A tailings dam is a structure that stores mining byproducts, including those that are toxic or radioactive. As a result, the structural failure of tailings dams and the ensuing release of toxic metals into the environment can produce many risks and hazards to an area. The standard of public reporting on tailings dam incidents is poor; a large number remain completely unreported, or lack basic facts when reported. There is no comprehensive database for historic failures. According to mining engineer David M Chambers of the Center for Science in Public Participation, 10,000 years is "a conservative estimate" of how long most tailings dams will need to maintain structural integrity.David M Chambers, "Long Term Risk of Releasing Potentially Acid Producing Waste Due to Tailings Dam Failure". Center for Science in Public Participation. Page 3 of 12. CSP2.org
Rate The lack of any comprehensive tailings dam database has prevented meaningful analysis, either gross comparisons (such as country to country comparisons, or tailings dam failures versus hydro dam failure rates) or technical failure analysis to help prevent future incidents. The records are very incomplete on crucial data elements: design height of dam, design footprint, construction type (upstream, downstream, center line), age, design life, construction status, ownership status, capacity, release volume, runout, etc.
An interdisciplinary research report from 2015 recompiled the official global record on tailings dam failures and major incidents and offered a framework for examining the severity and consequence of major incidents. That report shows a correlation between failure rates and the pace of copper ore production, and also establishes a relationship between the pursuit of lower grades of ore, which produces larger volumes of waste, and increasingly severe incidents.Lindsay Newland Bowker and David M Chambers, 2015. csp2.org For this reason, several programs to make tailing dams more sustainable have been set in motion in countries like Chile, where there are more than 740 spread across the country.
Environmental damage
The mining and processing byproducts collected in tailings dams are not part of the aerobic ecological systems, and are unstable. They may damage the environment by releasing toxic metals (arsenic and mercury among others), by acid drainage (usually by microbial action on sulfide ores), or by damaging aquatic wildlife that rely on clear water.Franks, DM, Boger, DV, Côte, CM, Mulligan, DR. 2011. Sustainable Development Principles for the Disposal of Mining and Mineral Processing Wastes. Resources Policy. Vol. 36. No. 2. pp 114–122
Tailings dam failures involving significant ecological damage include:
the Sino-Metals Leach Zambia dam disaster, Zambia in February 2025, when a tailings dam constructed for copper extraction by Sino-Metals Leach Zambia catastrophically failed, dumping approximately 50 million liters of acidic and highly toxic waste into the Kafue River ecosystem, killing riverine ecosystems and impacting the water and irrigation supply of 60% of Zambia's population. the Jagersfontein Tailings Dam Collapse, South Africa in September 2022, was a structural failure of a tailings dam used by a stockpile mineral reprocessor, resulting in a mudslide through the town and surrounding farmland. the Brumadinho dam disaster, Brazil, 25 January 2019, where as many as 252 people are unaccounted for, and at least 134 are dead. The disaster released 12 million cubic meters of iron waste leading to the Paraopeba River. the Bento Rodrigues dam disaster, Brazil, 5 November 2015, considered the worst environmental disaster in Brazil's history, killed 19 people when an iron ore containment dam failed and released 60 million cubic meters of iron waste. It devastated the Rio Doce river over hundreds of kilometers. the Mount Polley mine, British Columbia, 4 August 2014, which released 10 million cubic metres of water and 4.5 million cubic metres of metals-laden tailings from a holding reservoir.CBC News, August 2014. cbc.ca the Ok Tedi environmental disaster in New Guinea, which destroyed the fishery of the Ok Tedi River, continuously from 1984 through 2013 the Sotkamo metals mine, Finland, 4 November 2012, released "hundreds of thousands of cubic metres" of waste water which raised concentrations of uranium, nickel, and zinc in nearby Snow River, each to at least 10 times the harmful level.Mineral Policy Institute, August 2014, Chronology of Major Tailings Dam Failures the Ajka alumina plant accident, Hungary, 4 October 2010, which released one million cubic metres of red mud, a waste product of aluminum refining, flooding the village of Kolontár and killing the Marcal River. the Baia Mare cyanide spill, Romania, 30 January 2000, called the worst environmental disaster in Europe since the Chernobyl disaster"Death of a river", BBC, 15 February 2000 The Doñana disaster, southern Spain, 25 April 1998, which released 4 million-5 million cubic metres of acidic tailings containing heavy metals. the Merriespruit tailings dam disaster, South Africa occurred on the night of 22 February 1994 when a tailings dam failed and flooded the suburb of Merriespruit, Virginia. Seventeen people were killed as a result. the Church Rock uranium mill spill in New Mexico, 16 July 1979, the largest release of radioactive waste in U.S. history three uranium tailings dams near the town of Ak-Tüz, present-day Kyrgyzstan, collapsed in a December 1964 earthquake, releasing 60% of their radioactive volume () into the Kichi-Kemin River and its agricultural valleyI. Torgoev, A.T. Jakubick, quoted in an incident on 7 April 1961, released of uranium mine tailings from operations of the Soviet-era Wismut organization into the Zwickauer Mulde River in the village of Oberrothenbach the Mailuu-Suu tailings dam failure also in Soviet-era Kyrgyzstan on 16 April 1958, caused the uncontrolled release of of the radioactive uranium-mine tailings in to spill downstream into a portion of the densely populated Ferghana Valley
Tailings ponds can also be a source of acid drainage, leading to the need for permanent monitoring and treatment of water passing through the tailings dam. For instance in 1994 the operators of the Olympic Dam mine, Western Mining Corporation, admitted that their uranium tailings containment had released of up to 5 million m3 of contaminated water into the subsoil. The cost of mine cleanup has typically been 10 times that of mining industry estimates when acid drainage was involved., page 452-458
Casualties The following table of the deadliest known tailings dam failures is not comprehensive, and the casualty figures are estimates. Dam/incident Year Location Fatalities Details 1962 Huogudu(火谷都), China tailing pond failure 26 September 1962 Huogudu (火谷都), Gejiu， Yunnan, China 171 Few details available. A tailings pond at a tin mine operated by Yunnan Tin Group collapsed. 368M m3 surged. One source reports 171 killed and another 92 injured; another has the date as 26 September.The present situation and prospects for safety online-monitoring system of tailings pond (sic), by ZHOU Hanmin, YUAN Ziqing, SU Jun, YANG Xiaocong and ZHANG Da1, paper presented for the 3rd International Conference on Mechatronics, Robotics and Automation (ICMRA 2015) Mina Plakalnitsa 1 May 1966 Vratsa, Bulgaria 480+ A tailings dam at Plakalnitsa copper mine near the city of Vratsa failed. A total 450,000 cu m of mud and water inundated Vratsa and the nearby village of Zgorigrad, which suffered widespread damage. The official death toll is 107, but the unofficial estimate was more than 480. Certej dam failure 30 October 1971 Certej Mine, Romania 89 A tailings dam built too tall collapsed, flooding Certeju de Sus with toxic tailings. Buffalo Creek Flood 26 February 1972 West Virginia, United States 125 Unstable loose constructed dam created by local coal mining company, collapsed in heavy rain. 1,121 injured, 507 houses destroyed, over 4,000 left homeless. Val di Stava dam 19 July 1985 Tesero, Italy 268 Poor maintenance and low margin for error in design; outlet pipes failed, leading to pressure on dam and sudden collapse. Ten people were ultimately convicted of manslaughter and other charges. Mufulira 1970 Zambia 89 A tailings reservoir breached and collapsed into the copper mine below it, killing 89 night-shift workers. Aberfan disaster 21 October 1966 Wales 144 The collapse and landslide of a spoil tip accumulated above the mining town on geologically unstable ground killed 28 adults and 116 children (not an engineered structure) Hpakant jade mine disaster 25 October 2015 Myanmar 113 A slag heap reportedly used by multiple operators in this jade-mining region became unstable and flooded into nearby residences (not an engineered structure) El Cobre landslide 28 March 1965 Chile 300 Shaking from a magnitude 7.4 earthquake caused the failure of two tailings dams at the El Soldado copper mine. The resulting flow destroyed the town of El Cobre. Merriespruit Tailings Dam Failure 22 February 1994 Virginia, Free State, South Africa 17 Merriespruit tailings dam overtopped in heavy rains. The flow of an estimated 600,000 m3 (1.2 Million tonnes) of tailings reached the town of Merriespruit 2 kilometers away. With the seventeen fatal casualties, dozens of homes were engulfed. Taoshi landslide 8 September 2008 Linfen, Shanxi, China 254+ Iron mine tailings, formerly administered by the state and then put into private hands, collapsed into a village at 8 am. Bento Rodrigues dam disaster 5 November 2015 Mariana, Minas Gerais, Brazil 19 A tailings dam at an iron ore mine jointly owned by Vale S.A. and BHP and suffered a catastrophic failure releasing around 60 million cubic meters of iron waste into the Doce River which reached the Atlantic Ocean. Brumadinho dam disaster 25 January 2019 Brumadinho, Minas Gerais, Brazil 259+ A tailings dam at an iron ore mine operated by Vale S.A. suffered a catastrophic failure.
Largest The following list focuses on the largest tailings dam failures: Name Released volume Date of failure Country Environmental consequences Reservoir volume Dam type Notes Padcal No. 2 80,000AGHAM – Advocates of Science and Technology for the People, Center for Environmental Concerns (CEC), and Kalikasan People's Network for the Environment (Kalikasan-PNE) "Environmental Investigation Mission on the Impacts of the Philex Mining Corporation (PMC) Mine Tailings Pond 3 Failure TECHNICAL REPORT" , 2013. Page 2 (7/28). Accessed June 2018. Harvey Wood, 2012. Disasters and Minewater. IWA Publishing. Page 36. Accessed via EbscoHost e-book publisher.