R. E. Saunders, J. Roberts, B. W. Omundson
Ross River Dam is located immediately upstream of the twin cities of Townsville and Thuringowa. The population at risk from failure of the dam is approximately 110,000. A recently completed risk assessment has confirmed earlier studies that the dam does not satisfy current safety criteria and presents high risk levels in a number of areas. Importantly, the risk assessment has enabled the extent of these risks to be clearly identified. This paper summarises the risk assessment highlighting notable methodologies employed and the key findings of the study.
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Richard 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.
A. Ash, D. S. Bowles, S. Abbey and R. Herweynen
A preliminary risk assessment was undertaken of its three dams by the South East Queensland Water Board (SEQWB) in 1999. The risk assessment process used included a series of workshops that proved to be an important part of ensuring a worthwhile result. The combined expertise of the consultants together with that of staff from the Board and the Queensland’s Department of Natural Resources were used to improve the outcome. The results of the assessment showed that the process had both advantages as well as difficulties in comparison to a standards based approach for making dam safety decisions. Risk Assessment was seen to be a useful management tool for managing dam safety. It gave the owner the ability to quickly rank upgrade requirements or maintenance options on the basis of probability of failure, life safety risks and financial risks to the owner or economic risks to all stakeholders.
The entire historical record of rainfall archives held by the Bureau of Meteorology over the region of Australia affected by tropical storms has been examined and the extreme storms have been extracted. From this database, we account for site specific effects (moisture and topography) from each of the storms, allowing us to compare storms amongst each other. This then allows us to construct a theoretical maximum precipitation in a generalised sense. By then returning the site specific information for a particular region, we can infer the probable maximum precipitation at this location.
Steven Fox, Garry Fyfe
This paper describes some key details of the construction of the Lake Eppalock Main Embankment Remedial Works Project. This $8.25 million earthworks project was completed on a “live” storage to an accelerated program. As the dam owner Goulburn-Murray Water took the decision to directly manage the construction of these works with resultant benefits in timing, risk management and project management costs.
Failure modes and effects analysis (FMEA) has been increasingly utilised to prioritise and investigate dam safety deficiencies. It can be used to enhance dam safety programmes. Dam Surveillance, O & M procedures, and emergency plans can all be evaluated for their effectiveness in detecting and mitigating the applicable failure modes for a dam. Experience with a workshop process to carry out this evaluation and some of the improvements that have been identified are described.