High degrees of underground mining mechanization have long been the trademark of Viburnum Trend mines. The drilling equipment used for both primary and secondary extraction is essentially the same throughout the Viburnum Trend. Two-boom electric hydraulic jumbos with 4.3- or 4-m (14- or 16- ft) feeds are the standard and, with only a couple exceptions, are 1980svintage joy machines with JH-2 drifters. All jumbos have been rebuilt several times over the years, but there are no plans to replace them over the remaining life of the mines. Penetration in ore averages about 3 m/min (10 ft/min) for a 44-mm- (1 ¾-in-) diameter bit. Penetration rates in waste are slightly slower.