Estimate the hourly production (Bm/hr) of the rock excavation involved in preparing an industrial building site by drilling and blasting. The site is 89.5 m by 120.2 m and must be excavated to an average depth of 3.658 m. The material to be excavated is thinly laminated shale. The drilling equipment to be used will consist of an air-powered track drill and air compressor. The average drilling rate, including steel changes, moves and delays, is estimated at 32 m/h. Trial blasting indicates that 7.6 cm holes drilled in a 3.658 m rectangular pattern will provide adequate fracturing. A hole depth of 4.115 m must be drilled to yield a 3.658 m effective depth.