oothly-worn rock and well-rounded boulders. The original stream,
however, seemed to have turned in a westerly direction under 31st Street
to Eighth Avenue instead of crossing, as shown on General Viele's map.

[Illustration:
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
from east of Seventh Avenue and south of 34th Street. It was decided to
build this sewer of cast iron where it crossed the proposed construction
work, and also to replace with cast iron the brick sewers on 31st, 32d,
and 33d Streets from Seventh Avenue to a point east of the west end of
the standard tunnel section, and also the sewer on Eighth Avenue from
the north side of 33d Street to the south side of 31st Street. This
arrangement permitted: first, the removal of the sewer in 32d Street
between Seventh and Eighth Avenues, which was necessary, as that street
was to be excava