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JUNE/JULY, 2021 / CANADA’S FIRST MINING PUBLICATION / WWW.CANADIANMININGJOURNAL.COM

The reclaimed Holden Mine closure project in Washington state (photographed in 2019) is a great example of a sustainable mine closure. CREDIT: STANTEC TOP TRENDS IN TAILINGS CLOSURE

By Phillip Crouse facilities (TSF). Mine owners are updating Current TSF closure guidelines existing closure plans, as well as performing TSF closure guidelines are available from n 2019, a tailings dam at the Córrego do prefeasibility and feasibility studies on TSFs committees and organizations, both national Feijão iron ore mine near Brumadinho, and other mine waste facilities to deter- and international, with goals to advance the IBrazil, suffered a devastating failure. mine anticipated closure cost. Several mines mining sector’s safety, social, and environ- When the tailings dam collapsed, it released are beginning closure on large and complex mental performance. These organizations a massive mudflow that wreaked havoc on TSFs as they transition their properties to include the International Council on Min- the mine site, mine staff, and nearby com- other forms of mining – for example, from ing & Metals (ICMM), Mining Asso- munities. More than 250 people lost their surface mining to underground mining. ciation of Canada (MAC), International lives and there was a significant amount of Mine owners are being challenged to Organization for Standardization (ISO), damage done to the environment. provide sustainable closure strategies that and International Committee on Large Tailings dam failures like this example reduce long-term maintenance costs, Dams (ICOLD) along with country affili- have fuelled the mining industry to accelerate ensure public safety, and find ways to gen- ates such as the Canadian Dam Association the closures of their existing tailing storage erate revenue as part of the TSF closure. (CDA) and Australian National Committee TOP TRENDS IN TAILINGS CLOSURE, continued AUTHORIZED REPRINT

Lingan coal mine site remediation in Nova Scotia. 10 MW of wind power was installed at site – one of Stantec’s NetZero Mining projects. CREDIT: STANTEC

The mine owner needs to form a closure team that includes technical expertise from a variety of disciplines. CREDIT: STANTEC on Large Dams (ANCOLD). and maximum credible earthquake (MCE). materials to improve their properties for clo- ICMM, in partnership with the United New provisions in the closure plan will also sure is fundamentally needed when turning a Nations Environment Program (UNEP) address climate change and extreme events mine that’s a liability into an asset. and the Principles for Responsible Invest- such as fire and drought, as well as main- The TSF owner does not have to manage ment (PRI), established the indepen- taining and operating closure facilities like these closure changes alone. Organizations dent Global Tailings Review panel, which mine water treatment facilities. like Landform Design Institute establish a released the “Global Industry Standard on Mine owners will need to form multi- practice that allow mines to set clear goals, Tailings Management” in August 2020. The disciplinary TSF closure teams that include design objectives, and design criteria for the document sets standards for the safe and tailings planners, geotechnical engineers, reclaimed landscape. Academia, including secure management of mine tailing facilities surface water and groundwater hydrologists, the University of Queensland Geotechni- globally and includes principles applicable to geochemists, cover specialists, reclamation cal Engineering Centre, is teaching courses closure and post-closure requirements. specialists, revegetation specialists, wildlife in value-added rehabilitation. The Center Individual countries are revisiting tail- experts, and other technical people to sup- of Excellence for Tailings Dam Research – ing dam design, operation, and closure plement the Engineer of Record responsible a partnership between the Colorado School standards. For example, the Association for the design and operation of the TSF. of Mines, University of Arizona, and Col- of State Dam Safety Officials (ASDSO) There will be new trends in TSF clo- orado State University – is also dedicated in the United States is currently updat- sure, including more of a risk-based clo- to mine tailings research. We expect much ing the Federal Emergency Management sure approach using risk-informed decisions to come of TSF closure from organizations Agency (FEMA) Model State Dam Safety in addition to the traditional deterministic like these and more. Program (FEMA 316) on applicability to standards-based analysis. CDA (2019) pro- tailings dams. The US Society on Dams vides guidance on a risk-based approach to The goal of zero tailings (USSD) is the lead organization in devel- TSF closure. Approximately 99% of what is mined oping a FEMA technical guidance docu- becomes waste to produce 1% of value. ment to support and provide a technical Post-mining ‘asset’ Imagine switching the economic mineral basis for the Model State Dam Safety Pro- Adding value through closure will become and tailings fraction so that the waste pro- gram regulatory guidance document. In more common practice as closure costs con- duced by the mine process is a small fraction Canada, the CDA and MAC are in the tinue to increase and shareholders demand of the ore. Ideas in zero tailings produc- process of revising and updating guidelines reduction in liability costs. There will be a tion can start today in the planning of new on tailings dams. change in the narrative surrounding the mines. Imagine reducing or eliminating tail- TSF closure to re-focus on a post-mining ings from a mine operation. Not only are the What to expect in TSF closure guidelines “asset” rather than a “liability.” TSF clo- obvious environmental benefits realized, but and standards sure innovation is occurring now, but it will the reduction in energy demand in mining The technical criteria for closing a TSF at a become more prevalent in achieving closure would change the industry. mine, as per guidelines and standards, will objectives. Some of these objectives include New technologies in mine processing be more robust than the criteria during its reprocessing and relocation of the tailings technology will change what we know to be design and operation phase. Why? Because in-pit, integrating waste rock and tailings the typical mine. Digital mining, precision closure is forever whereas the operation of storages (termed Integrated Waste Land- sensing, information technologies, advances the TSF lasts only as long as the life of the form, or IWL), reducing tailings produc- in chemical systems, and artificial intelligence mine – a relatively short period of time com- tion, and improving operational practices to are technologies that can optimize the mine pared to forever. improve stability. in reversing the unbalanced ratio of waste to We can expect to see more robust Repurposing the closed TSF for renewable economic value. CMJ changes to managing water over the long energy production, such as photovoltaic solar term by eliminating the impounding capa- power, hydroelectric power, bioenergy, and Phil Crouse is the mine closure and reclamation bility of the TSF. We can also expect more wind power, presents the potential to provide practice leader at Stantec. Over the last three decades robust loading conditions for closure design, numerous benefits to mining companies and he has completed large closure projects including the adoption of the probable max- their communities. Research in biotechnol- on five continents. He can be reached at imum precipitation (PMP) storm event ogy and carbon sequestration using tailing [email protected].