2021 – Quantifying the minimum epistemic uncertainty required PSHA input models
Dr Mark Leonard
The quantification of the 85% and 95% hazard fractiles, as required by the ANCOLD 2019 Guidelines for design of dams, is investigated. It is found that there are four independent sources of uncertainty in the PSHA input models that have a significant effect on the hazard. So all four need to be quantified, particularly for Extreme and High A consequent dams. It is also found that the uncertainty of many of the other parameters, which are routinely included in probabilistic seismic hazard assessments, have minimal effect on either the mean or the higher fractiles so do not necessarily need to be routinely included. The complexity of the input models required to satisfy the new standards are substantially higher than those routinely used in prior decades.
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2021 Papers
2021 – WaterNSW Dam Safety Alert Trigger Framework
Learn moreDamien Bryan, John Sukkar, Erin Hughes, Michael Cawood
Alert triggers are a critical component of Dam Safety Emergency Management, aligning clearly defined adverse conditions with alert levels to initiate an appropriate emergency response. Early detection of these conditions allows for potential mitigation measures to be undertaken, early engagement of key stakeholders such as emergency agencies, and where necessary, the warning or evacuation of affected downstream communities. The Dam Safety Alert Trigger Framework provides WaterNSW with a consistent, repeatable, and defensible methodology for the determination of appropriate dam safety alert triggers. The framework was developed through the engagement of consultants, emergency and regulatory agencies (NSW SES & DSNSW), and several Australian large dam owners.
The determination of appropriate Dam Safety Alert Triggers is a challenge faced by all dam owners. Through the development and implementation of the Alert Trigger Framework, WaterNSW has achieved the ability to define defensible alert triggers through a consistent and repeatable methodology. This has resulted in an improved dam safety emergency response posture for WaterNSW, key emergency services partner the NSW SES, and greater protection for affected downstream communities. Concepts, processes and methodology covered in this paper could be used by other dam owners in addressing their own dam safety alert trigger challenges.
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2021 Papers
2021 – Ground shaking potential relating to eastern Australian active faults, an example of the Bendigo Region with relevance to water reservoirs and tailings dams
Learn moreDan Clark, Joanne Stephenson, Trevor Allen
We present earthquake ground motions based upon a paleoseismically-validated characteristic earthquake scenario for the ~ 48 km-long Avonmore scarp, which overlies the Meadow Valley Fault, east of Bendigo, Victoria. The results from the moment magnitude MW 7.1 scenario earthquake indicate that ground motions are sufficient to be of concern to nearby mining and water infrastructure. Specifically, the estimated median peak ground acceleration (PGA) exceeds 0.5 g to more than ~ 10 km from the source fault, and a 0.09 g PGA liquefaction threshold is exceeded out to approximately 50-70 kilometres. Liquefaction of susceptible materials, such as mine tailings, may occur to much greater distances. Our study underscores the importance of identifying and characterising potentially active faults in proximity to high failure-consequence dams, including mine tailings dams, particularly in light of the requirement to manage tailing dams for a prolonged period after mine closure.
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2021 Papers
2021 – Managing multiple concurrences estimating likelihood and consequence in dam break application, Rainfall based data sparse regions
Learn moreClaudia 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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2021 Papers
2021 – The Critical Link between Risk Assessments and Critical Controls
Learn moreRyan Singh, Jiri Herza, James Thorp, Michael Ashley
Performance-based risk-informed decision making is an underlying principle of the Global Industry
Standard on Tailings Management (GISTM). While owners make significant efforts to align with this
principle, commonly used risk assessment and management practices in the mining industry have largely been based on the HSE principles, which consider more frequent, lower consequence incidents.As a result, the existing risk assessment frameworks do not provide the owners with a comprehensive understanding of the risk profiles of their tailings storage facilities (TSFs). Without the understanding of a facility’s risk profile, the owners cannot appreciate how changes to their facility, processes and operational activities may impact the risk profile. A large step-change in thinking is therefore required in risk assessment practices for the owner to align their TSF management with GISTM requirements.
Beyond risk assessments, the mining industry has other valuable concepts to manage the safety of their tailings management practices, such as Critical Controls, however, commonly used risk assessment and management practices do not incorporate these concepts.
This paper explores commonly used risk assessment practices and the concepts of Critical Controls. It proposes how these concepts can be linked, with Critical Controls being embedded in the risk assessment process. The outcomes of linking these concepts result in an estimation of the effectiveness of the Critical Controls and how they can be improved to demonstrably reduce the risk presented by a TSF. A case study has been included to demonstrate the benefits of linking risk assessment with Critical Controls and how owners can readily identify deficiencies and efficiently manage the risk profiles of their facilities.
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2021 Papers
2021 – Emergency Preparedness for Tailings Dams
Learn moreOlle Wennstrom, Andrew White
Over the last few years tailings dams have come under increased scrutiny, partly due to two highly publicised TSF failures in South America, but also because of several other incidents in Australia and elsewhere in the world. As investors came under pressure to positively impact the projects they financed, the Global Industry Standard on Tailings Management (GISTM) was released in August 2020.
Topic 5 of GISTM, “Emergency response and long-term recovery”, comprises Principle 13: “Prepare for emergency response to tailings facility failures” and Principle 14: “Prepare for long-term recovery in the event of catastrophic failure”. The topic further introduces the term “Emergency Preparedness and Response Plan” (EPRP).
This paper explains what the term “Emergency Preparedness” means and how the owner/operator of a mine can achieve it. The paper also delivers a concept for long-term recovery planning.
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