A large
number of pumps were used at various points on the work, and practically
all were of Cameron make, the largest ones at the shaft being 10 by 5 by
13-in. The grout machines were of the vertical-cylinder, air-stirring
type.
SHAFT SINKING.
The sinking of the Intermediate Shafts was the first work undertaken by
the contractor.
The 33d Street Shaft was 34.5 ft. long, 21 ft. wide, and 83 ft. deep.
The rock surface averaged 5 ft. below the ground surface. Sinking was
started on July 10th, 1905, and was completed on October 3d, 1905, the
rock being hard and dry. The average daily rate was 0.73 ft. and an
average of 17.1 cu. yd. were excavated per day, with two shifts of 8 hr.
each. The first shift started at 6 A. M. and the second at 2.30 P. M.,
ending at 11 P. M. These hours were adopted in order to avoid undue
disturbance during the night.
[Illustration: PLATE LIX, FIG. 1.--AIR-OPERATED STEAM SHOVEL USED IN
TUNNEL.]
[Illustration: PLATE LIX, FIG. 2.--TIMBERING IN TOP HEADINGS ABOVE
I-BEAMS.]
[Illustration: PLATE LIX, FIG. 3.--FIRST SECTION OF CONCRETE LINING AT
FIFTH AVENUE.]
[Illustration: PLATE LIX, FIG. 4.--TIMBERING AND RUBBLE MASONRY OVER
I-BEAMS.]
Before blasting the first lift of rock, channel cuts 5 or 6 ft. deep
were made along the sides of the shaft, in order to avoid damage to the
walls of neighboring buildings.
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