SEQWater is the major supplier of untreated water in bulk to Local Governments and industry in the South East Queensland region of Australia, through ownership of Wivenhoe, Somerset and North Pine Dams. Wivenhoe Dam (Lake Wivenhoe) is located on the Brisbane River in Esk Shire. The storage provides both flood mitigation and water supply storage to Brisbane and Ipswich. The water supply storage capacity at full supply level is 1,160 GL. An additional 1,450 GL of storage above full supply level is used for flood mitigation.
Changes to the estimation of extreme rainfall events has resulted in significant increases in the estimates of the PMF since the original design of Wivenhoe Dam. To upgrade the flood security of Wivenhoe Dam, SEQWater has formed an alliance with Leighton Contractors, Coffey Geosciences, MWH and the NSW Department of Commerce.
This paper details the alliance delivery method, the latest estimates of the PMF based on the GTSMR method and details of the two preferred options being finalised by the Alliance.
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Many dam structures in Australia were designed and built in the 1950s and 60s with limited hydrological information. As a result existing spillway structures are under-sized for today’s revised probable maximum floods (PMF). Potential problems such as the generation of excessive negative pressure over spillway crest under increased flood condition could be encountered. This may cause instability or cavitation damage to the spillway. The raised flow profile may also have adverse impacts on crest bridges and gate structures.
Historically, physical models have been constructed in hydraulic laboratories to study these behaviours, but they are expensive, time-consuming and there are many difficulties associated with scaling effects. Today, with the use of high-performance computers and more efficient computational fluid dynamics (CFD) codes, the behaviour of hydraulic structures can be investigated numerically in reasonable time and expense.
This paper describes the two- and three-dimensional CFD modelling of spillway behaviour under rising flood levels. The results have been validated against published data and good agreement was obtained. The technique has been applied to investigate several spillway structures in Australia.
A survey of spillway gate systems and operations has recently been completed by dam organisations in Nth America, Australia and New Zealand. The survey sought to identify typical arrangements for spillway gate systems and common features pertaining to reliability such as system redundancy, actuation methods and back-up systems, gate and hoist types, remote and local operation, gate testing programmes, and human factors.
Sixteen organizations responded, covering sixty two dams and nearly four hundred gates. This Paper reports on the preliminary analysis of the data, providing an overview of the industries’ approach to spillway gate operation and control.
State Water # as manager of Keepit Dam has established a comprehensive upgrade project.
A portfolio risk assessment by State Water of its major dams placed Keepit Dam as the highest priority for an upgrade.
While extreme flood and earthquake dam safety are the main drivesr for this upgrade, the opportunity has been taken to integrate other key dam management considerations into the process including environmental improvements, flood mitigation and sustainable regional development.
The dam, which is located on the Namoi River some 45km upstream of Gunnedah, is, in tandem with Split Rock Dam upstream, a vital irrigation water supply for the Namoi Valley region in northern New South Wales.
In considering the most appropriate way of addressing the critical flood safety issue, it became very apparent that the solutions were many and they significantly impacted on the local community. Other important issues such as water quality and flood mitigation, and overall sustainable development in the valley, particularly system water reliability, could influence dam safety solutions and so also needed to be considered as part of the process. As such it was considered imperative that the local community be actively involved in determining both interim and long-term upgrade solutions.
To achieve the best outcome for the region, State Water since mid 2001, has used the community consultation approach to guide the project.
Currently interim works have been completed and long-term options are being evaluated.
An Environmental Impact Statement on the preferred proposal will be undertaken during the later part of 2004 and if approved, all works will be completed by end of 2007.
This paper will highlight our experiences to date including:
• the proposition of an integrated consultative process;
• the background to the project;
• the need for and extent of upgrade;
• an integrated consultation and communication approach including innovative processes and the creation of a high profile Community Reference Panel (CRP) to guide the upgrade project;
• some dos and don’ts from a consultation perspective, for use in other upgrade projects; and
• where to from now.
The paper highlights the fundamental importance of correct data selection and storage for the quality of Asset Management demanded for today’s water industry infrastructure.
In developing this theme, the concept of Risk driven maintenance is introduced to focus attention on those issues that not only the identify the appropriate data to be collected and stored, but also, by way of illustrated examples, the direct relevance and application of reliability engineering principles in Risk Analysis.
The author’s principle objective is to demonstrate that the historical data on reliability, condition and performance must be supported with detailed costing information if any worthwhile outcomes are to be forthcoming from analysis.
This paper discusses reliability issues of the fourteen 3.85m high by 7.89m wide radial gates at Glenmaggie Dam in Victoria and the twin 3.6m high by 16.5m wide drum gates at Little Nerang Dam in Queensland. The Glenmaggie dam radial gates are manually controlled using electrically driven (mains and diesel generator power supply) hoist motors with a petrol driven hydraulic pack for use in the event of complete electrical power supply failure. A detailed fault tree analysis was developed for the spillway gate reliability of the Glenmaggie Dam gates as part of the risk assessment for the dam, which was being completed at the time of publishing the paper. Each of the identified components of the spillway gates, including human error in operation was used to evaluate the probability of failure of a single gate or multiple gates for inclusion in the event tree to estimate the risk and assist the evaluation of the requirement for remedial works. The Little Nerang drum gates are fully automatic hydraulically operated gates with independent operating mechanics and a common override system in the event of automatic system failure. Drum gates are uncommon on dams and the system operation is discussed together with an assessment of the reliability and measures taken for handling operating risks during floods for the dam, which has some stability concerns.