Scientists warn that pouring water into mining waste ponds increases their risk of failure, a method used in the largest dams in the country, located in the Riotinto copper mine (Huelva), which has 182 million cubic meters of remains (sterile) in three colossal rafts. Geochemical experts warn that in order to avoid environmental disasters due to pond failures such as the one that occurred in Aznalcóllar (Seville) in 1998, the key is to thicken the sludge and reduce the water as much as possible. The constant increase in water multiplies the risk of liquefaction, the passage from solid to liquid of the stored material, which triggers its pressure towards the walls, which could burst the structures of the ponds, according to the scientists.
Since the Riotinto field resumed extraction in 2015, the constant discharge is 65% liquid and 35% solid, according to the company itself.
The largest ponds in the country, with up to 100 meters deep and a huge surface area of 595 hectares, each year incorporate 10 million cubic meters of toxic waste through transport and discharge through pipes that, from a bird's eye view, generate striking orange lakes and grayish beaches .
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“The actions of the Government and the industry must focus on reducing the entry of water into the ponds. The key factor is that the water balance must always be negative and a double drainage system would facilitate the expulsion of the water, as well as adequate instrumentation. The risk of the pond breaking is drastically reduced to below 80% of the degree of saturation [water content in the soil pores] ”, concludes the recent research led by Roberto Rodríguez-Pacheco, from the area of geochemistry and mining sustainability of the Geological and Mining Institute (belonging to the CSIC). After analyzing the casings of 67 dams (internal and external structure), the investigation
How to prevent failures in mining ponds
, published last February by Rodríguez-Pacheco and eight experts from three Spanish universities in the
Mine Water and the Enviroment
, warns of how the failure of 17 ponds in Spain since 1960 has been linked to heavy rains, an inadequate instrumentation system and a faulty drainage system.
If the Riotinto reservoirs were to break, it would lead to a river of toxic sludge with a maximum flow of 34,716 cubic meters per second, according to a study by the Ayesa company that in 2014 evaluated the risks of reopening the mine. The waste would travel 111 kilometers to reach the sea and on its way would affect three municipalities in the Odiel river basin —Gibraleón, Palos de la Frontera and Punta Umbría— as well as two neighborhoods in the city of Huelva (143,000 inhabitants). If the Aznalcóllar catastrophe meant the discharge of six million cubic meters of sludge with a high environmental cost and whose cleaning cost the public coffers 143 million pending collection (an amount that, added to the decontamination and restoration work, reaches the 240 million), Riotinto would pour 10 times more, 63 million cubic meters,according to said study. Ayesa estimated that only 35% of the stored waste would go downstream and that 65% would remain in the ponds in case of breakage.
Photogallery: The mining ponds of Riotinto
Two years ago, researcher Steven Emerman of the University of Utah made a grim prediction about Riotinto: the rafts would “almost inevitably” break in the next 20 years with a 95% chance and percentage risk of failure. it will be 28% this summer of 2021. Emerman placed the water table [below which the pores of the soil are filled with water] at only 2.9 meters below the surface of the dam, which denotes how the water is spread by the entire interior of the dam.
In addition, the expert detected uncontrolled leaks, "which indicates that both the dam and the waste are almost completely saturated with water," he stressed in his report for the NGOs London Mining Network and Ecologistas en Acción.
The multinational mining company Atalaya Mining that exploits Riotinto denies the minimum possibility of risk of breakage: “I can assure 100% that this has no possibility of breaking, it is impossible, there is a greater chance that a meteorite will fall. It is a sand storage facility that you can walk on, where the water is recirculated 100% and we build with rock, like a water dam, but without having it ”, affirms its CEO, Alberto Lavandeira. Regarding the danger of storing water in the ponds during the next 20 years of the mine's projected useful life, the manager disdains him: “It is irrelevant to pour at 35% or 5% solids, sand weighs more than water, where is it? is that water After six years there would be a lake and there isn't ”.
Riotinto discharges water to its prey because it needs a lot to purify the copper that is only present in 0.4% in the rock it extracts thanks to daily blasting.
The Romans and a century ago the English extracted the veins with the highest concentration of mineral, which today is residual but still lucrative.
Through the use of water and chemical processes, the miner manages to purify the rock to extract a 23% copper dust that is then sent to smelters, especially in China and Japan.
The world demand for copper is on the rise because after melting it is used in construction, solar plants and batteries or motors in electric cars.
A technician walks past one of the tanks where copper is purified.PACO PUENTES
The Council of Colleges of Mining Engineers, like the Geological and Mining Institute, also disagrees with Lavandeira's analysis: “There is an interest in reducing the water content that accompanies solid waste in the form of fine particles to obtain more manageable products. That is, to be able to pour pastes instead of sludge. The most technified mining companies in the world no longer dump sludge with a high percentage of liquids in the waste dams, but instead dump consolidated pastes, with a certain resemblance to toothpastes ”, comments Carlos López, board member and specialized mining engineer in mining. "With regard to water, it is known to all that it has a great destabilizing effect (...) you should not choose the cheapest technology, because it can be more risky and in the end cheap is expensive", he adds.
In parallel, the European Commission includes sludge thickening in its report on the best available practices for the management of mining waste. Between 30% and 40% of the water discharged into mining ponds is retained as water that fills the pores and capillary water among the waste, experts warn. There are more than 3,500 mining waste ponds worldwide, according to the International Commission on Large Dams, and since 2001 the rate of accidents has been one breach every eight months. “The secrecy of accidents was unheard of, but the last four major failures in Canada (2014), Australia (2019) and Brazil (2015 and 2019) caused technical reports detailing the causes of accidents to be made public due to the social pressure ”, comment industry sources requesting anonymity.
In Riotinto, apart from the Gossam basin - currently unused - both the Cobre and Aguzadera basins, inaugurated in 1970 and 1985, have been regrown after being clogged with the upstream construction method.
Brazil, Chile, Peru and Ecuador have prohibited this system of growth of the dam of the dam due to its dangerousness.
Since its reopening in 2015, Atalaya has not used this method in all the reinforcement of levees it carries out to minimize risks, which amounts to 10 million per year, but it was used in the re-growth of the immense structure of Riotinto over three decades, between 1970 and 2001.
Several technicians walk through the mud of the Cobre de Riotinto pool, with one of the lakes in the background.
PACO PUENTES / EL PAÍS
The position of Atalaya Mining, a multinational with Spanish, Chinese, American and Swiss capital that invoices 250 million a year and employs 460 workers, has changed over the years with respect to the thickening of sludge.
In 2011 he highlighted that in the "only viable technique" to pour into their ponds, "the sterile plants will be thickened to 50% solids before their deposition", according to the firm alleged before the Andalusian Board.
In 2014 the company accepted in an internal document that with the discharge of sludge without thickened, "by having a greater volume of water circulating in the system, the safety in terms of prevention of catastrophic accidents and their possible consequences is reduced".
In March 2016, Atalaya Mining asked the Board to exempt it from this obligation to thicken the sludge, wielding a report from the multinational Golder made by its mining experts in Chile. However, after a month the delegate of the Andalusian Ministry of Economy, Innovation, Science and Employment in Huelva, paralyzed the mine due to the latent risk of spilling with more liquids than solids: "The danger of ruptures and leaks in the dam increases to deposit waste with larger volumes of water (…) The way of operating the deposit will be with the systematic of sludge thickened to 50% by weight, in a first phase and by means of sludge thickened to 65% by weight in a second phase, as a more advantageous to reduce / avoid acid mine drainage ”.
The stoppage lasted barely 15 days, given that the General Director of Industry, Energy and Mines of the Board, María José Asensio - prosecuted for prevarication in the
- he rectified his delegate in Huelva and lifted the suspension based on a report by professors Ricardo Laín and Pedro Ramírez of the Polytechnic University of Madrid: “Using sludge thickened to 50% does not ensure that there is less water in the dams, since the water is recirculated 100% ”, they concluded. The daughter of the first professor, Eva María Laín, used the Atalaya Mining laboratories as a researcher at the time, but this did not make her father inhibit due to conflict of interest, and he ruled in favor of the company resuming its activity. The professor rejects that there was incompatibility. Your daughter works for the company today. In 2017 Laín issued a report to certify the stability of slopes of the waste facilities of Mina Cobre Las Cruces (Seville),and less than a year and a half later the deposit suffered a landslide of 14 million cubic meters of earth and minerals without victims.
Aerial image of the Riotinto mining ponds PACO PUENTES / EL PAIS
Since Atalaya resumed its activity in Riotinto in 2015, Ecologistas en Acción has questioned the safety of the rafts: “The Emerman report told us in 2019 that the risk of breakage is extreme as the years go by, so we send it to them to the mining, environmental and judicial authorities.
The rupture of these ponds would devastate the entire Odiel basin and the risk assessment of the works carried out for two years has not been done.
We do not want to be right and get to read the headline of
The ecologists have already warned of the risk of breakage
if the ponds break in a few years, ”criticizes Isidoro Albarreal, from the mining area of the conservation association.
Atalaya Mining plans to start up its thickening plant before the end of the year after seven years, but only to increase the percentage of solids from 35% to 50%. "We do not do it for safety, but to save energy and lime," says Lavandeira. The costs of thickened sludge range between 10% and 30% of the maintenance of a farm, according to sources in the sector. In parallel to the green light of the Andalusian Board, Atalaya ran into the definitive refusal of the Galician Xunta last March to reopen the Touro copper mine (A Coruña) due to an unfavorable environmental declaration.
The Andalusian Board ensures that the risk of failure of the Riotinto reservoirs is zero and last January approved the expansion of six meters of the main reservoir with a reinforcement of the dam's structural safety: new piezometers, inclinometers, bathymetries and monthly controls of its stability. Cristóbal Sánchez, Secretary General of Industry and Mines of the Andalusian Board, underlines the confidence in the technical reports collected: “The risk of breakage is unthinkable because the regulations establish controls that strengthen the safety of waste facilities. Projects are reviewed to a tremendously thorough and thorough degree ”.
Next October, the most dangerous mining ponds will have to provide a financial guarantee to face a possible environmental spill, confirm sources from the Ministry for the Ecological Transition and the Demographic Challenge.
After the inaction of the successive governments, the guarantee for the mining companies comes with a delay of 17 years after the European directive that already in 2004 established the principle of the polluter pays.
The sinister precedent of Aznalcóllar
In 1995, two and a half years before the failure of the Aznalcóllar reservoir (Seville) that dumped six million cubic meters of toxic sludge into the surroundings of Doñana, the mining engineer of the exploiting mining company Boliden, Manuel Aguilar, saw the disaster and denounced the leaks of the raft before the Andalusian Board: "If the aforementioned dams are not closed, they run the great risk of causing a natural disaster of incalculable consequences (...) As a consequence of poor execution, of the absolute lack of direction technical and no compaction, the filtrations to the Agrio river are constant ”, read his 11-page report.
Aguilar's complaint fell on deaf ears and the Environment Agency of the Andalusian Board avoided demanding that Boliden reinforce his waste pond and today, 23 years after the dam broke, it is still negotiating with the Swedish multinational to achieve that pay part of the 143 million it cost to clean up the polluting spill. The Doñana National Board also received Aguilar's report and did not move a file either.
After the disaster, the Court of First Instance and Instruction 2 of Sanlúcar La Mayor (Seville) imputed 21 technicians of the company, officials of the Board and of the Guadalquivir Hydrographic Confederation.
But on December 29, 2000, the judge closed the criminal proceedings and exonerated all the accused.
That day Aguilar heard on television how justice ruled that there were no criminal charges despite his previous complaints and the inaction of the Board, and died of a heart attack in León after verifying impunity for the announced environmental catastrophe.
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