Grupo Mexico has denied reports claiming it did not immediately report a massive acid spill from its Buenavista mine in northern Mexico, just about 40 km from the U.S. border, allowing toxic waste to flow into a river that supplies water to hundreds of thousands of people.
In a press release posted by SoyCobre.com (in Spanish), the company said it proceeded to build a retaining wall to prevent the 40,000 cubic meters spill from spreading as soon as it detected the toxic leak.
But Carlos Arias, director of civil defence for the northern state of Sonora, told AP yesterday that residents detected the sulphuric acid leak downstream the next day, at which point the mine operators hadn’t notified state authorities.
“The company deliberately concealed the accident,” Cesar Lagarda, an official at the National Water Commission (PROFEPA), told La Jornada (in Spanish).
He added the agency found concentrations of arsenic and some metals that exceeded levels permitted in the waters of Sonora, adding that authorities continue to monitor chemicals water quality at multiple points along the river.
Lagarda also said the accident was due to lack of proper supervision at the mine, along with rains and construction defects.
Despite dumping lime into the river to neutralize the acidity of the leaked chemical, local reports the contamination has already killed fish and cattle in the area.
Water supplies from the river have been cut off to about 20,000 people.
Top mining state
Sonora is home to more than a quarter of Mexico’s mining industry and leads in gold, copper and graphite production.
Mexico’s federal government recently opened up the country’s vital energy sectors such as electricity generation and oil production to private companies.
In 2009 an American subsidiary of Grupo Mexico, Asarco, paid the U.S. government a record $1.79 billion to settle hazardous waste pollution in 19 states.