12 Areas of Cleanup and Success report highlights work at Candelaria copper mine in Chile

The Blacksmith Institute has combined its World’s Worst Polluted Places Report 2009 with its partners Green Cross Switzerland for a new report called the 12 Areas of Cleanup and Success. The Institute says that “While previous reports spotlighted the most severe pollution problems and locations, our 2009 report focuses on 12 programs and strategies that have been effective in reducing pollution and improving health.” Featured at number four in the report is ‘Managing Mine Tailings to Protect Scarce Water Supply’ in Candelaria, Chile, where the copper mine tailings are at risk of contaminating limited water sources in the desert.

The Candelaria copper mine is located in the Sierra El Bronce mountain range in the Copiapó River valley around 20 km southwest of Copiapó in the Atacama region of Chile. At a 600 m elevation, this mine has an estimated life of 20 years. The report states: “Although biodiversity is relatively low in this desert environment, its scarce water resources are integral to agricultural irrigation, urban residential and commercial, and industrial purposes. Mining is the most significant source of economic profit for the region, followed by agriculture and small-scale industry such as copper refinery.”

Cyanide, which damages the brain and the heart, is commonly found in mine tailings. Short term exposure to this can cause brain damage and comas, and miners exposed to high levels of heavy metals could experience breathing difficulties, chest pains, vomiting, headaches, and enlargement of thyroid glands.

To tackle this problem, CCM Candelaria – currently owned by mining company Freeport McMoRan Copper and Gold – focused on proper disposal of tailings with impoundment technology as well as effluent leakage prevention. A baseline study was conducted to determine the content and extent of tailings effluent with tailings content trapped by spill collection systems and a temporary containment pond and re-circulated back to the processing facility for treatment. This facility thickens tailings to 50% solids content for easier disposal.

A major component of the 450 ha tailings disposal facility is the dam, which is constructed of waste material from the mine. The dam is divided into multiple stages to comprehensively trap and filter tailings from the water. This tailing impoundment/cutoff wall system was designed to contain more than 331 Mt of tailings combined and prevent storm surge with tailings content from entering the water treatment system. As a result, water pollution is prevented and through the recycling process, the quantity of limited ground and surface water supplies are preserved in this desert environment.

The remaining challenges for the operation according to the report: “Treatment systems similar to the one installed at the Candelaria copper mine are able to extract and treat a majority of the water locked up in tailings. The remaining 20% of water bound up in tailings is generally difficult to remove. Additionally, design of the tailings disposal/water treatment structure must be able to confine the smaller particles of tailings, as leakage of these toxic materials could yield negative environmental and health impacts.”

To read about the other 11 entries in the report, please visit www.worstpolluted.org