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Tailings storage facilities: A unique challenge for a critical industry

October 28, 2022
Tailings storage facilities: A unique challenge for a critical industry

Mining of our natural resources is a critical industry necessary for innovation toward a modern, sustainable lifestyle and economy. It provides the raw materials and minerals necessary for everything from household appliances, personal electronic devices, advanced medical devices, and public infrastructure to renewable energy production and storage. A lesser-known component of this critical industry are tailings storage facilities.

What are tailings storage facilities?

While most people are familiar with the open-pit mine or underground mine work from which ore is extracted, the tailings storage facility is a component of the mine that is largely unknown by the general public. As part of the mining process, the ore is crushed, ground, and/or processed to extract the valuable minerals and metals. The remaining materials are then referred to as tailings, which must be contained within the tailings storage facility and managed in a safe and sustainable manner.[1]

As noted by the Society for Mining, Metallurgy & Exploration (SME), containment of tailings can take many forms depending on site‑specific factors, including “environmental, climatic, seismic, and geologic conditions, ore type, processing method, production rate, geochemistry, and topography.”[2] For example, conventional slurry tailings are often deposited hydraulically into cells contained by earthen embankment dams, whereas filtered tailings are dry enough to be placed and compacted into mounds that may not require containment dams. Tailings may also be stored within abandoned mine pits or used to backfill underground mine workings. In addition to the solids, the tailings storage facility must also consider containment of water for reuse in the mining process and/or to minimize seepage to the environment.

What makes tailings storage facilities unique for engineers?

From the various site‑specific factors listed that influence tailings storage facilities, it isn’t surprising that each tailings storage facility is unique, and there are no standard solutions. Tailings storage facilities are large, complex projects requiring the expertise and collaboration of many different engineering disciplines to ensure they are designed, constructed, operated, and monitored in a safe manner. Furthermore, the lifecycle of a tailings storage facility may span over the entire career of an engineer, or even beyond, considering that closure of the facility requires safety into perpetuity.

Tailings storage facilities are large, complex projects requiring the expertise and collaboration of many different engineering disciplines to ensure they are designed, constructed, operated, and monitored in a safe manner.

Tailings management also requires specific technical knowledge about tailings processing methods, geotechnical characterization, and water management that are beyond the scope of typical engineering practice. Owners of tailings storage facilities and their engineers, along with the mining industry as a whole, must be dedicated to continued education and ongoing research to develop engineering tools and methodologies that are tailored to the unique nature of tailings.

For geotechnical engineers, who are responsible for the stability of tailings storage facilities, this requires an understanding that tailings are fundamentally different from natural soils encountered in other types of projects. Hydraulically‑deposited tailings may have high water content and be in a loose state, much more so than would generally be expected in nature. Tailings deposits are also extremely young on a geologic time‑scale, meaning they have not undergone significant aging or consolidation. Tailings may also be composed of very fine silt‑ and clay‑sized particles due to mineral processing, even though they may not contain clay minerology or exhibit the associated plasticity.

In combination, these factors make some tailings deposits susceptible to a phenomenon called static liquefaction—the sudden loss of strength when loose soil is loaded and unable to drain, usually caused by a triggering event. Several of the recent tailings dam failures have been partially attributed to this phenomenon, leading to heightened attention across the mining industry to this specific mechanism, as well as other considerations for safer tailings management.

What is the future of tailings storage facilities?

While tailings storage facilities have overall been well managed with few incidents of failure, the catastrophic consequences of recent tailings dam failures inspired a robust movement of technical advancement and development of governance protocol for tailings management. Groups, such as the International Council on Mining and Metals (ICMM) and the International Commission on Large Dams (ICOLD), have convened to develop guidance documents addressing technical and social aspects of responsible tailings management. Mining companies are also investing in research through academia and their consulting engineers to explore the best‑available technologies and practices.

For our part in the future of tailings storage facilities, Barr collaborates with the mining industry through involvement in various forums, committees, workshops, and conferences, sharing our expertise developed over decades of providing tailings management services. Examples of our involvement include contributions to the:

  • Canadian Dam Association (CDA) technical bulletin on tailings dam breach analysis

  • Canada’s Oil Sands Innovation Alliance (COSIA) tailings technology research

  • Society for Mining, Metallurgy & Exploration (SME) Tailings Management Handbook

  • Tailings and Industrial Waste Engineering Center (TAILENG) advanced academic research

  • Tailings and Mine Waste (TMW) conference proceedings and presentations

Interested in learning more? Connect with Barr staff Jed Greenwood and Nathan Toohey at the upcoming International Conference on Tailings Management taking place June 14 to 16 in Santiago, Chile.

Contact us to learn more about our tailings management services.

 

[1] International Council on Mining and Metals, Global Tailings Review. About Tailings.

[2] Society for Mining, Metallurgy & Exploration. An Introduction to Tailings Facilities.

About the authors

Iván Contreras, senior geotechnical engineer, has more than three decades of geotechnical engineering and project management experience for projects in the United States, Canada, and Central and South America. This work has ranged from the conceptual design of small reservoirs to detailed design of oil-storage-tank foundations and slope-stability remediation. Iván lends his expertise in the areas of mine tailings-dam design and management; embankment, slope, foundation, tunnel, and underground structure design; landslide stabilization; ground improvement and grouting; soil dynamics and earthquake engineering; dredged material management; and in-situ testing.

Jason Harvey, senior geotechnical engineer, has performed extensive work related to tailings management for mining clients in North America and internationally. His work has focused on in situ and advanced laboratory testing for the geotechnical characterization of mine tailings; analysis and design of tailings storage facilities; and performance monitoring and evaluations in support of ongoing tailings storage facility construction and operations. He has also performed dam safety reviews and contributed to independent third-party reviews of tailings storage facilities.

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Dry-stack tailings management

An industrial sand producer historically disposed of its fine tailings by slurrying them to old mine pits, but over time, the pits’ capacity for tailings disposal became unsustainable. Around the same time, one of its tailings basin dams failed due to uncontrolled seepage. Barr was hired to provide emergency response for the dam failure and to evaluate alternative tailings-management approaches.

Sand and gravel extraction.

Tailings dam safety inventory and semiquantitative risk analysis

Seeking to inform future decision making related to risk mitigation and environmental stewardship, Nutrien retained Barr to complete a system inventory and semiquantitative risk analysis (SQRA) for its more than 100 earthen dike segments across six potash mines in Saskatchewan, Canada.

instrument monitoring at a potash mine tailings basin.

 

Tags:

mining tailings

 

Iván Contreras, Senior Geotechnical Engineer
Iván Contreras
Senior Geotechnical Engineer

 

Jason Harvey, Senior Geotechnical Engineer
Jason Harvey
Senior Geotechnical Engineer
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