After a side cut about 20 ft. deep had been made, the side holes were drilled 20 ft. deep, and the holes were loaded and tamped for the full 20-ft. cut.  Under the terms of the specifications, the contractor was required to complete the excavation on the sides by drilling broaching holes.

The maximum length of drill steel was about 20 ft., and, where the excavation plane of broaching was more than 20 ft. in depth, the contractor was permitted to start the holes back of the broaching line, in order to allow for setting up the drills on the second lift.  A distance of about 8 in. was usually allowed for setting up a drill.  The broaching line was painted on the surface of the rock in advance of the drilling, and the batter of the drill was tested with a specially designed hand-level in which the bubble came to a central position when the face of the level was on the required batter.  Holes were also drilled in front of this broaching line, and, when the excavation had been taken out to within about 6 ft. in front of it, the holes immediately in front were loaded, and also about every third one of the broaching holes, and, unless the rock was very bad, it usually broke sharply at the broaching line.  Occasionally, the broaching holes which were not loaded were filled with sand, which gave rather better results than leaving them open.

In the steam-shovel work on the east side of Ninth Avenue, spring holes were used.  They were formed by drilling a 20-ft. hole and exploding at the bottom of it, without tamping, two or three sticks of dynamite, and repeating this process with heavier charges until there had been formed at the bottom of the hole a large cavity which would hold from 100 to 200 lb. of dynamite.  Face holes and breast holes were also drilled, and it was possible by this method to drill and break up a cut 20 ft. deep and 15 ft. thick.  The only place where spring holes were used on this work was on the east side of Ninth Avenue where the heavy cutting was sometimes extended beyond the east house line.

From the best records obtainable, the average progress in drilling was about 33 lin. ft. per 8-hour shift.  The average number of cubic yards of excavation per drill shift was 13.9, and the average amount of drilling per cubic yard of excavation was 2.4 ft.; this covered more than 27,000 drill shifts.

The dynamite was practically all 60%, and the average excavation per pound of dynamite was 2.2 cu. yd.  The contractor employed an inspector of batteries and fuses, who, using an instrument for that purpose, tested the wiring of each blast prior to firing, in order to discover any short circuits, and thus prevent the danger of leaving unexploded dynamite in the holes.

The average quantity of excavation per derrick shift of 10 hours, covering 7,400 shifts, 87% of the excavation being rock, was 50 cu. yd., and the average force per shift, including only foreman and laborers, was 13 men.  It was found that a derrick operating at the top of a 20-ft. cut would handle about 40 cu. yd. per shift, whereas, if operating at the bottom of the cut, it would handle about 60 cu. yd. per shift.  The elevator derricks at Tenth Avenue were very efficient, and each could take care of the material from four derricks at the bottom, hoisting 250 cu. yd. per shift a height of 60 ft.