Although the DM45 HP is capable of drilling the desired 8 m bench height, opting for the larger DML HP allowed the mine to increase the hole diameter to 216 mm.
The holes are drilled in a 5.5 m by 6.5 m pattern to a total depth of 9.2 m, including 1.2 m of subdrilling.
An Atlas Copco ROC L8 (now named FlexiROC D60) is used to drill 140 mm diameter presplit holes on double benches with a total depth of 16 m. The penetration rate averages 34 m per hour/rig and an average production of 28 holes or 2 520 meters drilled per shift. The waste-to-ore ratio is 3–1, producing 0.5 million ounces of gold in 2011.
Getting ready for growth
The mine has five pits in operation and a new sulphite processing facility is being built to process better quality ore while a new underground area named Centauro Bajo is being developed below the Centauro Alto pit. In addition a new open pit, Noche Buena, will be added.
The Centauro Alto pit is now at 250 m and it is estimated that it will reach 500 m in eight years. Underground Mine Manager Hector Contreras says underground operations will continue from there. “This mine has another 15 years in it and exploration is continuing. We don’t know the true extent of the reserves yet,” he says.
Equipment for the development process arrived in April 2012. This includes two Atlas Copco Boomer S1 D face drilling rigs, one Atlas Copco Boltec rock bolting rig and three Atlas Copco Scooptram ST1030 underground. The mine also has an Atlas Copco Robbins 73RH raiseboring machine.
Epiroc operated under the trademark “Atlas Copco” prior to January 1, 2018.