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As part of the mining process, large volumes of mine wastes—including waste rock and tailings—may be produced. We manage these wastes based on accepted best practices.

MANAGING MINE WASTE

Mining involves the extraction of ore—the rock containing economically recoverable amounts of desired metals—from the host rock. To access the ore deposits, waste rock must be removed and stored in waste rock dumps and, after processing, mine tailings may be produced and stored in engineered tailings storage facilities (TSFs).

Heap Leach Management

At some sites, gold ore is processed using heap leaching. With heap leaching, ore is generally crushed to approximately the size of large gravel particles and placed on an impermeable geomembrane liner system. The ore is then irrigated with a chemical solution that dissolves the desired metals; this solution is typically sodium cyanide (for gold recovery).

The composite liner, a combination of clay soils and impermeable synthetic membranes, is designed so that no solution escapes the leach pad.  Equally important, the composite liner system also allows Barrick to recover the leach solution carrying the dissolved metals for further processing. Leak detection, down-gradient monitoring, and other safety features are also typical of our designs. 

The crushed ore in HLFs remains after the gold has been extracted and the leach solution has been recovered. At the end of operations, the heap-leached ore is rinsed by recirculating solution and then is allowed to drain down, facilitating both maximum gold recovery and environmental protection. Any residual seepage, captured by the liner system after closure, is treated to meet water-quality standards before being released to the environment. We then work to re-integrate the closed HLF with the existing, surrounding environment. For example, at some sites we have re-contoured the HLF and capped it with a multi-layered soil cover that minimizes rainwater infiltration and allows revegetation.

Barrick did not experience any heap leach facility geotechnical incidents in 2017.

Waste Rock Management

Mining involves the extraction of ore – the rock containing economically recoverable amounts of desired metals—from the host rock. The waste rock—the rock that does not contain economically recoverable amounts of desired metals—must also be removed, though mining plans minimize the amount of waste rock relative to extracted ore as much as possible. In 2017, Barrick deposited 52.2 million tonnes of waste rock to waste rock facilities.

Because waste rock naturally contains concentrations of potentially harmful elements, the material must be properly managed to reduce the risk of contamination associated with acid rock drainage (ARD) and/or metals leaching (ML). Across Barrick’s operations, approximately 53% of the waste rock deposited in 2017 had the potential to generate ARD/ML. To manage this risk, Barrick has implemented mitigation management at operations where the waste rock, heap leach and/or tailings have demonstrated the potential to generate ARD/ML.

Waste rock is generally placed into engineered waste rock storage facilities which, once full, can be re-contoured, covered with soil, and revegetated.  In some cases, waste rock can also be used to backfill open pits or underground tunnels.  Waste rock that has high potential to generate ARD/ML can be encapsulated by non-reactive waste rock or co-disposed in tailings storage facilities where it is submerged to significantly limit geochemical reaction rates, thus minimizing ARD/ML. At times, non-reactive waste rock—material that does not have the potential to generate ARD/ML—may be used to construct road beds or tailings dams.

Barrick is a member of the International Network for Acid Prevention (INAP). We have participated in the ongoing revisions of the INAP Global Acid Rock Drainage (GARD) Guide, a worldwide reference for ARD prevention and mitigation. Experts from Barrick and several countries contributed their knowledge to the Guide’s development and revision. The GARD Guide will continue to be updated as knowledge increases. INAP is also currently working on identifying key areas for further research, including waste rock cover guidance.

Mercury Waste Management

Mercury is a naturally occurring element that is present, at some operations, in the ore we process. As a result of processing, mercury is separated from the ore. Depending upon mercury concentration in ore and other risk factors, Barrick employs a variety of controls, including retorts, scrubbers, condensation towers, and activated carbon filters, to trap mercury vapor before it can be discharged to the atmosphere. Mercury condensation and safe storage are part of our safe practices on site.

Mercury wastes generated from these air pollution control devices must be responsibly managed to minimize potential risks to human health and the environment. Barrick promotes responsible management of mercury by following our Environmental Management System, applicable regulatory framework, and the ICMM position statement on mercury risk management. In 2017, Barrick captured and stored 158 tonnes of mercury at our mine sites. ? In addition, the Veladero mine captured and stored 57 tonnes of mercury and the Porgera mine captured and stored 19 kilograms in 2017.

Managing Mercury Waste

Barrick employs a variety of controls, including retorts, scrubbers, condensation towers, and activated carbon filters, to trap mercury vapor before it can be discharged to the atmosphere.

Mercury ProducedMetric Tonnes

As required by the Mercury Export Ban Act (MEBA), Barrick ceased the export of elemental mercury from U.S. facilities in January 2013. MEBA mandated that the United States Department of Energy construct a federal mercury repository to accept elemental mercury generated by mining and other activities, but to date the repository has not been built. Therefore, elemental mercury captured from air pollution controls at our U.S. operations is currently stored pending the construction of the federal mercury repository. Mercury compounds are disposed of at a licensed hazardous waste facility in compliance with applicable law. Strict handling, packaging, and transportation procedures are in place to help protect both people and the environment against mercury exposure during shipping.

In the case of operations at Latin American sites, elemental mercury is currently securely stored on site in compliance with applicable law. However, the company is actively seeking responsible ways of stabilizing the elemental mercury in a solid form (as mercury sulfide or cinnabar) and then continuing with a safe and final disposal of this residue on a long-term basis. The objective of this initiative is to align with current international efforts, such as the UN Minamata Convention, to find alternative technologies for certain industrial processes that depend on mercury and to avoid, if possible, the availability of elemental mercury in the global market.

Non-Processing Waste Disposal

A number of non-process wastes are generated each year at our operations. These wastes may differ by country and by operation, but typically include scrap metals, waste oils, cans and bottles, spent tires, and office and camp waste. While we try to recycle these wastes as much as possible, this is not always feasible at some of our remote sites or at operations located in countries where recycling is not available. Non-hazardous waste that is not recycled is usually landfilled (either in municipal landfills or landfills constructed on the mine property) or incinerated ? Incineration is the process of treating waste by combustion of organic substances contained in waste materials., on or off the site.

We also generate a relatively small amount of hazardous waste each year. These wastes include batteries, fluorescent lights, certain oils, solvents, electronic waste, and laboratory assay wastes. As with process materials, the types of hazardous wastes vary among our sites; however, all are recycled or disposed of according to the appropriate regulation in the countries where we operate.

Riverine Tailings Management

The Porgera mine in Papua New Guinea is operated by Barrick Niugini Limited (BNL), an independent operating entity which is jointly owned by Barrick and Zijin Mining. The mine deposits the majority of tailings material into a nearby river under government permit and regulation and BNL’s own internal oversight.

When Barrick acquired the Porgera mine in 2006, we extensively investigated alternative waste management methods to replace the existing riverine tailings disposal process. No practicable alternatives were found due to a number of factors, including the steep and unstable terrain, high rainfall, frequent landslides, and seismic activity surrounding the Porgera mine.

Ongoing monitoring results show that the river system is operating as expected and that, downstream of the mixing zone, water quality and sediment are consistent with the stringent metal limits established by the Australia and New Zealand Environment and Conservation Council. To date, the mine has not exceeded environmental permit water quality compliance levels.

In the future, Barrick will build mines that rely on other methods of disposal of mining and processing material, and avoid riverine tailing disposal methods.

Despite this, in the future, Barrick will build mines that rely on other methods of disposal of mining and processing material, and avoid riverine tailing disposal methods.

More information about Porgera and riverine tailings disposal