Damage to fragile environments: Doņana National Park pollution
Cause: toxic waste spillage from the Boliden lead-zinc
mine
On April 25, 1998 one of waste lagoon dams of the Los Frailes
lead-zinc mine belonging to the Swedish - Canadian enterprise Boliden in
Aznalcóllar broke. Five million cubic metres of toxic sludge and acid waters
flowed over 60 kilometers of the Guadiamar River, the salt marshes and
Entremuros, eliminating aquatic life and depositing heavy metals throughout the
area. The avalanche of water and sludge was stopped just before arriving to the
Doņana National Park thanks to the rapid construction of an emergency dam.
The Doņana national park is Europe's largest wildlife reserve.
It covers over 75,000 hectares (185,000 acres) along Spain's southwestern coast,
providing shelter for millions of migratory birds and housing threatened species
such as lynx and imperial eagle.
Location of Doņana national park
Underlying Causes
Dam wall retaining toxic waste was badly designed
Poor safety inspections by the government
Mine waste lagoons constitute one of the greatest environmental threats, not
only in Spain but also worldwide
Until this event, fines for pollution in Spain have been so low, they have
been regarded as an acceptable business cost. It has been cheaper to pay the
fine than take adequate safeguards.
Millions of gallons of toxic water leaked from the dam
Reasons
for the dam failure
The reason for the foundation failure,
and the failure of the mine management to foresee the problem is still a matter
of discussion, although a number of theories have been proposed. The mine
operators claim that there was no way to foresee the incident and have
subsequently blamed construction contractors for misinterpreting the
geotechnical properties of the site.
A report prepared for the mining company
described the weak point of the dam two years in advance of the failure.
Geotechnical experts suggest that the
foundation failure was caused by chemical attack of the impounded acidic pyritic
slurries on the marl forming the dam foundation material.
Other experts suggest that the dam was
built on expansive clays which deformed with wetting and drying. They claim that
the expansion and contraction of the clays should have been accounted for in the
design of the dam. In addition, reports indicate that the subsoil was unsuitable
to support the mass of tailings that were piled up in the dam.
Acidic seepage, combined with continued
blasting in the nearby open pit mine would have contributed to the dam failure.
Other experts suggest that the dam was
designed with insufficient beach width and that the dam was being filled at a
rate higher that it was designed for.
Specific Causes and Effects
Causes
Effects
Mine waste lagoon dam wall collapsed,
releasing zinc, lead and cadmium toxic waste into the River Guadiamar, a fragile
wetland habitat
The sludge did not enter Doņana but coated nearby farmland
High river acidity levels
River bank vegetation killed
Death of thousands of fish and other wild life. The contamination reached
the food chain and stork malformations and tumours have been detected.
10,000 hectares of farmland along the banks of the river poisoned.
Thousands of farmers have seen their crops ruined. The farming commune of
Aznalcazar alone lost 3,500 hectares (8,645 acres) of fields growing rice,
cotton and citrus fruit. Some 250 farmers and 500 day-jobbers were estimated to
have "lost everything".
Loss of tourist income
Wells and groundwater contaminated
It could take 40 years for the farmlands and wetlands to recover. The toxic
metals do not naturally breakdown.
The authorities announced a $270m clean-up plan funded
by the Spanish Government and the European Union after the spill.
At the beginning of 2000, Boliden abandoned its mining activities in
Spain without undertaking the appropriate mine closure and firing its whole
staff, 425 workers
The company filed for bankruptcy in October 2000 to avoid
a $45 million fine imposed by the Spanish government.
Millions of gallons of toxic water leaked from the dam
The sludge did not enter Doņana but coated nearby farmland