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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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.
Karen Soo Kee
Strategic resource management has never been more important than it is today with the aging of the “baby boomers” and their ongoing exodus from the workforce. The vacancies they leave in professions such as engineering are just beginning to be felt and will exponentially escalate over the next few years. Specialised professions such as dam engineering and related professions will be hit the hardest as the knowledge and skills learnt over decades are depleted.
The lack of skilled staff and in fact the lack of interest of young engineers in entering the dam industry is one of the critical challenges for today. How do we attract professional staff into the field of dam safety before the exodus creates a “black hole” that can never be filled? And how can we ensure the knowledge transfer from existing skilled staff to newer staff to retain expertise within the industry?
Another issue for resource management is that tomorrow’s workers, the “X &Y generations”, will be unlike the current and previous generations of workers. These workers will be less likely to have a mortgage, will have fewer children and be more interested in lifestyle, not career. They will be extremely confident, well-educated and very mobile. The future will be a sellers market. The challenge here will not only be to attract and recruit talented workers but also to retain them.
C Lake and J Walker
Meridian Energy is the owner and operator of a chain of hydro dams on the Waitaki River in the South Island of NZ. It operates a Dam Safety Assurance Programme which reflects current best practice; consequently it has focused primarily on managing civil dam assets. Advances in plant control technology have allowed de-manning of our power stations, dams and canals through centralised control. The safety of our hydraulic structures is increasingly reliant on the performance of Dam Safety Critical Plant (DSCP) – those items of plant (eg water level monitoring, gates, their power and control systems, and sump pumps) which are required to operate automatically, or under operator control, to assure safety of the hydraulic structures in all reasonably foreseeable circumstances.
Recent dam safety reviews have highlighted that the specification and testing of our DSCP is based on the application of ‘rules of thumb’ which have been established through engineering practice (eg. “monthly tests”, “third level of protection”, “backup power sources”, “triple voted floats”). The adequacy of these engineering practices is difficult to defend as they are not based on published criteria. The realisation that such rules may not be relevant to the increased demand on, and complexity of, DSCP led us to ask “Which belts and braces do we really need?”
The current NZSOLD (2000) and ANCOLD (2003) Dam Safety guidelines give little guidance regarding specific criteria for the design and operation of DSCP. Meridian has identified the use of Functional Safety standards (from the Process industry, defined in IEC 61511) as a tool which can be applied to the dams industry to review the risks to the hydraulic structures, the demands on the DSCP, and utilise corporate “tolerable risk” definitions to establish the reliability requirements (Safety Integrity Levels) of each protection, and determine lifecycle criteria for the design, operation, testing, maintenance, and review of those protections.
This paper outlines the background to identifying Functional Safety as a suitable tool for this purpose, and the practical application of Functional Safety Analysis to Meridian’s DSCP.
The Water Act 2003 established a new role for the Environment Agency, that of the Enforcement Authority for the Reservoirs Act 1975 in England and Wales. The transfer of this regulatory role from 136 Local Authorities has had a significant impact on the regulated community. Further change is heralded with the forthcoming introduction of Reservoir Flood Plans, Post-Incident Reporting and a review of current regulations. The improvements sought in reservoir safety may be at risk due to a growing skills shortage and increasing financial constraints imposed by owners.
This paper highlights the issues impacting on the reservoir industry in England and Wales and in recognising developments made by ANCOLD members the author seeks to understand how they are being responded to in Australia.
G.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.