Goldcorp in a recent blog post raised the timely topic of how it and the industry can take tailings technology forward. Tailings dams rank among the largest engineered structures in the world, sometimes reaching up to 300 m in height. These dams are designed to permanently contain finely ground mineral processing waste, a watery slurry of rock particles that are left behind after mineral extraction and are placed in an impoundment.
“The greatest tailings management danger is dam failure. The most recent deadly dam collapse on January 25, 2019, at Córrego do Feijão near the Brazilian town of Brumadinho, resulted in an 11 million cubic metre tailings deluge (essentially a massive mud flow) stretching for 8 km, which engulfed buildings and anything else in its destructive path. Most tragically over 300 people may have lost their lives as many remain missing and are presumed dead. Many mining communities are now casting an anxious eye towards any wet tailings storage facilities in their locality, and are seeking assurances regarding their structural integrity and maintenance.”
“In Canada, Goldcorp has active tailings facilities at our Porcupine (PGM), Red Lake and Musselwhite operations, and a filtered tailings operation at Éléonore. Inactive tailings storage facilities in Canada are at PGM and at our closed sites at Equity Silver and Dona Lake. In Latin America, we have active tailings facilities at Peñasquito in Mexico, Cerro Negro in Argentina, and at Pueblo Viejo in the Dominican Republic (where we have an equity interest, operated by Barrick), inactive tailings storage at Marlin in Guatemala and inactive filtered tailings at El Sauzal in Mexico. Our Peñasquito Mine’s tailings embankment is Goldcorp’s largest tailings facility – at completion the structure will be 11 km long and almost 150 m high.”
In 2014, Goldcorp developed a tailings stewardship program to minimise tailings risks and ensure good practices for tailings construction, operation, maintenance, monitoring and, ultimately, closure and reclamation. The strategy addresses stakeholder concerns to ensure tailings facilities are well-managed, provide secure storage, reduce costs and impacts, improve operational excellence and are regularly and consistently monitored.
“We work to preserve and protect our environment through our Sustainability Excellence Management System (SEMS) and our Environmental Protection Standards. There are 13 Environmental Protection Standards (EP), and two specifically covering Waste Rock and Tailings:
EP 4: Waste Rock
Waste rock has the potential for leaching metals and other constituents of concern upon exposure to elements. This standard contains the requirements for waste rock management and monitoring as a critical aspect of operational controls at any site.
EP 5: Tailings
Goldcorp will manage tailings in a manner that effectively mitigates environmental, public health and safety, and community impacts while maximizing the long-term security of the tailings facility and sustainable land use options.
“All active Goldcorp tailings dams have a Tailings Steward and an Engineer of Record (EoR), and all inactive tailings dams still storing water also have a Tailings Steward. All but one inactive tailings site also have EoRs, and the final site is being assigned an EoR in 2019. Dam Safety Inspections (DSI) are performed annually and separately by the Tailings Steward and by the EoR. Each DSI group performs their reviews independently and publishes and submits separate reports. EoRs submit their reports to site, and Stewards submit their reports to Corporate. Dam Safety Reviews (DSR), a much more intensive effort, are performed every 5 years for all dams by the Tailings Stewards. Risk Assessments are updated annually supported by the Stewards and the EoRs for every dam. Summary reports are provided to each site and corrective actions are reviewed.”
Risks are categorized from low to extreme and a watchlist of all risks are monitored on Enablon, a leading provider of environmental, health and safety (EHS), operational risk management and sustainability software. Results from risk assessments are evaluated regularly to ensure risk mitigation is applied where needed.
“Goldcorp has also tested new technology that could ultimately improve tailings storage facility management with the potential to set a new standard for dam monitoring that exceeds industry and government regulations. The automated monitoring system includes a solar power source, data loggers, radio monitoring stations, automated survey station, weather station, digital cameras and strategically-placed sensors and prisms to monitor and capture up-to date information on water levels, pore water pressure, structural integrity of the dam, and other important parameters that ensure dam safety and reliability.”
Mike Jacobs, Goldcorp’s Director, Water & Tailings, is responsible for monitoring and reviewing Goldcorp’s tailings facilities and also serves on the Mining Dams Committee for the Canadian Dam Association and the Tailings Working Group for the Mining Association of Canada. “Tailings represent the most significant environmental liability for a mining company,” says Jacobs. “Our standards at Goldcorp exceed what is expected of us by law but as responsible corporate citizens and in fulfilling our vision of Together, Creating Sustainable Value, it is important that we be leaders in this effort and do what is right”.
Dewatering is an important part of traditional wet tailings storage. As tailings are added to the storage facility, water is usually returned to the mill for reuse. This also reduces the hydraulic pressure on the dam walls. Goldcorp has become a leader in filtered tailings (also known as “dry stack”). “We currently filter tailings at Éléonore and utilized filtered tailings at our closed Marlin and El Sauzal sites. Filtered tailings return significantly more water to the mill, which allow us to materially reduce freshwater make-up requirements as compared to traditional tailings impoundments.”
“We have taken this a step further in pursuit of our Towards Zero Water (H2Zero) vision and are developing our mine waste management technology called ‘EcoTailsTM’. The EcoTailsTMprocess [co-developed with FLSmidth] represents a transformational leap forward in tailings and waste rock management. In essence, EcoTailsTM is a co-mingled mix of dewatered tailings and waste rock blended in transit – creating a geotechnically stable product called ‘GeoWasteTM’. This process eliminates the need to keep conventional slurry tailings contained in a dam and submerged in water. Additionally, GeoWasteTM is stronger and drier than ‘dry stack’ tailings and has the potential to drastically reduce environmental risks.”
“We are in the process of completing our engineering feasibility study for the full-scale Prototype, which we hope to advance, following the installation at our Peñasquito mine,” said Simon Hille, Goldcorp’s Vice President of Metallurgy and Process, who envisions scaling-up the technology to make it cost-competitive against the industry standard and at high volumes, while producing a much more stable and lower risk facility for long-term tailings storage. “The recognition that mining is a water-intensive process led to this and other innovations such as our H2Zero initiative, and our aim is to both substantially reduce fresh water consumption and ultimately eliminate conventional slurry tailings, currently the largest store of unavailable water in the mining process.”
“The recent devastating tailings dam failure in Brazil serves as a reminder that the industry has a significant responsibility to ensure proper tailings management. Goldcorp’s progressive approach to tailings management and our broader environmental stewardship is essential for our mines which operate near host communities, not only to maintain our license to operate, but more importantly to build trust. Through our continued tailings management innovations, environmental and community impacts caused by tailings dam failures will be eliminated and allow mining to continue playing a vital role in society.”