Innovation in tailings management
Antofagasta Minerals manages its tailing and waste dumps to the highest safety standards and will continue to implement secure, innovative and efficient solutions for disposing of its mining waste, both during mining operations and after closure.
The Group’s commitment to the responsible management of its mining waste exceeds legal requirements. In 2016, the ICMM issued a new standard for tailing dams and for the prevention of catastrophes1, to which the Group adheres and is committed to implementing at its operations.
1 The complete document “Position statement on preventing catastrophic failure of tailings storage facilities” can be found at: https:// www.icmm.com/website/publications/pdfs/position-statements/161205_icmm-position-statement_tailings-governance.pdf
Every process used to separate minerals from rock produces considerable quantities of mining waste, deposited in sterile material dumps, and spent ore and tailings storage facilities. Tailings from copper mines are transported to purpose built facilities.
Chilean legislation sets specific conditions in which the construction of tailings dams and storage facilities can be undertaken. These regulations determine the facilities’ design and apply both during their operation and after closure. Compliance is monitored regularly by the relevant authorities.
Chile has the third largest number of tailings storage facilities in the world, and the volume of tailings produced could double over the next 20 years1.
Because of their mineral extraction processes, Antucoya, Centinela Cathodes and Zaldívar’s mining waste is spent ore, while Los Pelambres and Centinela Concentrates have tailings. All require sterile material dumps.
At Los Pelambres, due to the complex geography and size of the operation, the challenge facing the Group is to maintain the physical and chemical stability of the tailings storage facilities. The Quillayes tailings dam is a backup for emergency situations and the Mauro dam, in the Pupío Valley, has a capacity of 1.7 billion tonnes.
1 Taken from the study: “Mining – A Platform for the Future for Chile”.
Physical and chemical stability are two key concerns when designing and commissioning any tailings storage facility, which will contain water and tailings composed of materials such as fine sand, silt and clay.
Ensuring the chemical stability of mining waste involves separating natural water from process water. The tailings facilities at Quillayes, Mauro and thickened tailings at Centinela were designed to divert natural water before it encounters the waste. The water can then be channeled to a point below the dam’s retaining wall. The quantity and quality of the water that is returned to the natural watercourse is defined in the dam’s operating regulations and is inspected by the Water Agency and is also monitored by the community.
It is absolutely essential for local communities to have contingency plans in place in case of possible emergencies and disasters involving tailings storage facilities.
INNOVATION IN TAILINGS
The Group pioneered the use of thickened tailings technology on a large scale at Centinela. This uses water more efficiently and creates more stable tailings deposits that require less space. Its implementation posed several challenges, not least of which was achieving the required levels of thickness. The lessons learnt were then incorporated into Centinela’s Second Concentrator project, which will increase the capacity of the facility from 700 to 2,600 million tonnes of tailings, extending the life of Centinela until 2056.
In 2016, the Group generated more mining waste than in 2015, mainly due to the commissioning of Antucoya and the acquisition of Zaldívar.
ONLINE MONITORING OF TAILINGS DAMS
Antofagasta Minerals participates in a technology programme for the online monitoring of tailings storage facilities. This is organised by the Chile Foundation and participants include the public and private sectors as well as research bodies.
The programme seeks to develop an online monitoring system to improve the management of tailings dams and reduce the risk perception while improving communication with local communities. It involves the use of innovative technology to measure the facilities’ physical and chemical stability, thus providing real-time, quality information to different users. With this in mind, a pilot project is planned for the Mauro dam.
Mining processes generate hazardous and non-hazardous waste. The former, mainly oil and used batteries, is stored according to regulations for disposal or recycling. Examples of nonhazardous waste include mud, wood, high-density propylene sheets and tyres, all of whose management is standardised.
The recycling of reusable waste such as scrap metal, wood and cardboard is encouraged at all of the operations.