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The collapse on April 25, 1998 of a mine tailings pond in Aznalcóllar, near Seville, shocked the population. Numerous articles and studies which aims were to determine the reason of the break and especially, to determine the respective responsibilities, followed one upon the other.  According to the CSIC the environmental impact was almost 100 times major than the impact caused by the spillage of the Prestige. The ecological disaster and the potential affection tu Doñana’s National Park, led to a judicial litigation (Boliden Case) of the ‘Junta de Andalucía’ against the multinational Swedish Boliden, owner of the mining development and lastly, the closure of the mine in 2001.

The cut-slide failure of the geologic clay deposit where the pond settled, known as blue Guadalquivir marl, caused the accident due to the effect of the high fluid pressures. The collapse of the soil fits the description of ‘progressive break’, process that had been analyzed in details principally by Skempton in 1964 and Bjerrum in 1966.  According to this, the failure was technically predictable and foreseeable with the existing level of knowledge in the date of elaboration of the project. The main cause of the accident was to overlook this hypothesis of break, which made way for the overestimation of the resistance of the clay substrate. All in all, an involuntary human error and a repeated misjudgment were identified as the origin of the tragedy.Though the collapsing process was meticulously analyzed since it was the key to the judicial delimiting of responsibilities, the spillage and flow through the fluvial network got comparatively few attention. The break of the riprap closure of the perimetral dyke produced a spillage of approximately 2hm3 of sludge decanted after the spillage and  around 4hm3 of acid waters that reached rapidly the riverbed of the ‘Agrio’ river and later they arrived to the riverbed of the ‘Guadiamar’.  Fortunately, the muds did not reach the Doñana National Park, but ended in the ‘Guadalquivir’ and finally reached, when already less contaminated, the Atlantic Ocean in Sanlucar the Barrameda.

En la imagen de archivo de abril de 1998, vista aerea de la rotura de la balsa que provocó el vertido de la empresa Bolidén-Apirsa,que explota la Mina de Aznalcóllar (Sevilla).

In the archive image from April 1998, an aerial view of the breakage of the raft used by the Bolidén-Apirsa company, which exploits the Aznalcóllar Mine (Seville).

In total 4.400 hectares along more than 60 kilometres following the riverbed of the ‘Guadiamar’, were devastated. The environmental impact on the riverbeds was considered faunal, whereas the originated from the pollution and contamination of the areas exposed to the flooding was mainly considered pedological and botanical. In compliance with this, it was necessary the expropriation of plots and the removal of contaminated soil. These measures added to the project of regeneration of the basin have cost a total payment that overcame 300 million Euros in 2008.

The closure of the mining development had a negative impact in the economy of the zona, getting lost 2.000 work positions. In order to mobilize the resources of the zone and to reactivate the economic growth, the ‘Junta de Andalucía’ summoned on January 16, 2014 an international award contract for the reopening of Aznalcóllar’s mine, with the premise of demanding the maximum safety and environmental sustainability. Among the entities which presented offers to this contest, only Emeritus Resources España, S.L.U., and Group Mexico-Minorbis were selected for the second stage. After the selection in February 20, 2015 the Headquarter of Industry, Energy and Mines, of the Council of Economy, Innovation, Science and Employment of the ‘Junta de Andalucía’, awarded to the entity Minorbis the exploitation.

Recently the President-in-Office of the ‘Junta de Andalucía’ has announced the paralyzation of the concession award of Aznalcóllar’s mine to the consortium Magtel, constituted by group Mexico and Minorbis. The reason for the cessation is the pronouncement of the judge the past May 7, which revealed the possible breach of legal obligations, not fulfilling ‘te minimal requirements, not at  least to overcome the first phase of the contract award’  to proceed with the reopening of the mining complex.

It is not the first time that a contract award is called into question, nevertheless given the fragility of the environment and what happened years ago, it seems essential to clarify that the decision is based on the fulfillment of all the requirements. The controversy is immeasurably strengthened by the spill of 40.000m3 of acid solution of copper sulfate in a river, which has suffered the Mexican multinational in its more emblematic mine, in the north of Mexico.

Given the last reports, the question we are left with today is if even knowing the environmental risks inherent in the reopening of the mine development, the administration keeps putting other interests first. And we must ask ourselves if it is worth the risk, and if we are following the path towards a new disaster in Aznalcóllar.


•   Ayala-Carcedo. Instituto Geológico y Minero de España. La rotura de la balsa de residuos mineros de Aznalcóllar (España) de 1998 y el desastre ecológico consecuente del río Guadiamar: causas, efectos y lecciones. Boletín Geológico y Minero, 115 (4): 711-738 ISSN: 0366-0176

•   ‘El desastre ecológico de Aznalcóllar’ (Aguilar, J.; Dorronsoro, C.; Fernández, E.; Fernández, J.; García, I.; Martín, F.; Ortiz, I.; Simón, M.) Última actualización: 01/09/2000

•   Junta de Andalucía. Consejería de economía, innovación, ciencia y empleo. Portal Andaluz de la Minería. Mina de Aznalcóllar.

•   El Periódico: ‘Aznalcóllar, una mina marcada por el desastre ecológico de Boliden de 1998’. 13 de mayo de 2015

•   El Diario: ‘La Junta adjudicó Aznalcóllar a la empresa responsable de un desastre ecológico en México’. 13 de mayo de 2015.

•   El Mundo: ‘Susana Díaz paraliza la adjudicación de la mina tras estallar el ‘caso Aznalcóllar’’. 13 de mayo de 2015

•   La Información, noticias: ‘Aznalcóllar, el desastre natural que fue cien veces mayor que el Prestige’. 13 de mayo de 2015

Cristina Vila Martínez
Universidad Politécnica de Madrid

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