In an interview with Leaders and Mining, Adam Darby, a Principal in Golder Associates’ Mine Waste Management group, speaks to the recent recognition received for Best Presentation at the 1st Congress on Solid/Liquid Separation and Tailings Treatment organized by Edoctum, where he presented “Tailings Management Facilities. A case study: There are no magical solutions.”
In his presentation at the 1st Congress on Solid/Liquid Separation and Tailings Treatment held on October 13 and 14 at Hotel Enjoy, in Viña del Mar, Adam Darby stated: “In the last 15 years, both Golder Associates and I have worked professionally in the specific area of tailings management facilities, seeking to raise the profile of these structures and seeking recognition for the importance of understanding the requirements of operators, communities, and regulators, thus providing safe and reliable designs that meet everyone’s expectations. Being present in these forums to share knowledge and experience is necessary, as this is how our industry makes progress and improves”, says Mr. Darby, a professional with 20 years’ experience in design, construction and operation of tailings management facilities.
Within the context of your presentation at the 1st Congress on Solid/Liquid Separation and Tailings Treatment, what is the importance of safety in in the mining industry?
Recent high-profile failures, such as those involving Samarco in Brazil last year and Mount Polley in Canada in 2014, have once again placed the focus on the relevance of adequate management of tailings storage facilities.
In the mining sector, failure by a tailings storage facility is likely the event with the greatest environmental and social impact potential. The occurrence of these disasters in recent years has generated a significant loss of confidence by society in the industry, which may take decades to recover.
Failures in tailings storage facilities are often triggered by a combination of factors, including inadequate design or failure to operate within defined design parameters. Natural disasters, such as large earthquakes in the case of Chile, are an important part of the criteria that must be incorporated to ensure stability both during and after operation.
One of the main challenges faced is to ensure that both design engineers and facility owners learn from their past failures and mistakes and work together to prevent them from occurring in the future. The industry is making important efforts to standardize the requirements associated with the management of these facilities. An example of this is the recent legislative amendment in British Columbia, Canada, which has established the requirements and guidelines for periodic reviews of these structures, a process that must include a qualified individual, an Engineer of Record, and Independent Review Panels. There are clearly defined roles and responsibilities for each of them.
Ensuring that legislative frameworks around the world are kept up to date—hopefully in sync with advances in available technologies—is important. This does not mean that operators simply comply with the expectations of the legislation, but it must be ensured that the best international practices of the industry are being applied at all times.
What is the role of technology and its different applications in improving safety in mine tailings?
Since the 1970s, thickening and dewatering systems started being applied to mine tailings, but from the 1990s onward, in general, other technologies started being considered, from conventional thickening to paste tailings, filtering technologies, and to a lesser extent, co-disposal. I believe there is still much to be done, especially for regular, reliable application of these technologies, particularly in mining operations with large production tonnages. Their application also requires a clear understanding of the expected behavior of tailings in terms of their densities, deposition slopes, and seismic stability, and the generation of acid drainage or metal leaching, among many other factors.
Evidently, incorporating better dewatering technologies can have benefits in terms of recovering an asset as increasingly scarce and valuable as water, whether by reducing water content, improving safety, or in other ways. However, it is important to highlight that a single technology cannot be a universal solution. We must understand that all technologies have their strengths, weaknesses, and failure modes that must be understood and managed. Selection of one or another is defined by the specific needs of each project.
We must also consider that successful, safe implementation of these technologies and systems requires a greater level of involvement on behalf of the operator. In a conventional tailings storage facility, the primary and most important element is the dam. In thickened or filtered systems, the entire system is important—from thickener to dam—requiring a larger degree of management and design than a conventional system.
What is the importance of “what if” in the success of tailings storage facility operations?
The “what if” applies to nearly everything in the world. In the case of tailings storage facilities, all too often we see that design expectations are not met during the operation. Why does this happen? As engineers, we generally like to work with fixed variables without evaluating the relevance of whether the laboratory results—which are performed on a sample that is one billionth of the total to be processed—are really valid, or if variability is going to be accepted, which is inherent in the ore type we generally have. Although we believe, or tests tell us that we will reach, for example, a solids content of 68%, can we really design assuming that from day zero we will reach that value? Typically, at the beginning of the operation, the feed undergoes variations, thickener operators are new or do not know the equipment quite well, and it is usually expected that it will not operate within its design range.
There are many other factors and variables that must be considered and that are equally or more important to the operational success of the tailings storage facility than when we are operating within the design range.
What does it mean to you from a professional point of view to have your presentation acknowledged by the attendees as best presentation?
It is really gratifying to receive recognition from a varied spectrum of professionals in our industry. In the last 15 years, both Golder Associates and I, professionally, have worked in the specific area of tailings deposits, seeking to raise the profile of these structures and seeking recognition for the importance of understanding the requirements of operators, communities, and regulators, thus providing safe and reliable designs that meet everyone’s expectations. Being present in these forums to share knowledge and experience is necessary, as this is how our industry makes progress and improves.
For more information, please contact:
Golder Associates South America Ltd.
Elizabeth Bravo, Coordinator Regional Communications
Tel: +56 (2) 2616 2210