The New York Rapid-transit Subway

Proceedings.] PARSONS ON NEW YORK RAPID-TRANSIT SUBWAY. 35 The electric conduits of the surface tramways, like the elevated columns, could not be removed, but had to be carried in place during construction and left after construction in the same place that they originally occupied. The yokes are of cast iron, or in the more recent forms of steel members, set as a rule 5 feet apart, and encased in concrete. As it was necessary that these yokes should be given a firm support, and as the earth which was filled on the roof on top of the subway could not be counted on to give such support during the time required for its completion, it was decided to place the yokes on a masonry foundation consisting of small piers built beneath the yokes down to the roof of the subway. The problem of handling the water-mains and gas-pipes was practi- cally similar, and they may therefore be treated as one. These pipes differed from the elevated foundations and the trolley-conduits in that they could be removed during construction, could be given a different position after construction,and, if necessary, could be changed in form. In the laying of pipes in New York it is unfortunate that no systematic arrangement has been followed. In fact, in the older parts of the city even the records are incomplete, and it became necessary for the engineers of the commission to make an investiga- tion along the route in order to determine as nearly as possible what might be expected beneath the surface. In main thoroughfares the water- and gas-pipes, varying in size up to 48 inches in diameter, lie in a perfect tangle. A pipe which is on top at one point may be below other pipes at another, and pipes frequently cross to the other side of the street in order to secure a location or avoid previously-constructed obstructions. The result is that the mass of pipes and other conduits, exclusive of sewers, occupies a depth of about 6 feet. The earlier work indicated that the most serious limit to rapidity of construction would be the time required to readjust the sub-surface structures. At points badly congested by sub-surface structures the difficulty at times was avoided by depressing the subway-roof so as to clear the structures above. In other cases this was not possible, as the lowering of the structure would have caused a more serious interference with drainage problems. A typical case was that shown at 23rd Street and Fourth Avenue, where, in addition to the sewers, there were found in Fourth Avenue north of 23rd Street, on the east side seventeen different lines, and on the west side eighteen, witli all the necessary manholes and valve-boxes, and, in addition, the crossing and a junction at the street intersection of two double-track surface tram- ways. Some of tliese mains ran through ; others turned from one street to the other: all were in service and all had to be maintained. D 2