ts would come, to
prevent the subsidence of the track owing to the sag in the I-beams. As
much excavation, to a depth of about 20 ft., was taken out adjoining the
elevated railway foundations as could be done with safety. Fig. 2, Plate
XLVII, shows this condition of the work. The 48-in. brick sewer was broken,
and the sewage was pumped across the excavation.

The overhead girders "B" were then put in place, and two of the girders "C"
were used as temporary shoring girders at each column. These, as shown by
Fig. 3, Plate XLVII, were placed parallel to the elevated railway, with
blocking between them and the girders "B." Double bents, independent
of each other, were placed under the ends of these temporary shoring
girders, and these were braced securely to prevent possible dislodgment
during the removal of the rock. The weight of the structure was then taken
by jacking up the girders near the bents until the column was lifted off
the old foundation; blocking was put in between the girders and the bents
during the jacking, so that when the jacks were released the base of the
column was still clear of the old foundation. One 80-ton jack was used for
this purpose, and the general method is shown by Fig. 1, Plate LII.

[Illustration: FIG. 4. (Full page image)

METHOD OF EXCAVATING NINTH AVENUE PLAN AND ELEVATION SHOWING VARIOUS STAGES
OF THE WORK]

[Illustration: FIG. 5. (Full page image)

METHOD OF EXCAVATING NINTH AVENUE SECTIONS SHOWING VARIOUS STAGES OF WORK

No. 1

Condition Prior to Commencement of Work

No. 2

East side of Avenue cut down about 20 ft. Beams with Supporting Posts
placed under Surface Railway Tracks. Girders _B_ and Temporary Shoring
Girders _C_ for supporting Elevated Ry. in place.

No. 3

I's in place under Surface Ry. Tracks. Elevated Ry. carried on Temporary
Shoring Girders, and Girders _C_ in place. 24" Water Main carried on Timber
Cradle and sewage carried through Pipe _R_. Foot Walk carried on Girders
_C_ in place on West Side of Avenue.

No. 4

Elevated Railway carried on Bents under Columns. Temporary Shoring Girders
removed and Permanent Bents resting on Girders _C_ in place. Bents in place
on Girders _C_ carrying Surface Railway. East and West sides of Avenue
excavated down to Sub-Grade and Five rows of Permanent Steel in place on
each side. Bents erected on Permanent Steel to catch ends of Girders _C_
while 2 outside Concrete Piers are removed and 6th row of Permanent Steel
o