In the mining industry, the term “legacy mine” has evolved to encompass varying references to sites with remnants of historic mining activities. The International Organization for Standardization (ISO) recently introduced the new standard ISO 24419-1, which addresses the management of mining legacies. This standard defines legacy mines as their residual impacts, encompassing both positive and negative effects that have accumulated from mining activities (ISO, 2023).
Residual impacts can extend to liabilities and hazards, including safety risks such as open workings, pits, and compromised infrastructure. Environmental risks involve potential impacts to water quality, erosion, weed infestation, and damage from acid metalliferous drainage (Department of Industry, Tourism and Trade, 2023).
Recognizing the critical importance of addressing legacy mines and their potential long-term environmental and social challenges, factors such as environmental remediation, financial considerations, and stakeholder engagement, contribute to the complexities of managing these mining legacies. In this month’s Conversation on Closure, we will explore the features of legacy mines, the potential scopes of remediation efforts, the emerging opportunities, and discuss Okane’s approach to navigating the complexities associated with legacy mines.
As previously noted, ISO 24419-1 refers to legacy mines as sites with both positive and negative residual impacts resulting from mining activities. Another noteworthy reference to managing legacy mines comes from the Northern Territory, Australia, which is outlined in their newly proposed Legacy Mines Remediation Draft Bill.
In the draft bill, legacy mines are defined as an area where past mining activities occurred but lacked adequate security measures, including areas with extractive mineral leases, permits, authorities, mineral leases, or non-compliant existing interests (Legacy Mines Remediation Act, 2023).
The bill additionally specifies the features of a legacy mine. These features encompass any presently inactive plant, infrastructure, engineered feature, or any other feature that was initially constructed or used for mining activities, and lacks any associated mining security in place (Legacy Mines Remediation Act, 2023).
Further to defining legacy mines and delineating their distinctive features, the draft bill (2023) intends to provide a more flexible framework with the following objectives:
Both ISO and the Northern Territory’s references recognize the multifaceted nature of legacy mines. These definitions collectively provide a solid framework for understanding the complexities of legacy mines and identifying their impacts. It becomes imperative for governments, communities, and subject matter experts to collaborate and co-develop effective remediation strategies and implement necessary security measures.
Throughout the life of mine, is a progressive process integral to addressing and rectifying the environmental impacts resulting from mining activities. Important objectives of mine remediation range from ensuring the site's safety and stability to transforming it into a landscape capable of sustaining future land uses, such as agriculture or other beneficial purposes (Department of Industry, Tourism and Trade, 2023).
One prevalent social risk associated with legacy mine sites is the potential exposure to hazardous waste materials through migratory pathways such as soil, groundwater, and surface water (Chen, 2023; Nash, 2020). This exposure emphasizes the urgency for authorities to implement remediation and security measures to prevent direct adverse pollution impacts on surrounding communities (Nash, 2020).
With mine legacies, successful remediation efforts require comprehensive site investigations. These investigations aid in identifying areas requiring remediation to meet the current environmental benchmarks, as effective mine remediation not only involves rectifying past disturbances during the construction and operational periods of a mine site, but also proactively ensures present and future environmental integrity.
Remediation strategies must also consider soil erosion, water quality, vegetation restoration for potential weed infestation impacts, and ongoing monitoring and compliance with legal regulations to ensure the long-term success of these efforts and the overall health of the affected communities.
Collaboration among stakeholders, community members, Indigenous rightsholders, and subject matter experts, as outlined by ISO 24419-1 (2023), is equally critical. Collective efforts to mitigate risks associated with legacy mines ensure a comprehensive consideration of all perspectives, adherence to environmental standards, and the practice of responsible methods.
Still, in the wake of increased awareness and commitment to address the environmental consequences of legacy mines, various opportunities related to legacy mine remediation are emerging, such as job creation and beneficial land use.
For example, proposed reforms to the Legacy Mines Remediation draft bill aim to improve oversight, management, and implementation of mining remediation for legacy mine sites, emphasizing improved governance, transparency, and collaboration (Department of Industry, Tourism and Trade, 2023). This approach fosters increased opportunities for legacy mine remediation in regional and remote locations, creating expanded prospects for Northern Territory businesses and community groups, thereby contributing to economic growth in regions affected by the mining legacy (Department of Industry, Tourism and Trade, 2023).
Also, mining legacy remediation offers a transformative opportunity to reclaim the land for sustainable and responsible land use by addressing negative legacies through approaches like mining heritage tourism and renewable energy production (Nash, 2020). Therefore, it is important to identify values and plan for acceptable management options through community involvement and stakeholder consultation, as this ensures the success of these initiatives and the reclamation of land for beneficial purposes (Nash, 2020).
At Okane, we champion a collaborative and comprehensive approach to legacy mine sites. We like to develop thorough site biographies, examining past mining operations, construction, and waste management, to thoroughly understand the site's potential liabilities and risks. This understanding is pivotal in designing effective remediation and reclamation strategies that address the complexities of legacy mine sites.
We actively engage with subject matter experts, key stakeholders, and community members to ensure a holistic perspective, integrate diverse expertise, and foster a collective effort toward responsible and beneficial solutions.
Our expertise also encompasses full site design of landforms and cover systems, comprehensive risk assessment, and monitoring field trials. Through adaptive management strategies, we continually refine our designs based on field monitoring data and in-depth technical studies to ensure the effectiveness and sustainability of the landform and cover designs.
Okane’s approach contributes valuable knowledge to the wider field of mine legacy remediation by implementing measures that enhance public and environmental health and safety while establishing conditions that maximize the potential for sustainable post-mining land use alternatives in the future.
Chen, J. (2023). Study points to need to clean up legacy mining pollution that poses health risks to millions. Mining.com. https://www.mining.com/study-points-to-need-to-clean-up-legacy-mining-pollution-that-poses-health-risks-to-millions/
Department of Industry, Tourism and Trade. 2023. Mining and environmental reforms program fact sheet: Proposed legacy mine management [Fact sheet]. Northern Territory Government. https://industry.nt.gov.au/__data/assets/pdf_file/0007/1267729/fact-sheet-m1-proposed-legacy-mine-management.pdf.
Department of Industry, Tourism and Trade. 2023. Frequently Asked Questions: Legacy mines [Fact sheet]. Northern Territory Government. https://industry.nt.gov.au/__data/assets/pdf_file/0010/1267732/faq-legacy-mines.pdf.
International Organization for Standardization. (2023). Mine closure and reclamation – Managing mining legacies — Part 1: Requirements and recommendations (ISO Standard No. 24419-1). Retrieved from https://www.iso.org/obp/ui/en/#iso:std:iso:24419:-1:ed-1:v1:en.
Legacy Mines Remediation Act. (2023). Northern Territory of Australia. https://industry.nt.gov.au/__data/assets/pdf_file/0006/1267728/consultation-draft-legacy-mines-remediation-bill-2023.pdf
Nash, K. (2020). Chapter 9: Addressing legacy sites. In B. Oberle, D. Brereton, & A, Mihaylova (Eds.), Towards zero harm: A compendium of papers prepared for the Global Tailings Review (pp. 126-141). Global Tailings Review. https://globaltailingsreview.org/wp-content/uploads/2020/08/towards-zero-harm.pdf
A critical minerals strategy helps countries secure a responsible, diverse, and stable supply of critical minerals to support technological advancement, national security, economic growth, and environmental responsibility. The release of Australia's Critical Minerals Strategy in June 2023 provides an opportunity to highlight the similarities between the strategies developed by both Australia and Canada.
Both Australian and Canadian strategies for critical mineral resources are derived from their prevalent supply of natural resources, particularly rich deposits of rare earth elements (Natural Resources Canada, 2022; Department of Industry, Science and Resources, 2023). Australia’s and Canada’s critical minerals strategies aim to not only ensure a stable supply of critical minerals but also to set a global standard for responsible resource development.
In addition to sharing the objective of advancing geological surveys and mineral exploration, both countries emphasize their unique commitments to environmental, social, and governance (ESG) practices. This article explores how integrating closure planning into the life of mine planning can strengthen critical mineral projects and facilitate progressive reclamation initiatives throughout the mine’s operational life.
To strategically develop critical minerals resource projects, one of the objectives of the Australian critical minerals strategy is to improve sovereign capability for downstream minerals processing in order to extract the full value from the natural resources (Department of Industry, Science and Resources, 2023). This transition comes with challenges, including technical complexities, the need for high capital investments, additional energy infrastructures especially if critical minerals operations are remote, and market risks due to the limited data available to accurately forecast pricing (Department of Industry, Science and Resources, 2023).
The importance of secure financing for critical minerals projects is emphasized in the Australian strategy in order to reduce investment risks (Department of Industry, Science and Resources, 2023). Through the Northern Australia Infrastructure Facility (NAIF), $500 million will be allocated to support critical minerals projects aligned with the strategy. Australia’s critical mineral strategy also commits to establishing a National Reconstruction Fund for renewables and low-emission technologies (Department of Industry, Science and Resources, 2023).
To boost export value, Australia plans to prioritize critical mineral development projects that include domestic processing like the refinement of lithium to battery-grade lithium hydroxide (Department of Industry, Science and Resources, 2023).
One objective of Canada’s critical minerals strategy is to promote strong environmental management by reducing environmental impacts from mining operations and incorporating Traditional Knowledge into decision-making to align with the new Indigenous Policy Framework for Project Reviews and Regulatory Decisions (Natural Resources Canada, 2022).
Like most mining operations, critical mineral projects are resource-intensive, require significant capital investments, and are subject to rigorous regulatory assessments to meet high environmental and social standards (Natural Resources Canada, 2022). To streamline the approval processes for critical minerals projects from exploration to production, the Canadian federal government will be providing financial and administrative support for critical minerals mining, processing, manufacturing, and waste reduction projects, which include the circular principles of recycling and extracting value from waste (Natural Resources Canada, 2022).
Canada’s strategy also includes mandating the Critical Minerals Centre of Excellence (CMCE) to assist project developers in navigating regulatory processes and promoting collaboration with Indigenous peoples, provinces, and territories to meet their climate and economic objectives (Natural Resources Canada, 2022). The CMCE aims to coordinate critical mineral programs and facilitate regional engagement and communication within the sector to promote project development while respecting Indigenous rights and environmental protection (Natural Resources Canada, 2022).
Integrated life of mine planning for critical minerals projects encompasses the comprehensive, long-term strategizing of mining activities, efficient resource management, environmental stewardship, and socially responsible mining practices. It involves optimizing the entire mine lifecycle, from exploration, permitting, design, construction, production, processing, closure, and post-mining land use and adaptive management.
Integrated life of mine planning optimizes the use of resources throughout the mine’s lifecycle. By keeping clear operational and post-mining land use objectives in mind, careful planning and scheduling of mining activities can ensure a consistent supply of raw materials required for the low-emission energy transition while minimizing environmental impacts.
Integrated life of mine planning also involves partnerships with Indigenous rightsholders to embed multigenerational land and water stewardship principles into the full mining lifecycle, which aligns strongly with Canada's environmental and Indigenous collaboration commitments.
At Okane, we advocate for integrating mine closure into all phases of mining projects to maximize asset value while achieving positive environmental and social outcomes. Leveraging our global expertise in integrated life of mine planning, we collaborate closely with our clients to develop a life of mine plan that encompasses input from mine operators, stakeholders, rightsholders, and regulatory bodies to embed progressive closure activities into short and long-term mine plans. We identify opportunities to enhance the operating and closure plans to address ESG investment criteria, post-mining risks or liabilities, and closure costs.
Integrated life of mine planning aligns with Canada’s and Australia’s critical mineral strategies’ broader objectives for responsible critical mineral development and environmental management. By taking an integrated life of mine planning approach, critical minerals projects can enable a consistent and responsible supply of resources, minimize environmental impacts, reduce waste, and enhance full-lifecycle economic viability.
Department of Industry, Science and Resources. (2023). Critical Minerals Strategy 2023–2030: June 2023. Retrieved from the Australian Government Department of Industry, Science and Resources website: https://www.industry.gov.au/sites/default/files/2023-06/critical-minerals-strategy-2023-2030.pdf
Natural Resources Canada. (2022). The Canadian Critical Minerals Strategy: From exploration to recycling: Powering the green and digital economy for Canada and the world. Retrieved from the Government of Canada website: https://www.canada.ca/content/dam/nrcan-rncan/site/critical-minerals/Critical-minerals-strategyDec09.pdf
One of the most pressing issues in mine closure is the management of mine tailings, a mine waste byproduct resulting from the extraction and treatment of mineral ores. Traditional mine closure methods often involve depositing mine tailings in on-site tailings storage facilities (TSF), which can present environmental risks such as water quality compliance and habitat disruption (Ikotun et al., 2022).
The urgency to address these challenges has given rise to some innovative solutions. One particular solution is the repurposing of mine tailings sand as aggregates for concrete. The popularity of this innovative solution stems from a desire to embed the principles of circular economy; finding value in what was once considered waste.
Mine tailings sand consists of fine-grained materials comprising sand, silt, and clay. The specific composition of mine tailings sand can vary widely depending on the type of ore being processed and the extraction techniques employed. Generally, mine tailings sand has a higher mineral content compared to natural sand, making tailings sand potentially useful as construction materials (Ikotun et al., 2022).
One notable aspect of mine tailings sand composition is its diverse composition. Tailings sand often contains trace amounts of metals, such as copper, some of which can serve as cementitious materials in concrete mixes. This unique attribute enhances the concrete’s strength, durability, and workability, optimizing its overall performance (Ikotun et al., 2022). Chemical compounds also commonly found in tailings sand can include SiO2, Al2O3, CaO, and Fe2O3, although the quantities of these compounds can vary significantly (Gou et al., 2019).
The diversity of tailings composition means that classifying tailings based on their ore sources or refining processes is insufficient for material researchers looking to comprehend the nature of tailings and determine how best to repurpose them effectively (Gou et al., 2019).
Before incorporating mine tailings sand into concrete mixes, characterization and comprehensive testing of the tailings are critical to gain a thorough understanding of tailings properties and their potential for repurposing. Factors such as particle size distribution, mineralogy, and the presence of potentially harmful elements must be considered. This ensures that the tailings meet the required specifications for use in construction, assuring the safety and performance of the resulting concrete structures.
In most literature, common comprehensive tests of using tailings sand as concrete aggregates include:
Monitoring the sourcing, handling, and processing of tailings sand for quality control is equally important (Aguilar Veramendi & Lama Gutierrez, 2020). Quality control measures can include regular sampling and testing of tailings from various locations within the storage facility, as well as rigorous quality control protocols implemented during concrete production. With rigid quality control standards, the construction industry could confidently embrace mine tailings sand as a sustainable alternative to traditional aggregates while ensuring the safety and reliability of concrete structures.
The properties of tailings sand offer the potential to reduce the long-term environmental impact and waste management costs while meeting the supply demands of construction and infrastructure development. With the decreased availability of natural sand quarries for aggregate production (Kuranchie et al., 2015), traditional aggregates like natural sand may be costly to harvest and transport, making them more expensive to use in concrete mixes. Mine tailings sand may offer a more affordable option. Mining companies could potentially create new revenue by selling tailing sand or decrease their supply costs by using the tailings sand within their operations.
Reusing waste material can also lower expenses and resources related to tailings disposal (Kuranchie et al., 2015; Arbili et al., 2022). TSF structures demand continuous monitoring and maintenance to effectively manage the high level of associated risks (Peys et al., 2022). Repurposing tailings sand into useful construction materials reduces the volume of tailings that need to be managed within the closure plan, thereby lowering the costs associated with the decommissioning of these structures in the future.
Tailings’ unique composition is a challenge in terms of disposal and environmental management (Peys et al., 2022), and using tailings sand as concrete aggregates could be a form of mitigation. Due to the high mineral content in mine tailings, including potentially reactive sulphur compounds and heavy metals, unmanaged tailings can cause adverse environmental impacts (Kuranchie et al., 2015). Some research has shown that encapsulating tailings sand in cement mixtures, such as Portland cement mixtures, effectively immobilizes and insolubilizes these heavy metals, preventing their release into the surrounding environment, and decreasing pollution potential (Méndez et al., 2022; Lalangui et al., 2021).
Mine tailings sand has been found to exhibit favourable performance characteristics in concrete, offering good compressive strength and durability (Kuranchie et al., 2015). It also exhibits compatibility with various concrete mix designs, making it a versatile and adaptable material for construction projects.
Okane has international experience in mine closure and mine waste management, leveraging expertise in tailings management and environmental geochemistry to provide our clients with the best closure plan, uncovering the highest value future land use. As part of our mine closure vision and alternatives assessment process, we identify valorization opportunities for materials remaining on-site post-closure. We look for economic opportunities, like the repurposing of mine rock and tailings sand, to identify value in domains which have previously been considered only as liabilities. Our commitment to innovative mine closure solutions and responsible mining practices extends beyond our core services. We are passionate about collaborating across industries to realize opportunities like using mine tailings sand in concrete production for increased sustainable practices in the mining and construction industries.
Aguilar Veramendi, J. A., & Lama Gutierrez, J. J. (2020). Influencia de sustitución del agregado fino por relave, Mina Santa Luisa, sobre la resistencia a compresión del concreto [Influence of replacing fine aggregates with tailings from Santa Luisa mine on the compressive strength of concrete]. Escuela de Ingenieria Civil – Huaraz, 306. https://repositorio.ucv.edu.pe/handle/20.500.12692/58168
Arbili, M. M., Alqurashi, M., Majdi, A., Ahmad, J., & Deifalla, A. F. (2022). Concrete made with iron ore tailings as a fine aggregate: A step towards sustainable concrete. Materials, 15(18). https://doi.org/10.3390/ma15186236
Gou, M., Zhou, L., & Then, W. Y. (2019). Utilization of tailings in cement and concrete: A review. Science and Engineering of Composite Materials, 26(1), 449–464. https://doi.org/10.1515/secm-2019-0029
Ikotun, J., Adeyeye, R., & Otieno, M. (2022). Application of mine tailings sand as construction material - a review. MATEC Web of Conferences, 364. https://doi.org/10.1051/matecconf/202236405008
Kuranchie, F. A., Shukla, S. K., Habibi, D., & Mohyeddin, A. (2015). Utilization of iron ore tailings as aggregates in concrete. Cogent Engineering, 2(18). https://doi.org/10.1080/23311916.2015.1083137
Lalangui, L., Méndez, D., & Jiménez-Oyola, S. (2021). Caracterización de relaves mineros para su aprovechamiento en la fabricación de materiales de construcción [Characterization of tailings for their use in the production of construction materials]. Tesis de Minas. https://www.dspace.espol.edu.ec/handle/123456789/55505
Méndez, D., Guzmán-Martínez, F., Acosta, M., Collahuazo, L., Ibarra, D., Lalangui, L., & Jiménez-Oyola, S. (2022). Use of tailings as a substitute for sand in concrete blocks production: Gravimetric mining wastes as a case study. Sustainability, 14(23). https://doi.org/10.3390/su142316285
Peys, A., Snellings, R., Peeraer, B., Vayghan, A. G., Sand, A., Horckmans, L., & Quaghebeur, M. (2022). Transformation of mine tailings into cement-bound aggregates for use in concrete by granulation in a high intensity mixer. Journal of Cleaner Production, 366. https://doi.org/10.1016/j.jclepro.2022.132989
Ramos-Hernández, M.I.,Pérez-Rea, M.L. (2021). Characterization of mine tailings in their natural state and stabilized with cement, focused on construction. Ingeniería Investigación y Tecnología, 22(02), 1-9. https://doi.org/10.22201/fi.25940732e.2021.22.2.010