2006 – Design and Construction of the Gattonvale Offstream Storage
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.
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Papers 2006
2006 – Achieving Benefits From Instrumentation And Survey Measurements Of Dam Behaviour
Learn moreJohn D Smart
The paper presents the recent trends in the use of instrumentation and survey measurements at Bureau of Reclamation (Reclamation) dams. The underlying philosophy that has influenced those trends is presented and discussed. Based on experience at Reclamation, several factors that are considered key to the effective use of instrumentation and surveys are discussed. Several conclusions are offered.,
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Papers 2006
2006-Resource Crisis Or Imagination Challenge?
Learn moreRoger Vreugdenhil, Joanna Campbell
The dams industry is immersed in a changing environment. It is one of many industry sectors in Australia becoming acutely aware of the impacts of ageing practitioners and a competitive labour market. Shortages of skills and labour are impacting on all participants. The constraints around recruitment and retention are further amplified for dam owners in some States by increasing expenditure regulation and accountability.
People choosing to leave or retire from the dams profession per se does not necessarily pose a problem. Instead, problems arise if insufficient transfer of valuable knowledge has occurred prior to their departure, if the rate of replenishment is inadequate to cope with current and future industry workload, and if there is no innovation around what workforce is involved. Future work will likely be characterised by remedial works for existing dams rather than new dam construction, with an increased focus on environmental restoration, and optimisation of operations and maintenance to minimise losses and maximise productivity. These tasks require a great level of skills in leadership and innovation, equal to any level previously applied to this industry.
Organisational goals and decisions have to be realised through people and it appears that many people are taking up their roles differently than in the past. The authors, both Generation X, contend that the core issue is as much a challenge of imagination as it is a crisis of human resourcing. Greater imagination is required around: the image presented by the profession; retention and replenishment of personnel; appropriately connecting people of different generations to their individual roles; developing leaders comfortable with the sentient aspects of organisation life and capable of collaboration; and sustainable management of knowledge.
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Papers 2006
2006 – Specialist Dam Safety Instrumentation for Identifying and Monitoring Earthquake Damage at Aviemore Dam, New Zealand
Learn moreP Amos, N Logan, and J Walker
There are a number of geological faults in close proximity to Aviemore Power Station in the South Island of New Zealand, including a fault in the foundation of the 48m high earth dam component of the power station. Possible movement of the Waitangi Fault in the earth dam foundation is of particular concern for dam safety, and the effects on the dam of a fault rupture has been the subject of detailed investigation by the dam’s owner Meridian Energy Ltd. These investigations have concluded that the dam will withstand the anticipated fault displacement related to the Safety Evaluation Earthquake without catastrophic release of the reservoir.
The identification of damage to the dam following an earthquake and monitoring of the dam to identify the development of potential failure mechanisms are important for determining the post-earthquake safety of the power station. The first stage of the post-earthquake response plan is the quick identification of any foundation fault rupture and damage to the dam to enable immediate post-earthquake mitigation measures to be initiated, such as reservoir drawdown. Following initial response, the next stage of the post-earthquake monitoring programme for the embankment dam is longer term monitoring to identify a changing seepage condition due to damage to the dam that might lead to a piping incident. Such an incident may not occur immediately after an earthquake, and it can be some time before the piping process becomes evident.
This paper presents some key instrumentation installed at Aviemore Dam and included in the emergency response plan for the post-earthquake monitoring of the embankment dam.
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Papers 2006
2006 – The Ability of Monitoring to Detect Internal Erosion and Slope Instability in Embankment Dams
Learn moreRobin Fell
Internal erosion and piping within embankment dams may initiate in cracks caused by differential settlement or desiccation, in cracks caused by hydraulic fracture and in very poorly compacted layers of soil. It generally cannot occur unless one of these defects is present because backwards erosion, the other mechanism for internal erosion, will not occur in embankments under normal gradients and will not occur in cohesive soils unless gradients are exceptionally high.
As a result it is very unlikely that it will be possible to detect initiation of erosion with piezometers, and the most likely successful method is seepage observation and monitoring. However the time from the first detection of increased seepage to breach of the dam may be very short-a matter of hours in some situations.
Thoughtfully positioned and read piezometers are more likely to be successful in identifying the critical gradients which may lead to the onset of backwards erosion in cohesionless soils in the foundation of dams.
Piezometers are more useful in establishing the pore pressures for use in analysis of stability, but in most cases where stability is marginal undrained strength analysis is required and the pore pressures and effective strengths alone are not sufficient to assess stability. In a number of cases differential settlements, and acceleration of settlements have proven valuable in detecting the on-set of instability and the conditions in which internal erosion and piping to initiate. Once these conditions are recognised more detailed survey monitoring and borehole inclinometers can be valuable in better defining the geometry of instability.
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Papers 2006
2006 – Performance of New Orleans’ Hurricane Protection System: The Good, The Bad, and The Ugly
Learn moreG. L. Sills, N. D. Vroman, J. B. Dunbar, R. E. Wahl
In August 2005, Hurricane Katrina made landfall just east of New Orleans and inflicted widespread damage on the Hurricane Protection System (HPS) for southeast Louisiana. Subsequent flooding was a major catastrophe for the region and the Nation.
The response to this disaster by the U.S. Army Corps of Engineers included forming an Interagency
Performance Evaluation Taskforce (IPET) to study the response of the system and, among many lines of inquiry, to identify causes of failure of levees and floodwalls.Beginning in September 2005, the IPET gathered geotechnical forensic data from failed portions of levees and floodwalls. Major clues discovered at the 17th Street break, including clay wedges dividing a formerly continuous layer of peat, led to an explanation of the failures. Field data from the failure sites were interpreted within the regional geologic setting of the New Orleans area to identify geologic and geotechnical factors that contributed to the catastrophe. The data gathered provided a method that resulted in the “IPET Strength Model.” This strength was used in analyses of the I-walls and levees using limit equilibrium stability analyses, physical modeling using a powerful centrifuge, and finite-element analyses.
The results of all three types of studies revealed a consistent mode of failure that included deformation of the I-walls and foundation instability. The IPET also studied non-failed I-walls at Orleans and Michoud Canals, to identify geotechnical, structural, and geologic distinctions between failed and non-failed reaches.
Performance of the HPS during Hurricane Katrina offered many lessons to be learned. These lessons learned include: the lack of resiliency in the HPS; the need for risk-based planning and design approach; the need for the examination of system-wide functionality; and knowledge, technology, and expertise deficiencies in the HPS arena. In addition, understanding of the failure mechanisms and related causes of the levee and floodwall breaches provides a new direction for future designs of hurricane protection systems.
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