It was originally
intended to do all the work of construction from these four shafts.
Workings were started both east and west from the Intermediate Shafts,
and those to the west were to be continued to the Terminal Station.
After the change of plans, described in a previous paper, it was decided
to sink a third shaft on each line. These were known as the West Shafts,
and were located between Sixth and Seventh Avenues. Finally, it was
found necessary to build a portion of the tunnels on each line west of
Sixth Avenue in open cut. The locations of the shafts are shown on Plate
XIV.[C]
The First Avenue shafts were built by S. Pearson and Son, Inc., for the
joint use of the two contractors, as described in the paper on the
tunnels under the East River. While the shafts were being sunk, the
full-sized tunnels were excavated westward by the contractor for the
river tunnels for a distance of 50 ft., and top headings for 50 ft.
farther. By this means, injury to the caissons and to the contractor's
plant in the shafts by the subsequent work in the Cross-Town Tunnels was
avoided. The west half of the shaft was for the exclusive use of the
contractor for the Cross-Town Tunnels.
CONTRACTOR'S PLANT.
The method of handling the work adopted by the contractor was, broadly
speaking, as follows: Excavation was usually carried on by modifications
of the top-heading and bench method, the bench being carried as close to
the face as possible in order to allow the muck from the heading to be
blasted over the bench into the full section.
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