Safety |
j All of Vale’s mining dams are monitored 24 hours a day, seven days a week by the Geotechnical Monitoring Centre and undergo regular inspections by internal and external teams. Vale says it remains committed to complying with the best international engineering practices, always focusing on the safety of workers and communities neighbouring the structure. The mining company adds that “one of the pillars” of its work in guaranteeing that dam collapses such as Brumadinho will not be repeated is the elimination of all upstream dams in the country. This is to be carried out in the shortest possible time, with key consideration to the safety of people, workers and the environment. Since 2019, seven of the 30 mapped structures (four in Minas Gerais and three in Pará) have been de-characterised and reintegrated into the environment through the company’s R$ 10 billion De- characterisation Programme. As such interventions can increase risks, especially for dams with the most critical alert level (level 3), Vale built large containment structures to protect the communities that live nearby and enable the works to be carried out more safely. The company has also been developing, together with its suppliers, innovative technologies to improve worker safety. One solution is the remote operation of equipment such as tractors, excavators and trucks. On 8 February 2022 Vale announced that 40% of the
company’s upstream structures will be eliminated by the end of the year. The de-characterisation process has just started at Dike 4, of the Pontal System, in Itabira.
At the same time, and in line with international best practices for dam management, the company says it has intensified preventive, corrective and monitoring actions in its structures, advancing towards the goal of having no dam in critical condition (emergency level 3) by 2025. The latest update indicates that 90% of dams of this type will be eliminated by 2029 and 100% by 2035. According to Vale, the elimination of upstream dams is part of the cultural transformation process that the company has been going through since the Brumadinho dam collapse. In Brazil, the de- characterisation is also one of the main milestones in the evolution of Vale’s dam management model focused primarily on the safety of structures and people who live nearby. The model is in line with the Global Industry Standard for Tailings. Vale, as a member of the International Council on Mining and Metals, has made a public commitment to be 100% compliant with the global standard’s 77 requirements in all of its tailings disposal facilities by 2025. The company says it plans to end 2025 with a new and higher level of safety in its operations.
Innovative tailings monitoring Luna Innovations has launched a new structural health
Zululand tailings dam failure On 24 December 2021, a slurry dam wall failure at the Zululand Anthracite Colliery in South Africa resulted in a pollution spill of 1500m3
of coal slurry. An
engineering firm has been appointed to confirm the exact root cause of the failure and the investigation is currently in process. The end wall of slurry pond 3 had been newly installed following the loading out of dry slurry during November 2021. Four days prior to the failure 66mm of heavy rain was also recorded. Immediately after the spill, all pumping to the slurry ponds was stopped. The
end wall of the slurry pond was rebuilt and is awaiting professional engineer certification before being brought back into service. The integrity of the other slurry pond containment walls will also be checked, and improvements made where necessary. In the medium term, a filter press will be installed in the coal washing plant, to
remove the slurry from the water, and minimise the likelihood of slurry spilling in future. This action is planned for completion by the end of March 2022. Numerous surface and groundwater monitoring points have been utilised to monitor groundwater and surface water quality, and monitoring will continue for the next 12 months. Further monitoring downstream towards the estuary is being conducted in accordance with directives from relevant authorities. On 18 January, ZAC met with the joint operations committee made up of the Department of Mineral Resources and Energy, the Department of Water and Sanitation, the KZN Department of Economic Development, Tourism and Environmental Affairs, and Ezemvelo KZN Wildlife. ZAC provided them with relevant updates on clean-up efforts and investigations into the incident. It says it is complying with directives from relevant regulatory authorities and setting out monitoring of the potential negative impacts of the incident. ZAC has been producing and washing anthracite in the Okhukho area of Zululand for the last 38 years. It is located 25km from Nongoma, and 40km from Ulundi, in the heart of rural Zululand. Areas of interest bordering the mining area are the Mfolozi River, and the Mfolozi section of the Hluhluwe Mfolozi game park. ZAC employs 1100 people in the area, either directly or as contractors servicing the operation. As a vital cog in the local community, ZAC says it appreciates the importance of managing the varied demands placed upon it, while operating sustainably and for the benefit of the local community.
monitoring solution for the mining industry to monitor tailings dam structures. Combining Luna’s systems for both distributed sensing and discrete sensing, the new solution claims to be comprehensive and economical. Deployed in Canada, Brazil and Asia, Luna’s innovative fibre optic sensing solutions help mining operators mitigate risks by providing an early warning of a potential issue.
“Our deployments in tailings dams are a
clear example of how Luna’s breadth of fibre optic capabilities combines to deliver a more comprehensive and effective solution to help ensure the safety of infrastructure like tailings dams,” says Luna’s President and CEO, Scott Graeff. “With thousands of such dams around the world, Luna is pleased that our initial deployments throughout the globe are successfully operational and actively monitoring these critical structures.” In December 2020, Luna acquired distributed acoustic sensing capability with the acquisition of OptaSense. Throughout the course of 2021, the OptaSense products were improved and integrated with Luna’s fibre optic sensing solutions resulting in significant new capabilities for long-range monitoring of critical infrastructure. The tailings dam monitoring solution combines distributed acoustic and strain monitoring acquired from OptaSense, with Luna’s discrete point monitoring systems based on fibre Bragg grating sensors. The result is a comprehensive system able to monitor major events throughout an entire site while also able to look inside structures at critical parameters which can be precursors of potential events, such as pore pressure and spot inclination. This integrated structural health monitoring solution is also applicable to many other infrastructure projects beyond tailing dams such as bridges, tunnels and other major structures. ●
28 | March 2022 |
www.waterpowermagazine.com
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