Tailing management: The role of technology

Tailings are simply a by-product of mining. They are produced after ore containing an economicallyrecoverable commodity is mined from the earth. After the commodity of value is extracted from the ore material, the resultant waste is called tailings. Typically, mill tailings range from sand to silt-clay in particle size.

In order to safeguard the environment and people it is imperative that a high standard of Tailings management is observed. Tailings management involves storing the mining waste in speciallydesigned impoundments called tailings facilities (TSF).

The first step in designing a TSF is to identify potential sites and define the environmental compliance criteria and measurement points. Significant factors that influence the design of a TSF are the climate, geology, potential seismicity, topography, proximity to areas of human habitation, forest reserves, freshwater or marine ecosystems, and downstream infrastructure. The site criteria may influence the selection of an appropriate TSF site and or the configuration of the TSF, and or the method of tailings deposition and management.

The appropriate design of a TSF requires a high degree of sophistication and rigour. The ultimate capacity of a TSF is determined by the expected production over the life of mine. There is usually a negligible difference between the ore milled and the tailings that are generated. The life of mine is determined by the size of the ore body and the rate of mining or processing. Typically, this ranges between 5 and 50 years.

Commonly, the life of a mine is extended as additional resources are discovered. Therefore, the size of the TSF and its ability to be expanded should form part of the layout considerations.

All TSFs require deposition planning and modelling, but the level of rigour associated with these is site-specific. The deposition modelling typically builds upon stage capacity relationships developed to assess the rate of rise and total storage capacity requirements of the TSF.

At the early stages of design, key aspects considered include pond location and management, deposition points, numbers of spigots, and beach profile. Storage of tailings typically requires confining embankments of various types to form impoundments that retain the tailings solids, supernatant water, and rainfall. The construction method is named based on the direction the dam’s crest moves as additional levels (dikes) are added.

In Upstream Construction, the dam crest progresses upstream as the height of the tailings facility increases. Tailings adjacent to the dam must be welldrained and may therefore be used to support subsequent levels as the dam is raised. Downstream Construction on the other hand requires the dam crest to progresses downstream as the height of the tailings facility increases. The dam is constructed and supported on top of the previously placed material. And with Centerline Construction, the dam crest is raised vertically. The dam’s crest is maintained as the height increases.

The upstream portion is constructed on top of previously placed tailings while the downstream portion of the dam is constructed on previously placed materials.

Globally, there are thousands of mine tailings facilities that hold billions of tons of mining by-products. These tailings storage facilities pose significant environmental, social, and financial risks to mine operators and the communities in which they are located. Mine operators take these responsibilities seriously and are investing in new technologies to manage their tailings more effectively.

In response to recent events and the continuing risks, the Global Tailings Review has released the Global Industry Standard on Tailings Management dubbed the “Standard.”

The plan entails developing a design for each stage of construction of the tailings facility, including but not limited to startup, partial raises and interim confi gurations, final raise, and all closure stages.

Also designing the closure phase in a manner that meets all the Requirements of the Standard with sufficient detail to demonstrate the feasibility of the closure scenario and to allow implementation of elements of the design during construction and operation as appropriate. The design should include progressive closure and reclamation during operations.

The aim is to achieve the ultimate goal of zero harm to people and the environment with zero tolerance for human fatality. It requires Operators to take responsibility and prioritise the safety of tailings facilities, through all phases of a facility’s lifecycle, including closure and postclosure. It also requires the disclosure of relevant information to support public accountability.

In response mining companies have turned to technology to help then navigate the required standards of tailing management. Remote sensing for example can play a critical role in the monitoring of tailings facilities and includes satellite, aerial, and groundbased platforms. Satellites can capture Interferometric Synthetic Aperture Radar for early detection of structural changes, and multispectral platforms can quantify surface water content for quickly calculating beach lengths that can be compared against Trigger Action Response Plans (TARPs).

Using collected data, advanced analytics (i.e., AI and machine learning) can be performed to generate key business insights, indicate TSF risk levels and provide recommendations for mitigating actions. The TSF management workforce can view intelligent and intuitive visualizations to enable effective and timely decision-making processes for dam maintenance. Recording corrective actions and updating models accordingly help to further minimize risks.

Overall, improving TSF management practices, organizational approaches and corporate governance are achievable goals for the ongoing success of a mining operation—and for the mining industry to meet its societal and regulatory responsibilities.