Drills during Construction
Compressed air Burleigh drill
The compressed air Burleigh drill was most used during construction of the tunnel. The drill required four men to operate it in two shifts. Each drill could progress about 60 feet per month, at least four times as much as could be accomplished by hand labour and at a heavily reduced cost. The average cost of running it was about $62 per foot.
Ingersoll Rock Drill
Simon Ingersoll’s percussive drill was an improvement on the Burleigh. The drill was designed specifically for mining and tunneling and, with a skilled operator, could be capable of drilling at virtually any angle. The Ingersoll drill could move at 12 feet of drill hole in a shift of eight hours, further reducing construction costs. Although the drill was light and efficient, it had a serious drawback. Compressed air ran down the center of this drill and came out through a hole in the drill bit, blowing out the dust and debris which collected in the underground space during drilling. This created large amounts of air-borne dust, damaging workers lungs.