Barrick Gold recently acquired a DSC Wolverine Class dredge which is being used in the Pueblo Viejo gold-silver open pit mine in the Sanchez Ramirez Province of the Dominican Republic, located about two hours north west of the country’s capital, Santo Domingo. Barrick acquired the mining rights in 2006 when it took over Placer Dome. Due to the mine’s condition at the time of its acquisition, Barrick then began a wide-scale cleanup of the area, demolishing existing structures and building new state-of-the-art facilities, as well as remediation of significant environmental damage left by the previous mine operation, which closed in 1999.
Barrick’s efforts have included water treatment, restoring the Margajita River’s pH to a level low enough that the waters have returned to their natural color and quality; re-vegetating 3,500 ha of land to prevent soil erosion; and removing 180,000 m3 of contaminated soil. DSC’s Wolverine Class dredge was brought in to help maintain the sediment ponds that prevent additional contamination of the local water system. The process begins when buckets of mined material are fed through a screening system that uses water to clean the precious metals as they are reduced. The water that comes into contact with ore stockpiles or waste rock is contained onsite by a series of canals, channels and sediment ponds that hold it until it can be pumped through the facility’s water treatment plant. In addition to contaminated water, small grains of silt and sand also wash into these sediment ponds, creating buildup, which reduces their capacity for water storage. Each pond is approximately 150 to 250 m wide and 450 m long.
Dredging allows the silt and sand buildup to be regularly removed from the sediment ponds so the ponds can maintain their depth and prevent overflow into surrounding waterways. Barrick chose DSC’s 21 m Wolverine Class dredge, which is powered by a 440 hp Caterpillar C13 ACERT diesel engine. The Wolverine Class can dredge up to 7.6 m below the surface and offers a 25 cm discharge configuration, which allows particle clearance of up to 15 cm. The cutterhead, designed with six cast-steel smooth blades, is attached to a variable-speed, reversible, hydraulic cutter motor manufactured by Kawasaki. The dredge pump, a J30 Metso Minerals/Thomas Simplicity series, is rated for 61 m total discharge head at 15,900 litres/min. Five hydraulic winches, rated with a 2,040 kg line pull capacity, are used to swing the dredge, lift the spuds and lift the ladder.
