For those of you with a geotechnical background or have a general interest in learning about rock slides and slope failures, there is an interesting website and blog for you to follow. The website is hosted by the American Geophysical Union the world’s largest organization of Earth and space scientists. The blogs on their site are written by AGU staff along with contributions from collaborators and guest bloggers. Their website screenshot is shown below.
The independent bloggers have editorial freedom in the topics they choose to cover and their opinions are those of their authors and do not necessarily represent the views of the American Geophysical Union. This provides for some leeway on the discussions and the perspectives the writers wish to take.
One specific area they cover well in their Landslide Blog are the various occurrences of rock falls and landslides from any location around the globe. They will present commentary, images, and even videos of slope movements as they happen. Often they will provide some technical opinion on what possibly caused the failure event to occur. The Landslide Blog has a semi-regular email newsletter that will keep you updated on new stories as they happen.
The following links are a few examples of the type of discussion that they have on the website.
Here is a description of a small water dam failure in Greece.
Here is some video of the Samarco tailings runout in Brazil.
Here is some video of boulders raining down on some buses along the Karakorum Highway in Pakistan.
From time to time the Landslide Blog will examine mine slopes, tailings dams, and waste dump failures, however much of their information relates to natural earth or rock slopes along roads or in towns and cities. Some of their videos are quite fascinating, illustrating the forces behind some of earth’s natural erosion processes. Check it out for yourself.
My bottom line on all of this is that the less the mining industry is mentioned in the Landslide Blog, the better it is for all of us.
After the Mt Polley and Samarco tailings failures, there have been ongoing conversations about the benefits of filtered or dry stack tailings as the only way to eliminate the risk of catastrophic tailings failure. Mining companies would all like to see a similar risk reduction at their own project. However what mining companies don’t like is the capital and operating costs associated with dry stacking. The dry stack tailings processing cost and the transport cost are both costlier than for conventional tailings disposal and therefore would negatively impact on the overall value of the project. Obviously this reduction in value would get offset against an improved environmental risk and a better closure condition. So what’s a company to do?
In my experience when designing a new mining project, all mining companies at one point in time complete a trade-off study for different tailings disposal methods and disposal sites. Contrary to some environmental narratives, companies really do wish to know how the different tailings options compare because they would adopt the dry stack approach if it was the most advantageous method. The mining companies are fully aware of the benefits but the dilemma the company runs into is the cost and being able to somehow justify the technology. Complicating their final decision, companies also have options for reducing their tailings risk even if using another tailings disposal method and so the final decision can get very complex.
Often proponents of the risk analysis approach will use a risk-weighting approach to assign an expected economic cost to their tailings plans. For example, if the cost of a failure is $200 million and the risk is 0.1%, then the Expected Value is $200,000. The problem is that this is a theoretical calculation on an assumed likelihood of failure but in reality either the dam will fail or it won’t. So failure remediation money will be spent or it won’t be spent, it won’t be partially spent.
The degree of acceptable tailings risk therefore becomes a subjective factor. While implementing a dry stack may reduce the risk of catastrophic failure to zero, implementing a $100,000 per year monitoring program on a conventional tailings pond will reduce its risk. Implementing a $500,000 per year monitoring program would reduce that risk even further. Installing in a water treatment plant to enable periodic water releases may further lower the tailings risk. The company can look at different mitigations to keep lowering their risk, although recognizing that none of the mitigations would necessarily bring the risk down to zero. Finally the companies could compare the various risk mitigation costs against the incremental dry stack costs in order to arrive at an optimal path forward.
So the question becomes how low does one need to reduce the tailings storage risk before it is acceptable to shareholders, regulators, and the public. I don’t think the answer is that one must lower the risk down to zero. There are not many things in today’s world that have zero risk. Driving a car, flying in a plane, shipping crude oil by ocean tanker, having a natural gas furnace in your house..none of these have zero risk yet we accept them as part of living in modern society.
Environmental groups are always discussing ways of forcing regulators and mining companies to take action against the risk of tailings failure. This is commendable, however they generally fail to provide any guidance on what level of risk would be acceptable to them or to the public. It seems to be impossible for these groups to define what an acceptable risk is or provide any ideas other than the standard “shut down all mining” solution.
We know that in the long run mining is here to stay so we all should work together towards solutions. The solutions need to be realistic in order to be taken seriously and for them to play a role in redefining tailings disposal in modern mining. Dry stack may not be the only solution and we should be open to ways of improving the other tailings disposal methods so that companies have more low risk options available to them.
One of the technologies that’s still getting a lot of press lately is 3D printing; it seems new articles appear daily describing some fresh and novel use. Everything from home construction, food preparation and industrial applications, 3D printing continues to find new applications in a wide range of disciplines. Mining engineering is no exception.
In a previous blog “3D Printing – A Simple Idea”, I discussed the helpfulness of printing 3D topographic models for the team members of a mining study. I was recently contacted by a consulting firm from Texas that, amongst other things, specializes in the 3D printing of mining models. Here is their story and a few model images as provided to me by Matt Blattman of Blattman Brothers Consulting. (www.blattbros.com/3dprinting)
Their 3D printed models are used in the same way geologists and mining engineers have employed models for decades. We’ve all seen the physical models made of stacked mylar or plexi-glass maps, wood or foam core. We all recognized that there is value in taking two dimensional sections or plan maps and making a 3D representation which provides more that those viewed on a computer screen. Physical models convey scale, interactions and scope in ways that no other method can. 3D printing improves the model-making process by allowing for the addition of high definition orthophotos, reducing the model building cost, increasing its precision, and its delivery time.
The current 3D models can be made in a variety of materials but the primary three are extruded plastic, gypsum powder, or acrylics.
Plastic models (ABS or PLA) are cheap, fast and can created on relatively inexpensive, hobbyist printers. The downside to these models is that the number of colors available in a single model are limited, typically a single color.
Powder-based printers can typically print in 6.5M colors, allowing for vibrant, photo-realistic colors and infinite choices for title blocks, logos and artistic techniques. However, gypsum models can be as fragile as porcelain and require some care in handling.
Acrylic models allow for translucent printing (“looking into the ground to see the geological structure”) and are more durable than the gypsum. Nevertheless, acrylic models are significantly more expensive than the other two types and the color palettes are limited.