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Online Toolkit and Training for Strengthening Mine Tailings Safety


TEIA_Online Toolkit and Training

Industrial accidents at tailings management facilities (TMFs) have led to environmental catastrophes with devastating effects on humans and the environment within and across countries. Major industrial accidents in the UNECE region and beyond have motivated countries to develop and implement tools under the UNECE Convention on the Transboundary Effects of Industrial Accidents to strengthen mine tailings safety and to prevent such accidents in the future.

This online toolkit assists countries in strengthening TMF safety and management practices. It serves as a hub for anyone wishing to learn about the importance of, and the work and tools on mine tailings safety under the Convention. At the same time, it provides online training for countries, without physically meeting, to improve their knowledge about the impacts and challenges of mine tailings and to apply existing guidelines, including UNECE’s tools, to improve tailings safety. Through the drop-down menus below, this online toolkit and training includes four sections: background information on mine tailings safety; a 3-step practical training for countries to enhance safe management practices; a summary of UNECE’s mine tailings work and partners; and further reading on key reports and references.

Improving the management and safety of mine tailings increases countries’ understanding and governance of disaster risks, including through inter-institutional and cross-sectoral cooperation. As such, the work contributes to accomplishing the objectives of Agenda 2030, with its Sustainable Development Goals and the Sendai Framework for Disaster Risk Reduction. It also strengthens mineral resource governance, sustainable infrastructure and disaster resilience, both within and across countries.


Background information - A call for an urgent action


Mining is an important industry for several UNECE countries, especially those in the Caucasus, Central Asia and Eastern and South Eastern Europe. Many countries rely on the extraction and processing of mineral resources (e.g. copper, gold, mercury and uranium) and other commodities for economic and social development. However, mining also generates large amounts of hazardous waste which is generally stored in tailings management facilities (TMFs). TMFs can pose high risks to societies and the environment, especially if poorly constructed or maintained, leading to risks of TMF failures (e.g. tailings dam breaches). The safe management of mine tailings facilities is critical for preventing TMF failures and their consequences.

This section provides important background information to prepare you for UNECE’s practical training in the next section of this webpage.


Key Definitions

Tailings The fine-grained waste material remaining after extracting recoverable metals and minerals. This material is rejected at the “tail end” of an extraction process and is the size of particles, normally ranging from 10μm to 1.0mm
Tailings management facility (TMF) The whole set of structures required for the handling of tailings. For example, this could include tailings storage facilities, tailings dams, tailings impoundments, clarification ponds, delivery pipelines, etc.
Tailings storage facility The facility used to contain tailings, which often includes tailings dams and impoundments, clarification ponds, decant structures and spillways. Tailings storage facilities also encompass open pits, dry stacking, lakes or underground storages.
Tailings dam Structures, such as embankments, dam walls or other impounding constructions, designed to enable tailings to settle and to retain tailings and process water. They are constructed in a controlled manner.
Tailings impoundment The storage space/volume created by tailings dams where tailings are deposited and stored. Tailings dams and/or natural boundaries give boundaries to impoundments.

Tailings accidents are disastrous and costly

Past industrial accidents at TMFs have led to major environmental catastrophes with devastating effects on humans and the environment. For example, tailings dam failures have resulted in uncontrolled releases of hazardous substances and subsequent environmental damage and water pollution, within and across countries. Cleaning up such accidents also has severe cost implications for countries and businesses. Major accidents in the UNECE region and beyond illustrate the need for strengthening mine tailings safety:

  • In 2000, a TMF failure occurred when the dam of a tailings pond broke in Baia Mare, Romania. About 100,000 cubic meters of liquid and suspended cyanide-rich tailings waste spilled and contaminated the Sasar, Lapus, Somes, Tisza and Danube Rivers before reaching the Black Sea. The effects in Romania, Hungary and other downstream countries included contaminated supplies of drinking water and diminished fish stocks. The costs of clean-ups of accidents at similar scales have estimated at $170 million (US).
  • In 2016, mine tailings, containing cyanide and other hazardous substances, spilled into the Ulba and Filippovka Rivers following the failure of a water collector that was part of a TMF in the town of Ridder, Kazakhstan. The waste caused accidental water pollution that ​prompted communities in distant towns along waterways in Kazakhstan and the Russian Federation, including in Omsk over 1,000 kilometers away, ​to take precaution. This included stocking up on bottled water supplies.
  • In 2019, a TMF storage failure occurred in Brumadinho, Brazil. A tailings dam collapsed and spilled approximately 12 million cubic meters of mining waste, killing at least 259 people and causing 5 miles of destruction in the local town and countryside. This accident followed the 2015 tailings dam collapse in Mariana, Brazil, which is considered to be the largest ever recorded with pollutants spreading along 668 kilometers (415 miles) of watercourses.

Consequences are getting more severe

TEIA_Tailings accidents

Further to the above accidents, monitoring groups have reported and experts have assessed 63 major tailings dam failures around the globe in the past 50 years, including with increased high-consequence failures since 1990. Regrettably, many of these industrial accidents, which could have been avoided and of which important lessons could be learned, did not receive widespread news coverage.

Studies also show that the consequences of tailings failures have become more severe in recent decades. Failures result in higher numbers of fatalities, increased amounts of released waste and more widespread effects. Even if the loss of life could be avoided, failures often have long-lasting consequences on the environment, societies and economies. The remediation of these consequences is very difficult and costly.

Tailings failures can be prevented

A 2017 United Nations Environment Programme report analyzed the causes of tailings failures from 1915 to 2016. It found that the main reasons for failures were the lack of management continuity and inadequate resourcing (especially financial) for TMFs. This supports previous findings from a 2001 International Commission on Large Dams (ICOLD) report, which stated that poor management in combination with inadequate commitment to safety was the cause of most failures. The ICOLD report concluded that all 221 failures it examined were preventable. In view of the disastrous consequences of the tailings failures mentioned above, countries must become more committed to preventing such accidents.

The UNECE Convention on the Transboundary Effects of Industrial Accidents offers tools, guidelines and methodologies to strengthen mine tailings safety, which are available both to Parties and non-Parties wishing to strengthen mine tailings safety. The Convention, among other instruments, requires its Parties to identify their hazardous activities and take measures to prevent accidents from happening. A “hazardous activity” is any activity in which one or more hazardous substances are present or may be present in quantities at or in excess of the threshold quantities listed in Annex I (ENG, FRE, RUS), and which is capable of causing transboundary effects. Many TMFs therefore fall under the scope of the Convention.

Further to UNECE’s tools, guidelines and methodologies, other tools and guidance exist at the regional and global levels. Most recently, the United Nations Environment Programme (UNEP), International Council on Metals and Mining (ICMM) and Principles for Responsible Investment (PRI) developed the Global Industry Standard on Tailings Management. These standards, albeit voluntarily, provide a basis for industry. Another example is the Joint Research Centre of the European Commission’s Best Available Techniques (BAT) Reference Document for the Management of Waste from Extractive Industries, which provides data and information on the management of waste from extractive industries and recommendations for future work. Additional tools available are listed below in the section on UNECE’s partners.

Countries need to act now


The global demand for minerals and metals is expected to significantly increase in the coming years and decades. As one example, a recent World Bank report assessed the amounts of minerals that would be needed to produce the clean energy technology required for achieving international climate change goals (see graph); to meet the Paris Agreement’s maximum goal of holding global temperature rise to well below 2°C above pre-industrial levels, the demand for graphite, lithium and cobalt production, among other minerals and steel, could increase by more than 450% by 2050. Increased demands and production equate to more tailings and thus more facilities in which hazardous waste is stored. If not safely designed, managed and stored, tailings could be accidentally released into the environment with their toxic and hazardous substances. The safe management of mine tailings is therefore increasingly relevant for countries in the UNECE region and beyond.

In addition, climate change is increasing the frequency and intensity of extreme and unusual weather events. This impacts the probability of natural-hazard triggered technological accidents (“Natech” events). For example, landslides, floods and earthquakes can lead to TMF failures (e.g. a tailings pond breach) with potentially large-scale and transboundary effects. Also, droughts can cause tailings to dry out and wind can easily spread hazardous dust towards settlements in the vicinity. The combined increases in demand for mining and impacts of climate change require strong actions to be taken to ensure mine tailings safety.

Sustainable Development Goal (SDG) Target 12.4 aims, by 2020, to achieve the environmentally sound management of chemicals and all wastes throughout their life cycle, in accordance with agreed international frameworks, and to significantly reduce their release to air, water and soil in order to minimize their adverse impacts on human health and the environment. This target has not yet been reached. 2019 Global Chemicals Outlook explains how strengthening chemicals and waste management programmes at all levels is critical to achieving this and other SDG targets. It outlines the need for countries to accelerate progress and ensure higher levels of governance to be able to achieve the SDGs until 2030. Through the United Nations Environment Assembly, countries have already taken steps towards sustainable management of metal and mineral resources by adopting resolutions 4/5 on sustainable infrastructure and 4/19 on mineral resource governance; however, more action is needed to achieve the SDGs.



Strengthening mine tailings safety comes with many challenges. One challenge is to address safety issues at every TMF. The Global Tailings Review reported that more than 12,000 tailings storage facilities exist around the globe. IndustriALL Global Union estimated that at least 3,500 tailings dams exist; however, given the presence of approximately 30,000 industrial mines, the number of tailings dams is likely to be much higher. Moreover, TMFs can be categorized as: active; inactive or idle; neglected; temporarily or permanently closed; abandoned; or orphaned. Each category requires a different approach to strengthening mine tailings safety. Developing and maintaining safe management practices to eliminate risks of failures for all TMFs thus necessitates a comprehensive approach.

Another challenge is to ensure the safe management of TMFs throughout their entire lifecycles. TMFs require design, construction, decommissioning and siting in accordance with national legislation, which should be harmonized with respective regional and international frameworks (e.g. the Industrial Accidents Convention). Environmental impact assessments of hazardous activities should be regularly conducted, and the results should be considered for enhancing safe management actions. However, regardless of whether these steps are followed, many challenges remain in maintaining TMFs overtime:

  • Large amounts of hazardous substances are sometimes stored in abandoned, improperly handled and orphaned TMFs. If such TMFs collapse, they could have devastating impacts on humans and the environment.
  • The degradation of tailings can cause contamination of groundwater and damage to surrounding ecosystems and human health.
  • Accidental water pollution, due to TMFs leaking or failing, can affect water quality and quantity, and lead to severe transboundary effects.
  • The release of heavy metals and hazardous substances, such as mercury, can lead to soil pollution due to the formation of acid mine drainage.

Countries should take practical steps to strengthen mine tailings safety and overcome these and other challenges. The next section of this webpage provides practical training to reduce risks and ensure safe and environmentally sound practices. It’s important that mine tailings safety be assessed both at a large-scale (e.g. nationally) and on a case-by-case basis (e.g. for tailor-made approaches to specific TMFs). Since many potential accidents can have transboundary effects, countries should also cooperate on the regional, sub-regional and global levels. The Industrial Accidents Convention is a regional instrument aimed at supporting its Parties and beneficiary countries of its Assistance and Cooperation Programme in their work of prevention, preparedness and response to industrial accidents with transboundary effects, including TMF failures.

Practical training (3 steps)

The UNECE secretariat prepared this three-step practical training for countries in the region and beyond to use for strengthening mine tailings safety. Building on the background information above, the three steps include: (1) watching an informative video on mine tailings safety (English and Russian); (2) reading UNECE’s Safety Guidelines and Good Practices for TMFs (English and Russian); and (3) applying the TMF Methodology to determine priorities and actions to be taken on the ground. In moving through these steps below, countries will become better prepared to bolster their mine tailings safety and subsequently enhance protections for humans and the environment.

Step 1: Watch UNECE’s video on mine tailings safety



Step 2: Read UNECE’s Safety Guidelines and Good Practices for TMFs

UNECE member States recognized the need to improve mine tailings safety in the early days of the Industrial Accidents Convention entering into force. Under two UNECE Conventions, namely the Industrial Accidents Convention and the Convention on the Protection and Use of Transboundary Watercourses and International Lakes, the Joint Expert Group on Water and Industrial Accidents developed safety guidelines and good practices. The guidelines include safety principles and recommendations for governments, competent authorities and TMF operators. In 2008 and 2009, the governing bodies of the Industrial Accidents and Water Conventions, respectively, endorsed the Safety Guidelines and Good Practices for Tailings Management Facilities. In 2014, UNECE published an updated version of the Safety Guidelines and Good Practices for Tailings Management Facilities.

At its eleventh meeting (Geneva and online, 7–9 December 2020), the Conference of the Parties to the Industrial Accidents Convention adopted decision 2020/1 on strengthening mine tailing safety in the UNECE region and beyond (ENG, FRE, RUS). The decision urges Parties and recommends to all UNECE countries that extract mineral resources to use these safety guidelines and good practices.

Step 2 of the practical training involves reading the safety guidelines and good practices. They provide important information and advice that aims to limit the number of accidents at TMFs and the severity of the effects of accidents for humans and the environment. In the next section of this online toolkit, links are provided to projects under the Industrial Accidents Convention that demonstrate how many countries in the UNECE region already apply the safety guidelines.

The publication is available in English and Russian.


Step 3: Apply the TMF methodology

In order to support countries in the practical implementation of the above UNECE Safety Guidelines and Good Practices for TMFs, the German Federal Environment Agency (UBA) created a methodology for improving TMF safety and the UBA and International Commission for the Protection of the Danube River (ICPDR) have since further developed it. The TMF methodology helps competent authorities and TMF operators strengthen TMF safety and management. The most recent version is comprised of three main components: (A) Tailings Hazards Index (THI) and Tailings Risk Index (TRI); (B) Checklist methodology; and (C) Measure Catalogue. These components are summarized below, with links to spreadsheets and documents for competent authorities and TMF operators to download and use within their national or regional contexts. Completing these components will assist countries in strengthening mine tailings safety.

The TMF methodology has been refined overtime, including through projects implemented under the Industrial Accidents Convention. In 2015, it was developed within the project Improving the safety of industrial TMFs based on the example of Ukrainian facilities. Up to 2018, it was modified for educational purposes through the project Raising Knowledge among Students and Teachers on Tailings Safety and its Legislative Review in Ukraine and results from trainings conducted at the National Mining University in Dnipro, Ukraine. In 2018, it was used and improved under the project Assistance in safety improvement of TMFs in Armenia and Georgia. In 2020, the TMF methodology was further developed in the UBA and ICPDR’s project Capacity development to improve safety conditions of TMFs in the Danube River Basin. Through these projects, a number of countries in the UNECE region have already applied the TMF methodology. More information on these and other related projects is available in the next section of this webpage.

Further implementation of the Industrial Accidents Convention, including by using the TMF methodology to apply the UNECE Safety Guidelines and Good Practices for TMFs, can help raise awareness and increase the readiness and capacity of UNECE countries to work towards the safe management of TMFs.

(A) Tailings Hazard Index (THI) and Tailings Risk Index (TRI)

The TMF methodology provides tools for competent authorities to assess the hazards and risks of large numbers of TMFs (e.g. across an entire country). First, the THI involves a simple method of indexing TMFs to sort and prioritize existing TMFs according to how hazardous they could be. Applying the THI can provide a means for competent authorities to:

  • Create and/or update their TMF inventory;
  • Rank their TMFs according to potential hazards and/or risks;
  • Identify their most hazardous TMFs and prioritize actions to strengthen safety measures at those TMFs;
  • Optimize the use of their financial and institutional resources to improve TMF safety; and 
  • Map TMFs within countries or regions.

Second, the TRI was recently developed within the TMF methodology to complement the THI. Competent authorities can apply the TRI to assess the risks that potential TMF accidents pose to human health and the environment; it provides a means to consider the socio-economic and environmental values adjacent to TMFs. More specifically, the TRI can be applied to:

  • Provide an overview of risks in large areas, such as transboundary watercourses;
  • Identify the most hazardous TMFs within a country or region;
  • Allow various environmental and population risks to be evaluated and prioritized;
  • Support land-use planning and environmental planning activities; and
  • Map environmental and population risks within countries or regions, including to support risk assessments and contingency planning.

The UBA and ICPDR designed a spreadsheet  that competent authorities can use as a template to apply the THI and TRI according to TMFs within their country or region. The first tab of the spreadsheet provides instructions and second tab provides data descriptions. In summary, countries need to collect and input data on their TMFs into the spreadsheet. For the THI, the following data on TMFs is needed: tailings capacity; toxicity of stored substances; management conditions of TMFs; natural conditions at TMFs; and dam safety parameters. For the TRI, the following data on the areas around TMFs is needed: the 10-kilometer radius around TMFs; settlements and waterbodies within risk zones that are downstream of TMFs; populations in settlements within risk zones downstream of TMFs; and the discharge rate and water surface area of nearby watercourses and lakes within risk zones. Please note that the spreadsheet provides links to websites where certain values should be determined (e.g. the Water Hazard Class classification of substance toxicity). Also, certain cells in the spreadsheet have drop-menus for inputting information; for such cells, the drop-menu arrows appear once you click on the empty cell.

After collecting the above data and inputting it into the spreadsheet, countries can evaluate their data using a calculation procedure. The calculations are built into the spreadsheet so the THI and TRI results are automatically generated once data is correctly inputted. The results provide competent authorities with an overview of their TMFs in order to assess hazards and exposures and risks around their TMFs. Due to the fact that TMF sites can considerably vary, it is recommended to use the two indexes for ranking, prioritizing and optimizing management efforts. More detailed information on the THI, including on the data requiredthe calculations and a calculation example, is available in the UBA and ICPDR’s recent technical report (Chapter 3 and Annex D) and further information on the TRI is available in the technical report (Chapter 4 and Annex E) .

UNECE encourages countries to use the THI and TRI to gain an overview of their TMFs in order to best apply the UNECE Safety Guidelines and Good Practices for TMFs and ultimately to improve mine tailings safety.

(B) Checklist methodology

The TMF methodology includes a Checklist methodology to further support competent authorities, inspectors and TMF operators in applying the UNECE Safety Guidelines and Good Practices for TMFs. Once the THI and TRI components are complete, the Checklist helps with examining technical safety requirements at the facility-level and technical measures within the guidelines and other international standards. Thus, the Checklist provides a means for harmonizing safety across the region.

In summary, the Checklist methodology is a simple assessment tool involving three components:

  • Questionnaires for different groups: competent authorities to conduct “basic checks”; inspectors and TMF operators to conduct “detailed checks”; and competent authorities to “check inactive TMFs”;
  • A Safety Evaluation Tool to understand how safe TMFs are; and
  • A Measure Catalogue to determine measures to be taken at TMFs (see component C below).

The Checklist methodology can be completed through a spreadsheet that the UBA and ICPDR also prepared. Instructions on using this spreadsheet are provided in the first tab. In summary, once the Questionnaires are completed (per group) under the questions tabs, the Safety Evaluation Tool scores the answers in categories that allow for checking the safety of TMFs throughout their lifecycles. Results are provided for each group and overall results for full investigations. Further information on the Checklist methodology is also available in the UBA and ICPDR’s technical report (Chapter 6) and in other outputs from the ICPDR’s project on Capacity development to improve safety conditions of tailings management facilities in the Danube River Basin. The Checklist methodology was developed under the framework of the Industrial Accidents Convention and leadership of the Germany Environment Agency and ICPDR.

(C) Measure Catalogue and taking actions

The Checklist methodology’s Safety Evaluation Tool (see component B above) provides evaluations and results on compliance of TMF safety requirements and regulations. For cases of partial or non-compliance, countries can look to the Measure Catalogue for a list of actions that can be taken to strengthen safety. The Measure Catalogue is included in the Checklist spreadsheet (last tab). The catalogue contains lists of “problems to be solved” and respective “measures prescribed” and their “priority”. For example, if results show that dam characteristics are insufficient to retain tailings materials, then ten different actions are prescribed (e.g. equip the TMF with emergency spillways and additional tanks and ponds for collecting emergency overflows).

The Measure Catalogue thus offers countries recommendations of specific measures that can be taken to strengthen mine tailings safety and to ensure compliance of TMF safety requirements and regulations. The measures provided in the catalogue apply the lifecycle approach, as they include short-, medium- and long-term measures. Nevertheless, appropriate actions should still be determined for each problem detected at TMFs on a case-by-case or site-by-site basis.

Congratulations, you have now successfully completed the online practical training through these three steps. The tools covered within these steps were provided to assist countries in strengthening mine tailings safety. Safety is however a continuous process and never stops.
UNECE's mine tailings work and partners



UNECE supports countries in strengthening mine tailings safety through various activities and projects. In addition to this online toolkit and training, information on the organization’s efforts can be found using the links in the lists below. The links provide an overview of UNECE’s past work on implementation activities and projects and cooperation with other international organizations and partners.

While preparing this online toolkit and training, UNECE held a seminar on mine tailings safety in the UNECE region and beyond on 1 December 2020. The objective was to provide support to UNECE member States, including Parties to the Convention and beneficiary countries of the Convention’s Assistance and Cooperation Programme, in their efforts to implement the Convention and take action to strengthen TMF safety. The seminar was preceded by a related background information document and resulted in important conclusions, which have been integrated in the information throughout this webpage.




Further reading - Key reports and references on mine tailings safety