A well-managed environmental disaster
Aznalcollar is a mining town 40Km west of Seville.
An open pit zinc mine had operated here for many years until it finally closed in 1996.
However, an ore body with commercially retrievable levels of zinc, copper, lead and silver, had been discovered at Los Frailes one km to the east in 1988. When the old mine was depleted the owners, the Swedish Canadian company Boliden, moved the mine equipment over. The new mine produced 4 million tons of ore in 1997. Here are two pictures of the Los Frailes mine pit.
The ore was crushed and metals separated at a nearby treatment plant and the waste (the tailings) placed in two vast shallow ponds behind an artificial dam.
On 25 April 1998 disaster struck. The tailings dam wall failed and released about 5.5 million m³ of toxic tailings water and about 1.3 million m³ of semisolid waste.
The pollution accident
The spillage was terrible. The waste contained high levels of arsenic and many other toxic chemicals, and the liquid part threatened to reach Donana national park and cause tremendous damage to wild life.
The clean up
Fortunately the clean up was rapid. Boliden took charge of scraping up the solid waste that lay between the burst dam and the old Seville-Huelva road bridge near Sanlúcar la Mayor. The government dealt with the area south of the road bridge.
Boliden simply scraped up the solid waste and any contaminated earth, and placed it the old worked out Aznarcollar mine pit. They managed to remove most of it before the winter rains so minimising the amount of heavy metal leached into the ground.
The government contractors working downstream of Sanlúcar la Mayor also had to contend with toxic water running down the Guadiamar river and into Donana National Park. They bulldozed low earth walls in the park and diverted the toxix run off into the Gualdaquivir river.
The mine ceased operations temporarily after the accident. It restarted in 1999, but experienced technical problems with the ore processing facility, and the operators decided to close it once and for all when the current pit was worked out in Sept 2001.
The area today
I visited Aznalcollar in summer of 2006. You can see the breach repair clearly.
The surrounding area is now a pretty bleak industrial park.
Here is the dry bed of the Rio Agrio, which carried the pollution into the Rio Guadiamar
But there is no pollution to be seen at the road bridge near Sanlúcar la Mayor. Nor further downstream at the Roman bridge at Aznalczar. Click here for August 2006 pictures.
More importantly there is no visible damage in Donana. These pictures below were taken in August 2006 at the site where the temporary earth dams were built to divert water into the Gualdalquivir. The earthworks ran along the line of pylons.
The park is dry and barren but that is its normal state at the height of summer. Chemical tests on the land indicate that there is no residual pollution.
Here is a freighter running down the Gualdalquivir river from Seville to San Luca along the the edge of the park.
Jim Thornton Nottingham Sept 2006
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