On an April morning in 1998, a holding dam at the Los Frailes mine near Aznalcollar cracked open and released a wall of acidic sludge into the Andalusian countryside. Four to five million cubic meters of mine tailings -- laced with dangerous concentrations of zinc, lead, cadmium, and other heavy metals -- poured into the River Agrio, then into the Guadiamar, and raced downstream toward Donana National Park. Workers and emergency crews managed to halt the toxic flood after it had traveled roughly 40 kilometers and covered 4,600 hectares. But the damage was already catastrophic, and the cleanup would take three years.
Donana National Park sits between the provinces of Seville and Huelva, just east of the Portuguese border. It is one of the largest natural reserves on the European continent, a UNESCO World Heritage Site whose lagoons, marshlands, mobile dunes, scrub woodland, and maquis support an astonishing diversity of life. More than half a million birds winter there each year, migrating between Africa and Europe along one of the planet's great flyways. Perhaps half of all European bird species have been spotted within its boundaries at one time or another. The Guadiamar River is the park's main water source. When the tailings dam failed, the toxic plume was heading straight for the heart of this ecosystem.
The Los Frailes mine, owned by Boliden-Apirsa -- the Spanish subsidiary of the Swedish mining company Boliden -- produced zinc and silver from the mineral-rich Iberian Pyritic Belt. The tailings pond held the acidic waste byproducts of extraction, contained behind an earthen dam. When that dam gave way, the released slurry moved fast. It hit the River Agrio within hours, then merged into the Guadiamar's flow. Emergency teams scrambled to build containment barriers, and they succeeded in stopping the advance before the worst of the contamination reached the park's core wetlands. But the 4,600 hectares already engulfed were saturated with heavy metals that would persist in the soil, the sediment, and the water for decades.
Boliden-Apirsa spent more than US$52 million on cleanup, damage repair, and reimbursement to farmers whose crops were destroyed. In 2014, The Guardian reported that Spain had committed an additional 360 million euros to landscape restoration. Despite these efforts, elevated levels of heavy metals remain embedded in the soil and water, and have entered the food chain through wildlife. The disaster was one of the worst environmental catastrophes in European history. Twenty-six years after the accident, the mining company and the Spanish government remained locked in dispute over compensation claims. Scientists who study the affected area have documented the slow, incomplete process of ecological recovery -- a landscape healing, but carrying permanent scars.
Remarkably, there has been serious discussion about reopening the Los Frailes mine. Proponents argue that profitable ore remains underground and that a new operation could provide a thousand jobs to a region with high unemployment. Opponents point to the thousands of migratory birds that depend on the area and the obvious risk of repeating the catastrophe. Vicente Fernandez Guerrero, the secretary-general for Innovation, Industry, and Energy of Andalusia, stated that any new mining license would require modern techniques only, that no liquid waste processes would be permitted, and that Boliden-Apirsa itself would be barred from bidding. The debate distills a familiar tension: economic need against ecological memory, jobs against the possibility that the same ground could fail again.
Located at 37.52N, 6.25W, roughly 35 km northwest of Seville. The mine site is near the town of Aznalcollar. The Guadiamar River valley traces the path of the toxic spill south-southeast toward Donana National Park, whose marshlands and dunes are visible from altitude. Nearest airport: Seville-San Pablo (LEZL), approximately 40 km east-southeast. Best viewed at 3,000-5,000 ft AGL to trace the river corridor from the mine site toward the park.