24 Apr “We have to take tailings to a socially acceptable level of risk”
“Our challenge is to take tailings deposits to the level of risk that industry and society consider acceptable”
The international consultant Luis Valenzuela summarizes in this way the standard towards which tailing dams must advance. Currently and at an international level, the risk is much higher than the dams in other industries. The specialist assures that there is a need to move towards the implementation of new standards based on international best practices – far beyond what local legislation may require – a task that must be carried out together with all stakeholders related to mining.
In an interesting presentation at the 3rd International Seminar on Mining and Sustainability within the framework of Cesco Week 2019, which addressed in depth the challenges of mining tailings management, Luis Valenzuela said that to face the risks it is vital to go beyond the legal requirements which in general point to compliance with minimum conditions. The consultant said that it is an ethical requirement that companies incorporate in the design, construction, and management of tailings, all the recommendations and best practices proposed by various international organizations that are concerned with the safety of the dams.
“When a disaster occurs, after a while, nobody remembers a particular company, but it is the confidence in the entire industry that deteriorates,” he said, so it is necessary to install the issue of tailings deposits security at the highest level of mining companies, including their boards.
In an interview with Cesco, Luis Valenzuela referred to the main risks that currently exist in tailings deposits and the steps that Chile and other mining countries must follow to achieve an adequate level in relation to the safety of their tailings dams.
What are the main risks that currently exist in tailings deposits?
The biggest risk that mining has in general, and Chile in particular, is the possibility of other failures of tailings deposits, such as those that occurred in Brazil in 2015 and 2019 together with several others in this last decade in various countries of the world. In this sense, global statistics give us a clear warning sign. Tailing dams have failed with a frequency of the order of 1 in a 1.000, while water dams with various purposes such as irrigation, drinking water or power generation have failed with a lower frequency, about 1 in 10.000. Then, it could be interpreted that the tailing dams deposits are inferior in quality to the dams for water, statistically speaking. Therefore, what we have to do is a significant change to ensure that our tailings dams present a level of risk equivalent to that of other industries, a level of risk that is generally accepted by society. It is likely that with the developments of recent years, the level of risk of tailings deposits is lower than the one shown by the failure statistics mentioned. buThet the problem is that we have not assessed the level of risk and it is presumed that many of the tailings deposits do not reach thet level of risk that is considered acceptable.
How can we face this problem?
The only way to take action is to know what is the level of risk presented by each dam, especially those whose failure can bring serious consequences, not only economic but also in terms of human lives and/or contamination. Until now, the safety offered by tailings dams is measured not by determining the level of risk, but rather by deterministic concepts, that is to say, safety is measured or calculated from a physical model and from the definition of physical parameters selected as representative. As an example of the deterministic criterion, the concept of safety factor can be mentioned. In general, the legislation requires that this factor is greater than 1.5, that is, the forces resistant to a landslide, for example, are 50% greater than the requesting forces that would lead to a failure (a condition in which that factor would be 1.0). However, depending on the dam, in terms of design, construction, and operation, the same value of the safety factor can be associated with different levels of risk. To substantially improve the safety of tailings dams, especially those whose failure can have serious consequences, it is necessary to verify the level of risk presented by these dams through a formal quantitative risk analysis. If the level of risk calculated for a particular dam is greater than what is required, measures and actions must be taken modifying what has to be changed to reach an acceptable level.
What are the specific proposals to reduce the risk?
There are six basic activities, and the risk calculation we were talking about is the last one. First, you must have adequate engineering and not one that only complies with local legislation, but that goes beyond and complies with international best practices. Obviously, in the engineering process, a risk analysis must also be included. Afterward, the same thing is repeated for the construction and operation phase; it is necessary to follow the best international practices and avoid increasing the risk during the operation, where if there is no adequate supervision, everything that was considered in the design phase may not be respected. Then comes monitoring: through instrumentation, measurements to see what condition may have changed and to react in time. Then there is a very important condition that is the organizational one; it has been seen that many of the failures have occurred because there is a human organization where control and decision making is not possible or facilitated, as well as corrective measures in time. Therefore, it is necessary to introduce a series of measures and controls to neutralize this danger, which fortunately is already being done in several companies in Chile, such as Antofagasta Minerals, Codelco, Anglo American, and others, as well as internationally. Along with the above is the risk analysis, which allows to manage the risk and that is necessary to determine it on a continuous basis in order make the changes and take the necessary measures in such a way to be sure that the dam or talings deposit is at a level of a risk that is tolerable from the point of view of the company and also from the point of view of what society demands or accepts, which evidently expects the safest level that is rationally possible. I believe that it is not acceptable for mining to adopt risk levels higher than those required for other industries for similar structures, and that is the challenge: to ensure that our tailings dams and deposits present a level of risk that industry and society consider as acceptable.
What has been seen in the seminar – Tailing Deposit Program, tailings monitoring, the new National Tailings Policy that is being promoted by the Ministry of Mining, Are they going in the right direction?
All these initiatives are going in the right direction and all point to what I mentioned before, but what I think Chile is missing is a coordinated work together among all sectors: institutions, government, mining, engineering companies, and universities. This is what is being done in the specific case of the Tailing Deposit Project, but that same type of joint effort should also be applied to other aspects related to mining waste.
Laws and regulations should not be determined only by a sector – such as a Ministry or a State service – and sent to Congress so that the mining companies, the community, universities, research centers and other stakeholders interested in mining know them later. The regulatory framework has to be worked out together, and I think a good example of this is what Canada has done.
Furthermore, not all aspects, including details, should necessarily be part of a law, but should be thought of complementing the necessary laws with procedural guides, prepared jointly by all actors, and that all should accept and respect. Being more flexible documents, it would not be necessary to wait for a law to be drafted or modified to introduce modifications since they are very long processes.
But in the end, we must recognize that the mining industry is and must be absolutely responsible in relation to what happens with the handling of mining waste and therefore has to have a responsible attitude towards society. It cannot say for example “no, the law does not demand that from me”. Mining must have the attitude of responding to society by saying “I do what ethics and international best practice require, in addition to local legislation”.