Claudia Smith, Shannon Dooland, Adam Broit, Rachel Jensen, Samantha Watt
The estimation of real consequences from dam failure that directly link to the overall likelihood of the failure is a challenging task, particularly in data sparse locations. Previous regional methods have often relied on simplistic assumptions without consideration of the true joint probability of the volume of flow in the downstream tributaries of concurrent catchments. As a result, concurrent downstream flooding directly impacting the consequence in dam break assessment scenarios may be misrepresented. More recently, the adoption of streamflow-based joint probability has become the standard, particularly where consequence estimation is used within the context of risk assessment. This paper progresses the work completed by others to establish a practical treatment method based on rainfall analysis where suitable streamflow information is unavailable. A case study is also presented where this method has improved the understanding of the risk profile associated with a coastal storage based on a better estimate of the likely flood concurrence within the storage and downstream catchments.
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Chris Nielsen, Ron Guppy, Gary Hargraves, Robert Fowden
Dam safety upgrade projects of major dams typically involve a large capital investment. It is important that expenditure decisions are based on sound criteria, both technical and non-technical. Independent peer review of technical matters plays a key role in meeting design, construction and safety objectives within practical financial constraints and assuring robust, resilient and reliable project outcomes.
An independent technical review is recommended for all dam projects.
The Queensland dam safety regulator has developed guidelines associated with technical review for dam safety projects that considers scope and limitations, expertise and governance. The guidelines are informed by literature, recent projects, a commission of inquiry, internal and external review and industry feedback. The guidelines are being implemented across major dam safety upgrade business cases through preparation of terms of reference by the Queensland Government’s business planning and implementation entities, who maintain the responsibility of providing assurance to state government projects, as well as the state’s major dam owners.
The terms of reference, supported by the underlying principles in the guidelines, provide a platform for consistent and appropriate application of technical assurance to dam projects in Queensland. Among other matters, governance is highlighted as a critical factor for success as well as clarity of the roles, responsibilities and reporting lines of all parties. The application of both guidelines and terms of reference to recent projects is discussed.
Richard M Robinson, Siraj Perera, Gaye Francis
SFAIRP (so far as is reasonably practicable) is the ‘modern’ definition of ‘safe’. Shrouded in the legal
concept of the ‘safety case’, it is actually the judicial form of the principle of reciprocity – the golden rule – do unto others, incorporated into the common law by the Brisbane born English law lord, Lord Atkin in 1932.
In dam safety terms, it asks the question; “If you lived downstream of a dam, how would you expect the dam to be designed, operated and maintained in order for it to be considered safe?”
The answer is that it now requires a public demonstration that all reasonably practicable precautions are in place in a way that satisfies the will of our parliaments and our sovereign’s courts, otherwise known as a SFAIRP safety case.
Lindsay Millard, David T Roberts, Steven Cox, Andrew Berghuis, Anna Hams
Addressing historical impacts of waterway barriers on regional fisheries values is a major focus for fisheries regulators when assessing proposed water infrastructure projects such as dam safety improvements. To inform prudent investment decisions, it is essential to quantitatively determine the feasibility and benefits of various fish passage options to mitigate barrier effects. In Queensland, the regulatory frameworks require consideration of multiple options to achieve mitigation with the overarching goal to support and restore regional fish productivity. Addressing multiple objectives on large water infrastructure projects can be challenging, particularly for existing assets requiring retrofit solutions. There is a need to balance the requirements for dam safety, water supply reliability, while also mitigating the loss of fish habitat access upstream of barriers. Finding optimal fish passage solutions requires consideration of multiple options and using objective approaches that can weigh up the many aspects. The best solution may not always be the most obvious. Here we describe an approach that addresses multiple objectives through a novel off-site solution that provides increased benefit to the impacted fish community. Seqwater, Queensland,
The approach involved weighing up various fish passage options, informed by stochastic hydrologic
modelling to produce a range of probabilistic scenarios. 120 years of modelled water levels and discharges from the study site and the broader catchment, enabled an evaluation of the benefits and dis-benefits of different options in relation to dam safety, water supply reliability and fish migration opportunities. Inputs to the assessment process included fish habitat availability and migratory needs, capital and operational feasibility considerations. Numerous modelling scenarios were produced to assess a range of possible solutions, both on and off-site, to provide an objective weighting of the relative strengths of each scenario.
In this instance, while an onsite option could be feasibly engineered, it would be costly and given the
hydrology of the system, would operate so infrequently as to provide limited opportunities for fish passage and minimal regional fisheries productivity benefits. The optimal solution found was to provide fish passage on a higher order stream within the same catchment area that has impacted fish migration and access to upstream habitats for the same fish community. This option improves fish habitat access to a larger proportion of the catchment and over a wide range of flow conditions, thus providing greater regional fisheries productivity outcomes.
Our method demonstrated an objective approach to balancing multiple project objectives for dam
improvements. The use of hydrologic modelling combined with fish migration and habitat information, found an optimal solution for regional fisheries productivity goals, while also balancing the dam safety and water supply reliability goals.
Chris Nielsen, Irene Buckman
As individuals, we are concerned about how a risk affects us and the things we value
personally. We may be willing to live with a risk if it secures us certain benefits and if the
risk is kept low and clearly controlled. We are less tolerant of risks over which we have little
ANCOLD’s risk assessment guideline (2003) identifies an individual risk threshold as being
one where “the dam safety risk to an individual should be close to the average background
risk of the population”. This is a principle of equity, where “all individuals have
unconditional rights to certain levels of protection” (HSE, 2001). The definition of
population at risk applied to Queensland’s referable dams (DNRME, 2018), being
individuals within a residence or workplace and typically not participating in any risky
activities such as driving a vehicle or walking through flooded waters, provides further
justification of this right.
In practice addressing societal risk tolerances and duty of care considerations may result in
individual risks being substantially lower than the thresholds. This may not always be the
case and, irrespective, should not distort the purpose of the individual risk tolerance test;
the principle of equity that drives individual risk tolerability has foundations in our societal
values and is easily and widely understood as a core value. This should be succinctly
described when justifying expenditure on risky infrastructure such as dams.
This poster describes aspects to consider when selecting a threshold individual risk
tolerance. Subject to site-specific considerations of the particular age group of individuals
most at risk, the wider benefit of the dam to society and ALARP, a single threshold
individual risk tolerance of less than 10-5 per annum (or 1 in 100,000 years) would appear
The aspects described are elaborated in the revised Guidelines on Safety Standards for
Referable Dams, soon to be published on the Queensland Government website (RDMW,
Thomas Ridgway, Nic Polmear, Hugh Tassell
All industries, inclusive of the dams and tailings industry use some form of monitoring and reporting to confirm items or services are functioning properly or correct. In engineering, we seek to use both manual and automated systems to both qualifiably and quantifiably define the suitability of a process or structure/item. As the dams industry continues to evolve with technology and with ongoing developments in stewardship expectations for both water dams and tailings dams the industry is beginning to move into automation of their instrumentation systems. This process has recently been undertaken at a mine in NSW with the development of both a near real-time survey monitoring and visualisation system as well as a monthly photographic assessment system. This paper will set out the process undertaken to assess the surveillance monitoring requirements for the mine, details of the design, implementation of a near real-time monitoring system and the difficulties associated with the work.