by blasted materials. Fig. 3, Plate XLVIII, shows one of these bents filled
with blocking.

All structures being carried on girders "C," which, in turn, were carried
on the sides of the permanent viaduct, the central core was excavated. Fig.
4, Plate XLVIII, and Figs. 1, 2, 3, and 4, Plate XLIX, show various views
of the work at this stage.

The central portion of the viaduct was then erected, and, using concrete
piers and timber bents, all structures were placed on its deck. Fig. 3,
Plate XLIX, shows the piers under the elevated railway columns prior to the
removal of girders "C."

[Illustration: FIG. 6. (Full page image)

GENERAL ARRANGEMENT OF TEMPORARY AND PERMANENT STRUCTURES]

During the latter part of 1908 a 48-in. cast-iron water main was laid by
the city on a cradle built by the Railroad Company on girders "C" on the
east side of the avenue. This is part of the high-pressure system, and the
location and elevation of this water main were taken into consideration
when the underpinning was designed. This main, and the 48-in. cast-iron
sewer bracketed to girders "C," are shown on Fig. 4, Plate XLVIII.

Elevations had been taken on marks on the elevated railway columns
between 30th and 34th Streets at the time the original surveys were made,
in 1902, and these marks were used to test the level of the structure
during the progress of the excavation.

At the extreme south end of the work the procedure was changed. The east