READER’S QUESTIONS

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My good friend, Jagrut Jathal has asked me the following questions:

1. Are upstream tailings dams really to blame for the recent incidents in Brazil? Despite the inherent risks, there are several such facilities across the world that have operated and continue to operate safely.

2. Lessons learned from the major tailings dam failures this decade.

3. Are regulatory requirements based on conventional limit equilibrium definitions of factor of safety protective enough? Should there be more emphasis on using reliability and probability concepts in slope stability analyses?

4. Given the recent incidents in Brazil, I would like to know your thoughts on what can be done from a design, regulatory, construction and operations standpoint to manage risks in the future.

Good questions, Jagrut. Very timely and compelling. It is amazing how the industry-at-large is responding to this latest tragedy. And damn. You made me stop and think. The problem of failures isn’t really upstream constructed tailings dams, in general. A few years ago, at the Tailings and Mine Waste conference in Keystone, Colorado, my mentor and former teacher, Professor Norbert Morgenstern delivered the keynote address on the state of tailings management. This was before Mount Polley, and Nordie may have changed his mind since then, so please put this in perspective.

A brief interruption…

This reminds me of a question that the legendary soil mechanics pioneer Karl Terzaghi was once supposedly posed. This followed a lecture he delivered, and a member of the audience enquired, “Dr. Terzaghi, isn’t this the exact opposite thing that you taught us two years ago?” Terzaghi responded, “You don’t think I’ve learned anything in the last two years?”

Mic drop.

Anyway, back to Nordie. It was actually in a subsequent talk at the conference, when a presenter stated that in the future there will not be any upstream-constructed tailings dams. Nordie responded, “Perhaps you were not present for my keynote, but there is no reason to dispose of any useful technology, as long as it is applied correctly”. His words are not precisely that, but pretty close. I think I’ve captured his spirit. Upstream-constructed tailings dams can be done correctly, in the right time, for the right project, with the correct level of engineering, adequate construction and construction oversight, monitoring, operation and continued engineering involvement. Upstream-constructed tailings dams will likely never go away. Unless a future technology makes them go away. As you say, Jagrut, upstream-constructed tailings dam exist all over the world.

You bring up a good topic of risk. I truly believe that risk-informed design will be much more common, carrying forward. Factors of safety can’t account for everything. Maybe I’ll make the topic of risk-informed design the subject of an upcoming blog. It seems too important just to be so brief here.

Lessons… I think that are a lot of lessons to be learned from the most recent series of prominent and tragic failures. One pertains to the value of institutional knowledge that comes from retaining a long-term engineer-of-record. I’m really not at liberty to say much, but it is impossible for engineers to put everything that is in their heads onto paper. If that engineer is replaced, and there was some important knowledge that did not get put into a report, the next engineer is at a disadvantage. I think that another valuable lesson is for the design engineer to look beyond their current assignment. It isn’t good to go through life with blinders on, and sometimes the owner doesn’t know how best to develop scopes of work, and the obvious can be overlooked. Please enter into projects knowing that scopes of work (and contract) may need to be adjusted so that you may better serve your client. Another lesson is that each TSF needs the right amount of engineering. That is a mouthful. And yet it says nothing. I know. They are all snowflakes, and need to be approached individually so that they receive the right amount of engineering. I hate to get into “politics” here, but… regulators aren’t there to be the end-all, or to save us from ourselves, or the owners from themselves. We, as an industry have to respond and lead the way. But it isn’t with heroics. It is through setting up the right scope of work, with adequate budget to complete the scope. And then doing the work that is needed. But the other part of your question pertains to probability. And I’ll again add risk. I really think that risk-informed design will be a much larger part of the way we will complete our work in the future. Probabilistic analysis is also a great tool, and given adequate budget for field and laboratory testing, it can yield a very useful result, however they are a little more complicated to interpret, as you probably know.

Your final question is a big one. But firstly, I don’t think that additional regulations are the avenue. Some additional regulations could be good, depending on what regulations already exist, but we also need flexibility because each project has its own site-specific requirements and constraints. The State of Nevada has very good regulations for tailings management, and although I am less familiar with them, I believe that the State of Montana’s tailings management regulations are very progressive. Education will play a role in improvements to tailings stewardship in the future. By that, I don’t mean (just) at the college and university level, but in the field too. When I lived in South Africa, my former company, along with SRK and Fraser Alexander put on an annual 2-day clinic in Rustenburg (South Africa) for Anglo Platinum. The goal of the clinic was to help train/educate the operators of the tailings facilities so that they could be better equipped as the “first line of defense” for observing, spotting and alerting others if something “different” and unwanted occurs. Just monitoring change is important, whether it is a sudden and unexpected change to the readings from instrumentation, or the appearance of unusual vegetation in an area that is otherwise generally devoid of vegetation. Jagrut, my friend, our world has certainly changed because of the recent TSF tragedies, but with proper diligence, and standing up for what is right, even when that is difficult, together we can make industry better. Thanks again for the questions, and if anyone else has questions or comments to share, please feel free to leave them here, or on my LinkedIn page.

For sure I don’t have all of the answers, but I’m happy to be part of the conversation.

Until next week, I wish you all well.

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