Energy and Extractives Global Practice Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Including Standards to Improve Coal Mine Closure Practices and a Practitioner’s Workbook for Implementation The World Bank December 2024 © 2024 International Bank for Reconstruction and Development/ The World Bank 1818 H Street NW Washington, DC 20433 Telephone: 202-473-1000 www.worldbank.org This work is a product of the staff of The World Bank with external contributions. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. 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Any queries on rights and licenses, including subsidiary rights, should be addressed to: World Bank Publications The World Bank Group 1818 H Street NW Washington, DC 20433, USA Fax: 202-522-2625 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 3 Contents Introduction 10 More acronyms: terminology according to 43 gas provenance Going deeper: dealing with methane before and during 44 Module 1 12 coal mining After mining: residual methane emissions should 46 Executive Summary 13 be reduced Closing a mine and preparing for the future 13 Developing GHG policies that match the destructive 46 Mitigating risks to increase safety and preserve value 14 power of methane Evaluating resources for the post closure future 16 Global methane emissions will be monitored remotely 48 Assessing the risks associated with actions taken 17 Annex A: Supporting Information on 49 during mine closure Probabilistic Risk Assessment Introduction 20 Three pillars underpin successful transitions 20 Module 2 52 Standards to Improve Closure Practices 22 Closing a mine and preparing for the future 22 Executive Summary 53 Evaluating resources for the post closure future 26 The context of coal mine closure 56 Assessing the risks associated with actions taken 27 Risk based approach to mine closure and repurposing 58 during mine closure Hazard Identification – Hazard Assessment 60 Groundwater and Fugitive Methane Emissions from 30 Assessing residual risks after mine closure 68 Coal Mining Detailed risk assessment 72 Application of Good Practices to Coal Mine Closure 34 Risk Management and Mitigation 75 Checklist of good practices for implementing coal 35 mine closure Monitoring for mine closure 79 Considering options for mine closure projects at gassy 38 Beyond risk management – creating added value for 81 coal mines post mining lands and assets Mitigating Fugitive Emissions 40 Land Repurposing Methodology (LRM) 83 Coal-associated methane—an introduction 40 GIS-based Land Use and Repurposing Application (LURA) 85 Methane: the second most important gas for 40 climate change From land repurposing methodology and classification 88 Coal-associated methane: an unconventional form 41 to spatial planning of natural gas From “mining for closure” to “mining for repurposing” 89 Methane as a hazard and an opportunity 41 4 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Acknowledgements The preparation of the report Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines was led by Michael Stanley (Lead Extractives Specialist, IEEXI) and Wolfhart Pohl (Lead Mining Specialist, IEEXI) from the World Bank’s Energy and Extractives Global Practice, and supported throughout by Helen Nguyen (Program Assistant, IEEXI). This knowledge product represents a significant milestone in advancing sustainable and responsible closure practices within the mining sector, particularly in regions undergoing transitions away from coal. The task team extends its sincere gratitude to Ray Pilcher (Consultant, IEEXI) who provided much of the scientific and engineering underpinning for closure risk assessment and coal mine methane management. The team is grateful to colleagues across the World Bank for their valuable advice to this work, notably Rachel Perks (Senior Mining Specialist, IEEXI) and Justine Sylvester (Land Tenure Specialist, IEEXI). The team also appreciates the thorough reviews, insightful feedback and constructive suggestions provided by World Bank colleagues Harshit Agrawal (Senior Gas Specialist, IEFMR), Phillip Hannam (Senior Energy Economist, IEEGK), and Harinath Sesha Appalarajugari (Senior Environmental Engineer, SEAE2) for their instrumental inputs in enhancing the report’s quality and depth. Special thanks are extended to the World Bank’s leadership Demetrios Papathanasiou (Global Director, IEEDR) and Robert Schlotterer (Practice Manager, IEEXI) for their guidance and support throughout the development of this report. The task team acknowledges with gratitude the financial support provided by the World Bank’s Extractives Global Programmatic Support (EGPS) Multi-Donor Trust Fund. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 5 Figures In Module 1 Figure ES 1: Diagram of United Nations Framework Classification showing that each of the axes indicate directional increase 16 in uncertainty and risk correlated with the deficiency in knowledge of socio-economic viability, project feasibility under prevailing market conditions and knowledge of the geology and its impact on resources. Resources with the highest likelihood to be used in commercial projects are depicted by green cubes in the diagram, appearing on the E1 level, and proximal to the F1 and G1 rows. Figure ES 2: Matrix mapping the likelihood of a risk occurring versus the range in severity of its potential impact. Mine 17 management performing the assessment will use their professional judgement to determine the likelihood of occurrence and the severity of impact Figure ES 3: Example plot of coal production, liberation of drained and vented methane at a gassy mine ins southwest China 18 Figure 1: Diagram of United Nations Framework Classification showing that each of the axes indicate directional increase 27 in uncertainty and risk correlated with the deficiency in knowledge of socio-economic viability, project feasibility under prevailing market conditions and knowledge of the geology and its impact on resources. Resources with the highest likelihood to be used in commercial projects are depicted by green cubes in the diagram, appearing on the E1 level, and proximal to the F1 and G1 rows. Figure 2: Matrix showing the severity and likelihood of occurrence of risks 28 Figure 3: Example plot of coal production, liberation of drained and vented methane at a gassy mine ins southwest China 29 Figure 4: Plot of gas production that began in 1978 from closed mines in northern France 31 Figure 5: Schematic depiction of potential migration pathways for methane at an active mine. Many of the pathways 32 will be accessible after mine closure (UNECE 2019). Figure 6: Plot of methane emissions and coal production based on coal consumed using SSP2 from 2010 through 2100 33 Figure 7: Shows the amount of gas that was emitted from the West Elk Mine during the years extending from 2011 through 39 2019. During this period, 44.2 million tons of coal were mined and 13.4 billion cubic feet of gas was liberated to the atmosphere, without significant mitigation or abatement. A small burner using CMM for fuel was used to heat ventilation air at the intake to warm air in the winter to increase the comfort and safety of the miners. This represents 5.4 million tonnes of CO2e using a GWP of 25, but 18.6 million tonnes using the more appropriate GWP value of 86. A hyperbolic decline curve was fit to the data to model the emissions and show the downward trend in the volume of gas that was liberated by mining activities. The curve indicates that mining is effectively draining this unconventional gas reservoir. This mine was opened in 1982 and estimated to remain open until 2024 . It is critical that closure of this mine is conducted with a plan for capturing the gas that remains in the reservoir. No methane emission mitigation or abatement has taken place. Closed mine emissions could total as much as 25% of the emissions during active mining and last for decades to come. Figure 8: Estimated global anthropogenic methane emissions by source, 2020 40 Figure 9: Coal rank and the impact of depth on gas content 41 6 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Figures In Module 1 Figure 10: Coalbed Methane production in USA 1989-2017 42 Figure 11: Coal associated methane terminology 43 Figure 12: Percentage contribution by source for methane emitted from US coal mines 43 Figure 13: Methane production and the coal mining lifecycle 44 Figure 14: Fugitive emissions of methane emitted from active mines in major coal producing countries expressed in 45 million tonnes CO2e. Figure 15: Decline of methane concertation in the after initial release to the atmosphere 47 Figure A-1: Risk matrix and companion table showing the range of the bounding values for each probability quintile. 49 Green indicates the most favorable risk outcome and red the least favorable. Figure A-2: Normally distributed probability density function that shows the relative frequency for each quintile. 50 As an example, choosing the likelihood of occurrence for the probability band of p40-p60, the relative frequency ranges from 0.46 to 0.54 shown on the chart as 46 to 54 percent. Figure A-3: Probability frequency of score values used in risk table resulting from multiplying the probability of occurrence 51 by the probability of impact severity Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 7 Tables In Module 1 Table ES 1: Mapping of overarching post closure principles to operational domains 14 Table ES 2: Summary table of risks and mitigants that impact value of post closure land and resources. Overarching 15 principles are mapped using the colors used in Table ES 1 the numbers at the top of the columns correspond to the following domains: Column 1 Public Safety, 2 Land Stability, 3 Mitigation of chemical impacts, 4 Environmental, Reclamation, Emissions Control, and Post-Closure Land Use Table 1: The World Bank's three by three methodology dashboard that is used to assess the existing conditions in coal 21 regions that are experiencing mine closures and transition of the energy economy. This matrix depicts the logical phasing of mine closure and regional transition versus three pillars which underpin the World Bank’s approach to developing Table 2: Mapping of overarching post closure principles to operational domains 22 Table 3: Summary table of risks and mitigants that impact value of post closure land and resources. Note that overarching 23 principles are mapped using the colors used in Table 1 above onto the assets or resources at risk in each of the three operational domains 8 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Figures In Module 2 Figure 1: The range of potential contributions and benefits of land repurposing and spatial planning to three major 57 pillars of coal transition: (i) climate change mitigation; (ii) a diversified post carbon economy and energy production; and (iii) the environmental regeneration of mining lands. Figure 2: Tolerable risk in the form of fatalities or cost based on an annual probability of occurrence (Briaud, 2020) 58 Figure 3: Risk Management approach for mine closure 59 Figure 4: Intense dust formation due to strong winds over Kardia Mine in WM Greece. This is a significant, adverse 64 environmental impact, that would put restrictions on land use downwind of the mine. Figure 5: Rio Tinto river in Spain with flowing red acidic water 64 Figure 6: Forecast of future CMM and AMM emissions (Kholod, et,2020) 65 Figure 7: Water flow routs to and from a mine site (ICMM, 2012) 66 Figure 8: View of the landslide at Tylorstown in South Wales on 16 February 2020 (AGU, 2020) 66 Figure 9: Aberfan in the days immediately after the disaster, showing the extent of the spoil slip 67 Figure 10: Grassland at a coal mine in Baorixile, Inner Mongolia, is dotted with pits 67 Figure 11: Hierarchical mine closure residual risk assessment 68 Figure 12: Matrix showing the risk of increased needs for funding detailed risk assessment 71 Figure 13: Example plot of coal production, liberation of drained and vented methane at a gassy mine ins southwest China 73 Figure 14: Probabilistic slope stability analysis 74 Figure 15: Risk management and mitigation approach 75 Figure 16: Graphic characterization of four exemplary land repurposing scenarios, based on five defining criteria. 85 These “radar charts” allow a quick assessment, categorization and testing of lands’ suitability for a specific envisaged utilization Figure 17: Visual output from a land utilization repurposing assessment mine land use rating map carried out in 87 West Sumatra, Indonesia Figure 18: Remediation and repurposing hierarchy, demonstrating the progression from basic mine remediation towards 89 repurposing to achieve better socio-economic outcomes. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 9 Tables In Module 2 Table 1: Hazard identification from coal mine operation and mine closure 61 Table 2: Severity level impact assessment (modified from ANCOLD, 2012) 72 Table 3: Simple risk assessment matrix based on severity impact and probability of occurrence 73 Table 4: Reclamation strategies to reduce risk in preventive or protective conditions 76 Table 5: Evaluation criteria for post mining lands 83 10 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Introduction The following document (consisting of two The document consists of a summary of best practice standards modules) is intended as standard of what a for coal mine closure and aftercare, complemented by a practitioners’ guide. In combination these two modules can be successful coal mine closure should look like used by coal enterprises, line ministries, technical agencies (e.g. when following best international practice, and mining inspectorates, environmental protection agencies), as well provides practical guidance for applying best as development partners, looking towards mine closures some practice to post-closure risk management in coal 5-10 years ahead, to inform plans for closure, repurposing and mines. The underlying rationale of this work is transition that have yet to be drafted. that coal transition engagements exhibit a great This document aims to serve as benchmark and reference for the heterogeneity of post closure mine conditions World Bank's coal transition engagements, providing global good across countries, or within large countries practice guidance for coal enterprises and line ministries, as well (such as India and China), and of processes and as development partners. At the same time the two modules serve standards governing how coal mines should as a risk-management tool in a type of engagements that are by close. This represents a challenge for the World their very nature characterized by a high environmental and social risk baseline. Bank (and other development partners engaged in the just transition space) to calibrate the The two modules are designed to support the planning and approach how a coal transition engagement implementation of mine closures, repurposing, and transitions in would be implemented under such heterogeneity. a forward-looking manner over the next 5-10 years. Additionally, the document functions as risk-management tool, ensuring Hence, one purpose of the document is to serve thorough understanding and management of environmental and as benchmark and reference that all parties social risks associated with coal mine closure and post-closure engaged in coal transition could cite as global aftercare. These standards and guidance will be integrated into good practice. the World Bank's systematic coal transition approach, available to staff and clients. In conjunction with the Environmental and Social Framework (ESF), this work underscores the World Bank's commitment to proportionate due diligence and global knowledge sharing in coal mine closure practices. These standards also are an important enabler for a new paradigm of what the objective of mine closure should be: Mine closure should be envisioned as a business strategy that will reduce post closure risks and could enable increased end use value. The conventional objective of “mining for closure” has been to continuously reclaim and restore mined-out areas to leave mine lands in a geotechnically stable condition, with erosion resistant, well vegetated surfaces, and without environmental liabilities in form of effluences, gas emissions, dust or contaminated soils. Going beyond this, the new objective of “mining for repurposing” is to prepare the lands for optimum future productive uses and enhance their value to support a physical and socio-economic transformation in the wake of mining activities. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 11 For policymakers, this work yields three high-level messages that may be considered for shaping / implementing regulations related to coal mine closure and repurposing: • Many coal mining operations continue to bear risks and hazards for public health and safety and the environment well beyond their closure date. These standards and guidelines help to understand, identify and quantify these risks and design appropriate and proportionate responses. They also can support a country-wide sectoral / strategic risk-assessment and management approach of a mining portfolio. • Methane can be a key risk factor and pollution agent long after mine closure. Coal Mine Methane (CMM) represents more than 10% of total methane emissions from human activity; CMM abatement thus is an important factor for coal-intensive economies to meet their climate-related commitments and obligations as part of UNFCCC agreements / NDCs, or other regional commitments. Introducing legislation enabling monitoring and capture of CMM emissions can be an important contributor to complying with national climate targets. • Finally, post-mining lands and assets should be viewed as opportunities rather than liabilities, if proactively repurposed and redeveloped. Mine closure should be envisioned as a business strategy that can provide valuable physical space for a range of investments, from renewable energy to residential / commercial / industrial and green / nature-based uses. Enabling modifications of legislation relating to mining, land management, environment and spatial planning can support unlocking the economic potential of post mining lands and productively re-integrating them into national economies. 12 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Module 1: Summary of Good Practice in Coal Mine Closure and Post-Closure Risk Management Including Standards to Mitigate Fugitive Emissions from Closed Coal Mines Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 13 Executive Summary The World Bank’s “Achieving a Just Transition Sustainable closure encompasses many activities; however, this for All” envisions strong coal mine closure policy document focuses on the aspects of mine closure that mitigate greenhouse gas emissions and preserve the value of the remaining backed by good-practice technical standards natural resources and other mine-related assets. As an example, if and improved technical capacities which form there is high likelihood that there will be an incursion of water into the basis for effective regulatory processes. To the mine workings, precautions need to be taken to ensure that date, most countries have implemented “physical water levels do not reach the surface and become an environmental closure” rather than mine closures that promote risk and destructive to the local community or prevent mined sustainable development. Physical closure land repurposing. Similarly, the practitioner must recognize that involves the removal of equipment and blocking it is critical to prevent gas, which may build up in the mine, from migrating and causing explosion or fire hazards. Ultimately, it is public access to the mine, while reassigning some the practitioner’s responsibility to help formulate a plan for the workers and production to other operating mines. next chapter of resource utilization by preparing the mine area By comparison, closures that lead to sustainable for repurposing. Repurposing is key to a sustainable future for develop are successful because governments the mined land and associated community which has become strengthen or create and use policies that dependent on jobs associated with the coal mining industry. ensure institutional governance to support people and communities and facilitate mine land Closing a mine and preparing for the future repurposing in ways that promote sustainable While the technical specifications issued in many countries define development—we use the term sustainable mine some key criteria that mining companies should or must consider closure 1 to this refer to this process. when closing a coal mine, comprehensive technical standards for coal mine closure with quantitative and qualitative thresholds on The World Bank’s document, “Summary of Good Practice in Coal environmental reclamation and land remediation may not exist Mine Closure and Post-Closure Risk Management, Including Standards or may need updating. These standards, which are essential to to Mitigate Fugitive Emissions from Closed Coal Mines” provides post-mining safety and land use, may need to be developed or information and outlines activities which should be considered enhanced. when planning and executing sustainable mine closure. The intent of this guidance is to provide information to practitioners Coal mine closure requires modern procedures underpinned by who are striving to close coal mines in a manner that leads to a strong technical standards by which enterprises and relevant mine sustainable and prosperous future for the communities which are safety authorities can guide remediation and land reclamation. physically culturally and economically linked to coal mines which There are four overarching principles which correlate to existing are being closed, while protecting against hazards that may occur regulations and practices in most countries: public safety, land at the sites. This is an important precondition for prospective coal stability, mitigation of chemical impacts, and environmental mine repurposing, where both public financers (incl. multilateral reclamation, emissions control, and post-closure land use. These development banks) and private investors require assurance that principles serve to protect people and communities from hazards mine closure risks have been addressed, before a mine is developed and land instability, chemical pollution, ensuring that land is and upgraded beyond basic remediation and risk management. reclaimed and suitable for repurposing and should be incorporated in safeguards against fugitive methane emissions and unwanted and polluting water flows from coal mines. 1 The use of this term appeared in 2006 in a discussion paper that refers to the approach of integrating social, environmental, engineering, and financial aspects of mine closure Kunanayagam, R 2006, 'Sustainable Mine Closure Issues and Lessons Learnt', in AB Fourie & M Tibbett (eds), Proceedings of the First International Seminar on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 13-19, https://doi.org/10.36487/ ACG_repo/605_Kunanayagam 14 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Table ES 1: Mapping of overarching post closure principles to operational domains Operational Domains Surface Subsurface Legal and Regulatory Public Safety X X Land Stability X X X Overarching Principles MItigation of Chemical Impacts X X X Environmental Reclamation, Emissions X X X Control, and Post-Closure Land Use While these four overarching principles frame areas of social describing the intrinsic value of assets and resources which may and environmental concern, they do not capture the economic be associated with a mining property. They are grouped within dimension which is the third pillar of sustainability. Greater utility the surface, subsurface, and legal, regulatory, and financial is gained by increasing granularity and reorganizing the approach domains, recognizing that the issues and challenges which will to consider the risks to society, the environment, and how certain be met in each of these areas will require specialized expertise to actions, or lack of actions result in diminishment of the asset successfully repurpose the mine sites. value of remaining resources. Moreover, this approach reflects The table lists the risks and negative impacts which may reduce the interconnected nature of the issues that confront operating the options for repurposing or use if appropriate steps are not companies at the time of mine closure. Three categories taken to ensure against diminishment of the remaining value. or operational domains are designated, namely, Surface, To emphasize this point, unmitigated risks such as groundwater Subsurface, and Legal, Regulatory and Financial. Table ES 1 maps pollution, subsidence, and methane gas migration can profoundly the four overarching principles to the domains, or thematic areas, and deleteriously impact future use of the land and resources. in which related risks can be assessed and appropriate measures These risks can manifest as threats to neighboring operating can be taken to maintain or increase the asset value of the land mines through unexpected flooding and increasing gas pressure and other resources. which may endanger miners working underground. Mitigation of these impacts are possible. The last column provides suggested Mitigating risks to increase safety and actions that can be taken to ameliorate the listed risks. preserve value These standards should act as a checklist of assets that must be These coal mine closure standards are structured to reflect recognized for their remaining value to the local community and the multidimensional nature of problems that have arisen safeguarded against destruction or waste. This table may also be throughout modern coal mining history. The regulatory and used as an agenda for identifying issues that are not covered by policy regimes of coal producing countries address these issues existing regulation and policy or which may be adapted to become to greater or lesser degrees. These standards are not designed applicable to the unique geological and mining conditions found in to replace or controvert, but augment and strengthen existing a coal producing region. policies and regulations by introducing risk-based good practices as an approach to planning and executing mine closures in a sustainable manner. Table ES 2 summarizes these standards, Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 15 Table ES 2: Summary table of risks and mitigants that impact value of post closure land and resources. Overarching principles are mapped using the colors used in Table ES 1 the numbers at the top of the columns correspond to the following domains: Column 1 Public Safety, 2 Land Stability, 3 Mitigation of chemical impacts, 4 Environmental, Reclamation, Emissions Control, and Post-Closure Land Use Overarching Asset or resource Intrinsic Risks and potential Actions that will Principles at risk value negative impacts reduce risks Natural ground, Ecological Pre-mine planning and judicious placement surface features, Irreversible alteration or destruction preservation and management of mine waste. and landforms Land use planning coordinated with mine Useable land Agriculture and real Contamination of topsoil, planning and periodic monitoring and surface estate destruction of wildlife habitat review. Surface Domain Human resource mapping and progressive Workforce and local Human resources and Social and economic disruptions retraining during coal mine life. Train, up- community community strength skill, re-skill and relocate. Industrial ecosystem Careful planning and business community Neighboring centered on natural Mine closure and relocation of engagement. Development and implement industrial community resources and workforce causing economic loss long-term strategies and economic support. workforce Water supply for Plan to prevent and avoid unnecessary Surface water Chemical contamination, disruption community and impact on surface water sources. Monitor, resources or depletion of supply agriculture mitigate and report. Water supply for Subsurface Subsidence and strata relaxation Diligent mine planning and use of water local community, water resources disturb, depletes or destroys monitoring wells drilled into key aquifers. commercial and (groundwater) groundwater reserves Water supply clean-up. industrial uses Subsurface Domain Storage of valuable Use in-mine pipes to drain, monitor and resources. CO2 or Filled with disused equipment, fire, control gas and water migration. Storage of Mine void storage wastes may be stored collapse, and water flood, unwanted waste gases or liquids in well characterized or sequestered under migration of gases. deep mines with stringent monitoring. certain conditions Low-cost and Coal-associated Leakage, migration, loss, and Capture, use or abate. If sealed must relatively clean fuel hydrocarbons accidents monitor regularly. for uses Subsurface mineral Subsurface mineral, Lack of clear ownership will thwart Clarify legal rights and streamline transfer rights oil and gas rights development of mineral title after mine operations cease. Rights to Legal, Regulatory, and Financial Domain Subsurface water Rights are valuable and may be Clarify legal obligations and rights, transfer groundwater for all rights contested preventing use of water rights after mine operations cease. uses Rights required for Clarify legal rights and streamline transfer Subsurface rights to Unclear laws deter use and may storage or extraction of mineral title and remaining void after the mine void prevent extraction of resources of gas and water mine operations cease. Access to energy and Complex regulations may block easy Access to energy markets should be ensured Access to Markets commodity markets access and impede sales by appropriate legislation and regulation. Funding and insurance often difficult Special finance is needed for mine land Funding is needed for Access to Finance or impossible to obtain for coal mine repurposing, water clean-up, methane commercial projects projects capture and use, and mine voide utilization. Where appropriate, include along with other Lack of access to surface restricts Key to future titles, permits and necessary permissions Access to surface and impedes monitoring and development and to reclaim and repurpose land, surgace rights remediation of environmental repurposing rights may be necessary to allow access to problems and hazards subsurface void. 16 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Evaluating resources for the post closure future conditions (Figure ES 1). This classification system can be applied to anthropogenic resources. Anthropogenic resources are those It is critical to employ a systematic and transparent approach natural resources that remain after human activities, such as to assess the value of remaining assets which are key to a just mining, have ceased at an industrial site. At a coal mine, these transition and which could play a role in mined land repurposing. include resources such as coal, gas, industrial minerals, rare The World Bank encourages and supports the use of tools to earths and or water that remain after mining has ceased. Residual assess, evaluate, and classify resources. Moreover, this approach materials, such as mounds of mine wastes or contaminated recognizes the interconnected nature of the issues that confront water in settling ponds which may regain value after treatment operating companies at the time of mine closure and underscores and processing are also potentially valuable. Similarly, methane, the need for mine operators to develop a comprehensive resource a powerful greenhouse gas, may remain in gassy mines and management plan early in mine operation and periodically through become a source of fugitive emissions and a polluting greenhouse closure and repurposing . gas for decades after closure, but could become a valuable The United Nations Framework Classification (UNFC) is a resource if its use aligns with repurposing the mined land. Mined component used in a resource management system for classifying land itself should be classified as a resource on which projects natural resources. The UNFC incorporates knowledge of socio- may be developed based on its suitability for proposed use. It is economic suitability, feasibility of economic and technical through systematic resource classification that resources are performance, and geology to classify resources-based projects by managed, their value realized in markets and declared as assets their likelihood of attaining commerciality under defined market on corporate balance sheets. Figure ES 1: Diagram of United Nations Framework Classification showing that each of the axes indicate directional increase in uncertainty and risk correlated with the deficiency in knowledge of socio-economic viability, project feasibility under prevailing market conditions and knowledge of the geology and its impact on resources. Resources with the highest likelihood to be used in commercial projects are depicted by green cubes in the diagram, appearing on the E1 level, and proximal to the F1 and G1 rows. S l s 114 Comm rci l proj ct Production 113 112 124 111 123 E1 122 134 121 133 Pot nti ll comm rci l proj ct 132 SOCIO-ECONOMIC VIABILITY 131 Non-comm rci l proj ct nd risk incr s 214 Explor tion proj ct 213 212 224 211 223 E2 222 234 Addition l qu ntiti s in pl c 221 233 Unc rt int 232 231 Oth r combin tions 314 Extr ct d qu ntiti s 313 312 324 311 323 Non-s l s 322 334 E1 Codific tion E3 321 333 Production 332 345 F1 331 343 342 F2 341 PR F3 G4 OJ G3 EC F4 G2 TF G1 Un E A nd c rt SIBI B ILITY inc in LIT NOMIC VIA r sd t Y SOCIO-ECO olo ic l h rds ris Risk of s k int incr nd unc rt Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 17 Assessing the risks associated with actions analysis of the methane that was liberated during active mining. taken during mine closure Figure ES 3 was compiled from data collected at a mine located in southwest China and illustrates what the analysis could show. In Mine closure planning is essential to determine approaches that this case, the mine was sufficiently gassy to warrant installation not only fulfill the mine operator’s responsibilities under the and operation of a gas drainage system. The volumetric flow existing laws but to provide a series of steps that will serve to rates and methane concentrations of the gas drained, used, restore and preserve value of the remaining assets and resources. and or released to the atmosphere would have been recorded Consideration of risks associated with certain actions, or in some during active extraction and must be compiled for analysis. The cases the risks associated with not taking an action, are an engineer will also determine the amount of methane that was important part of the mine closure planning effort. exhausted from the ventilation system so that the total amount Figure ES 2 is a risk matrix designed to be used to conduct a of gas that was liberated during mining can be clearly understood probability-based risk assessment that predicts the likely and management can undertake decisions related to how the outcome of taking (or not taking) certain steps that will impact post-closure emissions will be handled. It is imperative that the the overall value of an asset. This risk matrix is constructed by engineer determines the rate of flooding and the expected final plotting the range in severity of economic damage to remaining equilibrium water level f in the underground workings as this will assets and resources along the x-axis and the likelihood of these directly impact methane production and migration. From the impacts occurring along the y-axis. The magnitude in severity history of mining in gassy coal basins, the hazards related to of impacts is valued from 5 to 1, with 1 being an insignificant methane migration after mines are closed are well known. If the impact and 5 designating major impact. Each of the risks and mine is gassy, the likelihood of methane escaping from a closed potential negative impacts listed in Table ES 2 should be assessed mine in the early years after mine closure is almost certain. Using using the scale to determine the severity of the potential impacts the matrix in Figure ES 2, the engineer might determine that the and the likelihood of occurrence. As an example, an engineer likelihood of leakage to the surface is greater than 90%. If the considering post-closure methane emissions at a mine that closed mine is near a building, say an apartment complex that was gassy during coal extraction would begin by preparing an will remain occupied after closure, the severity of the economic Figure ES 2: Matrix mapping the likelihood of a risk occurring versus the range in severity of its potential impact. Mine management performing the assessment will use their professional judgement to determine the likelihood of occurrence and the severity of impact Insignificant Minor Moderate High Major Increased Likelihood of Occurence 1 2 3 4 5 Improbable 0-20% 0.19 0.38 0.57 1.14 1.71 Unlikely 20-40% 0.42 0.84 1.26 1.68 2.10 Possible 40-60% 0.50 1.00 1.50 2.00 2.50 Likely 60-80% 0.58 1.16 1.74 2.32 2.90 Most Likely 80-100% 0.81 1.62 2.43 3.24 4.05 Severity of Economic Damage 18 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines damage may be moderate or even high, depending on the location UNFC (Figure ES 1) to determine the potential projects that could and the perceived potential for migrating gas to become trapped be developed considering the extent of geological knowledge of in the building and the methane concentration reaching the the methane deposit, the socio-economic viability, and project explosive level. feasibility. In this way, natural resources that could be a hazard and a source of fugitive emissions of a powerful greenhouse In this example, the engineer would take measures that would gas can be transformed into an asset or simply mitigated while ensure that the gas does not reach the building by detecting and ensuring community health and safety. sealing any migration pathways and would recommend that a monitoring program be established, including installing methane monitors that periodically record methane concentration in the building. Subsequently, the engineer would work with geologists to determine the magnitude of the gas resource and use the Figure ES 3: Example plot of coal production, liberation of drained and vented methane at a gassy mine ins southwest China Shih o Min CMM Dr in VAM Emissions Co l Production 4,000,000 110,000 100,000 3,500,000 Co l Production (tonn s) 100% M th n (m3) 90,000 3,000,000 80,000 2,500,000 70,000 2,000,000 60,000 1,500,000 50,000 01 Au 17 F b 05 S p 20 M r 10 Oct 28 Apr 14 Nov 01 Jun 2004 2005 2005 2006 2006 2007 2007 2008 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 19 20 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Introduction Three pillars underpin successful transitions ways that promote sustainable development—we use the term sustainable mine closure 2 to this refer to this process. Since the late 1980s, the World Bank has been a reliable partner in the work to support coal regions in transition. Physical closure of an open pit mine entails reclaiming the post Originally focusing on the coal sectors of Eastern Europe and mining land by restoring the surface to its original contours, Russia, the work continues in many other important coal regions replanting natural vegetation to resemble pre-mining conditions, which now face waning production from aging mines, highly filling the open area with sediment, reclining the pit walls to safe competitive and increasingly carbon constrained markets conditions, and installing safeguards to protect the public from which are responding to shifting energy and climate policies. potential hazards. If land development opportunity is identified, The Bank’s work in these regions led to the recognition that a physical transformation of the land also included. successful and “Just Transition for All” must be built upon three Physical closure of an underground mine entails removal of pillars: institutional governance, people and communities, and the environmentally hazardous objects from both surface and repurposing land and assets. These pillars Table 1 underpin the subsurface, reclaiming of the mine associated industrial yards to Bank’s approach to providing programmatic assistance aimed resemble pre-mining conditions, mitigation of all environmental at easing the transition to a new energy economy. As mines and geotechnical risks including water, subsidence, and emissions, close, a formalized assessment and evaluation of the remaining and installing safeguards to protect the public from potential assets and natural resources is crucial to the determination of hazards. If industrial yard and their surface infrastructure, as well an appropriate level of investment in the sustainable future uses as subsurface mine open void development opportunity is identified, of mined lands. physical transformation of the land, infrastructure, and void spaces Commonly, there are legal and regulatory bounds that frame are also included. Each of the steps are important but they address the rehabilitation of mined lands but generally, it must be only a portion of coal mine related impacts and comprise some rehabilitated to a point where it is safe, stable, and conforms to of the actions which must be undertaken to ensure a sustainable environmental standards. Sustainable coal mine closure and a future for the land, the mineworkers, and the local community. just transition means more than accommodating drastic social Sustainable mine closure requires a different orientation. Mine and economic change by infusing capital, it demands a balanced operating companies, with guidance and support of national, approach to multilateral investment which leads to the realized regional, and local governments, must work in concert with local value of repurposed mined land and encourages sustainable and regional stakeholders to develop an equitable approach socio-economic progress. which yields sustainable closure. The path to sustainable closure The World Bank’s “Achieving a Just Transition for All” envisions encompasses much more as it begins with development of a strong coal mine closure policy backed by good-practice technical closure plan that should be included in the feasibility study prior standards and improved technical capacities which form the to permitting and opening the mine, and at latest, during the basis for effective regulatory processes. To date, most countries pre-closure planning period. The closure plan should be structured have implemented “physical closure” rather than mine closures around a robust policy and regulatory framework which supports that promote sustainable development. Physical closure involves and encourages appropriate actions throughout the closure the removal of equipment and blocking public access to the mine, process and mined land repurposing and continues into the while reassigning some workers and production to other operating regional transition period. mines. By comparison, closures that lead to sustainable develop This phase sets important directions for the post-closure period: are successful because governments strengthen or create and on the one hand, continuous monitoring and management use policies that ensure institutional governance to support of any remaining potential geotechnical or environmental people and communities and facilitate mine land repurposing in 2 The use of this term appeared in 2006 in a discussion paper that refers to the approach of integrating social, environmental, engineering, and financial aspects of mine closure. Kunanayagam, R 2006, 'Sustainable Mine Closure Issues and Lessons Learnt', in AB Fourie & M Tibbett (eds), Proceedings of the First International Seminar on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 13-19, https://doi.org/10.36487/ ACG_repo/605_Kunanayagam Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 21 Table 1: The World Bank's three by three methodology dashboard that is used to assess the existing conditions in coal regions that are experiencing mine closures and transition of the energy economy. This matrix depicts the logical phasing of mine closure and regional transition versus three pillars which underpin the World Bank’s approach to developing Pillar 1 Pillar 2 Pillar 3 Institutional Governance People and Communities Environmental Reclamation and Re- purposing of Land and Assets Phase 1: • Institutional Governance and Policies • Worker’s policies & rights • Assessment of lands and assets for Pre-Closure partial environmental remediation and • Stakeholder engagement and • Assessment of short to medium term Planning repurposing participatory planning workforce transition 10-18 months • Roles & Responsibilities of State and • Social inclusion policies • Assessment of social impacts and social Enterprise sustainability outcomes • Spatial Planning • Transfer of Surface / Sub-• • Strengthening Social Protection • • Coordination across stakeholders Surface data and assessment of legacy Programs and Service Delivery Capacity infrastructure • Political Economy, Stakeholder mapping & • Identification of Social Transition Projects engagement • Fugitive Methane Abatement Plan • Regional economic planning • Community participation in plans for repurposing of land and assets • Energy transition planning Phase 2: • Introduction of improved HSE and • Implementation of social protection • Physical closure / decommissioning to • Closure Technical Closure Standards programs for workers and communities Technical Standards 2+ years • Special Purpose Entity SPE • Roll out of Re-skilling and Re-Education / • Spatial planning / repurposing options Active Labor Market Policies • Feasibility studies of transition projects • Transfer of lands and assets to • Mobility assistance government / SPE entities • Social performance capacity building at regional, municipal and asset levels, • Support for broader social impacts (GBV, including GRM, participatory monitoring social tensions, alcoholism, etc. Phase 3: • SPE coordination between government • Long term education for jobs of the future • Environmental reclamation of prioritized Regional agencies and investors lands and assets Transition • SME business / skills development • Market soundings of potential • Pre-permitting of lands and assets to investments • Access to financing capital 5-10 years incoming investors • Community Driven Development programs • New private sector investors • Smart Village investments • Special purpose entities that finance private investors with community benefits sharing hazards is organized, on the other hand, long-term repurposing while protecting against hazards which may occur, at the time of planning initiated, that makes optimized use of lands and assets closure and the future. As an example, if there is high likelihood for new, low-carbon and sustainable economic activities or that there will be an incursion of water into the mine workings, environmentally and socially beneficial uses. precautions need to be taken to ensure that water levels do not reach the surface or an aquifer and become an environmental This workbook provides information and an outline of activities risk and destructive to the local community. Similarly, the which should be considered while planning and executing practitioner must recognize that it is critical to prevent gas from sustainable mine closure. The intent of this workbook is to provide migrating and causing explosion or fire hazards. Ultimately, it is guidance and information to practitioners who are striving to the practitioner’s responsibility to help formulate a plan for the close coal mines in a manner that leads to a sustainable and next chapter of resource utilization by preparing the mine area prosperous future in the communities which are physically, for repurposing. Mine "Repurposing” entails a transformation culturally, and economically linked to local mining. Sustainable of mining land, void, infrastructure, emissions, and water and closure encompasses many activities; however, this document it is key to a sustainable future for the mined land and the local focuses on the aspects of mine closure that preserve the value of community that has built up around the mine. the remaining natural resources and other mine related assets, 22 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Standards to Improve Closure Practices Closing a mine and preparing for the future ENVIRONMENTAL RECLAMATION, EMISSIONS CONTROL, AND POST-CLOSURE LAND USE where revitalized landscapes can While the technical specifications or mining law sections issued in offer alternative energy uses and other benefits. In addition, many countries define some key criteria that mining companies fugitive methane emissions from underground coal seams must should consider when closing a coal mine, comprehensive technical be controlled, as it is a powerful greenhouse gas if released to the standards for coal mine closure with quantitative and qualitative atmosphere and may become a hazard to the local community, or thresholds on environmental reclamation and land remediation impact post-closure activities at the mine site. may not exist or may need updating. These standards, which are essential to post-mining safety and land use, may need to be While these four overarching principles frame areas of social developed or enhanced in most cases. and environmental concern, they do not capture the economic dimension which is the third pillar of sustainability. Greater Coal mine closure will require modern procedures underpinned by utility is gained by increasing granularity and reorganizing the strong technical standards by which enterprises and provincial approach to consider the risks to society, the environment, and departments responsible for mine closure activities can guide how certain actions, or lack of actions result in diminishment remediation and land reclamation. Four overarching principles, of asset value of remaining resources. Moreover, this approach which correlate to existing regulations and practices in most reflects the interconnected nature of the issues that confront countries, are introduced here. operating companies at the time of mine closure. Three PUBLIC SAFETY so that mines don’t represent a threat to categories or operational domains are designated, namely, communities and critical infrastructure at the time of mine Surface, Subsurface, and Legal and Regulatory. Table 2 maps closure and in the future, the four overarching principles to the domains, or thematic areas, in which related risks can be assessed and appropriate LAND STABILITY so that land subsidence and potential soil measures can be taken to maintain or increase the asset value of erosion have been mitigated, to the extent possible, and the land is the land and other resources. ready for repurposing, MITIGATION OF CHEMICAL IMPACTS where remaining materials in the surface and sub-surface don’t pollute water and soils, and Table 2: Mapping of overarching post closure principles to operational domains Operational Domains Surface Subsurface Legal and Regulatory Public Safety X X Land Stability X X X Overarching Principles MItigation of Chemical Impacts X X X Environmental Reclamation, Emissions X X X Control, and Post-Closure Land Use Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 23 Table 3: Summary table of risks and mitigants that impact value of post closure land and resources. Note that overarching principles are mapped using the colors used in Table 1 above onto the assets or resources at risk in each of the three operational domains Overarching Asset or Intrinsic Risks and potential Actions that will Principles resource at risk value negative impacts reduce risks Natural Drainage patterns, Destruction of natural drainage systems Pre-mine planning to avoid unnecessary ground, natural beauty, and natural habitat, destabilization of alteration of landforms adjacent to mining surface associated flora and slopes, alteration of intrinsic beauty, can property by construction and subsidence. features, and fauna result in reduced land value and uses. Judicious waste pile placement prevents landforms many interrelated problems to physical restoration Useable land Arable land, grazing Contamination of topsoil, sterilization, Land use planning coordinated with mine surface land, and real estate destruction of wildlife habitat reduces or planning and periodic monitoring. development destroys potential for food production and may delay or prohibit real estate Surface Domain development. Workforce Human resources and Social and economic disruptions Human resource mapping and progressive and local community strength retraining during coal mine life. Train, re-skill community and relocate. Neighboring Industrial ecosystem Mine closure and relocation of workforce can Careful planning and business community industrial developed around have detrimental effects on the industrial, engagement. Development of long-term community natural resources and commercial enterprises and service sectors strategies. workforce surrounding coal mines. Surface water Water supply for Chemical contamination, disruption or Mine planning which avoids unnecessary resources community and depletion of supply, reducing potential for impact on surface water sources, drainage agriculture alternative uses and limiting other potential patterns, and water quality. Monitoring and activities on repurposed land. quick response to accidents that imperil water supply is imperative Subsurface Water supply for Subsidence and strata relaxation as a result Careful mine planning and monitoring in the water local community, of coal extraction can disturb groundwater mine by use of water monitoring wells drilled resources agriculture, at the reservoirs often causing substantial into aquifers. Careful placement of in-mine (groundwater) coal mine, and for drawdown, especially if it is necessary to water dams may be used in some cases to other commercial and pump water out of the mine to remain safe. prevent mine-water movement industrial uses Water may appear at the surface when aquifers re-fill and the land surface has subsided below the recovered groundwater level, saturating the ground and pooling. These effects may significantly reduce potential use of land resources and bring pollutants to the surface. Subsurface Domain Mine void Space for storage Mine voids can collapse as subsidence takes Mine void collapse is often unavoidable, but storage of valuable place, miners may use the mine as a waste maintenance of remaining openings and resources, research repository or at the time of abandonment management of water during mine life is and development fill the shafts with unwanted equipment recommended if the mine void is likely to be activities, waste and materials, toxic chemicals, etc.—all of used after mining ceases. Pipes and other repository, natural which may cause groundwater pollution conduits may be left in the mine to access gas storage, and CO2 and reduce the potential for beneficial use deeper horizons so that, if needed, the void sequestration of the coal mine void. Many manmade and can be pumped to control water incursion naturally occurring openings into the mine and surface flooding. Similarly, pipes should may be present and become sources of gas be left as mining retreats for gas extraction and water leakage. that can be used or abated. Verifying and monitoring surface seals at mine openings is imperative. Coal- Low-cost and Leakage of CH4, a powerful greenhouse Capture and use, and if unlikely for gases to associated relatively clean fuel gas may also migrate into buildings and go on excursion into buildings and reservoirs, hydrocarbons readily available for groundwater reservoirs. the mine may be sealed and monitored heat, electricity, or regularly. chemical feedstock 24 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Overarching Asset or Intrinsic Risks and potential Actions that will Principles resource at risk value negative impacts reduce risks Subsurface Subsurface mineral, Mineral rights may be complicated by Review of the mineral estate after mineral rights oil and gas rights overlapping rights. Lack of clear ownership relinquishment is critical and rights must be including the rights is recognized as a major barrier to capture clarified, and any overlapping rights must be of hydrocarbon and and use of gases that escape post mine resolved. Paths to acquiring title and rights other gases closure. Escaping methane is most should be transparent and guaranteed abundant in the first few years after by laws and regulations. The process closure. Methane is most damaging to the for acquiring rights to the gas should be atmosphere during the first few years of streamlined and transparent. All rights must residency. be transferrable to ensure full commercial value and investment potential. Subsurface Rights to Water rights are valuable and often Review of the water rights after water rights groundwater for all contested. Lack of clarity related to water relinquishment is critical, and rights must uses rights can lead to lengthy legal disputes be clarified, and any overlapping rights must and can result in a lag in agricultural and be resolved. Paths to acquiring water rights commercial use, and industrial development. should be transparent and length of time for acquisition or transfer of rights should be brief. New legislation or administrative ruling may be required for resolution. Subsurface Rights to the mine Rights to the mined-out void at a coal Review of the rights to the mine void after Legal, Regulatory, and Financial Domain rights to the may be required mine can be extremely valuable, however, relinquishment is critical, rights must be mine void for development of laws covering these rights may be arcane clearly defined, and any overlapping rights storage, extraction and require lengthy adjudication in some must be resolved. Paths to acquiring mine of methane, and of countries as the rights may belong to the void rights should be transparent and water contained in mining company during mining but revert length of time for acquisition or transfer the void. Similarly, to the mineral owner or surface landowner of rights should be brief. New legislation or the rights to store after mining. Lack of title clarity can administrative ruling may be required for substances, sequester forestall use of the void or capture or use of resolution. Rights must be transferrable gas or conduct other anything contained in the void. to ensure full commercial and investment business may be potential. dependent to clear title. Surface access In some jurisdictions If the rights to the land overlying the mineral Review of the title to surface lands, mineral the rights to minerals, estate and the mined-out void are held rights and rights to the mined-out void is mine-out void and separately, conflicts can ensue. Conflict critical. Actions should be taken to package the ownership of can thwart any attempt to use the mine- the segregated rights to the surface, land may be held land and access the remaining minerals subsurface void and minerals so that a separately. or use the void and a way that promotes a comprehensive approach to repurposing is sustainable future. possible Doing so may require passing laws that encourage a comprehensive approach. Access to Access to energy Access to markets for energy products and Open access to energy markets should Markets and commodity other commodities recovered or generated be ensured by appropriate legislation and markets are essential from closed mines can be difficult and regulation. Enforcement of rights to access for monetization of may thwart agricultural, commercial is a necessity for which additional oversight resources and assets and industrial development. Laws may may be required. available to project guarantee access, but lax enforcement developers and can lead to low dispatch of electricity business operators at and below-market prices for produced closed mines gas making energy projects that reduce methane emissions uneconomic Access to Funding is needed Access to funding and insurance coverage Special finance is needed to provide funding Finance for commercial for coal mine related projects is nearly for mine land repurposing, water clean-up, project development, impossible to obtain except through some methane capture and use, and mine void methane abatement forms of carbon finance which is available utilization. and but limited to some countries and regions. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 25 In most cases, the structure of coal mine or mine closure standards in general reflects the multidimensional nature of problems that have arisen throughout modern coal mining history. The regulatory and policy regimes of coal producing countries address these issues to greater or lesser degrees. World Bank mine closure standard / practitioners workbook is not designed to replace or controvert country standard, but augment and compliment existing policies and regulations by introduction of risk-based good practices and approach to planning and executing mine closures in a sustainable and responsible manner. Table 3, summarizes World Bank mine closure approach, describing the intrinsic value of assets and resources which may be associated with a mining property and their associated risks when mine closure is considered. They are grouped within the surface, subsurface, and legal and regulatory domains, recognizing that the issues and challenges which will be met in each of these areas will require specialized expertise to successfully repurpose the mine site. The table lists the risks and negative impacts which may reduce the options for repurposing or use if appropriate steps are not taken to ensure against diminishment of the remaining value. To emphasize this point, unmitigated risks such as groundwater pollution, subsidence, and methane gas migration can profoundly and deleteriously impact future use of the land and resources. Mitigation of these impacts are possible. The last column provides suggested actions that can be taken to ameliorate the listed risks. These standards should act as a checklist of assets that must be recognized for their remaining value to the local community and safeguarded against destruction or waste. This table may also be used as an agenda for identifying issues that are not covered by existing regulation and policy or which may be adapted to become applicable to the unique geological and mining conditions found in a coal producing region. 26 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Evaluating resources for the post closure future Valuable and recoverable natural resources may remain on mined The World Bank encourages and supports the use of tools to land after a mine has closed. These resources can play a key role assess, evaluate, and classify resources. Moreover, this approach as a source of strategic and industrial raw materials, energy, and recognizes the interconnected nature of the issues that confront water. Extraction, treatment, and use of these resources may operating companies at the time of mine closure and underscores provide opportunities for jobs that help a community achieve the need for mine operators to develop a comprehensive resource a Just transition. However, the value of these resources will be management plan during the design and permitting stage of considered and recognized as assets only if they are appropriately development or at minimum, early in the mine operation. The mine assessed and evaluated through a systematic and transparent closure plan should be reviewed periodically through the mine approach. Assets and resources that may remain at the time of lifecycle and when critical decisions are being made setting the closure include gas, water, other natural resources and byproducts time of closure. of the extraction process that can be found in mine tailings One important tool that should be considered for use by coal such as rare earth elements, and industrial or building materials. mining companies is the United Nations Framework Classification (UNFC), a system used in a resource management system for classifying natural resources which incorporates knowledge of socio-economic suitability, feasibility of economic and technical performance, and geology to classify resources-based projects by their likelihood of attaining commerciality under defined market conditions (Figure 1). This classification system has been used for energy and mineral resources since 1997, but over time has been progressively adapted3 for other uses including renewable and anthropogenic resources. Anthropogenic resources are those natural resources that remain after human activities, such as mining, have ceased. At a coal mine, these include resources such as coal, gas, industrial minerals, rare earths and or water that remain after activity at the mine site have ceased and the mine is prepared for closure. Residual materials, such as mounds of mine wastes or contaminated water in settling ponds which may regain value after treatment and processing. Similarly, methane, a powerful greenhouse gas, may remain in gassy mines and become a source of fugitive emissions for decades after closure but could become a valuable resource if its use aligns with repurposing the mined land and its extraction and use is not hazardous to the surrounding community. Mined land itself should be classified as a resource on which projects may be developed based on its suitability for proposed use. It is through systematic resource classification that resources are managed, their value realized in markets and declared as assets on corporate balance sheets. 3 The UNFC is managed by a subsidiary body of the Committee on Sustainable Energy that convenes under the auspices of the United Nation Economic Commission for Europe. The subsidiary body, the Expert Group on Resource Management, rigorously maintains the framework and any expansion of the framework is done through formal procedures. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 27 Figure 1: Diagram of United Nations Framework Classification showing that each of the axes indicate directional increase in uncertainty and risk correlated with the deficiency in knowledge of socio-economic viability, project feasibility under prevailing market conditions and knowledge of the geology and its impact on resources. Resources with the highest likelihood to be used in commercial projects are depicted by green cubes in the diagram, appearing on the E1 level, and proximal to the F1 and G1 rows. S l s 114 Comm rci l proj ct Production 113 112 124 111 123 E1 122 134 121 133 Pot nti ll comm rci l proj ct 132 SOCIO-ECONOMIC VIABILITY 131 Non-comm rci l proj ct nd risk incr s 214 Explor tion proj ct 213 212 224 211 223 E2 222 234 Addition l qu ntiti s in pl c 221 233 Unc rt int 232 231 Oth r combin tions 314 Extr ct d qu ntiti s 313 312 324 311 323 Non-s l s 322 334 E1 Codific tion E3 321 333 Production 332 345 F1 331 343 342 F2 341 PR F3 G4 OJ G3 EC F4 G2 TF G1 Un E A nd c rt SIBI BILITY inc in LIT NOMIC VIA r sd t Y SOCIO-ECO olo ic l h rds ris Risk of s k int incr nd unc rt Assessing the risks associated with actions Figure 2 is a risk matrix designed to be used to conduct a taken during mine closure probability-based risk assessment 4 that predicts the likely outcome of taking (or not taking) certain steps that will impact The ultimate goal of mine closure planning is to cease mining the overall value of an asset. This risk matrix is constructed by operations, chart the close the mine in a manner that facilitates plotting the range in severity of economic damage to remaining other uses of the void space, and restoring and reclaiming the assets and resources along the x-axis and the likelihood of these surface so that the environmental damage is reduced as much impacts occurring along the y-axis. The magnitude in severity as possible and meets or exceeds the standards prescribed by of impacts is arbitrarily valued from 5 to 1, with 5 being an law. Mine closure planning is essential to determining approaches insignificant impact and 1 designating major impact. Each of the that not only fulfill the mine operator’s responsibilities under risks and potential negative impacts listed in Table 2 should be the existing laws but provides a series of steps that will serve to assessed using the scale to determine the severity of the potential restore and preserve value of the remaining assets and resources. impacts and the likelihood of occurrence. Consideration of risks associated with certain actions, or in some cases the risks associated with not taking an action, are an As an example, an engineer considering post-closure methane important part of the mine closure planning effort. emissions at a mine that was gassy during coal extraction would 4 Annex A contains background information on how this risk matrix is constructed. 28 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines begin by preparing an analysis of the methane that was liberated from the ventilation system so that the total amount of gas during active mining. Figure 3 was compiled from data collected that was liberated during mining can be clearly understood and at a mine located in southwest China and illustrates what the management can undertake decisions related to how the post- analysis could show. In this case, the mine was sufficiently gassy closure emissions will be handled. From the history of mining in to warrant installation and operation of a gas drainage system, gassy coal basins, the hazards related to methane migration after the rates and concentration of the gas drained, used, and or mines are closed are well known. If the mine is gassy, the likelihood released to the atmosphere would have been recorded during of methane escaping from a closed mine in the early years after active extraction and must be compiled for analysis. The engineer mine closure is almost certain. will also determine the amount of methane that was exhausted Figure 2: Matrix showing the severity and likelihood of occurrence of risks Insignificant Minor Moderate High Major Increased Likelihood of Occurence 1 2 3 4 5 Improbable 0-20% 0.19 0.38 0.57 1.14 1.71 Unlikely 20-40% 0.42 0.84 1.26 1.68 2.10 Possible 40-60% 0.50 1.00 1.50 2.00 2.50 Likely 60-80% 0.58 1.16 1.74 2.32 2.90 Most Likely 80-100% 0.81 1.62 2.43 3.24 4.05 Severity of Economic Damage Probability Lower Upper Matrix Quintiles Boundary Boundary Cell Colour p80-p100 0.00 0.72 p60-p80 0.73 1.04 p40-p60 1.05 1.35 p20-p40 1.36 1.75 P0-p20 1.76 4.32 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 29 Using the matrix in Figure 2, the engineer might determine that Figure 3: Example plot of coal production, liberation of drained and vented methane at a gassy mine ins southwest China the likelihood of leakage to the surface is >90%. If the closed mine is near a building, say an apartment complex that will remain occupied after closure, the severity of the economic damage may Shih o Min CMM Dr in VAM Emissions Co l Production be moderate or even high, depending on the location and the 4,000,000 110,000 perceived potential for migrating gas to become trapped in the building and the methane concentration reaching the explosive 3,500,000 100,000 level. In this example, the engineer would take measures that Co l Production (tonn s) 100% M th n (m3) 90,000 would ensure that the gas does not reach the building by 3,000,000 detecting and sealing any migration pathways and would 80,000 recommend that a monitoring program is established, including 2,500,000 installing methane monitors that periodically record methane 70,000 concentration in the building. 2,000,000 60,000 1,500,000 50,000 01 Au 17 F b 05 S p 20 M r 10 Oct 28 Apr 14 Nov 01 Jun 2004 2005 2005 2006 2006 2007 2007 2008 30 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Groundwater and Fugitive Methane Emissions from Coal Mining There is a rich history of mine closure in Europe and the United Coal mining’s legacy in the UK is still felt in parts of the country States that demonstrates the various ways in which mine closures as land is repurposed and real estate development continues. have been managed in wide array mineral resources. Mine closures Abandoned mines also continue to provide energy as methane gas, in Europe have taken place over many decades in coal mines, but which was the bane of the miner when the coal mines were active, recent closures in the UK, France, and Germany provide useful but now can be produced and used directly for heat and other insight into issues that confront all operators when closure is commercial purposes or converted to electricity. During the mid- mandated. In principle, the mine closure measures are mostly 1990s, Alkane Energy pioneered abandoned mine methane use similar, the coal mine closure has added challenges. from more than a dozen mines. Eighteen mines and the associated power production facilities were purchased in 2018 by Infinis United Kingdom Energy, an integrated renewable energy producer, for about 180 In the UK, the first wave of coal mine closures began in the 1980s, million USD. which was overseen by the National Coal Board (NCB). The NCB was formed in 1947 to run the nationalized coal industry until 1987 when coal mining was reorganized, the number of mines was Box 1 UK’s Coal Authority responds reduced, and the governing body was renamed the British Coal to coal mine related hazard Corporation. The name of the organization was changed again in Closed mines may still appear in the news, as did the 1994 to the Coal Authority. The remaining mines were privatized, Wallace Colliery recently when structural problems and only administrative responsibilities remained. The prime occurred in homes built in the 1930s adjacent to its responsibilities of the Coal Authority are: abandoned mine shaft located in the village of Whelley. • licensing coal mining in Britain The Coal Authority was called to act. Material used to • managing the safety issues that have resulted from years of fill the shaft when the mine was closed in the 1920s coal mining shifted and ground under the homes slumped, causing cracks in the foundations and walls of the homes. The • dealing with water pollution caused by mining Coal Authority, which assumes liabilities associated with • communicating information to the public so that informed abandoned mine properties, purchased the properties, decisions can be made dismantled the homes, and made repairs to neighboring The Coal Authority is a form of a Special Purpose Entity that is homes. The Coal Authority is a special purpose entity responsible for ensuring that risks to the public are managed which was created to manage risks and assume liabilities and that post-closure usage of the mined land is undertaken associated with mine properties in the UK. Over 1,300 with full knowledge of potential hazards. It does not deal with mines have been abandoned in the UK since 1952. Since fugitive methane emissions except when it becomes a hazard to 1979 about 130 mines have been closed. the local community. The private sector may apply for a license to capture and use methane, but no government actions are taken to mitigate gas emissions from closed mines. The Coal Authority has been effective in preventing hazards and environmental degradation and is exceedingly responsive to problems related to incidents which occasionally occur at legacy mine sites, most of which are related to subsidence (Box 1). Moreover, surface reclamation of closed mines is regulated to ensure safety and environmental compliance, but repurposing is left to the owners of the land surface. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 31 France (INERIS). However, critical environmental problems from the closed mines persist, such as water influx and gas emissions. Significant Charbonnages de France, the national coal company of France, flooding has taken place in the Lorraine-Saar coal basin as the was formed in 1944 but closed its last coal mine in 2004. The ground has subsided and water from deep subsurface reservoirs management of coal resources remains the responsibility of has flooded the mines and flowed out causing lakes to form on the national government but planned remediation of some the surface. This is not acceptable to the local communities, but environmental issues did not take place prior to the dissolution of solutions have not yet been agreed. Gas emissions in the most Charbonnages de France in 2007. prolific coal basin, Nord Pas de Calais, were well understood to Mine closures were the responsibility of Charbonnages de be a potential threat to local communities which overlie or are France, and similar to the UK, potential hazards to society and adjacent to the mine voids if not controlled (Figure 5). Gazonor, a environmental issues are managed by a government entity, the former subsidiary of the dissolved Charbonnages de France, was National Institute for the Environment and Industrial Hazards left with the responsibility of reducing methane related hazards Figure 4: Plot of gas production that began in 1978 from closed mines in northern France Avion Cumul tiv Production D sir Cumul tiv Production Avion Annu l G s Production D sir Annu l G s Production Divion Cumul tiv Production Cumul tiv G s Production (All Sit s) Divion Annu l G s Production Tot l A r t d Annu l G s Production for Min s 1800 70 1600 60 1400 Cumul tiv Production (Million m3) Annu l Production (Million m3) 50 1200 40 1000 800 30 600 20 400 10 200 0 0 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 32 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines and producing methane for civil use. Methane drainage systems Germany and surface vents put into service at these coal mines at the time There are substantial abandoned mine methane (AMM) recovery of closure are still controlled by the national government. Gazonor and utilization activities underway in Germany, with 37 individual is owned by a private sector company which owns the rights to projects reportedly in operation. These projects comprise power the gas resources in the mine voids and remaining coal seams, and combined heat and power projects, which together supply but access to the resources is via the government owned drainage more than 113 MW of electricity. German AMM projects mitigate sites and additional drilling or changes to the drainage and vent more than 400 million m3 of methane that would otherwise be systems are prohibited. The gas production data depicted in emitted to the atmosphere each year. Figure 4 is drawn from three mines located in the Pas de Calais region of northeastern France. This complex has produced These AMM projects were initiated largely due to the availability electricity from five electricity generation facilities with installed of subsidies, which made the projects economically attractive. capacity of 9MW. During the 40-year period from 1978 through Germany established the Electricity Feed-In Act In 1991, which 2018, Avion produced 1,068 million cubic meters of methane was the first green electricity feed-in tariff scheme in the world. while Divion and Desiree each produced 325 and 145 million cubic Germany passed the Renewable Energy Sources Act (EEG) in 2000 meters of methane, respectively. The total volume of methane and the Act has been modified several times over the ensuing produced from the three mines, 1,538 cubic meters is equivalent years. It comprises a series of laws which provided feed-in tariffs to nearly 22 million tonnes of CO2 using a GWP of 25 or 75.5 to encourage the generation of renewable electricity. The laws million tonnes using a GWP of 86. Annual gas production in 2018 were modified in 2014 and in 2017 to facilitate transition from for the three mine sites was 26 million cubic meters of methane. feed-in tariffs of the renewable energy to an auction system. Francaise de l’Energie, the operator of this complex, estimates After the transition and feed-in tariffs ended, no additional AMM that over 600,000 tonnes per year of CO2 emissions are avoided projects have been developed and some have been shuttered. annually using the methane as a fuel to supplant coal. However, the European Union Emissions Trading System does not include China methane, so these emissions reductions are not being monetized. Shanxi province is one of the top coal-producing provinces in China, extracting more that 980 million tons from 978 coal Figure 5: Schematic depiction of potential migration pathways for methane at an active mine. Many of the pathways will be accessible mines in 2019. Due to amount of gas contained in mineable after mine closure (UNECE 2019) coal seams and the surrounding strata, Shanxi coal mines are considered some of the most gassy and hazardous in the world, yet strong mine safety regulation, aggressive enforcement, training, investment, and dedication have given rise to a mine safety culture which has allowed Shanxi to operate large mines with ever decreasing accident rates. Nevertheless, management of methane during coal mining is a continuing and evolving challenge as mines increase in size and extract coal from deeper horizons. Supplying fresh air to miners, large fans are employed to force air through the mines to lower the concentration of methane in the active workings to a level well below methane’s explosive limits and protect the miners. At many mines, the amount of gas liberated during mining exceeds the capacity of the ventilation system to ensure a safe underground environment for the miners, so gas drainage systems are installed to remove methane through boreholes drilled into coal seams and the strata which underlie and Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 33 There are 12 provinces in China which have mines that are gassy In a recent paper Kholod and others, 2020, demonstrated enough to warrant dedicated gas drainage systems, venting that methane emissions from closed coal mines is a more than 100 million m3 annually; but two provinces, Shanxi growing problem. Methane will continue to escape the and Guizhou, are the dominant producers of drained methane; atmosphere for years after the mines are shuttered. The Shanxi alone produces 49.7% of China’s annual total. Many mines work used standardized shared socioeconomic pathways in Shanxi are nearing the end of their useful life, and with a (SSPs) to explore the impact of implemented policies on persistent production surplus, mines are being closed every year. the fugitive emissions of methane from active and closed In 2019, 18 coal mines were closed in Shanxi province which mines. The researchers used SSP2 which is a middle of the produced about 19 million tons of coal, and in 2020, another 15 road scenario that does not have strong policies against million tons of overcapacity will be cut. Mines with capacity of less methane emissions but is not without some government than 600,000 tons of annual capacity are targeted for closure, intervention to meet sustainable development goal. but over the last four years, 116 million tons of overcapacity have Figure 5 shows that if coal mining was completely halted been cut by closing 106 mines, with annual production of over in 2050, the shuttered mines could still emit around 30 one million tons each. Looming is another problem, one of which billion m3 per year. is just now beginning to be recognized as these mines are closed, the gas that was once a problem for the miners, will become an Figure 6: Plot of methane emissions and coal production based unintended and unmonitored problem for the local community on coal consumed using SSP2 from 2010 through 2100 and global environment methane will continue to escape to the Co l EJ AIM, bcm atmosphere through mine openings which were improperly closed, 300 80 or through cracks that were formed during mining as the mined- 250 70 out void spaces collapsed and causes subsidence and formation 60 of conduits to the surface and connection to groundwater 200 50 aquifers. As more mines are closed, this problem will increase, and AIM, bcm Co l EJ 150 40 unmitigated fugitive emissions from closed mines will become a 100 30 significant global problem. 20 50 Methane that would otherwise escape to the atmosphere from 10 closed coal mines has been produced and used in the United 0 0 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 States, the UK, France and Germany for decades: • Production and use of methane released from closed mines in the Pas de Calais region of northeast France began in 1978 overlie the mineable coal seams. The gas drainage systems are (Figure 4). critical components of managing methane in these mines, 70-80% • Substantial production of methane from closed mines began in of the gas liberated by mining is exhausted to the atmosphere the US, UK, and Germany in the mid-1990s. Hundreds of millions through the mine ventilation system at methane concentrations of cubic meters have been recovered and injected into pipelines below one percent. However, more aggressive gas drainage could and used for power generation. bring higher quality gas to the surface where it could be used or abated, reducing ventilation system emissions. • Feed-in tariffs have been applied in France and Germany, whereas, no special pricing has been applied in the UK, but sales In 2018 the total amount of methane that was drained from coal of carbon credits have help bolstered the economic viability of mines in China was 12.98 billion m3, of which only 41%, or 5.31 waste mine methane production in the United States. billion m3 was used—even after incurring the expense of draining the gas and transporting it to the surface, the rest was vented. 34 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Application of Good Practices to Coal Mine Closure Coal mine closure planning should be directed at mitigating the coal mine closure standards, the highest value of the closed impact of risks, which, if unaddressed, will increase the costs mine and the associated surface resources can be ensured. Use of mine closure, reduce the value of the remaining resources of the mined-land repurposing toolkit such as LURA, is key to and facilities, increase the potential for local health and safety an organized assessment of the potential and planning for the risks, and increase the potential for unintended local and global highest use of the land. Repurposing of the mine site and potential environmental consequences. Planning should envisage the future use of the land and other resources such as remaining gas and and highest use of the remaining assets at the point in time when water resources if present, offer a considerable future value. the mine operator relinquishes its rights to extract coal and should In addition, under specific geologic conditions that constrain assess the risks that can adversely impact the future value of unwanted migration of gas, the void space may be used for assets. Planning for mitigation of risks at the early stages of mine storage of natural gas5. Mines in the USA, France and Belgium development and periodically throughout mine life through the have been used for this purpose. mine closure process is a relatively low-cost, high-value activity Implementation of technical closure standards is best started that can facilitate mine land repurposing. while the mine is still in operation, so that final mining activities Actions that reduce risks are best addressed during the initial are guided by a technical closure plan. Activities should include phase of coal reserve prove-up. This a period during which data assessment of the activities needed and associated costs essential to mine development planning activities are collected. to remove unwanted plant and equipment and undertaking These data are essential for future planning and should be used environmental reclamation and re-purpose other useful physical to not only to develop coal resources in the most environmentally assets, including buildings and energy infrastructure. It is sound manner, but also enable mining companies to plan the especially important to understand that implementation of surface layout so that troublesome and complicating factors technical standards requires actions by both the mining company that may impact site restoration and reduce future use and value and a community of certified third-party enterprises. Given the are at least managed, and at best, mitigated or avoided. Data highly specialized skills required to close underground coal mines, collected during this period are used to evaluate the coal resources the World Bank reports that countries receiving past technical and assess the potential for methane gas hazards. It is also assistance on coal mine closure have exhibited a preference critical to collect and evaluate information related to the volume for establishing dedicated coal mine closure companies. These and quality of groundwater resources which may be used during companies absorb mine labor, engineering expertise and equipment mining activities or that could pose risk to underground safety. from the on-site mining enterprise to ensure proper reclamation This phase of data collection also establishes baseline conditions to national standards. And so, the creation of the coal mine and should be used to frame the potential for future restoration closure company assists in employment transition in the region. and repurposing. Although these actions should be taken for new The European Commission, in managing the “E.C. Coal Regions mine development, in reality most mines will close without the in Transition Platform”, has also reported on regions having a benefit of having had the opportunity for planning closure in these similar preference to establish highly specialized coal mine closure early stages of development. companies to capture the expertise of coal enterprises on-site and ensure regulatory compliance and adherence to national Without closure planning and assessment of re-development regulations. In most coal producing regions, government-certified, risks, the post-closure phase is often limited to land reclamation, third-party specialists are available to prepare mine closure comprising recontouring the land, installation of surface mine- plans using technical standards that would be provided by the water drainage monitoring systems, and decontamination of government. These third-party specialists could be a delivery land surface. However, further consideration is warranted. By mechanism for technology transfer to coal mining enterprises that implementing good practices that serve as the basis of the global would act as specialized closure companies. 5 A discussion of the gas storage in abandoned mines can be found in “Technical and Economic Assessment of Coalbed Methane Storage in Abandoned Mine Workings” https://nepis.epa.gov/Exe/ZyPDF.cgi/6000090B. PDF?Dockey=6000090B.PDF Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 35 The start date for implementation of technical coal mine closure subsidence, some government entities in China and elsewhere are standards varies globally. The ITUC’s global initiative “A Just encouraging repurposing for renewable energy generation, using Transition” is increasingly being applied as a guiding principle in this subsided terrain for solar and wind power generation and/or coal mine closure by seeking to put in place (ahead of all closure renewable energy storage (pump storage, molten salt storage). As activities) the concrete plans, policies, and investments needed an example, in the past few years, investment in Shanxi Province, for a fast and fair transformation. The World Bank’s technical China has converted some abandoned coal mines and subsidence assistance complements this concept by also envisioning areas into GW-scale solar PV bases under the national pilot solar strengthening of the necessary institutional reforms that PV auctions, and geological, forestry and agriculture parks. In the are needed to ensure effective implementation of standards Datong mining region, a 248-acre solar farm was built in 2017 on a by building up professional and institutional capacities. This depleted coal mine subsidence area. Occasionally, the subsidence would include technical standards to be enforced as part of the pose risks for the existing use of the land overlying mines where preparatory process which would include the compilation of the mine is beneath settlement areas. In this case, the retaining relevant data regarding the subsurface and surface, deleterious value of the overlying property and public safety becomes priority chemicals and other hazards that may be left onsite, pollution and maximizing of the closure measures are warranted. abatement measures that have been taken and will need to While the technical specifications issued in 2002 define some key be sustained, essential infrastructure necessary to sustain criteria that mining companies should look at when closing a coal abatement of fugitive methane, and the assessed status of land mine, there is currently no comprehensive technical standard for and assets that would be repurposed for future use. coal mine closure with quantitative and qualitative thresholds Technical standards also address the need for comprehensive on environmental reclamation and land remediation, which are environmental reclamation, which is being viewed globally through essential to post-mining safety and land use. The provincial a new perspective. Many jurisdictions are coming to recognize Department of Environment and Ecology reports that the mine that coal mining areas represent decades and/or centuries of closure plan is submitted to the provincial Department of Natural environmental degradation, and regulations based on the “polluter Resources, but the status of tracking and compliance of activities pays principle” where efforts would focus on returning post- is not readily available and post-closure monitoring is not known. mining lands to their original state, would be prohibitively costly and impractical. Moreover, many mining communities now want Checklist of good practices for implementing to use these lands and physical assets as part of the economic coal mine closure transformation of the region and returning them to forest and Developing the pilot mine closure project in a region requires open-space may be counter to industrial development plans. information and data that should be available from the mine For this reason, many older technical standards and regulations operating entity and/or government repositories. These data and are now seen to be working against the guiding principles of mine maps are critical to successfully plan closure and ensure ensuring a Just Transition for All, by placing binding constraints that the highest use is achieved as the property is repurposed on the mining enterprise to comply with regulations that may be for the next chapter in the use of the remaining assets and unaligned with the desires of the community post-mining. resources. Following is a list that lays out data and information that is essential for determining the risks associated with various Subsidence, which is caused by underground mining, can render actions that must be taken to close and repurpose the mine future uses of the land overlying the mines to be non-viable. and associated facilities and equipment. Mine closure will be an Subsidence of the ground’s surface above underground coal mines expense that can be anticipated and estimated as a part of early begins during active mining and continues after closure. In recent stages of mine closure planning. Many coal producing countries years, there is increasing awareness of repurposing closed coal have published regulations and guidance which recommend steps mine lands for other productive uses, and repurposing land and in planning for and prescribing processes that help prepare for assets must become one of the core elements of a region’s energy mine closure. The following comprises a list of activities that transition. Because of the irregular ground surface left after 36 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines should be among those considered when planning and budgeting 1.4.6.4. removal of equipment and toxic materials from for mine closure. This list is not comprehensive but acts as a base underground upon which to build an initial investigation and provides the steps 1.4.6.5. sealing underground mine entries to protect the to follow from data collection through assessment of technical public. Additional steps must be taken to seal the shaft if and economic feasibility. attempting to seal the entry to prevent leakage of gas. 1.4.6.6. sealing utility boreholes and other possible 1. Gather and collate information and records prepared by mine migration pathways for gas and water migrating from the owner/operator while operating that include but are not subsurface using non-flammable materials limited to: 1.4.6.7. designing, constructing, and hardening 1.1. Maps of surface, including cadastral surveys, facilities underground systems which will control water flow to the maps, surface topography, and subsurface workings, including surface pipes for water, gas , electrical utilities, etc. 1.4.6.8. laying pipe or maintaining existing gas drainage 1.2. Existing permits for operating, leases, mineral rights (coal, system to ensure flow of gas to surface if gas extraction gas and other), water rights. is desirable or necessary 1.3. Existing life of mine plan and design. 1.4.7. Determining which buildings and equipment will 1.4. Presently existing mine closure plan. Cost of closure and be useful for post-mining repurposing and identify preparation of the mined land may need to be estimated if the which buildings and structures must be removed and/or mine closure plan has not been submitted or is incomplete. demolished, including: If needed the following elements can be used for estimating 1.4.8. administrative and shop buildings, crushers, coal closure costs: beneficiation plants, conveyors, rail, foundations, coal 1.4.1. Estimating the greatest area of disturbance that will storage facilities, require final grading, topsoil replacement, and revegetation 1.4.9. other surface structures and systems including, 1.4.2. Estimating the largest volume of material to be power substations, winding gear, head frames, man and backfilled and graded so that the post mining land surface equipment lifts contours are acceptable for future use, including challenging 1.4.10. drilling, blasting, and other extraordinary landforms that cause additional material haulage and demolition work grading to achieve desired outcome 1.4.3. Identifying which roads need to be removed and the surface reclaimed and revegetated 2. Conduct a pre-closure assessment comprising the information and data developed in the previous steps and in addition 1.4.4. Tabulating longest haul distances between mine include the following: waste, topsoil storage and final placement 2.1. Hydrologic survey report of the present condition of the 1.4.5. Determining the greatest volume of material which will surface and groundwater volume, quality and expected rate be required and transported to cover refuse and disposal of water table (piezometric surface) rebound. Provide forecast sites of potential for mine flooding including the rate of mine filling 1.4.6. Identifying special needs that must be included in the and elevation to which the mine will fill with water. reclamation activities, including; 2.2. Provide information and data on the last 10 years of 1.4.6.1. removal of toxic materials, methane emissions if the mine had an active degasification 1.4.6.2. desilting settling ponds, pumping or treatment of system and/or exhausted gas through the ventilation system, surface water reservoirs, gather detailed information for analysis 1.4.6.3. transport of prime topsoil for agriculture Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 37 2.3. Provide a report on the status of surface contamination with CMM and VAM production and emissions to a closed mine and other surface pollution risks that will require remediation with AMM production and use facility. Determine costs for at the time of closure, focus on contamination that will modifying, constructing, operating and maintenance costs for impact new businesses that could be established on mine’s planned post-closure gas production and energy services. surface holdings 4. Prepare a prefeasibility study that examines the technical and 2.4.Provide status of subsidence and current forecasts of final economic feasibility of proposed uses for which a conceptual areal extent of surface damage. project design has been generated. Study should use forecasts 2.5. In addition to gas production, evaluate options for using developed in step 2.1 and include all costs including permitting, void---e.g. storage for gases, water storage and production, new construction, equipment purchases or leasing, operating solid mine wastes (from coal preparation plant or mine and maintenance, and financial costs. Revenues should include, production), among other items, the sales of energy products and services, use fees for access to surface and underground facilities, 2.6. Report on impact on local community, disruption of critical and transaction of fungible environmental attributes such as services, other social and economic issues carbon offset credits. 3. Develop a plan for gas production and use based on 5. Based on the results from the prefeasibility study, develop information provided through Step 2 activities. a robust business model that uses the best strategy to take 3.1. Prepare gas production forecasts based on available advantage of existing and developing markets and provide data and approaches contained in the UNECE Best Practice value to the transitioning community. Guidance for Effective Methane Recovery and Use from Abandoned Coal Mine. 6. With the assistance of the United Nations Economic 3.2. Compare legally mandated, required remediation to any Commission on Europe Group of Experts on CMM prepare and additional remediation which may be identified to be necessary hold an international workshop that invites knowledgeable in order to allow new businesses to be developed. experts to provide applicable experiences and international 3.3. Develop lists of business opportunities which will be case studies which will aid in project development. This available after mine-closure. Which of these businesses or workshop could present successes and failures and seek to existing business will require energy? What form (gas, heat, discover commonalities. Business models for specific projects electricity) and how much? can be presented and discussed with experts. The workshop 3.4. Examine existing licenses for coal associated gas. could include technical, financial experts as well as experts on Determine if any of the existing permits or licenses are useful the socio-economic impacts of transition from coal. for new business and determine if the licenses or permits can be transferred to post mine closure businesses. (Active mine could 7. Based on input from experts, produce full feasibility study and have permits for electricity production from CMM.) seek financing. 3.5. Provide road map for permitting and licensing that will be required for post closure energy business development. Determine the costs for re-permitting and new licenses. 3.6. Compile list of needs including infrastructure, existing monitoring systems for gas and water, specific information-- data, maps, and engineering drawings which will be required for smooth and cost-effective transition from active mine 38 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Considering options for mine closure projects • Water treatment in one form or another is likely to be needed at gassy coal mines at many mines. Using renewable energy and captured methane to pump, treat, and re-inject contaminated surface Project options for closed mines which were gassy during active water and groundwater, is a high-value use of the gas. This mining operations are numerous, but to date most projects have form of water treatment could be critical in providing the comprised: (i) mitigating fugitive emissions (see next section); (ii) energy for comprehensive water treatment and restoration of power generation; (iii) providing gas for pipeline injection after groundwater reserves. treatment or blending with high quality methane; (iv) fuel for • It is also possible to use methane from closed mines by applying transportation; (v) direct use for heating and (vi) flaring to destroy new technology and innovative design to develop hydrogen the methane and in some jurisdictions qualify for carbon credits. production using waste gas and mine water. Many countries Yet other uses for the mine void have been explored by some are exploring the decarbonization of its natural gas supply by innovative companies. blending hydrogen into its natural gas supply. This is possible if the pipelines are hydrogen-ready, meaning that they are • One such company in Germany is considering installation of gastight and can be trusted to safely transport a hydrogen- insulated vessels in a mine void in which molten salt can be natural gas blend to market. stored. This would act as a form of energy storage during off-peak hours, whereby the molten salt can be pumped into There are many opportunities to use the remaining assets a steam generating system that supplies the steam to spin a and resources of a closed mine to fit the purposes of the local turbine and generate electricity. Organic Rankine cycle systems communities and markets. Resilient business model development can be used to capture more of the heat energy to increase is crucial and development of alternative scenarios during a pre- power production efficiency. If the mine is gassy the gas could feasibility study is a good practice and offers the opportunity to be used to help melt the salt. test-drive ideas before discussing options with an investor.  Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 39 Publicly available coal mine methane emissions data reported to the USEPA allows analysis that can be useful to better understand the quantity of gas released during active mining through time and could be used to develop forecasts of potential gas release from a closed mine. This analysis can be used to determine the magnitude and potential steps that should be taken to prevent future fugitive emissions when planning for mine closure. Additionally, as mentioned above, some of the infrastructure can be preserved if it can be used to conduct the gas to the surface so that it can be used or destroyed. Mod l d M sur d 100 90 80 70 M th n (Million m3) 60 50 40 30 20 10 0 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Figure 7: Shows the amount of gas that was emitted from the West Elk Mine during the years extending from 2011 through 2019. During this period, 44.2 million tons of coal were mined and 13.4 billion cubic feet of gas was liberated to the atmosphere, without significant mitigation or abatement. A small burner using CMM for fuel was used to heat ventilation air at the intake to warm air in the winter to increase the comfort and safety of the miners. This represents 5.4 million tonnes of CO2e using a GWP of 25, but 18.6 million tonnes using the more appropriate GWP value of 86. A hyperbolic decline curve was fit to the data to model the emissions and show the downward trend in the volume of gas that was liberated by mining activities. The curve indicates that mining is effectively draining this unconventional gas reservoir. This mine was opened in 1982 and estimated to remain open until 2024 . It is critical that closure of this mine is conducted with a plan for capturing the gas that remains in the reservoir. No methane emission mitigation or abatement has taken place. Closed mine emissions could total as much as 25% of the emissions during active mining and last for decades to come. 40 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Mitigating Fugitive Emissions Coal-associated methane—an introduction Natural systems (wetlands, swamps, etc.) account for about 40% of the methane released in the atmosphere. Anthropogenic Methane liberated by coal mining activities is a global problem. methane, accounting for the other 60%, is emitted during the This powerful greenhouse gas is emitted from active and closed production and transport of coal, natural gas, and oil. Emissions coal mines. Emissions persist for decades after closure unless also result from the decay of organic matter in municipal solid the mines are flooded or sealed. USEPA estimated that active waste landfills, some livestock manure storage systems, and and closed mines will emit 7996 million tonnes of CO2e during certain agro-industrial and municipal wastewater treatment 2020. While coal mining and consumption in OECD countries are systems. Unlike other GHGs, methane can be easily destroyed gradually decreasing, the same is not true for Asia where coal or converted to usable energy. Capturing and using methane production is expected to continue growing, especially in China offers opportunities to generate new sources of clean energy and and India. Nevertheless, the global industry is seeing more mine mitigate global climate change. Overall, the coal mining industry closures and there is growing interest in abandoned mines as accounts for about 9% (Figure 8)8 of global methane emissions source of methane emissions. from human activities9. Emissions that occur after mining are often assumed to be Figure 8: Estimated global anthropogenic methane emissions small and many coal producing countries do not adequately by source, 2020 report coal mine methane emissions in their national inventories. However, measurements taken at closed mines and the large volumes of gas processed in AMM projects have shown that some Ent ric F rm nt tion Ric Culitiv tion closed mines can still produce significant volumes of gas after Oil & G s Oth r A ricultur l Sourc s abandonment. Addressing sources of emissions and planning Municip l Solid W st St tion r & Mobil Sourc s for closure before cessation of mining is so important, because Co l Minin A ricultur l (M nur M n m nt) capture, use, and abatement of fugitive methane emissions is W st w t r Biom ss most effective in the early years after mining ceases when the rate of emissions is highest. 3% 3% 4% Methane: the second most important gas 5% for climate change 27% Methane (CH4) is the second most abundant anthropogenic greenhouse gas (GHG) after carbon dioxide (CO2), accounting 7% for about 20% of global emissions. Though methane is emitted in smaller quantities than CO2, its global warming potential (i.e. 7% the ability of the gas to trap heat in the atmosphere) is 28-36 times that of CO2 for a 100-year time horizon7. It also has a short 9% residence time in the atmosphere, about 12 years, with a global 24% warming potential 84 times higher than that of CO2 over a 20- 11% year period. As a result, methane emissions are said to contribute as much as one-third of today’s anthropogenic GHG warming. 6 USEPA, 2019, Global Methane Emissions and Mitigation Opportunities fact sheet, https://www.globalmethane.org/documents/gmi-mitigation-factsheet.pdf, accessed June 2020 7 IPCC, 2016; U.S. EPA, 2017. 8 https://www.globalmethane.org/documents/gmi-mitigation-factsheet.pdf 9 Although many scholars argue that methane emissions from fossil fuels are underestimated, and recent studies show that some regions such as China and the Appalachian region of the US, methane may comprise a greater proportion of GHGs Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 41 Coal-associated methane: Another reason that CBM is considered an unconventional gas an unconventional form of natural gas resource is that methane is not stored in a coal seam’s open pore spaces in the same way it is stored in sandstone or other Coal-Bed Methane (CBM) is considered an unconventional form conventional reservoirs. Methane found in coal seams attaches to of natural gas found in coal deposits10. Natural gas found in coal carbon atoms and is held in place by the ambient pressure found seams varies in composition and heating value, but methane at the depth at which the coal is buried. Methane content of a coal predominates. seam increases as the gas gradually becomes attached or sorbed One reason that CBM is considered unconventional by the oil onto carbon atoms as burial deepens through geologic time11. For and gas industry is because the production of this gas requires a these reasons, the gas content of coal increases as coal matures different approach to drilling, wellbore completion, and production. and carbon becomes more concentrated, while volatile organic Gases found in coal seams are naturally generated during organic compounds and water escape during coalification. Methane maturation or coalification, which is the geologic process of trapped in this manner will remain in place until disturbed by converting plant material to coal as it endures the heat pressure mining activities or extracted by wells, where the ambient of burial. Coal rank is a measure of the progressive maturation pressure on a coal seam is lowered and the gas desorbs and is or increasing carbon content of coal and generally increases with released. This desorption process is pressure dependent, so after burial depth. The amount of methane that can be stored in coal is initial decline in production rates, the rate stabilizes, and methane correlated to the rank of the coal – anthracite has a higher carbon production may persist for decades. content and may store more methane than bituminous coal (Figure 8). Globally, most hard coal produced for commercial use Methane as a hazard and an opportunity is bituminous coal, which may be very gassy. To the coal mining industry, methane is a hazard. It is a colorless, odorless, relatively non-toxic and highly explosive gas – well Figure 9: Coal rank and the impact of depth on gas content known from its occurrence in underground coal mining. Mining disasters expose to the world the horror of methane gas Anthr cit Bituminous Subbituminous explosions which injure and kill miners, destroy communities, and in some cases cause devastating economic loss. There are no coal 30 producing countries which have mined gassy coal without serious accidents. As coal resources are depleted and extraction of deeper 25 deposits becomes more prevalent, the likelihood of methane related incidents increases. G s cont nt (m3/ton) 20 Beyond safety issues, the development of CBM has raised issues because of the potential environmental impacts. Most 15 importantly, to extract the methane, CBM operators drill wells into coal seams and pump out groundwater from the coal beds to 10 lower the pressure on the seam and release methane. Produced water or CBM wastewater may be used for various purposes if it is 5 fresh, but often due to its salinity, it becomes a waste byproduct that must be responsibly managed. 0 0 20 40 60 80 100 However, coal-associated methane also represents a potential energy source. Options for commercial methane utilization include 10 Coal has a large internal surface area (due to the relic organic structures of the plant material found in coal) and can store a surprisingly larger volume of methane-rich gas than conventional natural gas reservoirs. 11 There is a predictable correlation between the volume of gas contained in coal and the internal pressure of the coal seam from which it is extracted. The gas content of the current global underground hard coal mix is estimated between 13 and 18 m3/t for mining depths from 450 to 1120 m. 42 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines electricity production, combined heat and power for industry and/ Figure 10: Coalbed Methane production in USA 1989-2017 or urban areas, supply to commercial natural gas markets via pipelines, vehicle fuel in the form of LNG or CNG, district heating U.S. Co lb d M th n Production and other uses. Use of the coal-associated gas for these and other uses results in the monetization of the benefits of reducing 2,500 greenhouse gas emissions. The U.S. dominates CBM production globally, followed by 2,000 Australia. U.S. CBM production (Figure 10) peaked at nearly two trillion cubic feet (56.6 billion cubic meters) in 2008, but dropped Billion (ft3) 1,500 steadily in later years, with one trillion cubic feet (28.3 billion cubic meters) produced in 2017, mostly from Colorado, New Mexico, Wyoming, and Virginia. In 2017, CBM provided 3.6% of total U.S. 1,000 natural gas production12. Australia’s annual CBM production was approaching one trillion cubic feet (28.3 billion cubic meters) of 500 CBM in 2018. The Asia Pacific region is expected to be the fastest growing 0 market in the near future, primarily in coal rich countries such as 1990 1995 2000 2005 2010 2015 India, Australia, China and Indonesia. 12 US and Russia are by far the two biggest producers of natural gas globally. US production became the first one in 2009, was 686 bcm in 2013 and increased to 767 bcm in 2017. Burning natural gas produces nearly half as much carbon dioxide per unit of energy compared with coal. Natural gas is thus considered by many to be a “bridge fuel” that can help nations lower carbon emissions while they transition more slowly from fossil fuels to renewable, carbon-neutral forms of energy. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 43 More acronyms: terminology according mines. The relative percentages for the US emissions depicted in to gas provenance Figure 6 can be used to approximate the relative percentages for other countries, but geologic and mining conditions may impact CBM can be recovered from coal throughout the coal mining the ratio of gas drained to ventilated if miners are forced to drain lifecycle—before, during, or after mining operations. It can also be more gas to augment the ventilation system in order to keep the extracted from un-mined or “virgin” coal seams where mining is mine safe from build of methane in the workings. not occurring. Figure 11: Coal associated methane terminology Scientist, engineers, and mine operators have developed terminology that signifies the provenance of the gas which is liberated during mining (Figure 11). If gas is drained from coal reserves that are being mined, or will be at a later date, it is Co lb d M th n known by the general term, coal mine methane (CMM). Ventilation (CBM) air methane (VAM) is methane that has been diluted by fresh Co l Min air moved through the mine by large fans and evacuated to the M th n Ab ndon d (CMM) Min M th n atmosphere. If methane is present in a closed or abandoned mine (AMM) it is abandoned mine methane (AMM), and if it drained from coal seams that will be mined in an open pit mine it is termed surface V ntilt ion Air M th n mine methane (SMM). This terminology was developed to make Surf c (VAM) discussion related to the nature of coal-associated methane more Min M th n (SMM) descriptive, but the reason for the gas presence and the principle governing its drainage and emission remains the same in each case. Methane is a gas lighter than air which will migrate to a zone of low pressure, including the atmosphere if a suitable conduit exists. Coal mining begins where the coal is easily accessible, and for that reason most coal mines are located on a geologic Figure 12: Percentage contribution by source for methane emitted from structure where the coal seam has been pushed closer to the US coal mines surface by geologic forces. Gases contained in the coal bearing strata will migrate to the highest accessible point, whether the excursion begins in strata surrounding underground mine workings 226.5 6% 379.4 or an open pit. 311.5 10% 8% 427.6 Figure 12 depicts the relative percentage contribution from 12% surface and underground mines in the US in 2017. Note this 93.4 graphic also breaks out the source of emissions according to how 3% the gas was emitted, i.e. from the reporting underground mines’ 2,214.4 61% drainage system used to remove gas prior to mining the seam or during mining, and emissions that come from post-mine drainage of the mined-out void. Emissions from closed mines (abandoned mines, using the US Mine Safety and Health Administration Surf c min s Und r round min s - post-minin clos d terminology) are also estimated. Global coal mine methane Surf c min s - Und r round ctiv - emissions during 2019 were estimated to be 930.5 million tonnes d sific tion v nt d ctiv Und r round ctiv - Und r round ctiv - CO2e, of which 11.6 million tonnes CO2e from surface mines and post-minin v ntil tion missions the remainder is emitted from active and closed underground coal 44 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Going deeper: dealing with methane before unmined coal resources which would reduce the volume of methane and during coal mining that will be emitted into the mine and eventually to the atmosphere. Accidents are preventable, as are prodigious emissions of methane The coal mining lifecycle (Figure 13) begins with discovery of coal, to the atmosphere if best practices are adopted. and progresses through mine construction, coal extraction, and finally, mine closure. If methane is associated with a minable Gassy underground coal mines employ massive ventilation coal deposit it will be present throughout a mine’s life. There are systems to move very large volumes of fresh air through the opportunities to capture and utilize the gas which is trapped in mine workings. These systems dilute methane and remove the the coal bearing strata that will be liberated during the coal mine gas from the mine, thereby maintaining safe working conditions. life cycle. There is proven commercially available technology that In-mine methane concentrations must be maintained well below can be used to capture and use methane liberated during the coal the lower explosive limit, around 5% methane concentration in air, mine lifecycle—beginning with the first stages of exploration and so ventilation air exhaust contains very dilute concentrations of development, throughout extraction of coal reserves, and after methane, often only 1% or less. Coal mine ventilation systems may mining is completed. exhaust 4.25 to 8.5 thousand cubic meters per minute. During a mine’s life, its ventilation system will evacuate to the atmosphere During the exploration stage, methane content of the minable coal 60-80% of the gas liberated. resource and the surrounding strata must be quantified to ensure that a mine’s extraction plan incorporates measures to ensure the Deploying technologies that capture and destroy VAM emissions safety of the miners. or convert VAM into useful forms of energy can yield substantial GHG emission reductions. Only a few percent of total CMM Methane extraction should begin prior to mining, as methane poses emissions are utilized at present, given that the majority of hazards even in the early stages of mine development, but mining emissions are low-concentration emissions in ventilation air companies often ignore opportunities to drain the gas from the systems. However, in recent decades, awareness of methane’s Figure 13: Methane production and the coal mining lifecycle Coal Mining Life Cycle Mine Planning Active Mining Mine Closed Undeveloped Coal Reserves Developed Coal Reserves Depleted Coal Reserves Gas Resources Evaluated Gas Produced and Enhanced CH4 Recovery and Production Plan Adopted Sold During Mining and CO2 Sequestion Exploration Pre-mine and Gob Drainage Post-mining Gas Production Gas Production Life Cycle Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 45 environmental impact as a GHG, in conjunction with higher energy prices and the advent of carbon markets, has encouraged the USEPA estimates that global emissions of methane from coal development of a number of technologies for beneficially using mines will reach nearly 800 million tonnes CO2e, in 2020, CMM, including for town gas, electric power production, for accounting for 9 percent of total global methane emissions. industrial boiler fuel and even for vehicle fuel. Technologies that Fugitive methane emissions released in China by coal mining can destroy VAM are commercially available, but deployment activities amounts to more than 420 million tonnes CO2e (approximately 27 billion cubic meters annually). This represents has been limited due to high capital and operating costs. In some 42% of the fugitive emissions from coal mines in the nine jurisdictions carbon credits are the only source of revenue for VAM countries shown in Figure 332. abatement, but power produced using VAM as fuel has been sold The quantity of methane reported in this example is expressed in Australia and China, but electricity prices must be high in order as the equivalent mass of carbon dioxide (CO2e). It is calculated to support commercial VAM power production. As of 2021, 260 in this estimate based on the global warming potential (GWP) gas recovery and utilization projects were reported as active and of 25 for a 100-year time horizon; meaning that one tonne of an additional 34 are under development13. The majority of these methane released to the atmosphere is equivalent to 25 tonnes projects are located in China and were developed and financed of CO2. This value is used by USEPA for reporting global methane as a result of the Clean Development Mechanism (CDM) under emissions. However, methane has a short residency time in the atmosphere. After 20 years, only about 20 percent of the initial the Kyoto Protocol. These projects are predominantly power mass of the gas will remain; moreover, by the time that the 100- generation installations but others mirror the use of conventional year time horizon is reached, only 0.03 percent of the original natural gas and include, coal drying, towngas, industrial mass of the methane emission is remaining. For this reason, it is processes, chemical feedstock, vehicle fuel, and with further gas useful to consider the amount of damage that will be done during treatment, injection of gas into a natural gas pipeline system, and a 20-year time horizon. The average GWP for the shorter time transport as CNG and LNG. horizon is 86. If this value is used, the amount of methane that will be released from coal mines in 2020 is a staggering 2,752 In terms of GHG emissions, flaring CMM is considered a way to million tonnes CO2e. The greatest emissions from gassy active significantly reduce methane emissions that would have been coal mines occur in the early years of mine development. When mines are closed, they also emit the greatest volume of methane otherwise vented to the atmosphere. However, flaring alone, when in the first few years after closure. It is important to act early to utilization options are viable, wastes a valuable energy resource by maximize recovery, use, and/or abatement. emitting CO2 without recovering any beneficial energy. Figure 14: Fugitive emissions of methane emitted from active Pre-mine drainage is not always possible for technical or financial mines in major coal producing countries expressed in million reasons, but gas drainage may be conducted during and after coal tonnes CO2e. extraction. Gas drainage at coal mines are techniques designed to augment the ventilation system and are less efficient in producing 450 high quality methane than pre-mine drainage but use of the gas is 400 still possible. The greatest barrier to extracting more gas, increasing 350 300 the methane concentration and thereby the usability, is the CMM Emissions 250 permeability of the coal seam and surrounding strata. Permeability 200 is a measure of how easily gas and other fluids can move through 150 the rock mass. Many coal mines in China are faced with very low 100 permeability coal seams, and in many cases the coal is soft due 50 to shearing caused by geologic activity. This problem causes the 0 Unit d St t s khst n Pol nd Ukr in G rm n Chin Russi Austr li Indi boreholes to collapse and results in low efficiency drainage. K 13 Nazar Kholod and M.Evans, 2021 CMM and AMM Projects: Analysis of the 2021 CMM Project List https://www.globalmethane.org/documents/PNNL_2021_CMM%20Project%20Status%20and%20 Trends_v4.pdf 46 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines After mining: residual methane emissions how we can develop policies that produce an environmental co- should be reduced benefit which comes from capture and destruction of methane. It is important to understand the issues that may encountered After closure, underground coal mines continue to release when attempting to reduce methane emissions from coal mining methane into the atmosphere if they are not flooded or sealed— and apply for certification of the project as a emissions reduction but most mines cannot be sealed to the point where there is no project that is eligible for environmental attributes such as carbon methane emitted. Flooding stabilizes the hydrostatic pressure emissions reduction credits. on the coal seams, reducing emissions after a few years to near zero. Even in mines that have only slow incursion of water, the gas Gases that impede the transmission of excess heat radiated flow rate also declines rapidly over the first five years or so, but from Earth through the atmosphere are known as greenhouse emissions continue for many decades. Mine flooding is a function gases because they effectively trap heat rather than allow it to be of regional geology and hydrology. During active mining water radiated back into space. If the balance between the amount of charged strata are depleted by water control measures and it may heat the Earth gains and the amount radiated back to space, is a take years for the aquifers to recharge and rebound to pre-mining positive quantity, the planet will warm. The difference between the conditions. Presently, detailed information is needed to assess amount of heat stored by the earth and its atmosphere and that the impact of mine flooding at a global level. Regulations in coal which is radiated back into space is known as radiative forcing producing regions controls the way in which mines are closed. or climate forcing. Global Warming Potential (GWP) is a measure These standards are centered on public safety which may consider of the cumulative radiative forcing of a gas, and by convention, the excursion of methane into buildings or aquifers, but usually carbon dioxide has a GWP of 1 and is designated as the reference do not consider reducing fugitive methane emissions to slow gas to which all other greenhouse gases are compared. Climate climate change. Some mines are sealed, which slows the initial scientists have determined that the GWP of gases change through rate of emissions, but seals are not always effective at preventing time, varying their impact on the climate. The reduction in the atmospheric methane emissions over time. Moreover, good capacity of the gas to trap heat in the atmosphere is related to its practice may require that the mine is vented to prevent unwanted destruction and conversion into other chemical compounds. excursions of gas into buildings or aquifers. Extraction of coal from Methane has a short lifetime in the atmosphere, only about underground mines causes cracks to form in surrounding strata 12.4 years, but as molecules of methane are destroyed in the which may allow methane to migrate to the surface. atmosphere, other radiative forcing compounds are formed-- -carbon dioxide, water vapor and tropospheric ozone. GWP is Developing GHG policies that match the measured for different time horizons, commonly reported at destructive power of methane the 20 and 100-year time horizon which are chosen to illustrate It is not unusual to hear in the popular media that methane is a the relative impact that a gas will have upon its release to the powerful greenhouse gas, and that we should be concerned about atmosphere. The GWP for methane in the year of its release is the increasing amount of methane that is now finding its way 120, including the impact of the other GHGs which are created into the atmosphere. Methane is released from many sectors, but during the reactions that take place in the upper atmosphere, prevention of unconstrained release may be easiest and most is 86 at the 20-year time horizon. In reality, this value is the profitable if it is managed in the extractive industries, namely oil, average of its GWP from years 0 through 20, and similarly, gas and coal mining. What is it about methane that makes it such the average GWP for years 0 through 100 is 34. The half-life a threat, and why are governments doing more to stop it? Some of methane in the atmosphere is only 8.6 years, meaning that background on the science of methane as a greenhouse gas and half of the gas released in a pulse to the atmosphere has been the barriers that prevent future releases are important if we are to altered into other compounds during that time. After 20 years, develop policies that have the intended result—preventing methane only about 20 percent of the initial mass of the gas will remain; having a deleterious effect on our planet. We need to understand moreover, by the time that the 100-year time horizon is reached, only 0.03 percent of the original mass of the methane emission Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 47 is remaining (Figure 15). Clearly, the majority of the damage to trade when we consider methane’s high GWP, especially if the climate will occur during the first twenty years a methane additional steps are taken to prevent these climate forcers from emission pulse is present in the atmosphere. reaching the atmosphere. Understanding some critical aspects of the chemistry and physics of methane’s contribution to climate Carbon dioxide does not behave in the atmosphere in the same change is important when considering options for policies which manner as methane: as mentioned before, carbon dioxide has a promote methane emission reductions. GWP of 1, and it remains a potent GHG for most of a 100- year atmospheric residency time, nearly 40 percent of the original Commonly, the impact of methane emission reductions is emission is still active in the atmosphere. discussed relative to the 100-year time horizon, ignoring that the actual potency is much greater in the early years of a fugitive The most direct and impactful approach to mitigating damage emission of methane. Further, the GWP used in carbon emissions from methane emissions is to substantially reduce or halt offset methodologies, such as those that were developed for the emissions of the gas to the atmosphere. Unfortunately, this UNFCCC to satisfy the requirements of the Clean Development is not always possible under given economic and operating Mechanism under the Kyoto Protocol, and the California Air conditions. Abatement of methane emissions must include Resources Board cap and trade system is 25, not 34 which is more other considerations, including the most obvious factors, the accurate for the 100-year time horizon. Emission inventories also type and efficiency of technology that will be employed and the use the 100-year GWP so that all measured or estimated carbon associated capital and project operating costs. Further, it has emissions can be reported on a common basis, but this practice to be understood that abatement of use of methane also causes falls short in several regards: the release of GHGs resulting in the production of water and CO2. When methane is destroyed it produces one molecule of carbon • The early destructive impact of methane in the atmosphere dioxide and two molecules of water; nevertheless, trading a is not being fully recognized. National inventories must be molecule of methane for a molecule of carbon dioxide is a good improved to account for emissions from active and abandoned surface and underground mines accounting for methane’s Figure 15: Decline of methane concertation in the after initial release outsized impact. to the atmosphere • The impact of methane emission reductions is undervalued. As a consequence, income for credits generated by carbon 100 offset projects that recover and use of coal mine methane and abandoned mine methane often suffer from being underfunded 90 and with few exceptions remain largely unattractive to outside 80 of M th n r m inin (%) investors. Given the short lifespan of methane, a GWP of 86 70 would be more appropriate and the additional revenues paid 60 for preventing release of a greater equivalent volume of carbon dioxide would incentivize project development which result in 50 significant emissions reductions. 40 • The greatest emissions from gassy active coal mines are in 30 the early years of mine development. Mine construction should 20 include methane capture and use systems from the initial P rc nt 10 construction and development phase throughout the lifetime of the mine. At the end of the coal mine lifecycle a good practice to 0 include is closing the mine with gas drainage systems installed 0 20 40 60 80 100 which is designed to safely and economically drain the gas and Y rs sinc mission deliver it to the surface for use or destruction. 48 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines • The greatest emissions from closed and abandoned coal Global methane emissions will be mines occurs in the first few years after closure. Therefore, monitored remotely it is important to recognize that the strictures placed on AMM emissions will be particularly relevant in certain countries. production of gas from abandoned mines by carbon-offset China is by far the biggest coal producer in the world with more project methodologies and protocols have been developed to than 11,000 large coal mines (and more than that in total) . prevent inflated claims for emission reductions. This may not be The country declares having closed around 70,000 coal mines the best policy for preventing fugitive emissions. Many carbon (most of them small) in the last 20 years and is planning to close offset methodologies are based on the IPCC standards for down 4,000 small coal mines and 300 large mines, eliminating reporting abandoned mine methane emissions using a decline overcapacity and total annual output capacity of 500 million curve to estimate the amount of gas that will be released absent tonnes. In 2019, the USEPA estimated that China emitted 38.9 a mitigation project. These are models developed for reporting billion cubic meters of methane, or 661 million tonnes of CO2e from emissions but should not be used to restrict the quantity of gas its coal mines. Given the share of underground (versus surface) that can be drained from an abandoned mine by refusing to coal mining is said to be 95% in China, the potential for AMM validate the amount as a verifiable carbon emission reduction. emissions in the coming years will be very important. Most, if not all, gas in an abandoned mine will find alternate pathways to the surface, via natural fractures or those caused Mapping the location and determining priority mines for methane by mining activities and subsidence. Manmade openings cannot capture can reduce the legacy emissions of closed and abandoned and, in many cases should not, be sealed to protect against mines. Satellite detection and surveillance of methane emissions is mine gases going on excursion to neighboring buildings or other promising, one satellite dedicated to methane emission detection structures. The best approach is to remove as much gas from was launched in 2017 by GHGSat, another was scheduled to be the void as early as possible and allow the gas in the mine void placed in orbit in spring of 2020 but has been delayed, and the to reach equilibrium with the remaining coal reservoir at which Environmental Defense Fund is planning to launch one in 2021. time the gas pressure in the mine is reduced and emissions can These, along with conventional airborne platforms, are making be actively managed. remote detection and surveillance possible and cost effective. Detection of emissions from abandoned mines is possible, but additional conventional location mapping and ground-truthing will be required for learning sets to be constructed which permit machine learning and eventual reliance on remote sensing platforms for detecting important methane sources. Employing these technologies will aid in stemming methane emissions from closed mines and will also be useful for mined land repurposing. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 49 Annex A: Supporting Information on Probabilistic Risk Assessment The risk table used in this document is defined by two important land and remaining natural resources or even may become a measures of risk that an event will occur, and the magnitude of future hazard. It is equally important to gauge the uncertainty its severity will adversely impact the value of the mined land and associated with estimating the magnitude of severity caused remaining natural resources. There is uncertainty associated with by an adversely impactful event. Each risk metric is broken into estimating the likelihood that an event will occur and also with five categories. The likelihood that an event will occur is divided the severity of the impact. In order to assess the impact of an into five equal segments, or quintiles of 20 percent each, ranging event it is important to gauge the uncertainty associated with a from zero to 100 percent. There is quantifiable uncertainty that mining professional estimating the likelihood that an event will a mining professional can correctly deduce which of the quintiles occur, which if left unmitigated, will reduce the value of mined most accurately predicts the probability that an event will occur. Figure A-1: Risk matrix and companion table showing the range of the bounding values for each probability quintile. Green indicates the most favorable risk outcome and red the least favorable. Insignificant Minor Moderate High Major Increased Likelihood of Occurence 1 2 3 4 5 Improbable 0-20% 0.19 0.38 0.57 1.14 1.71 Unlikely 20-40% 0.42 0.84 1.26 1.68 2.10 Possible 40-60% 0.50 1.00 1.50 2.00 2.50 Likely 60-80% 0.58 1.16 1.74 2.32 2.90 Most Likely 80-100% 0.81 1.62 2.43 3.24 4.05 Severity of Economic Damage Probability Lower Upper Matrix Quintiles Boundary Boundary Cell Colour p80-p100 0.00 0.72 p60-p80 0.73 1.04 p40-p60 1.05 1.35 p20-p40 1.36 1.75 P0-p20 1.76 4.32 50 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Therefore, the risk table incorporates the uncertainty associated a low score for suitability depending on the purpose for which is with a mining professional correctly assessing the likelihood that being assessed. Again, the uncertainty associated with correctly an event will occur. gauging the potential severity of the impact that may occur is quantifiable and incorporated into the risk table. Similarly, the severity of impact metric is divided into five categories ranging from “insignificant” to “major” and a Probability distributions were constructed to model the likelihood numerical value was assigned to indicate severity. As is common of occurrence and the severity of impact for each potential risk practice during risk assessments, low scores indicate lower risk and the associated uncertainty. The probability frequency for and high values indicate high risk. The values that are assigned severity of impact and the likelihood that mining professional when a post-closure assessment is conducted to repurpose can correctly assess the probability of occurrence are assumed mined land using the World Bank’s Land Use Repurposing to be normally distributed. Normal distributions are continuous Application (LURA) range from 1 to 5. In a land repurposing functions symmetric about the mean in which the frequency of assessment, the highest score is a “5”, indicating that the occurrence of the value nearest mean is greater than that of the attributes which are valued for a given purpose have been values more distant from the mean. For that reason, there is a evaluated and found to be suitable for that purpose. Values that natural weighting towards the values that occur near the mean. are determined using the risk table can be used when evaluating These two metrics are used to form a 5x5 matrix, comprising the land for suitability for certain uses, but it is important to 25 cells with each containing a value that is the product of note that the scales of the risk assessment tool and LURA are multiplying the severity of the impact by the likelihood of set in opposite numerical order to each other. Nevertheless, a occurrence. Green indicates the most favorable outcome given a risk that is judged to have a high likelihood of occurring and probability of occurrence and less severe impact of a given risk. expected to have a severe impact when it does occur, may earn Red, of course, indicates the least favorable outcome. Figure A-2: Normally distributed probability density function that shows the relative frequency for each quintile. As an example, choosing the likelihood of occurrence for the probability band of p40-p60, the relative frequency ranges from 0.46 to 0.54 shown on the chart as 46 to 54 percent. Norm l Distribution P80 = 62% P100 = 100% P60 = 54% Prob bilit P40 = 46% P0 = 0% P20 = 38% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 51 Figure A-3: Probability frequency of score values used in risk table resulting from multiplying the probability of occurrence by the probability of impact severity Fit: Lo norm l For c st v lu s 440 400 0.01 P80 = 1.74 P100 = 4.07 360 320 280 P60 = 1.35 Fr qu nc Prob bilit 240 200 P40 = 1.03 160 120 P0 = 0.00 P20 = 0.72 80 40 0.00 0 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 An add-in to Microsoft Excel, called Crystal Ball, was used a lognormal distribution. In this model, simulated Monte Carlo to construct the probability distribution functions that routine was used to randomly sample the universe of outcomes. mathematically describe each of these risk metrics. These The simulation was set to run until a confidence interval of 99 probability functions were used in a Crystal Ball driven Monte percent was reached, in this case that level of confidence in the Carlo simulation to help develop a risk table by using the resultant result occurs after about 30,000 trials. potential outcomes. Figure A-2 is a probability density function The lognormal probability distribution is a continuous distribution that depicts the normally distributed frequency of occurrence function where the frequency of the logarithm of a random for the severity of impact, middle scores for severity are more variable is a normal distribution. The frequency distribution common in a normal distribution. is asymmetric with lower values more frequent than higher The Figure shows the relative frequency or likelihood that any values. Figure A-3 shows that the resultant likelihood that a predicted probability range will occur. For example, an engineer score calculated by multiplying the probability density functions using her experience and best judgement subjectively determines depicted in figure A-2 will occur. Recalling that in the discussion that the likelihood that the closed mine will be gassy is between above we stated that the lowest values are correlated with the 40 and 60 percent (p40-p60). Using the probability density most severe impacts and in Figure A-3 we can see that lower function show Figure A-2, we see that the probability that her scores are relatively more likely to occur than the higher scores stated prediction will turn out to be correct ranges from 46 to 54 (less severe impacts) which lie in the long tail of the lognormal percent. Stated another way, she will be correct 46 to 54 percent, distribution. or about half of the time. The values that define the boundaries of each quintile were used When the probability functions are multiplied by each other in as the delimiting values for the risk-based outcomes. a Crystal Ball simulation, the resultant distribution function is 52 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Module 2: Post Closure Standards A Practitioners Workbook Standards to improve risk management in the post-closure and repurposing phases of coal mine transition Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 53 Executive Summary World Bank is extensively involved in energy transition from often do not have a clear understanding of the complex conditions coal to more sustainable and environmentally friendly energy and adverse environmental implications they pose. The “Post production resources. The complexities of such transition need Closure Standards – A Practitioners Workbook”, provides guidance to be addressed in a comprehensive and well-organized manner on how to identify and address the residual risks left dormant if a Just Transition for All within coal regions is to be achieved. after mine closure, concurrently with a methodological approach Based on the World Bank’s extensive work in coal mine closure that enables re-purposing of land and infrastructure assets, for and transition, invaluable lessons have been learned which new uses by private sector investors. have produced three thematic areas that need to be addressed It is important to identify and quantify the residual risks that concurrently for “sustainable” rather than just “physical” remain during the post closure period particularly when only mine closure. Physical closure has been the norm in the past physical closure has been attained. Governing bodies need to or even current practice for many regions, leading to missed understand and legislate in a way that the residual risks will be opportunities for future economic development of former coal significantly reduced during closure and at the same time potential mining areas. The three thematic areas or “Three Pillars” seek to needs and drivers will be identified, focusing on the economic improve governance processes, manage impacts to workforce heritage that has been left behind or has been cultivated around that affect local communities and consider uses for former former mine areas which can be developed in a sustainable way. mine lands and assets which can produce future economic development in an environmentally friendly way, towards The residual risks for the post closure period need to be quantified a circular economy, clean energy production, facilitation of based on a risk assessment framework which identifies future investment projects and job creation. hazards, assesses the likelihood of occurrence in a detailed way and provides appropriate risk mitigation strategies. Hazard The World Bank’s document, “Post Closure Standards—A identification must consider that even after the most robust Practitioners Workbook, Standards to improve post closure mine closure, a “hole” in the ground will remain either from and transition period” provide insight and outline activities that former surface or underground operations. At the same time a need to be considered for the post closure period and to manage geologically new landform created by the waste rock placement a better transition. The lifecycle of a coal mine ends with its will remain which has not physically matured and presents “physical” closure undertaken most of the time by its Operator, many hidden or dormant legacies ranging from geotechnical and is usually constrained to surface contouring earthworks, instabilities to concentrated pollutants that can affect the nearby vegetation restoration and hazard mitigation, to ensure a environment. At the same time value can be uncovered in the legislative level of environmental restoration and public safety. remaining infrastructure such as the road or railway, the power Physical closure may not guarantee that during the post closure transmission networks or even the former plants and buildings. period which may even be perpetual, hazards and legacies will not appear and affect local communities, broader areas or even The Practitioner’s Workbook provides detailed tabulated the global environment. For example, acid mine drainage (AMD) assessment for hazard identification from environmental can appear long after a mine has closed and significantly affect conditions, gas emission, water resources and geology of former water bodies far beyond the former mine lands. Post closure surface and underground mines and severity of consequences to methane emissions from a deep underground gassy coal mine left possible future land uses, in a quick way to assess residual risks. unattended can produce a significant amount of greenhouse gas that affects the global environment. After mine closure, the associated residual risks, differ significantly between mine operations, mine regions and During the post closure period, the mine Operator has most countries. The residual risk is heavily dependent on whether probably left the area and may have even been released from all mine closure was planned and orderly executed or abruptly legal liabilities associated with the mine, thus leaving all hidden terminated due to economic, political or other prevailing legacies either unattended or placed unwillingly or unknowingly on conditions. Safeguarding the mine site and turning over essential local or regional authorities and stakeholders. These stakeholders 54 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines information pertaining to the surface and sub-surface conditions water resources etc., appropriate preventive or protective and assets is critical in order to prepare the site for repurposing. measures are presented and explained. It is during the closure phase that social protection programs for Risk assessment, risk management planning and actual impacted workers and communities begin, and steps are taken mitigation require appropriate and available data to to implement longer-term active labor market policies aimed understand the key closure risks and risk drivers at a mine site. at re-skilling and educating workers for jobs of the future. A Comprehensive monitoring of activities and conditions are of well planned and organized closure, designed from early on will paramount importance for detailed planning, mitigation and produce the lowest residual risk during the post closure period. post mining evaluation. A detailed campaign of data collection, The opposite is considered when a coal mine operation abruptly storage and interpretation is addressed in a way that will terminates with limited reclamation, remediation planning and contribute to better assessing the actual conditions during the financial resources. The post closure liabilities encumber, in a mining and mine closure periods and at the same time serve as precarious way, the local and regional stakeholders with limited a basis for the evaluation of residual risks in the post mining and resources to appropriately tackle such issues. At the same transition periods. Monitoring should continue after closure for an time remaining resources which can play a decisive role for the indeterminate time since many of the hazards can be long lasting economic development of the region, have to be evaluated and or even evolve due to future climate changes. The way to plan a put to appropriate use. monitoring program requires addressing appropriate parameters, A consequence-based approach is considered more appropriate methodology and instrument capabilities and robustness. The in the post closure residual risk assessment. With this approach responsible entities need to know how they will fund, execute, the detailed risk assessment is driven by the potential impact supervise and validate the collated data in a way that will become a hazard represents particularly in relation to loss of life and usable and useful for the future economic development of the environmental damage and how each residual risk will affect area. the nearby population and what the financial losses will be. In What is most important, is to understand that repurposing is a this way the stakeholders or the governing authorities can have way for sustainable redevelopment, of the former mine lands and a clear indication of how severely a residual risk can affect the assets. The transition process needs to address the needs and area and what resources are needed. It is recognized that coal drivers of the local community and work with the actual available mining areas represent decades, or in some coal basins, centuries conditions to optimize the needed funds to address residual risks of environmental degradation with significant residual risks, and and produce possible future economic development of the area. regulations and legislations based on the “polluter pays principle” Successful regional transition rests upon a cohesive approach and would be prohibitively costly and impractical, particularly near coordination among diverse stakeholders with disparate goals. the end of a mine lifecycle. Residual risks can severely affect the Success depends on identifying and successfully implementing surrounding area and population or even the global environment projects which exemplify and demonstrate the potential for and need to be addressed in a more comprehensive way. Among employing innovative business models which are designed to the most effective solutions are those that rely on government help new businesses thrive in the brownfield setting using the interventions that pay for remediation and indemnify current reclaimed and restored mined land for its highest value. occupants. The governing authorities need to know the residual risks and how to mitigate them. The exercise of considering land uses and eventually developing and implementing repurposing activities has a multi-faceted The Practitioner’s Workbook provides a methodological approach impact on many other transition activities—whether it be in job of how such residual risks should be mitigated with preventive, creation, circular economy, clean energy production, facilitation of protective or, as a last resort, emergency measures. It provides investment projects or in community engagement. reclamation strategies per hazard in previously mined areas in tabulated form. For particular hazards which have been identified in the detailed risk assessment, such as environmental, geological, Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 55 These standards are also addressing an important new paradigm: values for each criterion against the index value describing the that mine closure should also be a business strategy that will most appropriate post mining land utilization, and matches the reduce post closure risks and could enable and develop increased actual values for the five criteria with the best fitting optimum end use value. The conventional objective of “mining for closure” land use scenario. has been to continuously reclaim and restore mined-out A shift will need to happen from “mining for closure” towards areas to leave mine lands in a geotechnically stable condition, “mining for repurposing”. This approach will require a rethinking with erosion resistant, well vegetated surfaces, and without of mine planning and operations, which will need to plan further environmental liabilities in form of effluences, gas emissions, dust downstream towards identifying and preparing – while the or contaminated soils. Going beyond this, the “new objective” mine is still operational – areas for designated repurposing and of “mining for repurposing” is to prepare the lands for optimum redevelopment activities. Mining for repurposing will also require future productive uses. a different paradigm for environmental permitting, as well as A Land Repurposing Methodology (LRM), developed by the consideration of the local / regional development framework, World Bank, is an objective tool that can be utilized to evaluate and socioeconomic and spatial requirements regarding the final post mining land uses with a customized spatial resolution state of the mine. While all principles regarding public health and and a high degree of reproducibility. The methodology aims to safety, environmental control, and geotechnical stability are still identify conditions of former mining lands that allows a wide valid, more strategic and further downstream thinking has to be scope of subsequent, diverse land uses. This is of critical priority dedicated to providing added value to the post mining space, and in economic transition scenarios where land may be one of the thus achieve better environmental and socio-economic outcomes, most important assets available for development. LRM requires leave as many development opportunities to mining communities, five distinct steps, starting with stocktaking and site inventory, and allow a strong focus on renewable energy emplacement to continuing with the clarification of the legal, regulatory and compensate for the loss of coal fired power production. permitting situation of the former mining lands. Subsequently site The objective of the Practitioner’s Workbook for post closure investigation and monitoring data are collected and evaluated and transition is to provide practitioners, local authorities and which can then be used in the land classification methodology. governing bodies, a simple to use but detailed methodological The land classification categorizes discrete land parcels regarding approach for the residual risk assessment and mitigation during their post-transition utilization potential based on liabilities post closure, especially for not well planned or even abrupt mine and remaining resources. Finally land and asset repurposing closure. The aim is to identify the residual risks and mitigation strategies are provided as contributions for other spatial planning funding needed but at the same time to discover opportunities in instruments for the local or regional development of the area. the way that funding can be used optimally for land repurposing. Currently the World Bank has developed LURA, a user-friendly, The document steers beyond achieving environmentally stable cloud-based GIS application for executing the land classification. landscapes and complying with environmental permits as was LURA is based on five themes: environmental conditions and done in the past, but to develop former mining lands towards liabilities, morphology and hydrography, geotechnical risks, conditions that allow a wide scope of diverse land uses which can socio-economic factors and land value (both positive as added significantly contribute to new economic development. value and negative as remediation cost). Each criterion is further subdivided to capture the full extent of the land conditions in a simple and objective way. Each subcategory uses a five-scale rating procedure, ranging from the value “1” indicating the least favorable condition to “5” which is considered the most favorable condition for the particular sub-criterion. An average score is calculated based on the sub-criteria rating for the main criterion. A net differential algorithm automatically evaluates the actual 56 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines The context of coal mine closure Mine closure aims to produce physically safe lands for humans and they are appropriately managed and repurposed for future use. animals that are environmentally natural, geotechnically stable, Repurposing of mine lands and assets is an important enabling with minimum pollution and contamination potential and capable and supporting factor for coal transition in a variety of contexts of producing favorable post mining land uses. The most common and can produce significant added value in areas that have objective of mine closure has been to reclaim the mine lands to monopolized or developed strong mono economies in the past produce a stable and compatible landscape which resembles its based mostly on mine activities. Post mine land use should be pre mining conditions or to just promote the ecological integrity identified early on through consultation with local stakeholders, of the reclaimed land placing attention on meeting environmental regional authorities and state governing bodies but at the same criteria enforced by governments or mine governing bodies. Coal time consideration must be given to the consistently increased mine closure will require modern procedures underpinned by stakeholders expectations for the future of former mined land and strong technical standards by which enterprises and provincial the stringent environmental regulations that constantly evolve. departments responsible for mine closure activities can guide A methodological approach should be considered for mine closure, remediation and land reclamation. reclamation and repurposing beyond just meeting existing Mine extraction should be considered a temporary condition regulations enforced in most countries. Mine closure should be which takes place for a certain amount of time. Reclamation of envisioned as a business strategy that will reduce post mine risks mine lands is a process that should be fully integrated in the mine and could enable increased end use value. Implementation of coal plans from the start and adopted for mine closure procedures. mine closure should start with identifying liabilities and hazards Mine closure and land reclamation is an expensive aspect of the that can downgrade a former mine area, complicate reclamation mine life cycle and should be considered from the start or at least and increase the risk and needed funding for appropriate and as soon as possible during mine operations. Usually this is not sustainable future land and asset development opportunities. the case because a new or an existing mine needs to minimize Then potential needs and drivers should be identified focusing initial capital cost which is achieved though the NPV with the on the economic heritage that has been left behind or has been adoption of a high discount factor which in essence delays not cultivated around former mining areas. Emphasis should be immediate expenditure (Williams, 2016). In essence this precludes placed on location to infrastructure, human settlements, cities the early start of rehabilitation and when it takes place in later and transportation routes, scarcity of land and land value stages, it can be much more expensive because mine closure and considering built assets. Positive impacts of land repurposing reclamation works may need significant time and expenditure often reach well beyond the footprint of the original coal value after the mine extraction operations have been completed. chain as can be seen in Figure 1. Additionally, reclamation and environmental monitoring for a significant time span after mine closure should be considered and Greater utility is gained by increasing granularity and reorganizing planned for both physically and economically in collaboration with the approach to consider the risks to society, the environment, State or Regional governing bodies and local stakeholders. and how certain actions, or lack of actions result in diminishment of asset value of remaining resources. Moreover, this approach It is the global experience that aiming only to reclaim in reflects the interconnected nature of the issues that confront accordance with enforced guidelines and neglecting former operating companies at the time of mine closure. mining lands and associated coal assets removes development options. Moreover, it should be seen as a missed opportunity, both economically and as a contribution to post-mining environmental and social sustainability. This is enhanced because authorities and regulators require proof that “unconventional” rehabilitation can work in relation to conventional practices of reinstating former conditions which many times do not work. Additional value can be found in mine lands and former mine assets if Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 57 Figure 1: The range of potential contributions and benefits of land repurposing and spatial planning to three major pillars of coal transition: (i) climate change mitigation; (ii) a diversified post carbon economy and energy production; and (iii) the environmental regeneration of mining lands. Climate Change Mitigation Carbon sequestration R s rch nd CBM- Coal R ion l sp ti l D v lopm nt abatement reduction m st r-pl nnin (RE, co l tr nsistion) & optimi tion PV and Carbon CSP forest Land swapping Natural (e.g to generate quota habitats for building land) Agriculture Foresty Business parks, Chemical manufacturing Tourism stabilization waste mgmt. Post-Carbon Environmental Economy Regeneration 58 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Risk based approach to mine closure and repurposing Mine closure, reclamation and repurposing of land and assets is regional environment or the global climate. The causes of adverse inheritably fraught with uncertainty. Such uncertainty may be outcomes are identified as hazards. associated with: Risk should be considered in the context of increasing or • soil and rock materials and their impact on the geotechnical decreasing risk or transferable risk but rarely can risk be stability of slopes and subsidence; completely eradicated. Risk management approaches contribute • sources of pollution, its formation, diffusion, and transportation to keeping risk within tolerable limits. A way to evaluate risk is to and the ongoing effects on the environment; understand what risk is tolerated in everyday activities. Figure 2 (Briaud, 2020) which originated from MIT in the seventies is an • socioeconomic stability of communities and the people working example of what is acceptable risk to society in different sectors around mining operations which may become unprofitable; and at present in the form of fatalities or cost. As society evolves, the • future economic development the former mining area or region. acceptable risk to society is reduced and consequently increased Uncertainty should be evaluated and quantified in the form of risk management is anticipated which increases the cost of mine risk and appropriate measures chosen to reduce or mitigate it rehabilitation. It is interesting to note that Mine pit slopes have during and after mine closure in the form of Risk Assessment the highest acceptable risk during operation which may not be the and Risk Management. Risk has been identified by the Royal case after mine closure. On the other hand, dam tailings failure Society, 1992 as “A combination of the probability of occurrence which can affect significant parts of land and produce increased of a defined hazard and the magnitude of the consequences of loss of life, have a much-reduced acceptable risk. occurrence”. Risk in mine closure is concerned with the likelihood Risk based approach on mine closure can be addressed with the of an adverse outcome which negatively affects human health following questions in the framework of risk assessment (Figure 3): and wellbeing, society’s socioeconomic activities, the local or Figure 2: Tolerable risk in the form of fatalities or cost based on an annual probability of occurrence (Briaud, 2020). F t liti s 10 -2 10 -1 10 0 101 102 103 104 100 R d lin Hurric n Risk = 0.1 F t lit / r Min pit 101 prot ction Risk = $100,000/ r slop Annu l prob bilit of f ilur pr -K tirin Mobil H rt drill ri s 102 dis s Blu Lin Found tions Fix d C r Risk = 0.01 F t lit / r 103 C nc r drill ri s ccid nt Risk = $10,000/ r Offshor 104 structur s Gr n lin Brid scour D ms Risk = 0.001 F t lit / r 105 Risk = $1,000/ r Pl n cr sh 106 104 105 106 107 108 109 1010 Doll rs lost Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 59 HAZARD IDENTIFICATION. What are the hazards from mine Figure 3: Risk Management approach for mine closure closure that can cause adverse consequences? HAZARD ASSESSMENT. What is the likelihood or frequency (probability) of occurrence of the adverse consequences? Hazard RESIDUAL RISK AND DETAILED RISK ASSESSMENT. What types Identification of mine operation pose increased residual risk? How severe will their effects be? A comparison is made of estimated risk against established acceptable criteria. Hazard RISK MITIGATION. What should be done? Prepare specific Monitor Assessment strategies and action plans that with a cost effective approach can reduce the consequences. MONITOR AND REASSESS. What is the outcome of the action plan? It is important to monitor the effectiveness of risk management and allow for modifications or improvements. These may be due to changes in societal risk acceptance, new scientific Risk Risk knowledge or evolving natural conditions. Mitigation Evaluation Coal mine closure planning based on a Risk Management approach should be directed at mitigating the impact of risks: if unaddressed, these will increase mine closure costs, reduce remaining resource and assets value, and increase the risk of unintended consequences. Closure planning should envisage the future highest use of the remaining assets at the point when the mine operator relinquishes its rights to extract coal, and assess the risks that can adversely impact the future value of assets. Planning for mitigation of risks at the early stages of mine development and periodically throughout mine life through the mine closure process is a relatively low-cost, high-value activity that can facilitate mine land repurposing. Poor mine closure planning can increase repercussions for the operating mining company but also for the final outcome of the surrounding natural environment and social stability. Adverse effects that can manifest after mine closure, may not always be known but the risk they can produce should be evaluated and addressed keeping in mind that post mining period could be perpetual. 60 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Hazard Identification – Hazard Assessment Seven major aspects of post mine conditions and assets must be Union and other countries have stated the commitment to considered in the hazard identification and how future conditions achieve net zero emissions by 2050. It is possible that due to will effect such hazards: the financial pressure, only limited coal mines will be able to complete their planned life cycle and produce a complete planned • “hole” in the ground which could be the residual pit that will rehabilitation. The situation could be more onerous since many remain after reclamation or the underground mined space left companies have invested solely in coal production and will not be without backfilling able to sustain the financial burden of an abrupt coal production • waste rock deposits that will remain on the previously occupied termination. Such abrupt mine terminations can produce land increased future risks. • tailings storage facilities which can be in the form of large Some key issues that need to be addressed in order to identify liquid or semi liquid condition retained by natural obstructions post mining hazards and risks are associated with understanding and manmade dams. the long-term consequences of the physical and chemical • mine infrastructure such as thermal power stations, haul roads, alterations of open pit mine slopes and waste materials left in railways, conveyor belts, power lines and processing, servicing place or buried under a small layer of topsoil. How the abandoned and administration buildings. mines, waste rock and tailings may affect the local and regional • emissions from the mine, tailings, and waste rock facilities ground water conditions in the short term after mine closure which could be methane, carbon monoxide and carbon dioxide, and in the long term. Acid mine drainage (AMD) that is produced and other pollutants. either from the waste stockpile, the open pit or the underground • liquid residue which produced from post mining facilities void, can be by far a serious liability and require significant such as underground mine, tailings, and waste rock facilities; financial resources to be managed in the post mining period, if frequently, residue is a water mixed with dissolved sediments not properly addressed during mining and mining closure. Water and chemicals. contamination or tailings storage failures can affect not only the • naturally occurring radiation, artificially increased due to area of the abandoned mine but can have significant far reaching mining, and now above local baseline. environmental impacts on rivers, lakes and even the sea. One such recent example is the case of the failure of the wall of a As early as possible in the mine cycle it is important to identify post-processing settling pond at the Obed Mountain Mine near hazards pertaining to mining closure for each of the seven Hinton, Alberta which occurred on October 31, 2013 and released aspects stated above. Such identification in the early stages can approximately 670.000m3 of coal process water. The released be used to evaluate the coal resources left in place and assess plume reached the Athabasca River which was located about the potential for fugitive methane emission, identify hazards in 20km from the mine and altered the chemical composition of the form of slope instabilities, landslides and ground subsidence. the river water. The plume in a period of four weeks reached the Collection and evaluation of information related to the volume Peace-Athabasca Delta, after traveling approximately 1100km and quality of waste rock and tailings that will be left in place downstream. (Cooke et al, 2016). and how the groundwater conditions will be affected in the post mining period. And finally what will become of the stranded mine Table 1 presents major hazards and how these hazards can have infrastructure assets. consequences to wildlife, human activities, the environment and global climate. The table includes the major sources of hazards Unfortunately and especially in coal mine regions, some of which pertaining to environmental conditions, gas emissions, water date back to the 1600s, many mines have been abandoned resources, geotechnical instabilities for surface and underground without proper mine closure provisions, many will terminate their coal mines. The hazards included in this table cover naturally operation abruptly due to international pressure for reduced occurring or human assisted naturally occurring hazards. carbon emissions, increased carbon taxation or allowances Additional hazards which can be attributed to socioeconomic and increased use of renewable energy sources. The European conditions have not been included such as financial hazards, Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 61 sudden closure due to market changes, legislative changes and conditions and human activities. It must be noted that such a environmental restrictions or requirements etc. qualitative consequence assessment is site and country specific and only indicative ratings have been included. Further down the A simple consequence color scale has been implemented in the line of Risk Assessment such consequences should be investigated table with a four-scale rating starting from no or marginal effect and calculated in detail based on the available data that a mine, of a hazard (gray), going to a low effect (yellow) and then to a provincial government and state have collected and maintain. moderate (orange) and high effect (red) in the different natural Table 1: Hazard identification from coal mine operation and mine closure Qualitative Consequences General Detailed Hazard Hazard Wild Life Local Ecosystem Climate Livestock / Food Natural Individuals Communities Economy – Local or (Regional or agriculture chain Habitats Business Regional worldwide) Disrupt day Disrupt day Disruption of Reduce land to day lives to day lives local businesses, Air Disrupt living fertility, dangerous Reduce (cleaning house (cleaning house relocation Reduced pollution – conditions – to livestock quality of and cars), Effects and cars), Effects of business, quality dust mating and eating respiratory products on respiratory on respiratory prohibited types systems system system, of business Degrade quality of Cardiovascular Cardiovascular Air pollution products – reduced effects, eating effects, eating Reduce Effect the Relocation of Increase with toxic growth, increased disorders , disorders, exported Damage mortality of some businesses, halt pollution to elements – mortality rates , carcinogens, increased mortality product ecosystem species of operations atmosphere particles toxins introduced and respiratory rates, population price into food chain impacts, etc displacement Can impact Degrade quality Increase cancer businesses Exclude Surface of products – Increase cancer rates, increased that rely on products Damage water Increase mortality reduce growth and rates, increased mortality rates, surface water, from ecosystem pollution increase mortality mortality rates population recreation, markets rates displacement fishing etc. Environmental Increase cancer Exclude Ground Increase cancer rates, increased reduce growth, products Damage water rates, increased mortality rates, increase toxicity from ecosystem pollution mortality rates population markets displacement Exclude Reduce Acid mine Displace wild life agricultural population quality of drainage population products or displacement products livestock Degrade quality Soil pollution Exclude of products – Increase cancer Increase cancer with toxic Affect mortality products reduce growth and rates, increased rates, increased – heavy and eating habits from increase mortality mortality rates mortality rates elements markets rates Pollution Ingestion through Impacts on Increased birth Health issues Health issues and of agri. Air quality Radiation livestock and food quality of life, defects and birth defects birth defects products by impacts chain relocation driver dust Visual mining Visual Remaining scars in remnants project disturbance the landscape negative image No or marginal effect Low Effect Moderate Effect High Effect 62 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Table 1: Hazard identification from coal mine operation and mine closure (continued). Qualitative Consequences General Detailed Hazard Hazard Wild Life Local Ecosystem Climate Livestock / Food Natural Individuals Communities Economy – Local or (Regional or agriculture chain Habitats Business Regional worldwide) Trapped Disturbance Wild fire can Accidents and population gas ignition destroy crops death displacement of operations, or explosion relocation Gas Emission Intoxication loss of life, Disturbance of Increase mortality Intoxication of Accidents and CO, CO2, population operation, loss rates livestock loss of life H2S displacement of life Affect climate CMM change Affect climate AMM change Destroy habitats, Disruption of Water flow Reduce available Damage displace species, some type of disruptions farming land ecosystem increase mortality businesses Water Affect farming land Damage recovery quality ecosystem potential Water Disruption of outflow from Destroy habitats some type of mine adits businesses Water Resources Displace wildlife Reduce land Water logged Disturbance population, fertility and population areas – of operations, produce different livestock feeding displacement Marshes relocation habitats areas Significant Flooding economic damage, of near Disrupt leaving Significant population surface Disturb livestock conditions, economic displacement and structures farm operations inflict economic damage, potential health and damage relocation impacts from buildings molds, etc. River inflict economic Significant overflow Displace animals Destroy farmlands Significant Temporary damage to economic and flooding and modify natural and drown economic damage, shortage of property, damage, loss of low land habitat conditions livestock loss of life products possible life loss of life areas No or marginal effect Low Effect Moderate Effect High Effect Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 63 Table 1: Hazard identification from coal mine operation and mine closure (continued). Qualitative Consequences General Detailed Hazard Hazard Wild Life Local Ecosystem Climate Livestock / Food Natural Individuals Communities Economy – Local or (Regional or agriculture chain Habitats Business Regional worldwide) Surface Disturbance Disruption of Destroy nearby mine slope Property damage of operations, wildlife living areas farmlands instabilities relocation Surface Significant Disturbance Destroy nearby Geological – Geotechnical surface mines dump slope Property damage economic damage, of operations, farmlands instabilities loss of life relocation Surface Significant Significant Temporary impoundment Destroy habitats, Destroy extensive Property economic damage, economic or long term Damage slope displace species, farmlands and kill destruction, loss significant loss damage, loss shortage of ecosystem instabilities – increase mortality livestock of life of life of life products tailing dams Significant Significant Temporary Destroy habitats, Destroy extensive Property Flow slides – economic damage, economic or long term displace species, farmlands and kill destruction, loss landslides significant loss damage, loss shortage of increase mortality livestock of life of life of life products Economic Economic damage damage to Dump to property, business settlements – Property damage damage to property, deformations infrastructure exclude sensitive infrastructure Economic damage to Subsidence Economic damage business – ground Property damage to property property, deformation exclude sensitive infrastructure Geological – Geotechnical underground mines Economic Economic damage damage to Property to property, business damage, Sinkhole Disturb livestock reduced values property, accident, formation farm operations of properties, exclude sensitive possible loss relocation of infrastructure, of life communities possible loss of life Economic damage Economic to property, damage to Property reduced values business Temporary Massive Disturb livestock destruction, loss of properties, property, shortage of collapse farm operations of life relocation of exclude sensitive products communities, loss infrastructure, of life loss of life Economic damage damage to Induced to property, Property damage business seismicity reduced values of property properties, No or marginal effect Low Effect Moderate Effect High Effect 64 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Figure 4: Intense dust formation due to strong winds over Kardia Mine Several hazards and harmful effects may persist after surface or in WM Greece. This is a significant, adverse environmental impact, that underground coal mine closure. If the mines are abandoned this would put restrictions on land use downwind of the mine. will generate both short and long lasting consequences that may affect wildlife, people and communities, economic development, the regional environment and possible interaction with climate change. The impacts from mine closure from abandoned mines appear to be quite similar between different regions or even different countries. The major hazards that are present in post mining areas and can be transformed to major risks for the nearby area can be classified in four general categories which relate to environmental pollution, gas emission, water resources, and geotechnical stability of lands. Environmental impact during and after coal mine closure can range from air dust pollution coming from abundant open pits or spoils that have not been reclaimed appropriately. Air dust Figure 5: Rio Tinto river in Spain with flowing red acidic water pollution is produced from winds, moving vehicles and wildlife and can have a significant effect on the neighboring communities. The air dust pollution is aggravated in arid areas or areas where high winds and low precipitation produce dry soil surfaces on the mine or spoil slopes. Conditions may be even worse if surface mine operations are ongoing in a neighboring area. In Figure 4 such an environmental impact of dust pollution resulting from a mine close to closure in Wester Macedonia can be seen. In addition to mine dust generation, many times toxic or harmful trace elements can be present in the dust or in the air that could significantly contribute to human health risks. For example, dust particles or fly ash particles can contain toxic elements such as Arsenic (As) which is easily absorbed by vegetation and is found in higher concentration in leafy vegetables, rice, apple and grape juice, and seafood. Humans can be exposed from inhalation of atmospheric gases and dust (Agency for Toxic Substances & Disease Registry). Soil and water bodies (surface or underground) can be affected by pollutants such as sulfur; As, Cd, Cr, Cu, Ni, Pb, Zn; aliphatic, aromatic, polycyclic hydrocarbons. Water bodies in particular could be affected by dissolved oxygen, total oxygen demand (TOD), total organic content (TOC), hardness, conductivity, nitrate, ammonium. A significant environmental hazard from underground and open pit mines, is Acid Mine Drainage (AMD). The oxidation of Sulphur bearing minerals such as pyrite during coal mining operations can lead to acid mine drainage. When surface or underground water Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 65 comes in contact with the air, the iron present can be transformed Figure 6: Forecast of future CMM and AMM emissions (Kholod, et,2020) from its ferrous to ferric state and produce ferric hydroxide which gives the water an orange to light brown color (Figure 5). The AMM CMM water becomes acidic with low pH values and concentrated with 700 heavy metals and other toxic elements. The components of AMD mmissions, bcm that can seriously affect the environment and its inhabitants are 600 low pH, oxygen content in the water, chemical activity, dissolved 500 heavy and toxic metals, etc. 400 Visual “pollution” is another environmental impact, that affects 300 Tot l M th n human activity. For the extraction of coal or lignite, large earthmoving operations take place which greatly influence 200 the ground contours. Such operations produce exposed slopes 100 and openings in the ground and high spoil fill areas that can be 0 particularly intrusive to human vision. 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 The extraction of large quantities of ground in gas-rich rock masses forms an underground mining tank filled with mine gas. Depending on the type and composition of mine gas, surface gas emissions may constitute several risks or nuisances to people and Regulations in coal producing regions control the way in which property. Such risk could be asphyxia, intoxication / poisoning, or mines are closed. These standards are centered on public safety explosion. These risks increase when the mine gas is confined, i.e. which may consider the excursion of methane into buildings or not or only slightly diluted. They are evidently less important for aquifers, but not for reasons related to climate change. Some diffuse emission into the open air. mines are sealed, which slows the initial rate of emissions, but seals are not always effective at preventing atmospheric methane After closure, methane gas continues to desorb from fractured emissions over time. Moreover, best practices may require that coal seams in underground coal mines and the mines will continue the mine is vented to prevent unwanted excursions of gas into to release methane into the atmosphere if they are not flooded buildings or aquifers. Extraction of coal from underground mines or sealed. Even when sealed, most methane will eventually be causes cracks to form in surrounding strata which may allow released to the atmosphere through outcrops, fissures, and other methane to migrate to the surface. migration pathways although total release will likely occur over many years at low emission rates. All mines flood to some degree. Many studies ignore AMM because these emissions were Flooding stabilizes the hydrostatic pressure on the coal seams, believed to be small or because data were not available. Most reducing emissions to near zero at some mine, even within a few coal producing countries do not report these emissions in their years following cessation of mining. However, the rising level of national inventories. There is lack of data from key coal producing floodwaters also compresses any existing desorbed gas resulting countries about abandoned coal mines, but AMM is growing as in high gas emission rates at the surface until the mine is fully mines close and AMM’s share could become significant over time flooded. In drier mines that partially or minimally flood, the gas as shown in Figure 6. Paradoxically, aggressive climate policies flow rate also declines rapidly over the first five years or so, but that lead to coal mine closures because of concern over carbon emissions continue for many decades. Mine flooding is a function dioxide emissions may lead to growth in AMM emissions through of regional geology and hydrology. Many of these aquifers are time and their contributions to total methane emissions may depleted during active mining and may take years to recharge and increase as deeper mines are gradually closed. Clearly, methane rebound to pre-mining conditions. Presently, detailed information emission reductions must be considered when closing mines to is needed to assess the impact of mine flooding at a global level. ensure a sustainable future. 66 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Figure 7: Water flow routs to and from a mine site (ICMM, 2012) moving operations which significantly modify the landscape of the area, affecting the natural flow of water through a region. Existing waterways may have been blocked or not designed to adequately accommodate flooding waters during intense rainfall episodes. Significant risks can occur when water drainage stops due to mine closure and the water table wants to rebound to its original elevation. For underground mines such water recovery could flood existing openings or can create artificial lakes in open pits. In surface coal mine operations due to the landscape alteration and the large quantities of soil removed, depressions may have been formed that can be permanently water-logged when the regional ground water table rebounds. Geological – geotechnical hazards are important risk generators during and after mine closure. Some geological hazards can manifest long after a mine has closed but can have serious consequences for human activity. Such an example is the landslide that occurred on 16th of February 2020 in the village of Tylorstown (Figure 8). The landslide occurred in an area that appeared to be a spoil heap on the valley wall from the historic underground mining company “Tylor’s Colliery Company Limited”. The underground mines ceased production in 1936. The landslide The mining industry’s use of and impacts on water can result in a formed due to heavy rainfall storm Dennis that took place the range of environmental, social and economic risks. Communities previous days in the area. The slide which occurred some 84 years close to mine sites may be concerned about availability of after the mine operations closed, shows the long term liabilities water, security of their access to it and, the potential for that may be present in former coal mining lands. water contamination (ICMM, 2012). These issues become even more cumbersome during and after mine closure when water Figure 8: View of the landslide at Tylorstown in South Wales on 16 February 2020 (AGU, 2020) management is transferred to other governing bodies or local authorities with scarce resources. The situation can become even more troublesome when mines are completely closed outside compliance with any regulatory authority and without assets being assigned to any legally responsible party. The water cycle near a coal mine area is shown in Figure 7 in which a former mine may have reduced the water table due to mine dewatering for slope stability and operational safety, may have used large quantities of water for the cooling towers of thermal power plants, or may have polluted the existing surface or ground water table with heavy and toxic elements in fly ash dump sites or due to acid mine drainage. Hazards can manifest into real risk for nearby areas during or after mine closure from water resources. In many cases mining operations disrupt existing water courses due to large earth Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 67 Geological – Geotechnical hazards, come in many forms and Figure 9: Aberfan in the days immediately after the disaster, showing the extent of the spoil slip (Wikipedia) depend on the actual mining activity. Slope instabilities and landslides, occur at abandoned open pit mines or spoil fills placed in adjacent to the mine areas. The former present less of a risk because they end up in the opening of the old pit but may have significant consequences if human settlements or even cities are located near the crest. Landslides from spoil fills may have more dramatic effects because usually they are placed in the outer limits of a mining area and can be adjacent to populated areas or water streams or rivers and can block the natural flow or even transfer heavily polluted soil in the stream and end up in the water bodies. The Aberfan disaster was a case of a spoil landslide that occurred in 21st of October 1966. After three weeks of heavy rain the spoil was saturated and approximately 110,000 m3 of dirt slipped down the side of the hill and onto the Pantglas area (Figure 9) of the village where 5 teachers and 109 children were killed in the school. Other types of geological – geotechnical hazards pertain to underground mining activities after the underground space is abandoned. When an opening cannot self-support, a dome starts to form in the hanging wall, this dome gradually propagates towards the surface. If the space underground is large and the accumulated material cannot produce self-backfilling, then the dome may reach the surface. The development of an expansion dome may be slow and take many years or even decades to reach the surface, the surface manifest can be very sudden in the form of sinkhole (Figure 10). The horizontal manifestation of such Figure 10: Grassland at a coal mine in Baorixile, Inner Mongolia, is dotted with pits (Global Times, Photo: Lu Guang, Greenpeace) sinkholes range from a couple of meters to several tens of meters in diameter. The depth of the sinkhole depends on the depth of the mining activity but usually within flat sedimentary deposits which are the host rock of coal can, sinkholes can develop from mines up to 40-50m deep (Taylor & Fowell, 2007). More subtle geotechnical hazards can come from ground subsidence over underground mines or residual settlements of large spoils. The former tend to occur in a short time frame after mine closure, the later can evolve over tens of years, precluding areas for future economic development. During mine closure the hazards presented in Table 1 should be evaluated to produce the risk pertaining to the local community, the regional environment and the climate. 68 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Assessing residual risks after mine closure The associated risks after mine closure, or residual risks since financial pressures and decreasing demand for coal will abruptly the mine operations have ended, differ significantly between end their operation in a significantly smaller time frame that had mine operations, mine regions and countries. The residual risks been foreseen. For the second case, the residual risk after mine or the probability of a hazard occurring depends on many and closure, is increased since a proper mine closure plan may not be different factors, for example climatic conditions of the area, feasible. If such mines in addition to limited resources and reduced extent of mined land, type of operation, amount of rehabilitation rehabilitation, do not have sufficient financial guaranties in some and many more. A starting point of assessing the residual risk due type of insurance scheme then it is possible that reclamation to mine closure is to identify if the mine will close in an orderly will not take place or will take place in a very limited way, in planned way or if its operations will be abruptly terminated. At essence abandoning the mine site and allocating the closure and the same time depending on the region of operation, more or less rehabilitation works to some other stakeholder, usually the local or stringent rules of financial insurance may have been enforced regional government. during licensing which is a major enabler for reducing residual risk. The highest residual risk will be associated with an abrupt ending In figure 11 the initial residual risk estimate is presented which is mine operation which has not implemented a suitable mine closure independent on local conditions. and reclamation plan and does not have sufficient surety bonding Coal mines operate in many parts of the world and they can be to cover reclamation. Whereas, on the opposite side of residual risk classified in those that will terminate their operations in the near issue, is a mine that has planned and implemented closure prior to future in a controlled and planned way and the ones which due to relinquishing the leases and permits to the governing authority. Figure 11: Hierarchical mine closure residual risk assessment Operating mine Scheduled - Abrupt controled mine mine closure closure No financial Available guranties - limited guranties and closure plan closure plans Limited available Adequate funding or funding to facilitate insurance to facilitate mine plan closure the mine closure plan (VHR): (HR): (MR): (LR): Very high residual risk High residual risk Medium residual risk Low risk after after mine closure after mine closure after mine closure mine closure Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 69 Due to the shift from fossil fuel to renewable energy production, detailed risk assessment nor manage the associated risks of financial conditions may dictate the closure of coal mine post closure. The financial burden of executing such detailed operations for this reason, it is likely that many operating risk assessment will be allocated to different stakeholders and mines will not complete their mine cycle and will need to end most probably to the local or regional government. The financial their operation abruptly. Whether or not such closures follow a risk or financial burden can be qualitative or quantified based controlled plan will largely determine the residual risks left to on the type of closure defined above and the availability of local and regional stakeholders. Based on the residual risk defined data. A paucity of data will not enable the understanding of per type of mine closure as stated above, a more detailed risk key closure hazards and risk drivers. In most mine operations, assessment must be undertaken. The financial risk of funding the monitoring and collecting data, such as waste pile geometries, detailed risk assessment is proportional to the residual risk per waste material types and grades, chemical elements, water type of mine closure and availability of data. and air quality, ground water conditions etc. are often reduced during operation to those that meet operational or licensing It is evident that a mine ending its operation abruptly without requirements (McCullogh, 2016). any financial resources, will not have the funding to execute a 70 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Data gathering and monitoring is an essential tool for calibrating be essential for the detailed risk assessment. Mine operations and validating predictive models of future conditions and in with little or no data will require significant extra funding for essence contribute significantly to the detailed risk assessment. investigation (geochemical, geotechnical, hydrogeological, etc,) Data from the start of mining which provides adequate to provide appropriate data for a detailed risk assessment. The information of all types of operations and ground conditions will available data can be categorized in the following way: Full data sets from start of mine operation • Systematic data have been collected from start of operation. A • Data and monitoring cover all aspects of mine operation from ground water variation, meteorological data, chemical compositions of waste material and locations placed, geotechnical conditions and geotechnical properties of material, locations of instabilities, air polution, methane quantities etc • Data are stored in a well documented and easily accssable data base Significant data sets in recent times - partial from start of mine operations • Data have been collected in a systematic maner only in recent years but do not cover all mine operations and conditions B • Data have been collected in the past from start of mining but not in a systematic way and only covering some aspects of mine operations and ground conditions • Part of the data are easily accessable (the more recent ones) and older data need significant time to alocate and made available in a usable format Partial data in recent times and minimum data from start of operations • Data and monitoring is partly executed in recent years only C • Data coleted, cover some aspecsts of mine operations and ground conditions • They are not stored in a systematic way and are difficult to access • Significant time and resources are needed to make them usuful for use Full data sets from start of mine operation D • Data have been collected partially, in recent years and only for a minimum of conditions • Limited data have been collected but not stored and is very difficult to be located and used • Data have never been collected Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 71 Figure 12: Matrix showing the risk of increased needs for funding detailed risk assessment Availability of data Residual risk A B C D (full data) (significant) (partial) (limited) Likelihood of occuring LR 1 2 3 4 (low residual risk) LR 2 4 6 8 (medium residual risk) LR 3 6 9 12 (high residual risk) VHR 4 8 12 16 (very high residual risk) Increased funds needed for detailed risk assessment In figure 12 a simple risk matrix is provided in which residual risk or finance such a detailed risk assessment. It is always better to after mine closure (figure 11) is associated with the availability execute such an assessment while the mine is in operation and can of data to produce the qualitative financial risk of a detailed provide data and staff to accommodate the task. risk assessment. Each residual risk is assigned a numerical value between 1 and 4 and the same is done for the availability of data. Low residual risk (LR) with full data set (A) provide the lowest financial risk for execution of a detailed risk assessment which in some cases may already be available. Very high residual risk (VHR) with limited or no existing data lie on the opposite end of the matrix with increased financial burden of executing a detailed risk assessment. It is important for mine operation governing authorities, local and regional governments to undertake the initial residual risk assessment and risk of funding and to prioritize intervention per mine operation or mining company. Very high and high residual risks accompanied with high risk of funding have to be prioritized and a detailed risk assessment executed. This can be requested or enforced to mine operators, or undertaken by third parties assigned by the governing body. Before a mine is abruptly closed, it will probably have some or most financial capacity to undertake 72 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Detailed risk assessment A detailed risk assessment should evaluate the impact The ANCOLD Consequence Guidelines (2012) is proposed as an (consequences) of each type of hazard and the likelihood appropriate way of evaluating the severity level that will be used to of occurrence of such a hazard in the post mining period. A produce the consequence part of the risk matrix. Table 2 provides consequence based approach is considered more appropriate the severity level impact assessment for a tailings dam failure in the detailed risk assessment. With this approach the which can be considered as a major hazard in post mining lands. detailed risk assessment is driven by the potential impact a With minor adjustments mainly in the natural environment impact, hazard represents particularly in relation to loss of life and this table can be used as a general guide for severity estimations environmental damage. With this approach high priority is in coal mine closure impact due to the great scale and land they given to conditions that can produce catastrophic or significant affect. This table can be used for post-mine closure severity impact failures that will impact large populations and produce assessment since it provides indicators for: financial damage due significant financial losses. While this is similar to a risk-based to mine closure (not only due to some type of failure), business and approach, the requirement to consider specific criteria results social impact, public health and safety, impact period and general in a reduction of the likelihood component of risk, through environmental and climate impact. Such conditions apply to post application of higher criteria for higher risk facilities (Chapman coal mine regions socially affected from loss of income, relocation et al, 2019). of population and work force and business impact. Table 2: Severity level impact assessment (modified from ANCOLD, 2012) DAMAGE TYPE MINOR MEDIUM MAJOR CATASTROPHIC Infrastructure (dam, houses, commerce, <$10M $10M - $100M $100M - $1B >$1B farms, community) Crippling impact to local Dissolution and Significant impact of local Impact to business Some restrictions business business and severe to bankruptcy of local and regional some regional business <1000 people affected for >10.000 people affected for Public health and safety <100 people affected 100-1000 people affected more than one month over a year 100-1000 person months <100 person or <20 >1000 person months or >10.000 person months or Social dislocation business or 20-2000 business >200 business months numerous business failures months Impact area <1km2 <5km2 <20km2 >20km2 Affected region Neighboring town Part of the region Region of mine Country Impact duration <1 year <5 years <20 years >20 years Impact on environment Limited damage to Significant effects on rural Extensive rural effects, Extensive affects in the local environment land and local flora and significant pollution on all environment of the – insignificant effect fauna – some effect on regional water systems, region and part of the on climate change, climate change, extensive local and state natural country, significant effect remediation is possible remediation needed heritage, flora and fauna. on climate change and Limited on national or ecosystems, remediation world heritage and flora involves significantly – fauna in national parks altered ecosystem and protected areas – climate change is affected, remediation is difficult Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 73 Figure 13: Example plot of coal production, liberation of drained and As an example, an authority or a consultant considering post- vented methane at a gassy mine ins southwest China closure methane emissions at a mine that was gassy during coal extraction, would begin by preparing an analysis of the methane that was liberated during active mining. Figure 13 was compiled Shih o Min CMM Dr in VAM Emissions Co l Production from data collected at a mine located in southwest China and 4,000,000 110,000 illustrates what the analysis could show. In this case, the mine was sufficiently gassy to warrant installation and operation of 100,000 3,500,000 a gas drainage system. The rates and concentration of the gas drained, used, and or released to the atmosphere would have Co l Production (tonn s) 100% M th n (m3) 90,000 3,000,000 been recorded during active extraction and must be compiled for 80,000 analysis. The engineer will also determine the amount of methane that was exhausted from the ventilation system so that the total 2,500,000 70,000 amount of gas that was liberated during mining can be clearly 2,000,000 60,000 understood and management can undertake decisions related to how the post-closure emissions will be handled. From the history 1,500,000 50,000 of mining in gassy coal basins, the hazards related to methane 01 Au 17 F b 05 S p 20 M r 10 Oct 28 Apr 14 Nov 01 Jun migration after mines are closed are well known. If the mine is 2004 2005 2005 2006 2006 2007 2007 2008 gassy the likelihood of methane escaping from a closed mine in the early years after mine closure are almost certain. Based on the severity level, a risk matrix can be formulated. Figure Using the matrix in Table 3, the authority or the consultant 13 is a simple consequence based risk matrix that can be used to might determine that the likelihood of leakage to the surface assess the likely outcome of not taking remedial action that will is >90%. If the closed mine is near a building, say an apartment impact the overall value of an asset or region. Each of the hazards complex, that will remain occupied after closure, the severity of and potential negative impacts listed in Table 1 should be assessed the economic damage may be significant or even high, depending and the most significant impacts used to evaluate the severity. In on the location and the perceived potential for migrating gas to this way the post mining risk is related to the severity of impact. become trapped in the building or in some buildings in the local This approach produce risk matrix for decision making in relation town and the methane concentration reach the explosive level. In to available reclamation and repurposing funding. this example, the engineer would take measures that would ensure Table 3: Simple risk assessment matrix based on severity impact and probability of occurrence Minor Medium Major Catastrophic Almost certain > 90% Significant High Very high Extremely High Likely 30-90% Medium High Very high Extremely High Possible 10-30% Low Significant High Very high Unlikely 3%-10% Low Medium Significant High Improbable <3% Low Low Medium Significant 74 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines that the gas does not reach the building by detecting and sealing Figure 14: Probabilistic slope stability analysis any excursion pathways and would recommend that a monitoring program is established including installing methane monitors that periodically record methane concentration in the building. FS (deterministic) = 1.3 In a second example, an authority or a consultant considering post Probability of Failure closure landslide at a mine that had shown instabilities during for 5% excavation would begin with collecting all available geotechnical and monitoring data. The engineer will evaluate the geotechnical investigation data produced with drillings during mining, prepare geotechnical models of the slopes and assign different geotechnical domains on the slopes remaining after closure. They will execute a probabilistic slope stability analysis the outcome of which will take into account the uncertainty of soil strength properties, pore water pressures, and geometry and will produce a probability of failure as can be seen in the Figure 14. If the calculated probability of failure is found to be 5% and the slopes of the closed mine are in close proximity to a village or a town then, going back to Table 3, the engineer might determine that the likelihood of slope failure is >5%. If the slope failure is considered unlikely and the consequences or the severity of damage are minor to medium, then the risk to the village may be estimated to be low to medium. The likelihood of a slope failure has been found to be unlikely and the overall risk is estimated to be low to medium. The governing body or the mine authority, assessing the two example mines presented above and having limited funding has a clear indication on where to place appropriate funding for remediation. Since the post-closure methane emissions mine produce a significant risk in relation to the landslide area that produces low to medium risk the money is better spent in the gas liking mine. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 75 Assessing residual risks after mine closure For the post mining period, all hazards (Table 1) should be another form of risk mitigation. Usually protective measures recognized, and then, based on a consequence risk assessment are more expensive and more socially disturbing than preventive (Table 2 and 3), they should be categorized from the more severe measures, and they are used as a last resort. If we take the (Extremely High Risk) to the less severe (Medium or Low Risk) previous example of the mine with gas emission, the first approach and then prioritize what mitigation measures should be enforced. of preventive actions was to detect and seal any excursion Since funding is not unlimited, risk management and mitigation pathways of gas. If the protective approach was utilized, then the should follow a certain procedure on how to mitigate risks based building or buildings in close proximity to the mine could have been on the available funding. Mitigation actions can follow three major quarried by the mining company and demolished in order to avoid concepts (Figure 15): the consequences of an explosive accident. Usually protective measures are taken in later stages of mining or after closure, when a) preventive measures are used to lower the probability of the it is very difficult to enforce preventive measures. identified hazard from occurring. This type of action affects mostly the first column of Table 3. Emergency measures are the last resort for reducing a hazard b) protective measures are used to reduce the consequences of a or its consequences. Usually emergency measures are utilized in hazard. This type of action affects the first row of Table 3. unforeseen risks when it is too late to enforce either preventive or protective measures or the financial burden of taking such c) emergency measures are used when either the probability of measures is prohibitive. Usually emergency measures are a short occurrence cannot be reduced with preventive measures, nor term approach and further actions or measures are needed when the consequences can be lightened with protective measures the hazard has been completely or partially controlled. For the and is the last resort of risk mitigation. same two examples of the landslide prone waste fill and the gas Preventive measures in which the hazard is either eliminated leaking mine, a monitoring and early warning system could be or significantly reduced from occurring is the most appropriate implemented which will provide warning for evacuation from the mitigation. If such proactive measures are conceived and affected areas. Emergency measures come with an increased implemented during mining (mining for closure) then the financial physiological effect, can inflict social unrest and should only be burden could be allocated to the production cost. Furthermore, used as a last resource to avert hazards. early on hazard reduction has the benefit of requiring less effort and capital. Proactive measures can be enforced during closure or Figure 15: Risk management and mitigation approach post closure but many times the funding for such works may be prohibitive. An example of a proactive measure in the placement Eliminate of a waste fill is to produce shallow stable slope angles with hazard appropriate drainage conditions during mining operation. At this stage the extra cost is minimal since fill would be placed anyway Preventive Reduce measures hazard and only its outer geometries need to be addressed, possibly Reduce triggering through installation of a drainage layer in the foundation of the factors fill. These preventive measures may eliminate a landslide hazard of the waste material or significantly reduce its occurrence (its Eliminate consequances probability of failure). Such preventive measures can be utilized Risk Managment Protective and mitigation measures Reduce during closure or post closure, but at that time, significant consequances earthworks and funding will be required to excavate, transport and place in different locations the materials removed in order to Control hazard produce flatter slopes. Emergency measures Control Protective measures in which the consequences that can be consequances inferred by a failure or a hazard are reduced or eliminated is 76 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Table 4 below, is a summary of preventive and protective measures way. This table may also be used as an agenda for identifying issues during closure and post closure periods. They are grouped that are not covered by existing regulation and policy or which based on the general hazard pertaining to the environment, gas may be adapted to become applicable to the unique geological and emission, water resources, geotechnical instabilities of surface and mining conditions found in a coal producing region. The table is underground mines. These proposals should act more as a checklist not restrictive nor exhaustive and should be treated as an aid to of measures that can either reduce the risk in a proactive or reactive possible risk management measures. Table 4: Reclamation strategies to reduce risk in preventive or protective conditions General Hazard Detailed Hazard Preventive Measures Protective Measures Environmental Air pollution – Water spray of roads and dumps to reduce dust from Reduce movement of vehicles in post mine areas which dust moving equipment and strong winds. have not been reclaimed. Native vegetation cultivation which is appropriate and Relocate occupants near the former mine area. long lasting for the climatic conditions of the area. Air pollution with Top soil cover of areas with contaminated lands that can Suspend operation in ongoing power plants. toxic elements – produce air suspended particles. Relocate occupants near the former mine area. particles Use of appropriate filters in ongoing power plants. Relocate villages around the affected area. Permanent cover of areas with contaminated soils. Clean and make inactive pollutants or remove and appropriately dispose contaminated soil. Surface water Reduce or eliminate polluted mine drainage to nearby Restrict usage of water for irrigation or domestic pollution water bodies. consumption. Use special treatment plants to purify discharged water Restrict fishing or recreation on polluted water bodies. to water bodies Ground water Top soil cover of contaminated lands. Divert as much as Restrict usage of water for irrigation or domestic pollution possible percolating water from entering contaminated consumption. areas. Provide fresh clean water from nearby aquafers or water Remove contamination from the soil, construct bodies to the affected area and people (for irrigation or impermeable water barriers, pump and treat ground domestic use). water. Contaminated materials such as spilled fuel oil, asphalt and solid waste must be removed from the site and disposed of at an approved facility Acid mine Evaluate potential for acid generation or migration. Exclude the area from visitors. drainage Cover and use impermeable surface barriers (natural or Exclude the area for agricultural or horticultural use. man made) to reduce the amount of water and oxygen Evacuate the area for people and animals entering the mine spoil. Regrade area prone to AMD to reduce water infiltration or water outflow. Place a layer of non acid generation material before top soil cover to provide alkalinity. Soil pollution Preserve original top soil during excavation. Use Restrict crazing and farm land operations. with toxic – original top soil or blended top soil to temporary cover Restrict occupation and inhabitation of polluted area. heavy elements contaminated areas. Temporary seeding. Relocate people and animal from the polluted area. Permanent cover of areas with contaminated soils. Clean and make inactive pollutants or remove and appropriately dispose contaminated soil. Use top soil with native vegetation species. Visual Contour aesthetically pleasing landforms consistent Vegetation cover with the use of native vegetation disturbance with surrounding. species and establish self-sustainable vegetation Topography, remove or hide old buildings, equipment. growth. Repurpose buildings, utilities and power lines. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 77 Table 4: Reclamation strategies to reduce risk in preventive or protective conditions (continued) General Hazard Detailed Hazard Preventive Measures Protective Measures Gas Emission Trapped gas ignition or explosion Intoxication CO, CO2, H2S CMM Gas transport pipes in shaft and degassing station Installation for safe discharge of the gas protecting operates during closure. against incoming air when atmospheric pressure is greater than pressure in degasification system. AMM Degassing pipes in shaft for conducting gas to the Installation for safe discharge of the gas protecting surface. against incoming air when atmospheric pressure is greater than pressure in degasification system Water Water flow Pre-mine planning to avoid unnecessary alteration Reshaping of topography to accommodate natural Resources disruptions of landforms adjacent to mining property. Use native stream drainage systems or create artificial streams. vegetation to reduce soil erosion. Water recovery Termination of water drainage pumping. Reduce or eliminate outflows from underground mines potential and evaporation from surface mines. Water outflow Temporarily seal water outlets from underground mine Seal near surface adits with appropriate pressure from mine adits adits. sealing and plugs. Water logged Create temporary drainage paths or reduce but not Restrict crazing and farmland operations on areas – Marshes eliminate pump drainage. waterlogged areas. Create appropriate topography with low gravity Restrict occupation and inhabitation of possible water- discharge points. Install long term near surface pumping logged areas during heavy rainfall operations to keep ground water lower than ground surface. Flooding of Create temporary drainage paths or reduce but not Restrict office and industrial occupation of the area. near surface eliminate pump drainage. Restrict residential building and recreation and shopping structures and Create appropriate topography with low gravity centers. buildings discharge points. Install long term near surface pumping Reconstruct infrastructure above possible water operations to keep ground water lower than ground elevation. surface. Consider as a minimum a 1 to 50 years storm event. River overflow Construct temporary embankments and dams flood Restrict crazing and farmland operations on and flooding of control. waterlogged areas. low land areas Create permanent topography and land morphology to Restrict occupation and inhabitation of possible water- reduce river or stream overflow and prepare appropriate logged areas during heavy rainfall flood paths for water discharge. 78 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Table 4: Reclamation strategies to reduce risk in preventive or protective conditions (continued) General Hazard Detailed Hazard Preventive Measures Protective Measures Geological – Surface mine Control dewatering operation to reduce slope water pore Restrict access near the slope. Geotechnical slope instabilities pressures. Relocate businesses and farmlands near the slopes. surface mines Reshape slopes, backfill open pits, flood open pits with appropriate evaluation of minimum and maximum water elevation and graded gentle shoreline slopes. Surface dump Temporary toe backfill, native vegetation cover to Restrict access near the slope. slope instabilities reduce slope erosion. Relocate businesses and farmlands near the slopes. Reshape side slopes, reduce fill height, place toe berm, Restrict crazing and farming on top of the slopes. forest slopes. Restrict agricultural operations near or on top of the slopes. Surface Temporary reduce tailing water elevation. Restrict office and industrial occupation of the area. impoundment Investigate and strengthen tailing dams with grouting, Restrict residential building and recreation and shopping slope instabilities toe berms, geosynthetics and continue monitoring centers. – tailing dams of deformations and pore pressures. Consider as a Reconstruct infrastructure above possible water minimum a 1 to 100 or 200 years storm event based on elevation. downstream population and assets at risk Flow slides – Temporary exclude areas from operations, mine Restrict access near the slope. landslides activities and livestock. Relocate businesses and farmlands near the slopes. Reshape slopes, vegetation and forest cover, use Restrict crazing and farming on top of the slopes. toe berms, use arresting embankments, continuous Restrict agricultural operations near or on top of the monitoring of deformation and pore pressures. slopes. Dump Place fill and compact material. Restrict office and industrial occupation of the area. settlements – Exclude settlement sensitive operations and Restrict residential building and recreation and shopping deformations installations, avoid placing infrastructure or use centers. appropriate ground improvement methods. Relocate infrastructure sensitive to settlement such as rail lines, natural gas lines etc. Geological – Subsidence Backfill mine galleries and shafts. Create exclusion zones, permanent backfill mine Geotechnical – ground openings. underground deformation mines Sinkhole Permanent backfill mine openings, construct bridge Create exclusion zones. formation elements and covers with adequate structural capacity. Restrict office and industrial occupation of the area. Restrict residential building and recreation and shopping centers Backfill mine galleries and shafts. Relocate all inhabitants and animals and exclude the area form any form of development. Backfill mine galleries and shafts. Enforce increased seismic design of buildings and structures. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 79 Monitoring for mine closure Mine closure planning has to evaluate the short- and long-term for environmental impact such as water and soil chemical risk exposure of the environment, community and current and analysis, air pollution, gas emission (methane, CO2, CO, SOx etc.) future stakeholders. Risk approach planning requires appropriate and geohazards such as slope movements, ground deformation and available data to understand and rate the key closure risks and settlement as well as climatic data in the area such as wind, and risk drivers at a mine site. Such data should be systematically precipitation, temperature. All data should be seen as crucial to and appropriately collected and stored to facilitate future use risk assessment during mine closure and beyond and should be and understanding of liabilities and successful reclamation treated as irrecoverable if lost. practices. Monitoring and data gathering is often perceived as a Monitoring should be planned and executed if possible before legal or operational requirement which is used either to approve the mine starts operating. It is important to provide a baseline permit renewals or to satisfy operational safety during mining data report of the mine and surrounding area that will be used operations. Monitoring should be seen as also providing datasets for reclamation target setting. This monitor data baseline should to reduce the direct and residual risks of mine closure. be seen as a very important tool because it can significantly In addition to providing data required to develop a mining plan, reduce closure liabilities. A good example to understand the value during the design and starting phase of the mine operation, data of such a baseline report is addressing groundwater pollution collection at the earliest stage establishes baseline conditions and remediation. A mine area prior to mining has concentration and should be used to frame the potential for future restoration of a mineral resource (in the context of these guidelines: coal) and repurposing. This data is essential for future planning and which provides a particular identity of chemicals to the natural should be used not only to develop coal resources in the most groundwater in the area. If elevated concentrations of heavy environmentally sound manner, but also enable mining companies elements are found in the natural ground water, it may not seem to plan the surface and underground layout so that troublesome reasonable to request that, post closure water conditions reduce and complicating factors that may impact site restoration and heavy elements below such values. However, since the mine is reduce future use and value are managed, and to the extent responsible for bringing water to the surface the mine operator possible, mitigated or avoided. may be required to establish a workable management plan If such a baseline report does not exist, litigations and risks may increase Monitoring data should be used in collaboration with modeling when groundwater elements are considered higher than standards during mine closure planning to evaluate the potential risks and or regulations permit. mitigation measures. Collected datasets provide hard evidence that the adopted procedure is working as planned. They also Monitoring should be planned and executed during mine provide invaluable data for assessing the probability of occurrence operations. A careful execution plan of instrument types, location, of many hazards and how such hazards can be addressed installation, and frequency of data gathering is required. Such to reduce the post closure risk. For example environmental careful and systematic planning requires highly trained, dedicated monitoring (chemical data collection and analysis) of water and responsible people to execute it. It is always important to quality coming from a spoil dump can provide information if understand that monitoring-bound actual operational needs is AMD is forming. If covering of the spoil is reducing or eliminating an expansive endeavor like insurance policies, it is best to never water infiltration that reacts with pyrite in the spoil and produces actually need the data to protect you but if you need them they AMD or if a new strategy needs to be applied for AMD reduction. should be there. In other words, monitoring data can reduce post Monitoring reference sites can also advise on trends in the natural mining closure risks if used properly and can protect against environment; important when irrevocable changes have occurred future liabilities. to surrounding ecosystems such as are expected in many cases Monitoring should continue after closure for an indeterminate with climate change (McCullough, 2016). time period since many of the hazards can be long lasting or even Monitoring programs and data collection should address all evolve due to future climate changes. For example AMM can be hazards presented in previous chapters. Data should be collected emitted from a mine for many years after closure as explained 80 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines earlier in this document, or spoil instability can formulate long • What are the budget requirements during mine operation and after an area has been closed due to increased precipitation due to post mining activities? climate changes in an arid area. • How will the data be reported and how often? A well-planned monitoring program should define the project • Who will have access to the data? conditions prior, during and after mine closure. Such a program The monitoring data will be invaluable in the process of mine should record conditions that can be used to predict mechanisms closure based on a risk approach framework. The data can be that control ground behavior, water conditions and flow, gas used support planning and future repurposing and redevelopment emission etc. It is important prior to any monitoring campaign at mining sites where liabilities are well understood or have been to understand what questions need to be answered with the significantly reduced. proposed instrumentation and frequency of data collection. For example, measuring precipitation once every month will produce no actual or reliable data, on the other hand taking ground water   elevation measurements every minute will not produce additional accuracy beyond taking measurements once a day or even once every few days. An important aspect that is often ignored is the selection of change in magnitude of measurements made so that capable instruments are selected and also provision is made for sufficient data capacity required to safely store large data quantities. It is crucial that data is stored and archived in an appropriate manner and remain accessible for later retrieval. The approach to data archival should be considered in detail as data analysis and evaluation may be found be beneficial at a future date. If monitoring data are gathered but cannot be easily or effectively accessed, then they are likely to be ignored in the future. A well-planned monitoring program should address the following issues: • What parameters need to be measured, in what range and with what frequency? • What instruments are needed for such measurements, what is the life expectancy when exposed to the harsh mine environment and what accuracy, reliability and repeatability can they provide? In some instances, ruggedness may be more important than accuracy. • In what location will the instruments be installed? Are these locations appropriate for the actual conditions that are monitored? How will this location be affected during mining, reclamation, or closure operations? • How will data be collected, who is responsible for the collection, storage, and evaluation? Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 81 Beyond risk management – creating added value for post mining lands and assets In the previous paragraphs, the risk assessment methodology • The needed data and baseline conditions may not be for post closure mining conditions was presented. The risk available. It is difficult to assess the impact of ground water assessment can be undertaken from the mine company during pollution when the actual conditions before mine operation operations or during closure or it can be undertaken by relevant commencement are known. For example a naturally occurring authorities that foresee future liabilities and inappropriate heavy element present on a ground water can be attributed closure plans. Even though risk assessment is a major on the mine operation which may not be the case. This lack of contributor to manage the post mining lands and environment, baseline conditions may mean that even positive operational a detailed and complete risk assessment can be a daunting task activities during closure cannot be demonstrated to the for the following reasons. regulators or stakeholders (McCullough) and used to reduce the future risk. • The actual post mining period cannot easily be defined and it is strongly related to each hazard and consequence of Without closure planning and assessment of re-development occurrence. For example what would be the recurrence interval risks, the post-closure phase is often limited to land reclamation used to assess the probability of failure of a tailings storage comprising recontouring the land, installation of surface mine- facility in relation to design storm or earthquake? For a 100 year water drainage monitoring systems, and decontamination of recurrence interval event the probability of failure increases as land surface. However, further consideration is warranted. By the post mining period increase. Reclaimed mine facilities such implementing good practices that serve as the basis of the global as soil covers, waste slopes, open pit slopes will remain in place coal mine closure standards, the highest value of the closed mine for decades and will require to be designed for more extreme and the associated surface resources can be ensured. Use of the events. This is contradictory to past or even current mine mined-land repurposing toolkit, LURA, is key to an organized operations, for which the probability of failure or likelihood of assessment of the potential and planning for the highest use occurrence are acceptable even with high values. Based on the of the land. Re-purposing of the mine site and potential use of selected post mine period, the risk will increase. the land and other resources such as remaining gas and water resources if present, offer a considerable future value. In addition, • The actual financial impact of a future hazard is difficult the void space in deep mines may be used for storage of natural to assess taking into account that present legislations and gas, or for carbon dioxide sequestration under rare circumstances environmental allowance limits are more likely to be less if appropriate geological conditions exist. However there may be stringent than future limits because society is continuously substantial objections from nearby or adjoining communities. evolving towards more stringent environmental limits. A mine that closed 20 years ego faced much less environmental Implementation of technical closure standards are best started limitations than one that is planned to close today and certainly while the mine is still in operation so that final mining activities one that will be closed 20 years from now. It is not easy to are guided by a technical closure plan that includes an assessment assess the risk of contamination in the future when the limits of of the activities needed and associated costs to remove unwanted the polluting agent is not known, the rainfall intensity per year plant and equipment, undertake environmental reclamation and cannot be predicted due to climate change etc. re-purpose other useful physical assets including buildings and • The actual reclamation strategies have not been tested for a energy infrastructure. And, implementation of technical standards significant time period and may not have foreseen the need for often requires actions by both the company and a community of future development. Final slope angle selection for fill waste can certified third-party enterprises. Given the highly specialized skills be designed to be stable and covered with a limited thickness required to close underground coal mines, the World Bank reports of top soil for grassing and utilized for grazing. Is grazing the that countries receiving past technical assistance on coal mine actual future use? How will climate change affect the erosion of closure have exhibited a preference for establishing dedicated coal top soil in the long term? Land created for grazing can become mine closure companies. These companies absorb mine labor, waste land in the future due to poor quality of grass, limited engineering expertise and equipment from the on-site mining interest in cattle farming etc. enterprise to ensure proper reclamation to national standards. 82 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines And so, the creation of the coal mine closure company assists in and impractical. Moreover, many mining communities now want employment transition in the region. The European Commission, in to use these lands and physical assets as part of the economic managing the “E.C. Coal Regions in Transition Platform”, has also transformation of the region and returning them to forest and reported on regions having a similar preference to establish highly open-space may be counter to industrial development plans. specialized coal mine closure companies to capture the expertise For this reason, many older technical standards and regulations of coal enterprises on-site and ensure regulatory compliance are now seen to be working against the guiding principles of and adherence to national regulations. In most coal producing ensuring a Just Transition for All, by placing binding constraints regions, government-certified, third-party specialists are on the mining enterprise to comply with regulations that may be available to prepare mine closure plans using technical standards unaligned with the desires of the community post-mining. that would be provided by the government. These third-party Subsidence which is caused by underground mining can render specialists could be a delivery mechanism for technology transfer future uses of the land overlying the mines to be non-viable. to coal mining enterprises that would act as specialized closure Subsidence of the ground’s surface above underground coal mines companies. begins during active mining and continues after closure. In recent The start date for implementation of technical coal mine closure years, there is increasing awareness of repurposing closed coal standards varies globally. The ITUC’s global initiative “A Just mine lands for other productive uses, and repurposing land and Transition” is increasingly being applied as a guiding principle in assets must become one of the core elements of a region’s energy coal mine closure, by seeking to put in place (ahead of all closure transition. Because of the irregular ground surface left after activities) the concrete plans, policies, and investments needed subsidence, some government entities in China and elsewhere are for a fast and fair transformation. The World Bank’s technical encouraging re-purposing for renewable energy generation using assistance complements this concept by also envisioning this subsided terrain for solar and wind power generation and/or strengthening of the necessary institutional reforms that renewable energy storage (pump storage, molten salt storage). As are needed to ensure effective implementation of standards, an example, in the past few years, investment in Shanxi Province, by building up professional and institutional capacities. This China has converted some abandoned coal mine and subsidence would include technical standards to be enforced as part of the areas into GW-scale solar PV bases under the national pilot solar preparatory process which would include the compilation of PV auctions, and geological, forestry and agriculture parks. In relevant data regarding the subsurface and surface, deleterious Datong mining region, a 248-acre solar farm was built in 2017 on chemicals and other hazards that may be left onsite, pollution a depleted coal mine subsidence area. abatement measures that have been taken and will need to While the technical specifications issued in 2002 define some key be sustained, essential infrastructure necessary to sustain criteria that mining companies should look at when closing a coal abatement of fugitive methane, and the assessed status of land mine, there is currently no comprehensive technical standard for and assets that would be repurposed for future use. coal mine closure with quantitative and qualitative thresholds Module 1 of this document provides background on coal mine on environmental reclamation and land remediation, which are closure standards, and risk-anchored guidance for coal mine essential to post-mining safety and land use. The provincial closure. Department of Environment and Ecology reports that the mine closure plan is submitted to the provincial Department of Natural Technical standards also address the need for comprehensive Resources, but the status of tracking and compliance of activities environmental reclamation, which is being viewed globally through is not readily available and post-closure monitoring is not known. a new perspective. Many jurisdictions are coming to recognize that coal mining areas represent decades and/or centuries of environmental degradation, and regulations based on the “polluter pays principle” where efforts would focus on returning post- mining lands to their original state, would be prohibitively costly Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 83 Land Repurposing Methodology (LRM) The Land Repurposing Methodology (LRM) represents an objective The objective of land repurposing is to think and plan beyond procedure for the determination of post mining land use with a achieving environmentally stable landscapes and complying high spatial resolution and a high degree of reproducibility. The with environmental permits to develop former mining lands LRM is based on specific themes with respective parameter groups: towards conditions that allow a wide scope of diverse land uses. morphology, hydrography, geotechnical risks, environmental, gas Of course, the environmental quality of repurposed lands should emission, socio-economic factors and land value (both positive be maximized, and remediation and reclamation should start as added value and negative as remediation cost); further preferably while mining operations are still ongoing (“mining parameters, e.g. permitting requirements or restrictions can be for closure”). Repurposing should be economically efficient and added as required by the various stakeholders. The LRM is not a technically effective, delivering fit-for-purpose lands for a variety standalone instrument but needs interfaces and integration with of utilization options. In cases of abrupt mine abandonment other planning frameworks and tools. LRM provides basic facts such repurposing activities should be considered in the context and data needed for decision making around repurposing planning. of initiating low carbon economic development and should be The methodology informs on which types of post-mining use make included in the overall master plan design. The process should sense to plan for on a given parcel of land but does not prescribe a be transparent and result in the generation of net value when all specific investment scenario (Table X); this would be a level more factors - redevelopment potential, socio-economic, environmental granular, e.g. in the realm of an SSP – special spatial plan. / ecological quality, and climate effects - are accounted for. Table 5: Evaluation criteria for post mining lands Theme Criteria Favorable for… Unfavorable for… Location Distance to infrastructure and Any industrial process depending on delivery and Recreational areas, research parks and other non- utilities shipping of goods or materials by road, water and industrial uses may be negatively impacted by energy; producing significant amounts of solid and proximity to infrastructure. liquid waste. Distance to human settlements Recreational, business / research facilities would Industrial activities creating noise, emissions, profit from closeness. odors and other risks / impacts should be isolated from settlements. Geotechnical Expected residual ground Almost irrelevant for agriculture and forests, Can be extremely important for large scale stability settlement of spoil fills. recreation and tourism. structures with high loads and low tolerances esp. Subsidence from underground for differential settlement. coal mining Slope stability – seismic risks Potential risk for any utilization scenario. Can be actively hazardous for community health and safety, and infrastructure near the slopes of OD. Relevant for almost any use scenario; seismic risks need to be factored into stability assessments Sinkhole formation or massive Minimum risk agriculture and forests if surface Serious risks for large or extended and frequent collapse due to underground manifestations are small. surface manifestation of sinkholes especially for abandoned mines industrial and business park developments Impact of groundwater Almost irrelevant for agriculture and forests, Can be very relevant and have negative impacts rebound (applies especially recreation and tourism; can have positive for large scale structures with high loads and to interior dumps) and for biodiversity impacts due to creation of lakes, low tolerances esp. for differential settlement. underground mined space ponds and wetlands with high ecological value. Potential agricultural / recreational issues due (room and pillar, access to water percolating through fly ash layers with galleries etc elevated heavy metals or AMD, unfavorable for underground space storage or other underground developments (research, waste repository etc) Topography Natural and manmade ground Placement of PV on berms on high, stable slopes, Any development requiring large, level space and and surface contours, gradients if exposure appropriate; forests and natural stable ground; this will include almost any built hydrography and landforms reserves on slopes for stability, biodiversity, structures. timber production or as carbon sink. 84 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines Table 5: Evaluation criteria for post mining lands (continued) Theme Criteria Favorable for… Unfavorable for… Topography Surface water resources, Poor drainage and resulting standing water can All other uses require well drained surfaces, and and stream flows and gradients be irrelevant, even and advantage for recreational tolerate neither stagnant water, nor erosion due to hydrography use or biodiversity enhancement. high flow velocities. Ground water flow and outflow Water supply for local community, agriculture, Water may appear at the surface when aquifers at the coal mine, and for other commercial and re-fill and the land surface has subsided below industrial uses the recovered groundwater level, saturating the ground and pooling. These effects may significantly reduce potential use of land resources and bring pollutants to the surface. Hydrological risks – extreme Limited tolerance for forestry, recreational use or Very limited or no tolerance for all other uses. precipitation events and biodiversity enhancement Floods are particularly hazardous where they flooding, underground water may interact with poorly consolidated dumps, circulation or outflow which have high erosion potential. Flooding of underground mines can deteriorate support and produce increased sinkhole phenomena. AMD can outflow from abandoned underground mines due to increased recharge which could be harmful for any type of development. Environmental Presence of soil / GW Likely of low relevance for all industrial uses Highly relevant and significant risk for agriculture; risks contaminations or hazardous moderate risk / deterrent for recreational / materials; acidic soils, Acid touristic uses. mine drainage (underground or from spoil) Current / manifest Limited relevance for industrial activities (which High relevance / potential negative impacts for environmental impacts of themselves may create noise, emissions, odors recreation and tourism, as well as “white collar” ongoing above and below etc.), and for forestry. Moderate to significant type activities such as R&D or office parks. ground mining operations relevance for agriculture activities – dust could (dust, noise, vibrations, traffic, e.g. create negative impacts. odors, pollutants) Proximity to operating TPPs, Irrelevant for all uses except industrial processing When processing fly-ash into secondary products including post-repurposing, of fly-ash. (e.g. concrete) need to ascertain acceptable levels lignite bunkers, fly ash of potential contaminants, especially heavy stockpiles, mine shafts and metals. mine adits Gas emission Trapped gas ignition or Potential risk for any utilization scenario Can be actively hazardous for community health explosion, Intoxication CO, and safety, and infrastructure near the CO2, H2S AMM emission Energy projects such as power generation, Unfavorable for agriculture. Can be actively providing gas for pipeline injection after treatment hazardous for community health and safety, and or blending with high quality methane, use for infrastructure built above underground gassy district heating mines Development Added surface land value due Any low-cost investments such as agriculture, Highly relevant, significant risk for investments opportunities to its development potential forestry, natural habitats. requiring stable ground conditions with minimal Geotech. risks and no residual settlements, Added space value for storage of valuable resources, research and Highly relevant, significant risk for investments underground storage development activities, waste repository, requiring stable ground conditions with natural gas storage, and CO2 sequestration, minimal geotechnical risks and no residual, utilization for pumping storage, big data substance, sinkhole or underground servers, recreation and exploration, cultural combustion or explosions heritage Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 85 GIS-based Land Use and Repurposing Application (LURA) The objective of land repurposing is to think and plan much criteria rating for the main criterion. A net differential algorithm beyond just achieving environmentally stable landscapes and automatically evaluates the actual values for each criterion compliance with environmental permits, to recondition post- against the index value describing the most appropriate post mining lands allowing a wide scope of diverse uses. Of course, the mining land utilization, and matches the actual values for the five environmental quality of repurposed lands should be maximized, criteria with the best fitting optimum land use scenario. with remediation and reclamation preferably underway while These scenarios define the land repurposing categories for a given mining operations are still ongoing (“mining for closure”). post-mining area. A land category basically means that for a Currently the World Bank’s LURA methodology is based on five defined area, an optimized utilization scenario has been proposed themes: environmental conditions and liabilities, morphology and based on various potential combinations of the criteria described hydrography, geotechnical risks, socio-economic factors and land in the table above and explained next: bio-physical and chemical value (both positive as added value and negative as remediation characteristics; liabilities and constraints imposed naturally or cost). Each criterion is further subdivided to capture the full due to the mining history; the geographic situation with respect extent of the land conditions in a simple and objective way. Each to existing infrastructure, settlements and economic clusters; subcategory uses a five-scale rating procedure, ranging from and the potential added value development options and the the value “1” indicating the least favorable condition to “5” which opportunity cost of sub-optimal development. The methodology is considered as the most favorable condition for the particular takes cost sensitivity into account, striving to avoid e.g. costly sub-criterion. An average score is calculated based on the sub- remediation or upgrading measures for a particular purpose, Figure 16: Graphic characterization of four exemplary land repurposing scenarios, based on five defining criteria. These “radar charts” allow a quick assessment, categorization and testing of lands’ suitability for a specific envisaged utilization For sts/ Loc tion 5.00 A ricultur Loc tion 5.00 N tur l H bit ts 4.00 4.00 3.00 3.00 2.00 2.00 Cost 1.00 G ot chni l Cost 1.00 G ot chni l s nsitivit 0.00 st bilit s nsitivit 0.00 st bilit Environm nt l Topo-/ Environm nt l Topo-/ risks h dro r ph risks h dro r ph En r / Loc tion 5.00 Busin ss/ Loc tion 5.00 Industr 4.00 R cr tion 4.00 3.00 3.00 2.00 2.00 Cost 1.00 G ot chni l Cost 1.00 G ot chni l s nsitivit 0.00 st bilit s nsitivit 0.00 st bilit Environm nt l Topo-/ Environm nt l Topo-/ risks h dro r ph risks h dro r ph 86 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines if other areas are equally or better suitable and require lower Repurposing criterion 2: investments to be fit for purpose. Figure 14 explains how various The Geotechnical Stability criterion. This criterion has three combinations of land properties and characteristics were analyzed subcriteria, which evaluate the possible expected residual and matched with optimized utilization scenarios, that minimize settlements of dump fill, the slope stability of cut or backfilled the exposure to risks and liabilities and maximize the potential slopes and sloping areas, and impact of ground water rise due added value of redevelopment. Here are four utilization scenarios, to mine closure. The subcriteria have been assigned for open graphically depicting the five underlying criteria. pit mines, but additional subcriteria will be added to consider The mine (or extended) area that will be classified for repurposing underground coal mines which can produce, subsidence, sinkholes, is selected from a satellite image. To enable the application of extended collapse. For example, the slope stability subcriterion LURA the mine is subdivided in segments / pixels with a user evaluates the presence of slopes either for open pit cuts or spoil defined length and width to produce a land matrix. The length fills, and it takes into account with predefined limits the slope and width selected is based on the level of detail needed for a height, inclination, factor of safety from stability analysis (if particular assessment and the granularity and quality of available available). Areas with high slopes and steep inclination or prone data. If a very detailed assessment is needed and a large amount to landslides are assigned a lower rate between 1 and 2 in relation of data are available for the different criteria used, then a high to areas that are flat, with no significant fill slopes. The rating resolution matrix can be defined and populated with individual considers the land “as is” and not as it can be transformed after ratings. Then areas that need to be excluded from the rating additional land reclamation and landform contouring takes place. scheme such as government restricted use lands are selected from the matrix and are excluded from the rating. These pixels Repurposing criterion 3: are assigned the actual restriction description. The GIS-LURA The Topography and Hydrography criterion are used to evaluate application works with the following rating criteria. a pixel based on three sub-criteria, describing the surface gradient and relief with the use of current topographic maps of the land. Repurposing criterion 1: Low scores are assigned to steeply sloping areas that are easily The Location criterion is then used to evaluate the distance of the erodible and higher rating values are assigned to areas of mild pixel that is rated to nearby infrastructure such as road networks, inclination or flat areas. Again specific limits are provided for intersections, water and gas utilities, power cable networks. A five rating selection. For example, a low rating is provided for spoil fills scale rating is used to assess the proximity to such infrastructure. with slopes steeper than 34o with easily erodible slope materials The Distance to human settlements criterion is used to evaluate (with now vegetation cover). On the opposite end, flat areas or the location in relation to human inhabited areas. The proximity slopes with inclination no more than 5o are given a high rating. to inhabited areas can have a positive or negative impact on Surface drainage is the second subcriterion which evaluates areas a certain repurposing scenario. For example, an area that will that can be permanently waterlogged or for extended periods of be considered for industrial use or waste treatment facilities, time or at the high end waterlogging is extremely unlikely. Finally, would have a negative impact on nearby settlements. This is hydrological risks of flooding are rated for the area. appropriately weighted in the algorithmic rating used to assess such a proximity for different repurposing types. The 5-scale Repurposing criterion 4: rating for location and distance to human settlements is based The Environmental Risk criterion is used to evaluate the pixels on clear distance indicators which are incorporated in LURA and based on three sub-criteria which are used to assess the presence are site or country specific. Mining areas that are located in very of contamination in dumped fill materials, the environmental remote but vast areas, have higher distance limits, while mining burden placed by ongoing coal production and related dust, areas in densely populated regions have much smaller distance emissions, noise and vibration and its proximity to an operating limits for rating selection. TPP, which may also be repurposed in the future. This criterion is used to take into account the presence of dust, toxic air pollution, Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 87 water (surface and underground) polluted with toxic elements, low Western Sumatra, Indonesia, is seen in Figure 17, where a map pH values which denote formation of AMD and soil contamination. of colored pixels covers former mining areas. The colored pixels Methane emissions and impacts of climate change must be indicate optimal future use of repurposed areas, optimizing the considered if relevant at the site. Additionally, rating is given to “match” between prevailing conditions on post-mining lands and ongoing mining and power plant operations in the area which the requirements of the various repurposing typologies. The LURA adversely could affect a nearby repurposing land. tool is highly useful and efficient as an assessment and planning tool, as well as in the context of stakeholder consultation for lands Repurposing criterion 5: repurposing in the context of mine closure. The Development Opportunities criterion is based on the general Figure 17: Visual output from a land utilization repurposing assessment mine land use rating map carried out in West Sumatra, Indonesia assessment of the area in relation to all other criteria, including the potential for use of remaining resources, such as water and methane if useable for industrial or commercial purposes. If a cluster had moderate to high rating for the other criteria it was considered as an area with higher potential added value, which would encourage future high value development with expected high returns (hence, this is a reinforcing criterion). Conversely, if a cluster has low rankings in other criteria, then lower development opportunities with lower potential added value generation will prevail. Once the rating of each segment is completed, the algorithm automatically produces the optimal post mining land use and presents it in a map with a color-coding per segment for each land utilization option. Additionally, the score of all possible land uses is calculated and shown, to provide additional information on other possible utilization scenarios, which may – for a variety of reasons – be considered, even if this would mean accepting higher costs for land reclamation, conditioning and development. A final map of the mine area with colored clusters with post mine land use is created with additional information for the user such as the actual land area rated15,1the number of clusters (segments), the length and width of the cluster utilized. Furthermore, for each post mining land use the actual land typology and area are presented in the resulting map. The system is robust so that different users with the same data are likely to produce very similar outcomes in terms of utilization scenarios. Also, the conditions that define a post land use type can be easily modified to better reflect local conditions if needed (e.g. for deployment and application of LURA in other regions / countries, or for Forestry/biomass Business/comm Agriculture other mining types, such as underground hard coal mining). As Residual pnd Renewable energy an example of the outcome of LURA for a former coal mine in 15 There may be areas with existing constraints that preclude the application of the LRS / LURA; e.g. areas that will be submerged after mine closure, or for which firm redevelopment scenarios have already been defined. 88 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines From land repurposing methodology and classification to spatial planning Spatial planning systems (SPS) refer to methods and approaches used by the public and private sector to influence the distribution of people and activities in spaces of various scales. SPS involve the coordination of practices and policies affecting spatial organization and often synthesize data from discrete professional disciplines such as land use, urban, regional, transport, energy, water and environmental planning. Regional/spatial planning gives geographical expression to the economic, social, cultural and ecological policies of society. It is a scientific discipline, an administrative technique and a policy directed towards a balanced regional development and the physical organization of space according to an overall strategy. The basis of this planning element is the land use zoning map produced under the land classification activity with LURA. The output of the land classification will be a land utilization zoning map, which delineates areas classified according to their optimized types. This allows a first, approximative assignment of spatial elements and dedicated zones that incorporate both the constraints imposed, and opportunities presented by the physical and chemical characteristics of former mining lands. The key spatial elements to be considered for linking the surrounding (external) lands to the former mine lands are the following: (i) infrastructure and transport (roads, railways, canals, transmission lines, pipelines, conveyor belts); (ii) agricultural areas; (iii) natural habitats and forests; (iv) industrial and commercial zones, business parks; and(v) generally equivalent land use patterns. Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines 89 From “mining for closure” to “mining for repurposing” As the concept of repurposing mine lands and assets for future This may affect many of the reclamation and remediation productive uses becomes more widespread, the paradigm of how activities which are routinely carried out in the mining operation: to proceed during mine operations in order to optimally prepare for external overburden dumps might be subdivided into areas repurposing is also beginning to shift. Hitherto the best practice that will be conventionally greened and vegetated to provide approach of mining was a “mining fore closure” concept: during its biodiversity value, others in contrast may be preserved with stable lifetime at any given moment the mining operation would have only surfaces, but a minimum of vegetation, to accommodate future a minimum of active mining footprint, and closure and remediation renewable energy (PV), industrial or business installations. With activities were conducted in parallel to the extractives operations16. 2 a view to the final mine layout areas may already be identified during a mine’s operational life, which are well connected to When considering a proactive approach to repurposing of mine transport and energy networks and could be singled out as prime lands, mine operators have to think even further into the future: investment areas for industry or commercial activities after The objective of closure is to leave mine lands in a geotechnically being decommissioned. Areas which are characterized by lesser stable condition, with erosion resistant, well vegetated surfaces, connectivity, which may have some environmental liabilities, but and without environmental liabilities in form of effluences, gas are morphologically favorable and geotechnically stable, may be emissions, dust or contaminated soils. Going beyond this, the goal designated for large scale renewable energy investments. This will of “mining for repurposing” is to prepare the lands for optimum require in many cases that the classical remediation approach future productive uses (see figure 18). Figure 18: Remediation and repurposing hierarchy, demonstrating the progression from basic mine remediation towards repurposing to achieve better socio-economic outcomes. Productiv nd Sust in bl R purposin Addition l m sur s Up r din for R d v lopm nt b ond r quir m nts to r purpos nd thus up r d l nds to llow productiv r -us nd Enh nc d B n fici l Us ncour inv stm nts Public H lth nd S f t Usu ll cont in d in th pprov d min closur pl n s compulsor m sur s Ch mic l St bilit to obt in th closur p rmit Ph sic l St bilit 16 See for example the World Bank’s Mine Closure Toolbox for Governments for an explanation of the mining for closure approach: https://documents1.worldbank.org/curated/en/278831617774355047/pdf/Mine- Closure-A-Toolbox-for-Governments.pdf 90 Mine Closure Standards and Improved Post-Closure Risk Management for Surface and Underground Coal Mines is not implemented, but that areas are assessed regarding their repurposing potential with LURA and then brought into conditions that are accommodating for their future repurposed uses. Moreover, many coal mines operate according to a concept where the majority of lands remains under some operational use up to the end of life of the mine. This concept is counterproductive to “mining for repurposing”, as it blocks the repurposing of valuable land that could already be productively reused for either renewable energy production or sustainable economic investments while the mine is still operational. A smooth and gradual transition is thus hampered or even blocked by an operational concept which is designed to retain a maximum of lands under operational use. This may be motivated or encouraged by some legislations which require the mine operator to decommission and relinquish lands that are no longer operational. This approach will require not only a rethinking of mine planning and operations, but also of environmental permitting, as well as consideration of the local / regional development framework, and socioeconomic and spatial requirements regarding the final state of the mine. While all principles regarding public health and safety, environmental control, and geotechnical stability are still valid, more strategic and further downstream thinking has to be dedicated to providing added value to the post mining space, and thus achieve better environmental and socio-economic outcomes, leave as many development opportunities to mining communities, and allow a strong focus on renewable energy emplacement to compensate for the loss of coal fired power production.