Engineering & Mining Journal

SEP 2018

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Page 47 of 75

TAILINGS MANAGEMENT 46 E&MJ • SEPTEMBER 2018 If visual prominence is an indication of status on typical plant flowsheets, tail- ings rank below even the least valuable byproduct. The vague "To tailings…" box at the bottom right of most process diagrams says it all — get this material out of the plant quickly and store it some- where, preferably as cheaply as possible. However, the industry's approach to- ward tailings is changing, influenced by regulatory scrutiny, societal concerns and an expanding awareness by producers that tailings management involves decisions relating to many of the same resources — water, land and energy, for example — used in primary metals production. And, because each of these resources carries a monetary value, improvements in tailings management may present opportunities to cut costs and reduce capital expendi- ture. In rough mathematical terms, better tailings management ≈ money. Perhaps even more important than budget relief is the stark realization that unplanned natural events, inattention to or shortchanging of tailings storage prac- tices can result in company-damaging di- sasters such as the failures of the Fundão tailings dam in Brazil in November 2015 and the Mount Polley dam in British Co- lumbia in August 2014. Already this year, the WISE project, which publishes an on- line chronology of major tailings dam fail- ures, lists four major failures through June with the largest in Mexico, involving a re- ported release of 249,000 m 3 of tailings and 190,000 m 3 of embankment material. The high-profile failures in Brazil and Canada and others galvanized the indus- try, regulatory agencies and engineering companies to take a more focused look at tailings handling and storage practices. As in most cases involving mine sites, the eventual outcome of this scrutiny won't be a one-size-fits-all solution. Worldwide, depending on which country, state or province it's located in and its size and height, a tailings dam can be subject to oversight by several legislative acts and agencies. A recent report published by the United Nations Environment Program (UNEP) acknowledges that mining is a complex industry, but in order to improve the safety of tailings storage facilities, it requires a change of focus. "Industry and regulators need to adopt more holistic thinking, which is flexible enough to allow for site variation, but which also clearly identifies best practices. Most important- ly, these best practices need to be compe- tently implemented," it concluded. Check the List One of the more comprehensive docu- ments to emerge from the industry's in- creased attention is the third edition of the Mining Association of Canada's (MAC) Guide to the Management of Tailings Fa- cilities, which was updated after a review of the association's tailings management policies following the Mount Polley in- cident. A major feature of the guide is the inclusion of checklists that provide a starting point for developing a site-spe- cific tailings management system. The checklists, according to MAC, also assist tailings storage facility (TSF) owners in exposing gaps within existing procedures, identifying training requirements, obtain- ing permits, conducting internal audits, and aiding conformance and due dili- gence, at any phase of the life cycle. The study pointed out that while new mines have the luxury of selecting the latest and most appropriate tailings man- agement technology and facility location during the conceptual planning and design phases, existing facilities may not be tech- nically or financially able to fundamentally change the technology used for tailings management. However, other aspects of technology associated with tailings man- agement should be re-evaluated based on the results of updated risk assessments and evolving technology that could be ap- plied to further reduce current and future risk. Management measures also need to be re-evaluated throughout the life cycle to ensure that they remain appropriate as the risk profile, or environmental or operating conditions of the tailings facility change. Another recent document is the Study of Tailings Management Technologies (MEND Report 2.50.1) produced by engineering firm Klohn Crippen Berger on behalf of the Mine Environment Neutral Drainage (MEND) Program and sponsored by the MAC. MEND is a Canadian program aimed Don't Let Tailings Management Slide As technology advances to handle increasing volumes of tailings, experts recommend periodic reviews of TSF operations and options to maintain efficiency and safety By Russell A. Carter, Contributing Editor The 117-ha tailings facility at Vedanta Resources' new Gambsberg zinc mine in South Africa was designed by Knight Piésold and features a concrete decant penstock that incorporates precast concrete members to act as sacrificial form work, enabling faster construction. Instrumentation was also installed to monitor the liner tempera- ture during operation to better understand tailings behavior and impact on liner life.

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