The drilling necessary to remove the rock was very large in amount and
also per yard excavated. In order not to damage the retaining walls and
the rock underlying them, holes spaced at 5-in. centers were drilled
1 ft. away from the face of the walls and on the same batter. These
breaking holes alone amounted to a total of 210,000 lin. ft., or 1 ft.
of hole for each 3½ cu. yd. of rock excavated; and the regulations of
the Bureau of Combustibles, which prevented springing, caused the
blasting holes to be placed very close together and required a total of
about 420,000 lin. ft., making 630,000 ft. If to this is added the block
holes, for some of the rock broke very large, it will show at least
1 ft. of drill hole for each cubic yard of rock excavated, about ten
times the average on general railroad work.

[Transcriber's Note:
The three numbered Tables were originally printed at full width, with
columns (1)-(13) displayed in a single row.]

TABLE 1a.--Record of Retaining-Wall Sections, Terminal Station.

West Thirty-first Street from Seventh Avenue to Ninth Avenue.

(1) Section No.
(2) Stations.
(3) Contents of section, in cubic yards.
(4) Barrels of cement used for facing.
(5) Cubic yards of facing mortar equivalent.
(6) Barrels of cement used for bed mortar.
(7) Cubic yards of bed mortar equivalent.
(8) Cubic yards of embedded stone.