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Travelling at up to 120 km/h, the tailings wave first touched the foot of adjacent Dam No.6, then hit the mine's loading station, its administrative area (including a cafeteria where many workers had lunch at the time), and two smaller sediment retention basins (B4 and B4A).
The slurry wave then traveled approx. 7 km downhill until reaching Rio Paraopeba, thereby destroying a bridge of the mine's railway branch, and spreading to parts of the local community Vila Ferteco, near the town of Brumadinho.
The slurry wave killed 259 people, and 11 are reported missing.
The slurry was then carried further downstream by Rio Paraopeba, thereby killing all life in the river and inhibiting production of drinking water in settlements along the river. It is expected to arrive at the dam of the Retiro Baixo hydroelectric plant approx. 300 km downstream within two weeks.
At 5:30 AM on Sunday, January 27, 2019, residents of Brumadinho were evacuated, as it was feared that Dam No.6 could fail, as well, since dam monitoring instruments detected an increase in water levels. Around 15:00, it was determined that the risk had decreased and residents were allowed to return to their homes.
According to Vale, the dam was built in 1976 by Ferteco Mineração (acquired by Vale on April 27, 2001), using the upstream method. The dam was 86 meters high with a crest length of 720 meters. The disposed tailings occupied an area of 249,500 m2 and the disposed volume was 11.7 million m3.
The dam last received tailings in July 2016 and was "deactivated" thereafter. There apparently was no ponding water on top of the tailings except for a small section.
For reasons so far unknown, the slope of the dam appears to have gone through a sudden massive rotational failure that extended across the full width and height of the dam.
There are no reports of any external events that are typically known to trigger such failures, such as earthquakes or heavy rainfall.
It is known that dam slopes with marginal safety factors may fail upon slight vibrations, such as caused from trucks passing nearby.
In this case, the trigger might have been the drilling of a monitoring well that was ongoing in the middle of the slope as it collapsed.
If this drilling activity actually triggered the dam failure, then the safety factor of the slope must have been on the brink. It is unclear how this can have gone unnoticed, given that, according to Vale, the dam had 94 piezometers (instruments for measuring the pressure of a liquid) and 41 water level indicators to monitor its integrity.
Information surfacing bit by bit in early February 2019 appears to confirm that the factor of safety of the dam was inacceptably low and that there were serious deficienies with monitoring of the dam stability:
On Dec. 12, 2019, the Expert Panel released its report on the technical causes of the dam failure. This investigation was commissioned by Vale.
"In summary, the following history created the conditions for instability in Dam I:> Download: Report of the Expert Panel on the Technical Causes of the Failure of Feijão Dam I
The Panel found that the failure and resulting flow slide was the result of flow liquefaction within the tailings in the dam. The history described above created a dam that was composed of mostly loose, saturated, heavy, and brittle tailings that had high shear stresses within the downstream slope, resulting in a marginally stable dam (i.e., close to failure in undrained conditions). Laboratory testing showed that the amount of strain required to trigger strength loss could be very small, especially in the weaker tailings. These were the main components that made flow liquefaction possible.
- A design that resulted in a steep upstream constructed slope;
- Water management within the tailings impoundment that at times allowed ponded water to get close to the crest of the dam, resulting in the deposition of weak tailings near the crest;
- A setback in the design that pushed the upper portions of the slope over weaker fine tailings;
- A lack of significant internal drainage that resulted in a persistently high water level in the dam, particularly in the toe region;
- High iron content, resulting in heavy tailings with bonding between particles. This bonding created stiff tailings that were potentially very brittle if triggered to become undrained; and
- High and intense regional wet season rainfall that can result in significant loss of suction, producing a small loss of strength in the unsaturated materials above the water level.
The Panel concluded that the sudden strength loss and resulting failure of the marginally stable dam were due to a critical combination of ongoing internal strains due to creep, and a strength reduction due to loss of suction in the unsaturated zone caused by the intense rainfall towards the end of 2018. This followed a number of years of increasing rainfall after tailings deposition ceased in July 2016. The calculated pre-failure strains from this combination of triggers match the small deformations of the dam detected in the post-failure analysis of satellite images from the year prior to the failure. The internal strains and strength reduction in the unsaturated zone reached a critical level that resulted in the observed failure on January 25, 2019."
Vale knew Brumadinho dam was unsafe as early as 2003: internal report:
An independent investigation requested by Brazilian iron ore miner Vale SA into the causes of the Brumadinho tailings dam disaster that killed 270 people a year ago found the company knew about the problem but failed to deal with it.
An executive summary of the report published by Vale on Thursday (Feb. 20) said the company had information dating as far back as 2003 that pointed to the fragility of the main B1 dam. But steps taken to deal with the structural problem and heighten the dam's security were limited and ineffective, the report said.
The internal report serves as a damning condemnation of the firm, some of its employees and various auditors. While concerns were raised at various points in time about the dam's safety, those concerns were repeatedly ignored or minimized over the course of 16 years. (Reuters Feb. 21, 2020)
> Download: Executive Summary of the Independent Investigation Report , Feb. 20, 2020 (324kB PDF)
Minas Gerais cancels licenses to operate tailings dams at two other Vale mines in wake of disaster:
The Brazilian state of Minas Gerais canceled Vale SA's license to operate a dam at one of its largest mines, the company said on Wednesday (Feb. 6), following the collapse of another dam in the state that killed an estimated 300 people.
The state canceled Vale's license for Laranjeiras dam. It had been used in the operation of the Brucutu mine, which had already been suspended by a court order, freezing nearly 9 percent of the company's output.
Minas Gerais also canceled Vale's license to operate its Jangada mine, which has been paralyzed since the dam close to the Córrego do Feijão mine burst in the state, killing at least 150 people. Another 182 people are still missing from what is possibly Brazil's most deadly mining disaster.
The cut in output from Brucutu forced Vale to declare force majeure in iron ore and pellets contracts on Tuesday (Feb. 5). (Reuters Feb. 6, 2019)
Brazil set to ban upstream tailings dams after collapse kills hundreds:
Brazil's mining agency plans to ban upstream tailings dams used for storing mining waste, a director at the National Mining Agency (ANM) said on Thursday (Feb. 7), after such a dam burst last month, likely killing at least 300 people.
Eduardo Leão, a director at ANM, said the agency aims to issue an ordinance on Friday (Feb. 8) requiring that such dams be taken down or converted into other types of dams.
Brazil has 88 upstream tailings dams, according to Leão. It was not immediately clear what kind of deadline the dam operators would face to take down or convert the dams. (Reuters Feb. 7, 2019)
Federal Public Prosecutor's Office calls for emergency measures to prevent failure of tailings dam at former Poços de Caldas uranium mine (Brazil):
> See here
Minas Gerais Public Prosecutor's Office tries to suspend deployment of large tailings dam of Vale near condominiums in Itabirito:
The Minas Gerais Public Prosecutor's Office (MPMG) is trying to stop the implementation of Vale's Maravilhas III ore tailings dam with a capacity of 108.86 million cubic meters in Itabirito, in the Central Region of Minas Gerais.
The petition, which was filed at the 1st Public Treasury Court of Belo Horizonte, requests, as a matter of urgency, the revocation of an earlier court decision, which allowed for the implementation of the enterprise. The risk is that if this reservoir is broken, two residential condominiums and at least four rural properties could be hit by mining tailings. According to preliminary information, the dam would have a waste storage capacity nine times larger than the Brumadinho dam. (Jornal Estado de Minas Feb. 7, 2019)
> View MPMG release Feb. 7, 2019
Bill to toughen mining rules back to deal in Minas Gerais Assembly:
After being rejected last year, a proposal to siege and tighten the rules in the mining sector is back in the Legislative Assembly of Minas Gerais (ALMG) . [...] The expectation is that it will be voted shortly in the Public Administration Commission, where it was presented on Monday (Feb. 4).
The project, which has as its mouthpiece in the Assembly the deputy João Vítor Xavier , was built in partnership with the Public Prosecution and civil society. The text is a regulatory framework for dam safety in Minas Gerais.
"We want an effective regulatory framework. Economic issues can not continue to overlap with human and social issues," said promoter Andressa Lanchotti, coordinator of the Operational Support Center of the Environmental Defense Prosecutor's Office and coordinator of the task force that manages the disaster of Mariana.
The joint proposal touches on points such as the use of better technologies, the existence of people in the self-rescue zone and also provides for an environmental bond. It is a matter of forcing the miners to reserve money or have insurance-guarantee to, in case of disaster, to deal with socio-environmental issues and reparation to the victims. "Samarco and Vale are two giants of the sector, but what if a tragedy occurs with a company without capital or in abandoned mine?", warns the developer.
Deputy João Vítor recalled that the substitution was made on the basis of a technical note from the MP, of 18 pages, pointing out the weaknesses of the PL currently underway in the Assembly. (Jornal Estado de Minas, Feb. 7, 2019)
Three towns evacuated for failure risk of tailings dam at Vale's Gongo Soco mine in Barão de Cocais, Minas Gerais:
The National Mining Agency has ordered the withdrawal of about 500 people from the communities of Socorro, Tabuleiro and Piteiras, all in Barão de Cocais, in the Central Region of Minas Gerais, because of the Southern Superior Dam of Vale's Gongo Soco mine. The residents were evacuated at dawn on Friday (Feb. 8), around 1am.
According to the miner, Warm Consulting denied the Stability Condition Statement of the structure. From there, the company began to perform level 1 of the Emergency Plan of Mining Dams. Sirens were triggered and people started to leave their homes. (Globo Feb. 8, 2019)
> View: Vale release Feb. 8, 2019
Town evacuated for failure risk of tailings dam at ArcelorMittal's Serra Azul mine in Itatiaiuçu, Minas Gerais:
Residents of the town of Pinheiros, in Itatiaiuçu, Metropolitan Region of Belo Horizonte, were removed from their homes at dawn this Friday (Feb. 8). Altogether, about 50 families were evacuated from their homes.
According to the city's Military Police, the request for support of the withdrawal came from the Civil Defense, which warned of the risk of breaking the dam. The village is 1.5 kilometers from the dam. The families were taken to hotels in the city of Itaúna, in the Central-West Region of the state. The dam belongs to the mining company ArcelorMittal . Wanted, the company has not yet returned to the story. (Globo Feb. 8, 2019)
> View: ArcelorMittal release Feb. 8, 2019
Eight other tailings dams at risk of failure:
At least eight ore tailings dams in Minas Gerais are also at a severe risk of disruption. In a public civil action signed on February 1 in a secretive, now broken, case, the Public Prosecutor's Office asked Vale to urgently comply with measures that would reduce the possibility of new tragedies such as Brumadinho, where dam 1 of the Córrego do Feijão Mine was broken, leaving, so far, 165 people dead and 155 missing. According to the document, Vale has already known about these risks since October 2018.
The MP action was filed on February 1, five days after the Brumadinho disaster, based on the mining company's own inspection documents - issued in October 2018. The eight dams mentioned are located in the cities of Barão de Cocais (Dam Laranjeiras) , Nova Lima (Capitão do Mato Dam, Barrage Dam B and Dam Taquaras), Ouro Preto (Dam Fork I, II and III) and another in Brumadinho, within the Córrego do Feijão mine complex (Menezes II Dam). (Jornal Estado de Minas Feb. 12, 2019)
Two more tailings dams at risk of failure: The number of dams at risk of severe disruption in Minas Gerais increased to 10. According to a lawsuit filed by the State Attorney General's Office (MPMG), the Sul Superior dams (Mina Gongo Soco) in Barão de Cocais (Central Region) and Vargem Grande in Nova Lima (Grande BH) are also in threat. On Tuesday (Feb. 12), the agency had already released a document containing eight other dams at risk. (Jornal Estado de Minas Feb. 13, 2019)
NGOs create information platform on social and environmental impacts of Córrego do Feijão dam failure:
With the creation of a Civil Society Crisis Office, civil society organizations will monitor the situation of those affected by the rupture of the Vale dam in Brumadinho.
Composed of environmental NGOs and human rights activists, the office will monitor actions related to the rupture of Vale's tailings dam at the Córrego do Feijão Mine, request the punishment of those responsible and defend victims' rights, support and propose measures to prevent new disasters and tragedies and to give visibility to the impacts of mining on communities.
Other issues addressed will be the role of the company and the various actors after the tragedy and the perspective on water security in Belo Horizonte and the Metropolitan Region and the future regarding the possibility of new disasters related to the rupture of mining tailings dams.
The main instrument of the cabinet will be a digital platform that is already available. (Globo Feb. 14, 2019)
> View: Gabinete de Crise Sociedade Civil
Town evacuated for risk of tailings dam failure at Vale's Mar Azul mine in Nova Lima, Minas Gerais:
The Minas Gerais Fire Department has now informed that it will evacuate a risk area of the B3/B4 dam at Vale's Mina de Mar Azul mine in the municipality of Nova Lima (MG). Between 170 and 200 people will have to be removed from the site, which covers about 49 buildings, between homes and commercial establishments.
At the request, Vale reported that it activated Level 2 of the Emergency Action Plan for Mining Dams (PAEBM) for the B3/B4 dam at the Mar Azul mine, in Nova Lima, MG, on Saturday (Feb. 16). According to the company, the measure was taken "for safety". According to the company, the measure is "preventive." "The decision is a preventive measure and takes place after reviewing the data of analysis reports of specialized companies hired to advise Vale. It should be noted that the structure is inactive and this initiative has a preventive nature," said the company in a note sent by its press office.
According to the Fire Department, the audit refused to certify security of the structure, which motivated the preventive evacuation. B3/B4 have about 3 million cubic meters of tailings. That is, it was built with the same type of structure as Dam I of the Córrego do Feijão mine, which broke at the end of January, in a tragedy that goes to have more than 300 dead. (Estadão Feb. 16, 2019)
> View: Vale release Feb. 16, 2019
Minas Gerais has 11 dams without stability attestation:
In addition to Mariana and Brumadinho, the concern with the dams in Minas Gerais should serve as an alert for Grande BH to the south of the state, passing through the Triângulo Mineiro. They impose risk structures in Caldas, Caranaíba, Carandaí, Itatiaiuçu, Ituiutaba and Rio Acima. Eleven dams of ore tailings and industrial use in Minas do not have stability guaranteed by the agencies in charge of overseeing these structures.
In addition, 46.6% of the 88 tailings dams built in the upstream method in Brazil, the same used in the structures that broke in Brumadinho and Mariana, and in what terrified on the weekend residents of Macacos, in Nova Lima, are located in the state. These dams are considered to be more fragile and prone to disruption, since the elevations (the elevation of them to increase the storage capacity) are made on the tailings. (Jornal Estado de Minas Feb. 18, 2019)
Government orders elimination of all upstream dams until 2021:
The Agência Nacional de Mineração has ordered the elimination of all "upstream dam" type dams, such as the one that broke in Brumadinho (MG) and left 169 dead and 141 people missing. The government's resolution was published in the "Official Gazette of the Union" this Monday (18).
According to the published text, dams upstream or unknown method that are deactivated should be eliminated until August 15, 2021 and those that are in operation, until August 15, 2023. The resolution also stipulates that companies responsible for mining dams are prohibited from maintaining and constructing any work or service facility of the company in the self-rescue zone of the dam. In the case of the Vale dam, the employee's cafeteria was close to the dam. According to the text of the resolution, the entrepreneur responsible for mining dam considered high risk will have until February 15, 2020 to install a monitoring system with full-time monitoring.
In a list of 717 mining tailings dams in Brazil, at least 88 have a method of building "upstream or unknown upheaval," according to the National Mining Agency. Among them, 43 are classified as dams of high associated potential damage.
The upstream method is the same as the Vale dams that broke in Mariana in 2015 and Brumadinho in 2019 and are considered less safe by specialists. The other types of construction, considered safer, are upstream, center line and single stage. (Globo Feb. 18, 2019)
Government determines that miners withdraw workers from the area near dams until August:
A resolution of the Agência Nacional de Mineração (ANM) published on Monday (18) prohibits miners from maintaining and building any facility, work or service in a region up to 10 km below the dams or that can be reached by eventual flooding in up to 30 minutes.
The resolution gives as an example purposes of living, eating, health or recreation that have "human presence." In the case of Brumadinho, the employee's cafeteria was close to the dam. The breakup left 169 dead and 141 people missing until the last report released Sunday (17).
Existing installations, works and services in the dam area should be deactivated until August 15 of this year. The determination holds true for mining dams of all construction methods. (Globo Feb. 18, 2019)
Residents at five more tailings dams to be evacuated:
Vale said Wednesday (Feb. 20) it will withdraw about 75 people living near five dams located in Nova Lima, in the Metropolitan Region of Belo Horizonte and Ouro Preto, in the Central Region of Minas Gerais.
The dams are: Vargem Grande, Forquilha I, Forquilha II, Forquilha III and Grupo. The structures are part of the 10 dams of the type "upstream raised" and according to the company, the structures are already inactive. (Globo Feb. 20, 2019)
Assembly of Minas Gerais approves bill to impose stricter dam measures:
The Legislative Assembly of Minas Gerais (ALMG) approved, on Friday (Feb. 22), in the second round, the bill that determines more stringent measures for the mining of the state.
The vote was held at an extraordinary meeting earlier this evening and had 65 votes in favor and none contrary to PL 3.676/16. According to ALMG, the final draft of the bill was approved minutes later. With this, the president of the House, Agostinho Patrus (PV), can now refer you to the sanction of Governor Romeu Zema (Novo), which should be done this Monday (Feb. 25).
After a week of many controversies over the subject in the House, the text that was approved in plenary came to include almost all the content of the project that became known as "Sea of Mud Never Again." On a popular initiative, it had more than 50,000 signatures and was drawn up after the Samarco dam broke, whose owners are Vale and BHP Billiton.
Before going to plenary, the PL had an opinion approved in the second round by the Public Administration Commission. The rapporteur, Mr João Magalhães (MDB), expressed his approval for substitute No. 1, rejecting the text approved with amendments in the first round.
Among the main points of the text is a ban on the installation of upstream dams - the same type of structures that broke in Mariana in 2015 and in Brumadinho this year.
See substitute points:
The state security plan for dams in Minas Gerais entered into force on Tuesday (Feb. 26), with the publication of law 23.291, which provides for the prohibition of installing upstream tailings dams, that is the type that broke in Mariana, three years ago, and in Brumadinho, on January 25.
According to the legislation, the entrepreneur responsible for the dam by the upstream method in operation will promote migration to alternative technology within three years. This type - which grows through steps made with the tailings itself over the initial dam - is also forbidden in a recent resolution of the National Mining Agency (ANM) , however the state norm provides for a shorter period of adequacy. The ANM stipulated a period of five years for dams in use. The text says that the companies installed in Minas Gerais will have the deadline of 90 days to present a schedule of planning of the replacement of technology in upstream dams. This is established for operational and inactive dams. Those that are not in use should be decommissioned, which can occur, for example, by reintegration into the environment.
Also in accordance with the law, it is also prohibited to grant permits for the installation, expansion or elevation of dams that have communities in the self-rescue zones. The delimitation considers the greater of the two distances: 10 kilometers or the area that can be reached by the flood within 30 minutes. The distance can be increased to 25 kilometers, depending on the location of the inhabited areas and cultural and natural heritage of the region.
Nor can licenses be concomitant, that is, be issued simultaneously for different phases of environmental licensing. By the state norm, the entrepreneur is responsible for the safety of the dam from planning to decommissioning. (Globo Feb. 26, 2019)
Excess water compromises stability of tailings dam at Araxá Mining Complex in Alto Paranaíba:
One more on the list. After an inspection at the B1/B4 Dam of the Araxá Mining Complex in Alto Paranaíba, it was verified that the structure is not in stable condition. Despite the finding, so far, no residents had to be removed from their home. The dam is the responsibility of Mosaic Fertilizers , a mining company in the United States.
In the afternoon of this Friday (Feb. 22), Mosaic classified the risk of breaking as level 1; the scale has three stages. The problem detected involves excess water in the structure. According to the Civil Defense of Minas Gerais, the first stage is triggered when an anomaly situation is detected.
According to the Fire Department, the mud would take about 34 minutes to spread through the dam's Self-rescue Zone (red spot). This area is 10 kilometers downstream from the dam. The flood spot is blue in the image. According to the miner, in case of dam rupture, there is no risk of mud reaching the urban area of the city. Rural dwellings would also be out of reach. However, Mosaic reported that all residents of the countryside were alerted and registered with the mining company.
According to the Fire Department, this is a dam built in the process of center line, type of elevation considered safe by the specialists. However, the last 10 meters of the structure were built upstream, the same type of upwelling used at the Fundão dam in Mariana and at the B1 Córrego do Feijão Mine in Brumadinho. According to the mining company, the entire structure is built on the center line lift, a process considered safer than upstream.
Altogether, the B1/B4 Dam has a capacity of 24 million cubic meters of tailings, almost double the Brumadinho (12.7 million). According to Mosaic, the tailings accumulated in the structure are from the production of phosphate and have no contaminants.
(Jornal Estado de Minas Feb. 22, 2019)
Mundo Mineração's tailings dam in Rio Acima has no stability attestation:
The security crisis in dams, which in addition to spreading death and destruction by Brumadinho in the Greater Belo Horizonte, demanded evacuations of neighboring populations of mining complexes in other four mining cities, spread fear for several other municipalities, and one of the most worrisome is Rio Acima, also in the metropolitan region of the capital. In addition to housing the tailings dam abandoned by Mundo Mineração, considered at "maximum danger" by the Public Prosecutor's Office, the municipal territory houses the worst-performing enterprise among those who still need to have their stability attested this year. Two dams of Nacional Mineração of the Companhia Siderúrgica Nacional (CSN) group are among the 36 structures in this state, according to a survey carried out by the State Secretariat for the Environment and Sustainable Development (Semad) at the request of the State of Minas Gerais. One of them, B2 Auxiliar, is the only one on the list that, even before the process triggered by Vale's catastrophe in January, was no longer guaranteed stability.
If the worst happens and the 75-meter-high B2 and B2 Auxiliar dams break, a tailings load of 9 million cubic meters could reach the Rio das Velhas in less than 20 minutes. In case of rupture of the structure, the resulting wave would enter the manatee 10 kilometers from the capture of Copasa de Bela Fama, responsible for 60% of the water supply in Greater Belo Horizonte.
According to the survey of Semad, as well as the other 34 structures, the Nacional Mineração dams were erected by the upstream raising process. It is the cheapest and least stable technique, since it consists in increasing the capacity of the reservoir (raising) by supporting the embankments on part of the contents of the dam itself. It is the same process adopted in the dams that broke in Mariana in 2015 and Brumadinho in the beginning of the year.
The B2 and B2 Auxiliar dams have a history of concern, which led the Public Prosecutor of the Nova Lima district to obtain their interdiction in Justice, in April of last year, as the State of Minas showed at the time, with exclusivity. The dams are located in the Fernandinho Mining Complex, between Itabirito (Central Region) and Rio Acima. The Mining Dam Emergency Action Plan foresees only five families in the so-called self-rescue zone - an area where people need to escape from an eventual accident on their own, since there is no time for intervention by public agencies. Alert sirens were installed in the valley below the dam to warn this directly threatened population. (Jornal Estado de Minas Feb. 23, 2019)
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