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April 25, 1998



This database records all failures and significant adverse events in all components involved in the deposition and storage of mineral tailings, including post-extraction downstream-generated tailings, e.g., at smelters or refineries. The original impetus for creation of the ICOLD/UNEP 2001 compilation, Bulletin 121, was an increasing frequency of high-consequence tailings failure events post-1990. That the trend of high-severity tailings failures has continued upward is indisputable. Without major changes to law and regulation, and to industry practices, and without new technology that substantially reduces risk  and increases loss control, our current prediction is for 19 Very Serious Failures between 2018 and 2027.

We ask all users to read all guidance and commentary provided here before planning and publishing a work using this database.


Current as of March 1, 2019

History & Purpose Of Failures Database

The purpose of the database is  to provide a meaningful resource of factual authoritative data for analysis of trends, causes, and consequences, with a view to the changes that will result in effective loss prevention related to tailings management. The aim is to give voice to the narratives of every significant failure, not replace or overshadow the existing narratives.

Of course, it is important to note at the outset that, while tailings failures are a leading cause of the most consequential mine failures to communities of origin, to the environment, and to the investors whose trust  finances production of the minerals the world needs, large and significant losses occur even at facilities with no on-site tailings or with adequate and even  state-of-the art tailings management.  This database is important because it is a surrogate for all loss.  It is the only known publicly available compilation of loss, the only window we have into the legal frameworks and corporate practices that create high-risk and high-loss conditions.

The core of the database is the ICOLD/UNEP  compilation by an international expert panel convened between 1995 and 2001, and published in 2006.  WISE continued  the global compilation by integrating all the Bulletin 121 failures and posting all new failures reported to them. The WISE chronology dropped most of the Bulletin 121 data descriptors and now reports only “significant” events since 1960.

World Mine Tailings Failures (WMTF)  expanded the original Bulletin 121 compilation with independently researched, authoritatively  compiled  failures from 1915 onward, and integrated all WISE updates and additions through 2015, reformatting to the full Bulletin 121 layout. Missing descriptors in the WISE and ICOLD/UNEP compilations were filled in  element by element from many sources, principally legal documents and technical reports.

The statistical value of ICOLD/UNEP dam-descriptive and cause-of-failure data elements has not been fully established or explored, but WMTF continues all of them.

The data are meaningful only at aggregations of 10 years.  No other aggregation level holds up for any kind of meaningful analysis or presentation. Presentation of the number of “failures” for a given year is meaningless. No comparisons by country or company or resource sector are meaningful without production data ( failures per ton of processed ore or failures per ton of finished product) for a period of 10 years or more.

Three main expansions give voice to the failure narratives in terms of both cause and consequence: severity coding, magnitude index development, and the inclusion of economic history.


The ICOLD/UNEP expert panel intended to distinguish failure events by severity, but the established coding did not lend itself to  statistical analysis. They distinguished “failures” from lower consequence “accidents,” but this two-layer severity class had no structure that supported meaningful analysis, especially trend and correlation analysis. Within the designation “failures,” ICOLD/UNEP intended, and we have continued, to record all  failures of any component of a tailings management system.

The Bulletin 121 international panel established  three measures of severity (release, runout, and deaths), which also frustrated statistical analysis.

A four-level severity code system has therefore been created for WMTF from 1 (“very serious”) to 4 (“potential failure,”  meaning an observed condition that, if left unattended, could evolve to failure over time).  The four-tier system relies primarily, but not exclusively, on the three severity variables created by ICOLD/UNEP (release, runout, and deaths), but it also places great reliance on authoritative narrative. At present, only two of the classes, “very serious” and “serious,” perform well in statistical analysis and it seems clear in correlation and other analyses that the trends for both severity levels are shaped by a common set of root causes in mine-specific and global economics.

Figure 1 above shows present linear trend lines and Figure 2 below shows the actual values for release, runout, and deaths by decade through 12/31/2017.


The severity coding alone allows examination of only the frequency of high-severity incidents over time, but not the degree of severity. Although, as shown in Figure 2, the decadal summaries of release, runout, and deaths give an impression of increasing severity, it was not possible to do any meaningful statistical analysis with the data in  this form.

An index is an econometric tool, especially used in trend analysis, which allows disparate data elements to be unified via reference to a base year or period and then combined by aggregation, with or without weighting, as evaluated by the index developer.  This approach was used to build the magnitude index setting 1991 to 2000, the “red flag” decade of Bulletin 121, as the reference period.  For each incident, each element (release, runout, deaths) was expressed as a ratio to the reference average, after which all three index scores were combined to form a single numerical index.  It was determined that raw scores gave each element an equal weight (i.e., no weights were needed).  Complete technical documentation is available to anyone interested from compiler@worldminetailingsfailures.org.

The index proved to be a very valuable statistical tool with strong correlations to price and grade as shown in Figure 4 above.  The relationships over time clearly show that magnitude increased as grades fell and prices rose, dispelling a popularly cited paper, asserting without econometric analysis, that failures occur in lagged response to falling prices.

The magnitude index also, as expected, correlated significantly with storage capacity and dam height at failure. (Larger facilities are, of course, expected to cause more damage when they fail, which is not the same as larger facilities having  an inherently greater propensity to failure. Data are not presently available to evaluate the latter.)

We invite, and hope ourselves to do, much further exploration of the magnitude index.  At this point, we are satisfied that it is a vetted and valid data element with an important place in the database and in future research into cause and consequence.

We assign severity code based on narratives and on authoritative documentation of release, runout, and deaths. However, we not do not code magnitude if there is not sufficient  complete information on release, runout, and deaths, as it relies exclusively on the given numerical values of these elements.


The increase in failure rates per million tonnes of ore produced  from 0.00044 (1998-2007) to 0.00045 (2008-2017) appears to be significant and to forecast a continuing upward trend.


The ICOLD/UNEP expert panel acknowledged the powerful and important role that mine-specific and global economics played in the failure trend to which they were pointing.  Most papers on cause, while tending to focus  on  engineering  causes,  recognize the adverse effect of falling grades, the resulting increase in mining costs per ton, and the attending squeeze on margins.

The predecessor  of this database was a data set developed for three research  papers exploring  these effects of mine-specific and global economics in depth on the frequency and severity of catastrophic failures.

Bowker Chambers (2015) Bowker, L.N. and Chambers, D.M. The Risk, Public Liability, and Economics of Tailings Storage Facility Failures. Earthworks Action 2015.

This mapped the world trend of  frequency of “very serious” failures against the world trend in falling grades, establishing through canonical correlation analysis the likely existence of a strong linear relationship in data known as of 12/31/2009.

Bowker Chambers (2016) Bowker, L.N. and Chambers, D.M. Root Causes of Tailings Management Failures: The Severity of Consequence of Failures Attributed to Overtopping 1915–2015.

This used the same data set as Bowker and Chambers (2015) and examined the distribution of “very serious” failures across all thee ICOLD/UNEP expert panel-established cause-of-failure elements, finding that, except for codes associated with liquefaction (earthquake and slope instability), the distribution of high-severity failures was essentially the same,  suggesting a common root case, previously posited as global and mine-specific economics.

Bowker Chambers (2017) Bowker, L.N. and Chambers, D.M. In The Dark Shadow of The Supercycle: Tailings Failure Risk & Public Liability Reach All Time Highs, Environments 20174(4), 75; doi:10.3390/environments4040075

Bowker and Chambers (2017) used a greatly expanded data set of pre-2010 failures and included all known failures through 12/31/2015 and the addition of  economic history of the mines at which failures occurred.  These data were contributed by Dr. Bill Williams, a noted long-experienced economic geologist, from his own files. Dark Shadows ( Bowker and Chambers, 2017) was therefore able to reconfirm key findings of Bowker and Chambers (2015, 2016) with a more complete data set for a longer period, as well as to examine the role of mine-specific economics.  Dark Shadows showed that, contrary to previously asserted and widely-cited work, high-consequence failures are more frequent in periods of rapid sustained price rise due to the greater participation of marginal mines as producers.

The strong linear relationship between grade and frequency of high-severity failures was also revealed in linear regression (Fig. 5)

While still very sparse,  the  data presently available do support meaningful, although  limited, inquiry and analysis.  One of our development goals is to expand data to include at least more details on already known  “serious” and “very serious” failures.

To explore failures in the context of global mineral economics trends, a parallel mineral economics database was created  and is also available free in Excel file format.  The parallel database provides annual data on copper grade, world mine production, price, and estimated world ore production from 1915.  Extensive technical documentation is embedded in the download file at this site.

Download Mineral Economics Data Now


The framework for management and continued development of the database is given in our bylaws. World Mine Tailings Failures is presently incorporated as a nonprofit corporation in the state of Maine and we are in the process of filing for incorporation under U.S. laws as a 501(c)(3).

Reflecting the scope of our chartered mandate to provide a multifaceted analysis of all authoritative work about or with a direct bearing on mine tailings failures, the work of compilation is conducted by five principal volunteer compilers each with primary responsibility for compilation and analysis on one of five facets of cause and consequence.  The core team of volunteer stewards is  supported by a broader team of tailings experts who have volunteered to serve as peer reviewers and contributors. Our Board also reflects the balance of expertise of compilers and is responsible for general oversight of our work as well as for approval of all policy and database development plans and budget priorities.

The Compilers

Chief Compiler & Executive Director Lindsay Newland Bowker (Bowker Associates Science & Research in the Public Interest, USA) has four decades in empirically-based law and policy, heavy construction risk management, and risk finance that framed and informed her noted work in the economic causes of Tailings Storage Facility (TSF) failures. It is primarily Lindsay’s work that has evolved the database to its present form, assembled the team of stewards for its future development, and framed the mandates of the nonprofit corporation  established to care for and further develop the database.

Chief Compiler, Engineering, Roberto Lorenzo Rodriguez (Instituto Geológico y Minero de España, Spain)  is a recognized expert in tailings risk management, most notably in areas of causes (ultimately related to consequences) that have not received needed attention in law, policy, and practice. He has authored 146 papers with 524 citations. The aim of his present research is to identify opportunities and strategies for loss prevention and risk minimization.

Chief Compiler, Environmental Consequences Seeking volunteer

Chief Compiler, Community of Origin Consequences, Cristiana Losekann (Department of Social Sciences, Universidade Federal do Espírito Santo, Brazil) does her main work in the interface between social movement and political change, and in the disempowerment that results from loss of community. Cristiana’s work  on the community and social impacts of the Fundão failure bring forward aspects of community and citizen loss beyond the customary discussion and response of compensation to rarely acknowledged issues of adequate disaster response and relief, and loss of voice through the dispersion of displacement.

Chief Compiler, Economic Causes & Consequences of Failures, Bill Williams (Mine Analyst and Developer, USAis an economic geologist with over 35 years of experience in the exploration, development, and exploitation of oil and gas and mineral deposits, mostly in the Americas and Europe. He currently serves as a consultant and advisor to the mining industry, most recently with Zinc One Resources, Inc., and Forrester Metals, Inc.  He is a former CEO, President, and Director of Orvana Minerals Corp., prior to which he was a Vice-President for Phelps Dodge Exploration, overseeing activity in the Americas. He holds a Ph.D. in Economic Geology from the University of Arizona and is a licensed Professional Geologist. Bill has been a major contributor to the present form of the database, adding the section on mine-specific economic context from his own extensive personal files.

Acting Chief Compiler, Governance, Lindsay Newland Bowker is still seeking a permanent volunteer for this important post at WMTF that will document how existing law and policy affected the formation of a failure event and the response to it.

We welcome and encourage all contributions with proper citations and documentation, especially from individuals  with technical expertise who speak Chinese, Portuguese, Spanish, Swedish, Norwegian or other foreign languages, and who are on the ground in countries where mine production is occurring.  We do foreign language searches for tailings failures and mine failures,  but without multilingual input from associates,  we are not capturing all relevant information.  We provide primary sources for every entry.

Our aim is to provide more complete data on each failure with a bearing on cause and consequence, not to provide a 100% complete list of all failures that have ever occurred.

Many have helped and been actively involved in  framing and launching WMTF and will be part of a larger distinguished panel of experts who have agreed to serve as both contributors and peer reviewers. We are in the process of formalizing this larger pool of collaborative expertise as an Advisory Committee.

We have invited a very distinguished panel of experts in different stakeholder sectors to serve on our Board of Directors and the compilers will actively seek and welcome their guidance on future development of the WMTF.  The Board is formalized and very active in our first year ..

We would welcome additional adjuncts and associates in each category and always welcome informed input.

Next Steps

Federal Nonprofit Status

Free public access databases are usually compiled and maintained by governmental organizations who determine content and access.  What was a data set, and is now a database, used by researchers, NGOs, governmental agencies, mining consultants, investment portfolio managers and advisers, and even grassroots organizations, has no natural governmental umbrella among any existing  global organizations.  It is too important to rely on what time can be given to it outside of other mainstream work, as has been the case to date. Incorporation as a nonprofit  allows a suitable structure  for expanding and formalizing a broader stewardship for the database, as well as providing a structure through which others can  help finance its basic needs and future development.

We are already a nonprofit in Maine and have obtained our federal status as a 501(c)(3).


The data are only meaningful to the extent that they accurately summarize or present key elements in narrative, and capture or present those data elements most closely associated with cause and consequence, and with mitigation of harm.  The story of every failure is the complete narrative, which changes over time, bringing new insights, new facts, and new data. A principal goal is to rebuild narratives for all consequential failures,  expanding from only engineering analysis to the role (positive or negative) of law and policy, and mine-specific and global economics, as well as to a fuller description of consequences, both human and community of origin, and environmental.

Each of the original Bulletin 121 failures had a small narrative. To date, except for brief narratives presented in the appendix of Bowker and Chambers (2015), the narrative in the failures database has been represented only in the bibliography of resources used to develop the data record for every failure.

Our aim here at WMTF is to create a complete narrative, failure by failure.

We will publish the narratives one by one, as they become available, in a to-be-added section on narratives.

Additional Data Elements

The volunteer compilers will propose to the Board their recommendations for data element expansions and develop a budget estimate and project description for each proposed addition. We anticipate only very limited funding support.

The data elements created by the UNEP/ICOLD expert panel have not been fully explored as to their value in analyzing causes and trends.  It is clear that some elements, especially “runout” are not sufficiently clear as indicators of severity.

It is clear, though, that the data descriptors are somewhat out of date, especially on the TSF itself and the characteristics of the tailings and their degree of consolidation and saturation at failure.  It would be helpful to have a clearer, better coded, picture on the condition of tailings at deposition and the means of deposition.

Our aim will be to prioritize the addition of new data elements according to deliberative and analytical value, seeking guidance and help from all stakeholder sectors and from our eminent Board of Directors.


There are no other failure-specific, publicly available, global databases. However, there are many other global databases that can link to characteristics of national or provincial governance, such as indices on public benefits of the minerals sector by nation, and indices on the responsible mining policies of individual mining companies. Re-coding and additional coding of the deposit, the parent company, and country can facilitate these linkages by other researchers, even if the external databases do not contain elements that themselves belong in the failures database. One possible near-term objective, for example, might be  to add latitude and longitude and the USGS unique deposit ID.


We thank Dr. David M. Chambers for sharing part of a generous unsolicited grant from a small foundation, given specifically in support of the work that Dr. Chambers and Lindsay Newland Bowker have done together on the failures database.  Dr. Chamber’s donation from this grant created this website and funded its basic web hosting and incorporation costs for the first three years.

We will shortly add a description of  several small projects where funding would help with important expansions.  The database needs and welcomes this financial support.

The chief compiler and associate compilers receive no salaries or other form of remuneration.  Through funding, though, we hope to be able to retain research assistants to assist in the main research and coding work  of each development goal. Also we need annual funding for the statistical analysis packages we use for analysis  and presentation of the database.  Our plan is to create a page on  WMTF compiler-recommended, Board-approved development goals with a description and budget for each, so that donors can match their gifts of support with their own main interests, work and commitments.