The to-and-fro movement of a dense traffic on a four-track railway requires a large amount of switching, especially when each movement is complicated by junctions of two or more lines. Practically every problem of trunk line train movement, including two, three, and four-track operation, had to be provided for in the switching plants of the subway. Further, the problem was complicated by the restricted clearances and vision attendant upon tunnel construction. It was estimated that the utmost flexibility of operation should be provided for, and also that every movement be certain, quick, and safe.
All of the above, which are referred to in the briefest terms only, demanded that all switching movements should be made through the medium of power-operated interlocking plants. These plants in the subway portions of the line are in all cases electro-pneumatic, while in the elevated portions of the line mechanical interlocking has been, in some cases, provided.
A list of the separate plants installed will be interesting, and is given below:
Location. Interlocking Working Machines. Levers.
MAIN LINE.
City Hall, 3 32 Spring Street, 2 10 14th Street, 2 16 18th Street, 1 4 42d Street, 2 15 72d Street 2 15 96th Street 2 19
WEST SIDE BRANCH.
100th Street, 1 6 103d Street, 1 6 110th Street, 2 12 116th Street, 2 12 Manhattan Viaduct, 1 12 137th Street, 2 17 145th Street, 2 19 Dyckman Street, 1 12 216th Street, 1 14
EAST SIDE BRANCH.
135th Street, 2 6 Lenox Junction, 1 7 145th Street, 1 9 Lenox Avenue Yard, 1 35 Third and Westchester Avenue Junction, 1 13 St. Anna Avenue, 1 24 Freeman Street, 1 12 176th Street, 2 66 ---- ---- Total, 37 393
The total number of signals, both block and interlocking, is as follows:
Home signals, 354 Dwarf signals, 150 Distant signals, 187 ---- Total, 691 Total number of switches, 224
It will be noted that in the case of the City Hall Station three separate plants are required, all of considerable size, and intended for constant use for a multiplicity of movements. It is, perhaps, unnecessary to state that all the mechanism of these important interlocking plants is of the most substantial character and provided with all the necessary safety appliances and means for rapidly setting up the various combinations. The interlocking machines are housed in steel concrete "towers," so that the operators may be properly protected and isolated in the performance of their duties.
CHAPTER X
SUBWAY DRAINAGE
The employment of water-proofing to the exterior surfaces of the masonry sh.e.l.l of the tunnel, which is applied to the masonry, almost without a break along the entire subway construction, has made it unnecessary to provide an extensive system of drains, or sump pits, of any magnitude, for the collection and removal of water from the interior of the tunnel.
On the other hand, however, at each depression or point where water could collect from any cause, such as by leakage through a cable manhole cover or by the breaking of an adjacent water pipe, or the like, a sump pit or drain has been provided for carrying the water away from the interior of the tunnel.
For all locations, where such drains, or sump pits, are located above the line of the adjacent sewer, the carrying of the water away has been easy to accomplish by employing a drain pipe in connection with suitable traps and valves.
In other cases, however, where it is necessary to elevate the water, the problem has been of a different character. In such cases, where possible, at each depression where water is liable to collect, a well, or sump pit, has been constructed just outside the sh.e.l.l of the tunnel. The bottom of the well has been placed lower than the floor of the tunnel, so that the water can flow into the well through a drain connecting to the tunnel.
Each well is then provided with a pumping outfit; but in the case of these wells and in other locations where it is necessary to maintain pumping devices, it has not been possible to employ a uniform design of pumping equipment, as the various locations offer different conditions, each employing apparatus best suited to the requirements.
In no case, except two, is an electric pump employed, as the employment of compressed air was considered more reliable.
The several depressions at which it is necessary to maintain a pumping plant are enumerated as follows:
No. 1--Sump at the lowest point on City Hall Loop.
No. 2--Sump at intersection of Elm and White Streets.
No. 3--Sump at 38th Street in the Murray Hill Tunnel.
No. 4--Sump at intersection of 46th Street and Broadway.
No. 5--Sump at intersection of 116th Street and Lenox Avenue.
No. 6--Sump at intersection of 142d Street and Lenox Avenue.
No. 7--Sump at intersection of 147th Street and Lenox Avenue.
No. 8--Sump at about 144th Street in Harlem River approach.
No. 9--Sump at the center of the Harlem River Tunnel.
No. 10--Sump at intersection of Gerard Avenue and 149th Street.
In addition to the above mentioned sumps, where pumping plants are maintained, it is necessary to maintain pumping plants at the following points:
Location No. 1--At the cable tunnel constructed under the Subway at 23d Street and Fourth Avenue.
Location No. 2--At the sub-subway at 42d Street and Broadway.
Location No. 3--At the portal of the Lenox Avenue extension at 148th Street.
Location No. 4--At the southerly end of the Harlem River tube.
Location No. 5--At the northerly end of the Harlem River tube.
Location No. 6--At the portal at Bergen Avenue and 149th Street.
In the case of the No. 1 sump a direct-connected electric triple-plunger pump is employed, situated in a pump room about 40 feet distant from the sump pit. In the case of Nos. 2, 4, and 7 sumps, automatic air lifts are employed. This apparatus is placed in those sump wells which are not easily accessible, and the air lift was selected for the reason that no moving parts are conveyed in the air-lift construction other than the movable ball float and valve which control the device. The air lift consists of concentric piping extending several feet into the ground below the bottom of the well, and the water is elevated by the air producing a rising column of water of less specific weight than the descending column of water which is in the pipe extending below the bottom of the sump well.
In the case of Nos. 3 and 5 sumps, and for Location No. 1, automatic air-operated ejectors have been employed, for the reason that the conditions did not warrant the employment of air lifts or electric or air-operated pumps.
In the case of Nos. 6, 8, 9, and 10 sumps and for Locations Nos. 2, 4, and 5, air-operated reciprocating pumps will be employed. These pumps will be placed in readily accessible locations, where air lifts could not be used, and this type of pump was selected as being the most reliable device to employ.
In the case of Location No. 3, where provision has to be made to prevent a large amount of yard drainage, during a storm, from entering the tunnel where it descends from the portal, it was considered best to employ large submerged centrifugal pumps, operated by reciprocating air engines. Also for the portal, at Location No. 6, similar centrifugal pumps will be employed, but as compressed air is not available at this point, these pumps will be operated by electric motors.
The air supply to the air-operating pumping devices will be independent from the compressed air line which supplies air to the switch and signal system, but break-down connections will be made between the two systems, so that either system can help the other out in case of emergency.
A special air-compressor plant is located at the 148th Street repair shop, and another plant within the subway at 41st Street, for supplying air to the pumps, within the immediate locality of each compressor plant. For the more remote pumps, air will be supplied by smaller air compressors located within pa.s.senger stations. In one case, for the No. 2 sump, air will be taken from the switch and signal air-compressor plant located at the No. 11 sub-station.
CHAPTER XI
REPAIR AND INSPECTION SHED