This paper reviews the general principles of duty of care which assist in the understanding of responsibilities that may exist for surveillance of dam safety, including the inter-play of the common law and statutory law. Only when there is a foundation in the general principles can obligations upon dam owners/operators with respect to surveillance and instrumentation be interpreted. Some legal issues around the development and use of industry guidelines are also explored.
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Nerida Bartlett, David Scriven, Peter Richardson
The failure of a number of consecutive wet seasons has resulted in storage levels in Eungella Dam being at dangerously low levels such that supply could be exhausted by June 2007. Eungella Dam supplies bulk water to the Bowen Basin coal fields as well as the Collinsville power station and the Collinsville township.
The Collinsville township, power station and coal mine as well as the Newlands mines take water from the Bowen River Weir which is supplied from Eungella Dam some 95 kilometres upstream. Transmission losses of the order of 25 to 50% have been experienced for releases from Eungella Dam to Bowen River Weir.
The Eungella Dam catchment area is 142 square kilometres. Significant flows occur in the Bowen River downstream of Eungella Dam, the catchment area above Bowen River Weir being 4,520 square kilometres. The topography in the surrounding area (near Collinsville) is not suitable for dam construction.
The opportunity existed for the construction of an offstream storage adjacent to the Bowen River Weir so that the downstream flows could be captured reducing the demand on Eungella Dam thus making more water available for upstream users.
A 5,200 ML offstream storage, associated pump station and rising main was designed, constructed and filled within a period of 12 months.
Foundations at the site are highly permeable sands. Marginally suitable clay for a seal was in short supply as was suitable rock for slope protection. A fixed price budget had been set by the contributing customers.
This paper describes the hydrology, site conditions, design and construction of the project.
Marius Jonker, Malcolm Barker and Gary Harper
This paper provides a framework for conducting an effective Failure Modes Analysis. It explains the fundamental principals and methods of Failure Modes Analysis. The current international state of practice on Failure Modes Analysis is discussed, and the objectives, benefits and limitations of Failure Modes Analysis assessed. Guidelines are given on how to apply the outcome of Failure Modes Analysis in dam safety management and surveillance.The effective application of Failure Modes Analysis is illustrated in a case study where the process was applied in the safety review and risk assessment of Rocklands Dam for Grampians Wimmera Mallee RegionWater Authority in Victoria.
A brief overview of dam surveillance is given from a South African perspective and more specifically the perspective of the Department of Water Affairs and Forestry (DWAF). DWAF’s Ten Commandments for the design of dam monitoring systems serve as introduction and this is followed by a summary of the design steps. The various parameters that can be measured and the South African preferences are discussed briefly followed by a synoptic description of crack and joint monitoring in South Africa. This provides the background for DWAF’s recent developments in 3-D Crack-Tilt gauges. Some of DWAF’s achievements as well as some of the blunders made by the author during the past 30 years are illustrated by means of a few case histories.
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.