Peter Allen, Malcolm Barker, Shane McGrath and Chris Topham
Are we there Yet? The question we all ask in Tolerability of Risk. The answer is in the journey, which we are all on as owners, regulators or designers.
A number of authorities in Australia are applying risk assessment for the evaluation of dam safety upgrades in accordance with the October 2003 ANCOLD Guidelines on Risk Assessment. A fundamental requirement for the evaluation of risk below the limit of tolerability is the use of the As Low As Reasonably Practicable(ALARP) principle. In making a judgement as to whether an ALARP position may have been reached, ANCOLD suggest the evaluation of a Cost to Save a Statistical Life, good practice, level of existing risk, social concerns, affordability and duration of risk. ANCOLD also suggests consideration of the USBR Criteria for evaluating risk. Recent guidelines on the Acceptable Flood Capacity for Dams developed by the Queensland Dam Safety Regulator provide further insight into the application of ALARP.
The objective of the paper is to make dam owners, regulators and designers aware of some current practice regarding the evaluation of ALARP in Australia, highlight the challenges of applying this principle and to encourage further discussion.
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M Gillon, T Logan, N Logan
The paper has been prepared to support the key questions selected for the ANCOLD Dam Instrumentation and Survey Seminar to be held in Sydney in November 2006 and to provide a New Zealand perspective. The paper is not a ‘state of dam monitoring practice in New Zealand’ dissertation but is rather a targeted summary of the authors’ experiences and observations from practicing in this area.
These experiences and observations on dam monitoring are grouped under the following headings, reflecting the key questions:
When undertaking a program of quantitative surveillance of dams the potential to make expensive decisions based on inaccurate and/or inappropriate data always exists. The implementation of a ‘quality’ based system of quantitative surveillance as identified in the ANCOLD Guidelines On Dam Safety Management 2003 can reduce the likelihood of making these inappropriate decisions.
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.
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.
Lawrie Schmitt and Angus Paton
As the owner of most of the large dams in South Australia the South Australian Water Corporation (SA Water) is responsible for the safety of these structures and their designed function of water supply and flood control. In order to meet these responsibilities SA Water monitors the performance of the structures using engineering deformation surveys and various forms of instrumentation. This paper outlines the instrumentation and survey monitoring undertaken at SA Water large dams and discusses the issues arising.