Seventh Avenue to Eighth Avenue. The 20-in. main was relaid from Seventh
Avenue and 31st Street down Seventh Avenue to 30th Street and through
that street to Ninth Avenue. The 16-in. main was relaid from Seventh
Avenue and 32d Street north to 34th Street and through that street to
Eighth Avenue. The service mains in 32d Street were no longer required,
and were taken up and not replaced. The houses on 31st and 33d Streets
were provided with service by two 6-in. wrought-iron mains back of the
retaining walls in each street, that location being chosen to avoid
damage by gas drip to the water-proofing of the street bridges. As the
permanent structures under the avenues were not to approach the surface
nearer than 19 ft., only slight rearrangements, sufficient to permit the
new sewers and water lines to be laid, were necessary.

There were no large water mains to be cared for, in fact, those in the
streets were too small for ample fire protection, being only 6 in. in
diameter. The main in 32d Street was taken up and not replaced, and
those on 31st and 33d Streets were replaced by 12-in. pipes laid back
of the retaining walls. No changes were necessary in the mains in the
avenues, but, before approving the rearrangement for the streets, the
Department of Water Supply, Gas and Electricity added a 48-in. main in
Eighth Avenue to be laid as a part of this construction, the pipe being
supplied by the City.


LOCATION AND DESIGN OF RETAINING WALLS.

The plans, from the earliest stages, contemplated founding the
retaining wall on the surface of the rock, where of suitable quality,
and afterward excavating the rock in front of the toe of the wall
to sub-grade. This plan was definitely adopted soon after the borings