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What are tailings and tailings storage facilities?

Tailings are the left-over materials from the processing of mined ore. They consist of ground rock, unrecoverable and uneconomic metals, chemicals, organic matter and effluent from the process used to extract the desired products from the ore.

Tailings generally leave the mine processing plant in a slurry form (diluted with water) and are often but not always stored on the surface in storage facilities called tailings dams, or tailings storage facilities (TSFs).

TSFs are dynamic structures that could comprise of multiple dams (or cells) that have contiguous, structurally similar interconnected walls but are operated under the same tailings disposal regime.

How tailings dams differ from conventional water dams

The principal difference between tailings dams and conventional water dams is that tailings dams are dynamic structures that grow over the life of the mine to accommodate increased tailings. Tailings dams, and particularly ‘upstream’ dams (see types of dams below), often rely on the strength of hydraulically placed tailings that are variable in strength due to mine processing changes, operational practices on deposition and climate variations.

Tailings dams are usually constructed from earth and rock waste materials from the mine with variable design life whereas water storages can be constructed from earth and rock and also concrete and other materials.

Life cycle of tailings dams

Tailings dams need to evolve over their life cycle, from planning, design, construction, operation, closure and post closure. There may also be periods of care and maintenance between operational phases.

 

Life of tailings 

 

The closure phase of a tailings dam can often exceed the operational phase. It may include transition from operations to active care such as ongoing water, geochemical and physical management to maintain integrity.

Over time, inactive TSFs may transition to passive care when the ongoing water, geochemical, and physical management requirements are reduced or eliminated.

Types of tailings storage facilities construction

There are three broad types of tailings dam construction. The choice of design is based on factors such as dam siting, geology, seismicity, climatic conditions, construction materials and the nature of the tailings.

 

 

 

Key factors that may influence tailings dam integrity

Maintaining dam integrity requires ongoing focus on appropriate engineering design, quality construction, operating discipline and effective governance. Key factors that influence dam integrity include: consideration of site conditions (such as seismicity, climatology, geology, hydrology, tailings characteristics, etc.), the quality of assurance and quality control of dam construction, and ongoing dam operating discipline, including: tailings characteristics, water management, monitoring and considerations of changes.

For more information on how BHP approaches management and governance of our TSFs, please see Tailings storage facility management: Governance, our strategy, risk management and key target.


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