Mine Tailings Storage: Safety Is No Accident

cubic metres of toxic tailings into the Agrio, Guadiamar and Los Frailes Rivers (WWF 2002). The contamination affected 62 kilometres of waterways and 4 286 hectares of land, including farmland in the fertile Guadiamar basin and part of the ecologically significant Doñana National Park – a Natura 2000 and World Heritage Site. The emergency construction of barriers stopped more extensive waste intrusion into the park, which is the largest reserve in Spain and significantly, home to 361 bird species (Grimalt et al. 1999). The high acidity (pH 3), low dissolved oxygen and turbidity caused by the spill resulted in the widespread death of aquatic organisms. Thirty-seven tons of dead fish were collected from the river mouth and all shellfish disappeared (Grimalt et al. 1999). The possibility of heavy-metal contamination (Figure 20) resulted in the closure of over 50 irrigation wells for a period following the spill. There was also a ban on the sale of agricultural produce from affected farmland. The land was not considered suitable for future agriculture and the government of Andalusia began a programme of compulsory acquisition. The disaster had major economic impacts on agriculture, fishing, tourism and the mining sector in the region.

these quickly began to oxidize and form more mobile, water- soluble sulphates.

Immediately following the spill, clean-up work began to create a green corridor along the Guadiamar River, connecting two large natural areas – the Doñana National Park and the Sierra Morena (Rico et al. 2008). The cost of remedial and restoration works reported in 2013 was estimated at more than €170 million (BIO Intelligence Service et al. 2012). Most of the deposited tailings and 4.6 million cubic metres of contaminated soil were excavated and placed into the open-mine pit. This was successful in removing a significant amount of contamination from the Guadiamar River channel and floodplain, although elevated levels were still present in samples collected six months after the first remediation programme (Hudson-Edwards et al. 2003; Kemper and Sommer 2002). The clean-up activities, however, changed the structure of the river and floodplain and removed the riparian vegetation that provided a natural refuge for fauna (Macklin et al. 2003; Rico et al. 2008). Reptile populations, for example, were still found to be severely depleted eight years after the dam collapse. The green corridor failed to meet the requirements for their reintroduction due to the absence of shelters (Márquez- Ferrando et al. 2009).

The metals released were mostly in the form of insoluble sulphides, but when exposed to oxygen in the environment,

Estimated amount of metals released into the environment

0

3000

6000

9000

12000

14 500 tonnes of zinc and lead

9 000 tonnes of arsenic

3 600 tonnes of copper

900 tonnes of antimony

45 tonnes of cadmium and silver 27 tonnes of mercury 90 tonnes of thallium and bismuth 100 tonnes of cobalt

18 tonnes of selenium and other metals

Source: Grimalt et al 1999

Figure 20. Estimated volume of heavy metals released into the environment by the Los Frailes tailings dam failure

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