Paredones Amarillos gold mine, halted in Sierra de la Laguna

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Baja California, Mexico
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Photo: Acid mine drainage at US mine. Credit: Earthworks

Thanks to AIDA and our partners in Mexico, the Mexican government has denied a critical environmental permit for the Paredones Amarillos gold mine, halting the project for the time being and protecting an important natural reserve. The proposed gold mine threatened to contaminate the Sierra la Laguna Biosphere, a pristine area recognized by the Mexican government and the United Nations for its rich biodiversity. 

To protect this jewel, AIDA helped educate community groups and decision-makers about the mine's risks, enabling them to build the political momentum necessary for the government to deny the permit.

To extract gold from the Sierra la Laguna mountains, the Canadian company, Vista Gold, proposed to carve out huge quantities of rock –each ton containing a mere gram of gold– and grind it into a sludge. It would have treated the sludge with cyanide, an extremely dangerous chemical that dissolves the gold into a liquid so it can be collected. This process would have produced massive amounts of toxic waste from the left-over cyanide-treated ore.

The company planned to contain this waste ore (called “tailings”) in a dam intended to store the toxic slurry forever. Unfortunately, these dams can break for various reasons, as happened at the Porco mine in Bolivia in 1996. When the Porco tailings dam collapsed, more than a quarter million metric tons of tailings flooded the river and contaminated 800 km of waterways in three countries: Bolivia, Argentina y Paraguay.

This type of open-pit gold mining can also cause a devastating problem called “acid mine drainage.” When sulfur-containing rocks are exposed to air and water, sulfuric acid is created, which can cause toxic heavy metals to dissolve and drain into the watershed. The risk of acid mine drainage occurring in Sierra la Laguna was significant and the human and environmental cost would have been tremendous: thousands of people and countless wildlife in the reserve desert rely on this water for survival.

Mining companies also store cyanide solutions and contaminated waters in reservoirs which, like tailings dams, can rupture or overflow. In 2000, in the worst environmental disaster in Europe since Chernobyl, a wastewater reservoir gave way causing 3.5 million cubic feet of cyanide-contaminated water to spill into several rivers, killing all of the fish and seriously harming the river ecosystems.

Depleting freshwater is a further threat because mines use tremendous quantities of water. Owing to the scarcity of water in the reserve, Vista Gold proposed to build a plant on the Pacific coast to remove salt from sea water via a highly energy-intensive process, and then pump the water 45 km to the mine site. The desalination plant posed a threat to the leatherback sea turtle, famous for its gigantic size and endangered status.

With gold selling for more than $1,000 an ounce, the mine would likely have been lucrative for Vista Gold. The long-term benefit to Mexico and nearby communities was not as clear. Few industries wreak as much environmental damage as mining. In the United States alone, 179 abandoned mines are listed on the national priority list as hazardous waste sites in need of cleanup.

Such cleanup is very expensive, and governments and taxpayers often end up paying the bill. Unfortunately, because it takes time for acid mine drainage to appear, the full extent of environmental harm caused by mining may not become apparent until long after the mining company has left.

Fortunately, with your support, AIDA has helped prevent this type of environmental disaster in the Sierra la Laguna Biosphere.  We will continue to guard this important source of freshwater.

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