measured automatically and the data are transmitted to a permanently manned control centre. The Dam Safety Engineer has to inspect the dam at least once a year. His annual report to the Water Authorities must contain an assessment of the safety of the dam. The Federal Dam Supervisory Department of the ministry checks the annual reports and carries out an in-depth inspection of the dam at least every five years.
In the case of extraordinary events, the Dam Safety Engineer has to assess the situation and he has to set appropriate measures. An Emergency Action Plan is available for all dams of the said category.