Rorah seam. The mine produces about 600,000 tons of coal annually at an average
stripping ratio of 17:1. The overburden is made up of grey, well-laminated, non-marine
shales, overlain with up to 40 feet of glacial outwash clays and sand channels. The
overburden is fragmented through blasting prior to removal. Overburden removal is
mainly by carry dozers. However, the final overburden is removed by a Hitachi EX1900
hydraulic shovel (14.4 yd3 dipper) and 150-ton, rigid frame, haul trucks. Both the shovel
and trucks have on-board data logging systems that were used to collect data on engine
load factor and fuel consumption, respectively.