The giant Antamina tailings dam, the highest of its kind in the world, will have the capacity to store 570 MT (metric tons) of waste rock material or 330 MT3 during its 23 year useful life span.
Built in the Huincush Ravine and three kilometers from the Concentrator Plant, this tailings pond has a 135 meter deposit base, with a reinforced concrete inner plate then increasing by 75m downstream with mine material that does not produce metal leaching. This elevation is protected, in turn, by high intensity geo-membranes to avoid possible leaks from the tailings pond outside. Drainage tunnels, concrete injections of up to 80m on the lateral supports and rainwater collector channels with end capacities of 25m3/sec., supplement this high technology work which ensures the protection of the environment, as well as its structural stability.
Currently, the tailings dam is undergoing its fourth dam heightening to reach 215 meters (at 4.090 meters.). Final height is expected to reach 240m, with 1.3 km in length in its final peak. Its seismic resistance is 0.48g, equivalent to a major grade 8 earthquake on the Richter scale with its epicenter beneath the dam at a depth of 65Km. It is designed to withstand the area’s maximum probable flood even when all dam bypass channels fail. This is the equivalent of a volume of 28Mm3 in a 96 hour period.
Also, the tailings dam is not only used to dispose of the small non commercial residual amounts left over from the mill process, but also to recycle from 93 to 97% of the water used by the concentrator. Thus, Antamina does not impact high altitude Andean water bodies but rather minimizes fresh water use in its operation.
Discharges from the tailings dam into the Ayash valley reach compliance levels above 99%, according to regular observations recorded since 2004, and this ensures the free availability of this resource in the valley as an ecological continuous flow all year long of at least 150 liters / second.
In January 2003, the consulting firm Golder Associates Ltd. won the “2002 Canadian Consulting Engineering Award” of merit in the mining and industry category for its design and engineering services related to the construction of Antamina’s tailings dam. The award was presented by the Association of Engineering Consultants of Canada.