MAC: Mines and Communities

Long-running leak of contaminated water at Mexico's largest gold mine revealed

Published by MAC on 2016-08-28
Source: Reuters

Levels of selenium rose in groundwater monitoring wells since October 2013

Goldcorp struggles with leak at Mexican mine

Allison Martell, Frank Jack Daniel and Noe Torres

Reuters -

Aug 24, 2016

Mexican regulators said they are examining whether mining company Goldcorp broke any regulations in its handling of a long-running leak of contaminated water at Mexico's biggest gold mine.

The move follows questions from Reuters about the leak, which until now has not been disclosed to the public.

Levels of the mineral selenium rose in one groundwater monitoring well near Goldcorp’s Penasquito mine as early as October 2013, Goldcorp data reviewed by Reuters shows.

The Canadian company reported a rise in selenium levels in groundwater to the Mexican government in October 2014, after which the contamination near its mine waste facility intensified, according to internal company documents seen by Reuters, and interviews with government officials.

Two weeks ago, the company told Mexican regulators that contaminated water had also been found in other areas of its property.

There is no evidence that the leaks at the mine have endangered public health or caused environmental damage, Goldcorp and regulators say.

Goldcorp said it has not informed villagers living near the mine because its tests showed the leak had not affected groundwater beyond its property line or contaminated the local drinking water.

The company was not legally required to tell the community, Mexican regulators said. The head of the industrial inspection unit at Mexico's environmental prosecutor Profepa, Arturo Rodriguez Abitia, said it would have been preferable for Goldcorp to inform the local community about the leaks, but that it was not obliged to do so if the problem had not spread beyond its boundaries.

The company said its monitoring program worked as intended and helped quickly identify the problem at the mine, which lies in a semi-desert region of the northern state of Zacatecas and which in 2015 produced 860,300 ounces of gold, a quarter of Goldcorp's total production.

"We have managed the issue within the confines of our property and continue to monitor and operate our tailings management system to prevent any external impacts," Goldcorp said when asked when the leak was discovered and whether it was ongoing.

Selenium is sometimes released into the environment by mining and can be present in waste stored in what are known as tailings ponds. High concentrations in water can damage human health and cause deformities in wildlife.

In recent years its effect on fish and waterbirds has led to successful lawsuits against North American miners including U.S.-based Patriot Coal, which filed for bankruptcy in 2012 under $443 million of selenium water treatment liabilities.

Vancouver-based Goldcorp declined to disclose how much it was spending to monitor and fix the leak, saying only that there was a "sufficient allocation of resources.”

“This issue is one that we have taken seriously and we are taking the necessary measures to resolve,” said Michael Harvey, the miner’s Latin America director for corporate affairs and security.

Two weeks ago, after receiving questions from Reuters, Goldcorp met with Mexican regulators in Zacatecas. A presentation dated March 2016 but delivered at that meeting said one of the steps the company was taking to address the leak was to relocate a pond that reclaims water from the tailings. The company told Reuters that project should be completed next year.  


Selenium levels in the well rose for months after the miner alerted authorities in October 2014, the company data seen by Reuters shows. The concentration began falling in April 2015 and from September at least through January it was steady at 0.01 mg/liter.

Canadian province British Columbia, where Goldcorp is headquartered, and Mexico both establish maximum selenium concentrations of 0.01 mg per liter in drinking water. Mexico sets maximum concentrations of 0.008 mg/l in fresh water bodies and 0.02 mg/l in water for agricultural use. 

Levels in the groundwater at Penasquito rose to more than five times that level, the data shows.

A September 2015 internal Goldcorp presentation -- which was released onto the Internet by unidentified hackers earlier this year -- laid out "key risks and opportunities" associated with the spill. One risk, according to the presentation, was that "community knowledge and understanding of potential groundwater contamination may raise national and international attention."

The presentation also warned of the risk of "long term impacts to human health and the environment if the plume is not adequately mitigated."

Profepa's Rodriguez told Reuters his unit was examining the case to see whether Goldcorp had downplayed or not fully disclosed relevant information. He did not specify which regulations Goldcorp could have violated.

Goldcorp says it has complied with all Mexican requirements for notifying regulatory authorities.

Mexico's Conagua water regulator did not conduct its own tests of water quality around the mine in response to the leak, but said its regular monitoring of the aquifer through its own network of pumping stations had not shown a change in water quality. After receiving questions from Reuters, the regulator said at least two new wells would be built near the mine to monitor water quality.      

Villagers in the area around the mine have previously made at least two complaints to environmental authorities about alleged seepage from the wall of the tailings dam. Inspectors from the state unit of Profepa reported that there was nothing out of the ordinary in both cases.

At the meeting with Profepa two weeks ago, Goldcorp described leaks in three other areas to the west and south of the facility, in addition to the original well.

The company’s presentation, seen by Reuters, showed that two of the leaks were just to the north of Las Mesas, a community of about 90 families who mostly raise cattle or grow corn and beans. Authorities in Las Mesas could not be reached for comment.

(Editing by Stuart Grudgings)

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