The ever increasing complexity of decision making for dams, in compliance with the requirement of transparency and accountability, requires new approaches for economical and safe operation, for maintenance and for overall management. One of these possibilities is risk assessment. The principles of risk assessment are logical and rational, and must be taken into account by all countries when making decisions regarding dams. This bulletin is intended to encourage discussion within the profession, to move towards a widely accepted position on the role of risk assessment. It is also intended to serve as a complementary tool for engineers, project owners and regulatory authorities in order to fulfill their obligations in all areas of dam safety.
Geohazards comprise a subgroup of natural hazards associated with geotechnical, hydrotechnical, tectonic, snow and ice, and geochemical processes that can pose a threat to worker and public safety, asset integrity, and asset management lifecycle cost. Like for most types of threats, the risks from geohazards can be assessed qualitatively or quantitatively and used to inform a geohazard management program. Most mining companies use risk matrices to aid in the assessment, prioritisation, communication and management of corporate risks. These matrices use standardised descriptions of likelihood and consequence to help users assess risks of negative outcomes to health, safety, the environment, assets, and reputation, and are tailored to each organisations types of risk exposure and level of risk tolerance. Geohazards and related geotechnical failures can represent low-probability, high-consequence events that plot in the highest risk zones of most corporate risk matrices. Variability in spatial and temporal probabilities for people and infrastructure exposed to geohazards can have a large influence on risk exposure, and this can be challenging to assess and communicate effectively with some risk matrices. Risk is scale-dependent: the business risk due to rockfall from a single slope along a mine access road is vastly different than the total risk due to rockfalls from all slopes along that road, yet guidance is often missing on how the risks from these scenarios should be plotted on a risk matrix. These and other pitfalls associated with use of corporate risk matrices for informed geohazard management are explored.
This paper reviews the progressive growth of awareness, adoption and practices with respect to geotechnical risk in mining in Australia over the last four decades, with a particular focus on underground mining. Initial experience in the 1980s was drawn from other high-risk industries such as nuclear and petrochemical sectors, and whilst the mining industry recognised the issue of a changing hazard and risk environment, it did not change practices significantly. Subsequent growth in understanding of the evolving discipline of risk management, coupled with major changes in mining legislation to a more enabling legislative framework, have led to a far more risk-aware industry where risk assessment and risk management practices have become a fundamental component of the overall mining management systems. In underground mining, geotechnical risk is at, or close to, the top of the risk priority list for proactive mine management today. The recognition of what are referred to as core risks associated with particular mining methods was a further development in the maturity of the industry management systems, with implications for all levels of management, right from feasibility through to design, planning and operations. One of the problems with the growth of risk-based management practices in Australia is that because we do so many risk assessments and develop so many hazard plans, we have, in some cases, become too blasé about them and do not give due recognition and priority to the ongoing management of important risks with the potential for serious consequences through lack of attention to detail and lack of integration of risk management into the mine management system. In an effort to overcome this issue and place higher priority on the most critical risks facing a mining operation, the International Council of Mining and Metals (ICMM) Critical Control Management (CCM) system, for focusing on the most critical risks, and then directing more attention to the actual control practices required to manage them, has been a valuable trend in recent years. In the Australian coal sector over the last 10 years, the industry-funded RISKGATE system has also been an extremely useful documentation of industry experience and a tool to assist operators either investigate incidents or plan risk assessments on new topics or areas. Geotechnical topics make up at least three of the 18 major topic areas covered by RISKGATE. This paper will briefly outline how RISKGATE operates and is applicable to the industry in the geotechnical space.
Mineral exploration projects in tropical environments can be exposed to a range of geohazards, including landslide, rockfall, debris flow, flooding, and subsidence. Understanding the geohazard types present, and their potential consequences at a proposed drill pad or camp site, is critical to managing the projects geohazard risks. During the early stages of exploration, typical datasets used to map and evaluate geohazards, such as stereo airphotos and airborne LiDAR data, are often not available; as a result, engineers and geologists must rely on reconnaissance-level desktop studies and field observations of the geomorphology to estimate the risk of geohazard exposure. In order to effectively estimate geohazard risk at individual sites in a systematic manner, an evidence-based system was developed employing a standard risk equation. The components of the field-based geohazard risk assessment system include identifying the geohazard type and estimating the annual probability of occurrence at a specific location, estimating the spatial probability of the geohazard reaching the elements at risk, estimating the vulnerability of the elements at risk to the geohazard, and estimating the temporal probability that the elements at risk would be present when a geohazard occurs. This approach enables credible geohazard threats to be rated and facilitates appropriate risk management approaches suitable for each location and geohazard type. In parallel with the geohazard risk ratings, geohazard risk can be managed through more detailed assessment, awareness training, engineering measures, relocation of drill sites and infrastructure, and trigger action response plans. This paper presents a case study that employs the methodology at a greenfield exploration project site in tropical jungle in mountainous terrain.
Rio Tinto Iron Ore operates 16 different mine operations in the Pilbara region of Western Australia. Across these operations, there could be more than 100 operational open pits at any given time. This poses a considerable challenge for the effective management of geotechnical risks with finite resources. There are also a number of external legislation and internal compliance requirements that need to be adhered to. A number of standardised systems and tools have been developed by the geotechnical teams to manage the geotechnical risks and this paper introduces the different components of Rio Tinto Iron Ores geotechnical management System (GMS). The GMS covers the complete process, from the geotechnical design of a slope, through implementation to verification of performance and feedback to the design engineer. The focus of the paper will be on the Geotechnical Risk and Hazard Assessment Management System (GRAHAMS) which is used to assess and document the safety and economic geotechnical risk assessments of different slope areas. A number of reports and visual summaries of the risk assessments are available in the system, offering leaders the opportunity to identify areas of elevated risk and allocate resources accordingly. Details of realised risks (geotechnical hazards) are also captured and GRAHAMS provides a process to communicate the hazard and relevant controls to operational personnel. The GRAHAMS system was recently enhanced, moving from a Microsoft Access front-end to a web-based platform. This will enable a number of system improvements to further increase its effectiveness.
Mount Isa Copper Operations (MICO) is one of the oldest and deepest mines in Australia, comprising the largest underground network of mine development in the world. During the early operational years, ground support, particularly surface support, was not routinely installed. Although rehabilitation in recent years has drastically reduced the amount of tunnel without support, there remain tens of kilometres of excavation with limited to no ground support installed. In addition, older development was often mined within close proximity to unfilled or partially filled stopes and vertical openings. The voids pre-date modern 3D mine plans and scanning technology. Furthermore, access to the voids to conduct scans is limited, this results in an imperfect understanding of the void sizes and proximity to accessible drives. The lack of ground support and knowledge of void status poses significant ground failure risks at MICO. A significant increase in rock related near-hit incidents occurred during the second half of 2014 and the first half of 2015. A number of these incidents had the potential to cause severe or fatal harm. The incidents triggered internal investigations that aimed at understanding and reducing the ground failure risk. The outcome of the investigations was the creation of a series of interlinked systems, namely the tunnel condition risk assessment (TCRA), mine closure areas (MCA), ground awareness training (GAT), vertical opening pillar hazard assessment and control (VOPHAC), stope void review (SVR), manual scaling crews, fall of ground database and the quality assurance/quality control management plan (QA/QC MP). The individual components of the system are specialised and simple. However, the system is comprehensive and robust. Each of the components, as well as how they interlink, is discussed within this paper. The interlinked systems and practices provide controls and have proven to be effective at reducing the ground failure risks. Although the systems were developed at MICO, they have the potential to be easily adapted and utilised at other mine sites.
Risk-Informed Decision-Making (RIDM) is a method of dam safety evaluation that uses the likelihood of loading, system response given the loading, and consequences of failure to estimate risk. This risk estimate can be used to inform decisions regarding dam safety investments. This approach has many benefits including a greatly improved understanding of the safety of the dam and identifying dam safety vulnerabilities that have not been identified using standards-based evaluation techniques. This website includes dam safety guidelines to evaluate consequences of failure and is intended for use on water dams.
Releases of mining tailings effluents and solids from containment facilities around the world have heightened awareness that risk associated with tailings impoundments must be fully addressed during all phases of a mine life. Bruce Geotechnical Consultants Inc. and Oboni Associates Inc. have developed a quantitative risk assessment process that allows mine owners and operators to quickly and successfully identify problem areas, and assess mitigative methodologies and priorities. The numerical method allows comparison between mines on a company wide basis and provides a platform for decision making as part of a risk management program. This paper focuses on how to conduct a quantitative risk assessment and provides a series of examples highlighting the principles involved and the advantages and disadvantages of using a quantitative risk assessment.
Investor confidence is largely driven by a mining companys ability to deliver on the guaranteed return on investment. Thus, robust due diligence processes, functioning as part of a mining companys corporate governance, become essential tools to identify hazards that can impact production, assess the associated risks and introduce controls to manage the risks. The geotechnical practitioner is tasked to manage one of the biggest risks on the mine; that of a rock mass instability. Since an instability, or collapse, need not be large to have a significant impact on production, the challenge is to develop an optimised life-of-mine design with a risk management plan that suits the risk requirements of the mining company and investors, whilst meeting acceptable, minimum safety standards. The concept of a Geotechnical Review Board has been adopted in the industry as a vehicle to provide assurance that the geotechnical risks on a mine have been identified and are being properly managed. The review relies on external parties providing appraisals of the design and processes, and experienced oversight of the active operations. In general, these reviews tend to have a unique style; often a combination of the current, visible, critical issues on the mine and issues deemed as important by either the reviewer or a third party. Coupled with the challenge of fluidity in modern planning environments, the geotechnical practitioner is often still faced with uncertainty in the level of geotechnical risk associated with any given mine plan. This paper introduces a geotechnical risk assessment tool that has been developed for use as a leading indicator within AngloGold Ashantis international operations. The authors aim to provide the reader with insight into how the tool can be utilised to understand a mines ability to proactively identify and manage geotechnical hazards, by exploring the following components:
The movement towards risk-based design and operation of tailings storage facilities (TSFs) has taken place over the last few decades. The establishment of the consequence of failure of a facility is used to determine the design criteria to be used in its design. These criteria generally set the acceptable return periods for seismic and hydrologic events that the facility must accommodate. In addition, there are generally several levels of risk assessment of the design carried out to highlight technical risks that require particular attention and controls to manage. These are usually addressed in the design phase of project development. Despite this focus on technical risk assessment at the design phases of the development of a TSF, there is still a significant number of failures occurring every year. In recent times, there have been a number of high profile TSF failures in facilities owned by major mining houses and/or located in highly regulated, first world countries. In almost every case, the investigations into the failures have been carried out by high profile, internationally recognised geotechnical engineers who have identified the technical reasons for the failure. In many cases, it has been shown that the root causes of the failures have been a failure in governance, capital constraints, change management, independent reviews, construction supervision, operation, etc. The investigation of failures and reports to the public are almost exclusively focused on the technical cause with much less focus on what is often the underlying root cause. A number of international mining industry groups have recognised the lack of effective governance as being a major risk that could lead to TSF failures. The Mining Association of Canada (MAC) and the International Council on Mining and Metals (ICMM) are two examples. In this paper, the various methods for risk assessment and management are described. Non-technical risks that arise in the design and operation of TSFs are discussed and importance of good governance and continuity of its application during the full lifecycle of the facilities is emphasised.