SUSTAINABILITY Tailings Storage Facilities

Tailings Storage Facilities

Background

Tailings are the mineral waste remaining after ore processing to extract mineral concentrates and are typically stored within an engineered containment structure known as a tailing storage facility or TSF. Tailings differ from overburden: the waste rock or other material that overlies an ore or mineral body and is displaced unprocessed and stockpiled separately (or co-disposed with tailings) during mining.

Tailings can be in the form of liquid, solid, or a slurry of fine particles.

The first step in designing a TSF is to identify potential TSF sites and define the environmental compliance criteria and their point(s) of measurement. 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 mine is extended as additional resources are discovered. 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 embankment type under consideration may need to be constructed to the standard typically attributed to water retention dams. The confining embankments are typically raised progressively through the life of the TSF in either an upstream, downstream, or centerline direction.

Gold Fields continuously works to earn the trust of the communities in which they operate and to gain the support and approval of stakeholders. At Gold Fields, stakeholder consultation, information sharing, and dialogue are paramount. We strive for this to occur throughout the TSF design, operation, and closure phases, so viewpoints, concerns, and expectations can be considered for all aspects of planning execution. Regular, meaningful engagement between Gold Fields and its affected communities is significant for developing trust and preventing conflict.

The overall closure design objective is to construct a facility (or facilities) that will sustainably retain the tailings at that site in perpetuity. Gold Fields TSFs incorporate closure objectives and expected outcomes, the final TSF landform, and agreed ultimate land use. From an environmental perspective, the tailings management plan's most critical aspects are incorporating environmental factors in the design criteria and the operational management of environmental risks integrated into the operating manual.