In 2007, CDA published a set of technical bulletins to supplement Dam Safety Guidelines. The technical bulletins suggest methodologies and procedures for use by qualified professionals as they carry out dam analyses and safety assessments.
This document provides oil sands mining operators with guidelines for the audit and assessment process consistent with the requirements set out in the Performance Management documents from COSIA. There is a requirement for a 5-year audit and assessment by an independent team of audit/assessors. Through this process, the audit and assessment team will: 1. Assess the reasonableness of the relevant plans and reports. 2. Provide an opinion as to whether the mine closure plan is realistic and the progressive management of FFT is on track to the desired closure outcome.
There are growing expectations of mining companies to operate in a more sustainable manner, with a strong business case for improving waste management and reducing environmental impacts. As the stewardship of tailings come under increasing scrutiny, decision-makers are urged to adopt a robust approach to the selection of a tailings management strategy that encompasses design for closure, and leading practices to lower the risk of catastrophic dam failures, optimise the use of resources, and mitigate environmental impacts on climate change. An integrated analysis, considering economic, environmental, social, and risk aspects of the operation can therefore provide decision-makers with balanced information to ensure the right projects proceed with an optimal business case so that the most cost-effective solution, that does not externalise costs, can be selected. However, literature review revealed that fundamental shortcomings exist within traditional evaluation approaches used for economic comparisons. This paper reports on life cycle cost analyses conducted for comparing various tailings management options under different scenarios. A conceptual case study for the disposal of gold tailings in Western Australia as a slurry, as thickened, or as filtered tailings, was considered. This was done for examining the extent to which potentially hidden costs impact on the total cost of a project. It is suggested that the proposed approach will lead to selection of a tailings management alternative that ensures sound economic, environmental, and social performance is achieved.
The new Technical Bulletin: Application of Dam Safety Guidelines to Mining Dams, complements the Dam Safety Guidelines re-published by CDA in 2013 by providing additional explanation of how the concepts described in the guidelines apply to mining dams. The Bulletin identifies some specific issues that should be considered during the design and safety evaluation of both tailings dams and water retention dams used in the mining industry. Available in hard copy only.
This bulletin considers the environmental impact assessment that must be made at the planning stage. It also provides consideration of the environmental stability to be achieved during the years of tailings dam construction and the period after completion and rehabilitation.
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.
The majority of seismic hazard assessment tools are solely based on statistical analyses of several seismic source parameters such as event rate and time, and seismic moment. These analyses are often applied to the entire mining area which can impact the accuracy and reliability of the hazard assessment tool in each zone. Experience has shown that mining geomechanical risk is complex and its mitigation needs a broad understanding of other geotechnical factors such as rock mass properties, geological structures, mining method, stress regime, etc. Since all the contributing parameters and their impact are not entirely understood, it is critical to apply a range of geotechnical/geomechanical analyses in correlation to each other and quantify the changes in the rock mass behaviour. The goal of this paper is to develop a seismic hazard assessment tool calibrated for each geotechnical domain within the mine. To develop the tool, we incorporated mine geotechnical and geological data, seismic source parameters, and tomography analyses from a hard rock underground mine in North America. There exist several sub-vertical faults and one horizontal structure in the mine which create clear contrasts in rock mass behaviour across the structure. The results show good correlation among the different datasets, and a calibrated seismic hazard tool has been developed that provides ongoing updates to the mine operation.
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.
The Guidelines consist of principles that are applicable to all dams, and an outline of processes and criteria for management of dam safety in accordance with the principles.
Geomechanical risk in mining is universally understood to depend on many apparently disparate factors acting together such as stress, stiffness, mine geometry, rock mass character, rock type, structure, excavation rate and volume, blasting, and seismicity. We have worked on many case studies over the years in both underground and open pit mines with the objective of discovering and documenting the correlation of such factors with the experience of geomechanical failure. Whether that failure is slope failure, strainbursting, fault slip-induced rockbursting, roof fall, or any other of many possible failure types, statistical correlations among the different classes of data can be found, and predictive rules for understanding geohazard based on their quantitative combination can be established and deployed in day-to-day operations. This data-driven approach requires application of methods and avoidance of pitfalls that can be standardised into a universally applicable workflow. We discuss the workflow and the pitfalls in analysis to be avoided through case study examples.