DIFFICULT PIPE WORK—BROADWAY AND 70TH STREET
At 42d Street and Park Avenue the road passes under the Hotel Belmont, which necessitated the use of extra heavy steel girders and foundations for the support of the hotel and reinforced subway station. (See photograph on [page 48].)
Along the east side of Park Row the ascending line of the "loop" was built through the pressroom of the "New York Times" (the older downtown building), and as the excavation was considerably below the bottom of the foundation of the building, great care was necessary to avoid any settlement. Instead of wood sheathing, steel channels were driven and thoroughly braced, and construction proceeded without disturbance of the building, which is very tall.
At 125th Street and Lenox Avenue one of the most complicated network of subsurface structures was encountered. Street surface electric lines with their conduits intersect. On the south side of 125th Street were a 48-inch water main and a 6-inch water main, a 12-inch and two 10-inch gas pipes and a bank of electric light and power ducts. On the north side were a 20-inch water main, one 6-inch, one 10-inch, and one 12-inch gas pipe and two banks of electric ducts. The headroom between the subway roof and the surface of the street was 4.75 feet. It was necessary to relocate the yokes of the street railway tracks on Lenox Avenue so as to bring them directly over the tunnel roof-beams. Between the lower flanges of the roof-beams, for four bents, were laid heavy steel plates well stiffened, and in these troughs were laid four 20-inch pipes, which carried the water of the 48-inch main. (See photograph on [page 49].) Special castings were necessary to make the connections at each end. The smaller pipes and ducts were rearranged and carried over the roof or laid in troughs composed of 3-inch I-beams laid on the lower flanges of the roof-beams. In addition to all the transverse pipes, there were numerous pipes and duct lines to be relaid and rebuilt parallel to the subway and around the station. The change was accomplished without stopping or delaying the street cars. The water mains were shut off for only a few hours.
SPECIAL RIVETED RECTANGULAR WATER PIPE, OVER ROOF OF SUBWAY AT 126TH STREET AND LENOX AVENUE
As has been said, the typical subway near the surface was used for about one-half of the road. Since the sewers were at such a depth as to interfere with the construction of the subway, it meant that the sewers along that half had to be reconstructed. This indicates but very partially the magnitude of the sewer work, however, because nearly as many main sewers had to be reconstructed off the route of the subway as on the route; 7.21 miles of main sewers along the route were reconstructed and 5.13 miles of main sewers off the route. The reason why so many main sewers on streets away from the subway had to be rebuilt, was that, from 42d Street, south, there is a natural ridge, and before the construction of the subway sewers drained to the East River and to the North River from the ridge. The route of the subway was so near to the dividing line that the only way to care for the sewers was, in many instances, to build entirely new outfall sewers.
THREE-TRACK CONCRETE ARCH—117TH STREET AND BROADWAY
A notable example of sewer diversion was at Canal Street, where the flow of the sewer was carried into the East River instead of into the Hudson River, permitting the sewer to be bulkheaded on the west side and continued in use. On the east side a new main sewer was constructed to empty into the East River. The new east-side sewer was built off the route of the subway for over a mile. An interesting feature in the construction was the work at Chatham Square, where a 6-1/2-foot circular brick conduit was built. The conjunction at this point of numerous electric surface car lines, elevated railroad pillars, and enormous vehicular street traffic, made it imperative that the surface of the street should not be disturbed, and the sewer was built by tunneling. This tunneling was through very fine running sand and the section to be excavated was small. To meet these conditions a novel method of construction was used. Interlocked poling boards were employed to support the roof and were driven by lever jacks, somewhat as a shield is driven in the shield system of tunneling. The forward ends of the poling boards were supported by a cantilever beam. The sides and front of the excavation were supported by lagging boards laid flat against and over strips of canvas, which were rolled down as the excavation progressed. The sewer was completed and lined in lengths of from 1 foot to 4-1/2 feet, and at the maximum rate of work about 12 feet of sewer were finished per week.