MEXICO CITY (AP) — Mexico's top environmental official said Tuesday that a mining company lied about a spill of millions of gallons of acids and heavy metals that contaminated two rivers and a dam downstream.
Environment Secretary Juan Jose Guerra Abud said the mine falsely claimed the spill earlier this month was caused by unusually heavy rain. Officials say a construction defect at a holding pond allowed mining waste to flow out.
"At the start, they told us it was excessive rain" that caused the containment pond to overflow, Guerra Abud said. "That was totally false," he said, saying there were no rains on that scale.
"They said there would be a series of aid programs for the populations, which also did not happen when they said they would," he added at a news conference.
Guerra Abud said the Buenavista del Cobre copper mine could face fines of up to $3 million for violations of safety and environmental standards. The mine is owned by the Grupo Mexico consortium, which earlier said in a statement that "torrential and unusual rains" were to blame and that it responded immediately by trying to contain the Aug. 7 spill.
The spill sent about 10 million gallons (40,000 cubic meters) of mining acids into two rivers and on to a dam that supplies water to the capital of the northern state of Sonora.
Authorities have ordered a shut-off of water use from the dam until its safety can be ensured. The Environment Department office has also ordered an inspection of all Buenavista del Cobre's properties to verify the company is complying with environmental laws.
National water commission head David Korenfeld said acids and pollutants like arsenic have been so diluted they are now within acceptable limits at the dam. A decision to renew use of the dam's water could come as early as Friday, after multiple tests are carried out, he said.
But Korenfeld said the dam would have to raise intake levels for years to avoid stirring up possibly contaminated sediment. "The procedures for operating the dam are going to have to change for the next few years," he said.
The mine piles up crushed rock and then leaches out metals using acid that collects in containment or transfer ponds until it is processed.
Arturo Rodriguez, the head of industrial inspection for the Attorney General for Environmental Protection, said lax supervision at the mine, along with some rain and construction defects, appeared to have caused the spill. Rodriguez said mine operators should have been able to detect the leak before such a large quantity got into the rivers.