Fig. 1.
PROFILE OF ROCK SURFACES IN THIRTY-FIRST AND THIRTY-THIRD STREETS,
BETWEEN SEVENTH AND NINTH AVENUES]


SEWERS.

The arrangement of the sewers in the streets in the vicinity of the
Terminal Site, previous to the beginning of the construction, and the
drainage area tributary to those sewers, is shown by Fig. 2. The main
sewer for this district was in Eighth Avenue, and was a 6-ft. circular
brick conduit within the Terminal area. The sewers leading to it from
the west, in 31st, 32d, and 33d Streets, were elliptical, 3 by 2 ft.,
and egg-shaped, 4 ft. by 2 ft. 8 in., although in no case did they drain
more than one block, and they were on a heavy grade. Draining into
Eighth Avenue from the east, the one on 31st Street was 4 ft. by 2 ft.
8 in., egg-shaped, and drained a length of two blocks, and those on 32d
and 33d Streets were circular, 4 ft. in diameter, and drained the
territory for three blocks, or as far east as Fifth Avenue. There were
no sewers in Seventh Avenue within the Terminal area, except small
vitrified pipes, each less than 200 ft. in length.

It was desirable that the size and number of the sewers in the streets
and avenues surrounding the Terminal should be reduced to a minimum, on
account of the difficulty of caring for them during construction and
also to reduce the probability of sewage leaking into the underground
portion of the work after its completion. With this in view, the plan
was adopted of building an intercepting sewer down Seventh Avenue from
north of 33d Street to the 30th Street sewer, which, being a 4-ft.
circular conduit, was sufficiently large to carry all the sewage coming