Jay-Smith Street and Fulton Street Subway (1934)
Municipal Engineers of the City of New York · Paper No. 173.
The Planning of Portions of the New York Independent City-Owned Rapid Transit System: The Jay- Smith Street Subway and Part of the Fulton Street Subway in the Borough of Brooklyn
By Alfred Brahdy, M.M.E.N.Y. Designing Engineer, Board of Transportation, New York City. Presented April 25, 1934. With discussion by Robert Ridgway, Aaron I. Raisman, Morris Serating, Jr., Arthur C. Forbes, Rudolph P. Smith, Harry D. Winsor, Kenneth Mott, and the author.
The portion of the "Independent City-Owned Rapid Transit System" built in the Borough of Brooklyn consists of three subway routes, divided into twenty contract sections. Five of these contract sections, three along Jay and Smith streets and two along Fulton street, will be described to illustrate some of the problems that had to be solved in designing subways for the Borough of Brooklyn. Bids for the first of these contract sections were received in September, 1927. The construction of these subways has been completed and trains are now being operated under Jay and Smith streets. The contractors on the work being described were:
|Route||Section||Contractor||Bid Price||Linear Feet of Track|
|109||1||Carleton Company, Inc.||$3,800,000||8,500|
|109||2||Rosenthal Eng. Cont. Co., Inc.||4,900,000||12,500|
|109||2-A||Rodgers & Hagerty, Inc.||3,200,000||12,100|
|110||5||Necaro Company, Inc.||4,300,000||13,600|
As a preliminary step to subway construction, various possible routes are investigated and one of these is legalized in accordance with the provisions of the Rapid Transit Act. With the completion of this phase of the project, the engineering work proceeds in successive stages to the ultimate operation of trains. Base-line surveys, details of surface topography, data on subsurface structures, borings, and information regarding building foundations, obtained and recorded by the field engineers, form the basic data for the planning of a subway. The designing engineers use this data to lay out a preliminary alignment, a profile, and to locate the stations. This is followed by studies to determine the type of structure best suited for the conditions encountered. Sometimes, the structural studies change the preliminary scheme and thus, by a series of adjustments, the final plan for the contract drawings is developed.
Click to enlarge.
The contract drawings for a subway section consist of track-alignment plans, structural drawings, sewer drawings, drainage plans, ventilation drawings, and architectural plans. Based on these contract drawings, an engineer's estimate of the quantities for all items of the work is prepared.
Lithographed copies of the contract drawings, the specifications, the engineer's estimate, and blueprints of the field data previously mentioned, are available to intending bidders to enable them to determine upon unit prices for each item of the work. From the quantities of the engineer's estimate and the prices bid for each item, totals are determined which form the basis for the award of a contract by the Board of Transportation.
Comparison of the first subway (1900) and of the Independent system (1925). Courtesy of "Civil Engineering." (Click to enlarge.)
For the more convenient preparation of working drawings for construction, a subway contract section is divided into a number of subsections, each several hundred feet in length. The working drawings are detailed amplifications of the contract drawings. The sequence and the time of issuing these drawings for each subsection are determined from a study of the most likely procedure in the construction operations. The structural drawings issued to the contractor are also used as a basis for the preparation of shop details by the subcontractor furnishing the steel.
Along tangents, the tracks are spaced 13 feet 6 inches center to center, this distance being increased varying amounts along curves to allow adequate clearances for center excess, end excess, and excess due to super-elevation. The inside dimensions of the subway structure are based on cars 60 feet 0 inches by 10 feet 0 inches with a truck spacing of 44 feet 7 inches, and having a height of 12 feet 2 inches above the top of rail. A height of 13 feet 2 inches from base of rail to the underside of the roof is maintained throughout, as the parabolic vertical curves used at the intersections of grades require so little additional height that this factor can be neglected for practical purposes. A trough extending 1 foot 2 inches below the base of rail and 10 feet 8 inches wide is provided for track installation.
The subway roof is designed to carry a dead load of 100 pounds per square foot for each foot of depth, measured from the underside of the roof to the crown of the street. The difference in weight between earth and the structural materials of the roof is compensated for by the hollow spaces of the jack arches. The live load is assumed to be 600 pounds per square foot of surface area. The minimum total dead and live load on a subway roof is taken at 1,500 pounds per square foot, and where the depth from the street surface is less than five feet, the structure is analyzed for concentrations due to heavy truck loads. Sidewall columns are designed for a combination of horizontal pressures and vertical loads.
Where the subgrade of the subway is below groundwater the floor is of reinforced concrete or steel, designed to distribute the dead load uniformly on the soil under the entire width of the structure. Above groundwater the loads of interior and sidewall columns are transmitted to the underlying soil by the concrete track benches or by footings, and a 12-inch thick concrete floor is used for the trackways.
The basic tensile stress for structural steel and for reinforcing rods is 20,000 pounds per square inch. Reinforced concrete was designed for a maximum compression of 600 pounds per square inch prior to 1930, when the allowable stress was increased to 850 pounds per square inch. This increased stress was adopted as a result of tests conducted by the Materials Inspection Division of the Board of Transportation on concrete used for subway work.
Columns of elevated railroads, where encountered, are temporarily underpinned during excavation and construction and are ultimately supported on the roof of the subway. The portions of the subway structure supporting elevated railroad columns are designed to conform to the loads, specifications, and stresses of the elevated railroad.
In order to obtain the maximum resale value for property acquired where the subway extends inside of the building lines, the structure is designed to support buildings of six to thirty stories in height, the type of development provided for depending on the value of the land and its probable use. Where located within private property, the subway is designed in accordance with the requirements of the Building Code of the City of New York.
Type of Structure
For subway structures built in excavation from the street surface, the frame-work consists of steel beam-and-column bents spaced five feet on centers. This uniform spacing of the steel bents, while not always theoretically economical, standardizes the timbering of the excavation and it also permits the re-use of forms for concreting to the greatest possible extent. Steel bents have an advantage over reinforced concrete in that they can be erected in small groups, and utilized to support street loads or brace the sides of the excavation as soon as they are erected. At platforms and at mezzanines of stations the interior columns are spaced 15 feet apart parallel to the center line of the structure. These columns support longitudinal members which in turn carry the intermediate 5-foot bents.
The entire roof of the subway is covered with waterproofing, protected by a layer of concrete. The waterproofing of the sidewalls and of the floor depend on local conditions.
Mezzanines are provided at all island platform stations and also at side-platform stations where this can be done at little additional expense. Access from the street to the side-platforms via a mezzanine reduces operating costs, because a single control can then be used instead of the separate controls that would otherwise be required for each platform. At important street intersections four station entrance stairways, one at each corner, are provided, while at other streets only two stairways are built with provisions for additional street entrances should traffic warrant their construction in the future. Frequently, arrangements are made for entrances through buildings which adjoin subway stations.
Platforms at stations were in most cases built 600 feet long to accommodate ten cars, as it is planned to operate 10-car trains until the traffic warrants the use of 11-car trains. Where it would be difficult or expensive to extend the platforms to their ultimate length in the future, the subway was built to provide 660-foot long platforms as part of the original structure.
Adjacent to express stations, at junctions to branch lines, at storage yards and at other locations where required, the plans provide spaces for crossovers. These crossovers are for the sorting out of trains to the various branch lines of the system, for short line or emergency operation, and for taking trains in and out of storage yards. At some locations crossovers to lay-up tracks are provided so that a bad order train may be taken off the running tracks with a minimum interruption to train operation.
Auxiliary structures are required for ventilation, for drainage, for emergency exits, for the supply of power, for operating and maintenance crews, and for the signal system. While these auxiliary structures do not involve engineering problems of the magnitude encountered in the planning of the main subway structure, they call for careful studies of the requirements and details in order that they may best serve their respective purposes.
Ventilation flues constructed of reinforced concrete connect the subway to sidewalk outlets which are covered with gratings. These flues and gratings are so proportioned that the piston action of the trains will renew the air in the subway every fifteen minutes at a velocity of 100 feet per minute. Longitudinal walls along the center of the subway and automatic louvers at the gratings serve to increase the effectiveness of this system of ventilation. Ventilation gratings are also located at the approaches to stations so as to relieve the air pressure caused by incoming trains and thus prevent to a great extent unpleasant drafts at the platforms of stations.
Sump and pump chamber. (Click to enlarge.)
Fan chambers placed midway between stations provide auxiliary mechanical exhaust ventilation through gratings at the sidewalks. The fan chambers are located alongside or on top of the subway, depending on the conditions encountered, and they are designed of structural-steel frames similar to the main subway structure. The fan chamber equipment for the entire subway system is operated from a central control station.
Seepage or surface water finding its way into the subway is drained along the track trough or through pipes to sumps located at low points of the subway. The average capacity of a sump below its inlet is 5,000 gallons. The usual equipment of a pump room for a sump consists of two automatically operated motor-driven pumps, one of 100 gallons per minute capacity for normal operation and a 500 gallons per minute pump for emergencies.
Emergency exits leading from the trackways to nearby sidewalks are located midway between stations. Trap doors which are counter-weighted so that they can be easily opened from within, cover the sidewalk openings of the emergency exits. These emergency exits are generally built of reinforced concrete.
Twenty or thirty ducts for signal and power cables are located in benches inside of the sidewalls. Manholes are constructed about 350 feet apart for the installation of cables in the duct lines. The cables are drawn in from the street through a chimney 2 feet 8 inches in diameter, or through a 10-inch pipe. The manholes are accessible from the subway through sliding doors.
Power for operation of the Brooklyn portion of the subway system is supplied by the high-tension network of the Edison Company through 3,000 k. w. mercury are rectifiers, located about 0.5 miles apart along the subway. Underground chambers 50 feet by 20 feet in plan and from 15 to 18 feet in height are required to house the rectifiers with their transformers and other accessory apparatus. The rectifier chambers are provided with two exits and with ventilation to the street. A 10-foot by 15-foot section of the roof over the rectifier chamber is designed to be readily removable for replacing the larger units of the equipment. All rectifiers are controlled from a supervisory board located in a central location.
After the subway structure is completed, dispatchers' offices, signal towers, compressor rooms, and quarters for maintenance crews are provided by partitions within the structure. These rooms are built under station finish contracts in accordance with architectural plans prepared for that purpose.
Topography and Geology
Jay Street is a 60-foot wide north-to-south thoroughfare extending from the East River to Fulton Street. Smith Street is a continuation of Jay Street south of Fulton Street. Along the 1.5 miles of Jay and Smith Streets occupied by the subway, the surface elevations vary considerably. There are three summits, at Concord Street, at Fulton Street, and at Second Street, with corresponding valley lines at the East River, at Tillary Street, at Wyckoff Street, and at the Gowanus Canal.
Fulton Street is 80 feet wide and is one of the main thoroughfares radiating from the Brooklyn Borough Hall district. Along the part of the Fulton Street subway here described, the street surface is fairly level at Elevation 150 for 0.5 miles up to Buffalo Avenue. In the next three-quarters of a mile to the east, the street surface rises 50 feet and attains Elevation 200 at Rockaway Avenue. Elevations are referred to a datum 100 feet below mean high water of New York Bay.
The soil in the territory traversed by these two subway routes is a glacial deposit of sand, clay, gravel and boulders. Ledge-rock is not encountered on any portion of the Brooklyn subway work.
The Jay-Smith Street Subway
The four-track Jay-Smith Street subway is part of the Brooklyn trunk line of the new rapid transit railroad system. It begins at the junction of two pairs of single-track river tunnels from Manhattan. Two tracks from downtown Manhattan turn into Jay Street at High Street on 650-foot radius curves, eased with 200-foot long transitions, and continue as the two middle tracks of the four-track line through the Jay Street-Borough Hall station. The two other tracks from Rutgers Street, Manhattan, reach Brooklyn at the foot of Jay Street and rise on a 3-per-cent grade to form the two outside tracks of the four-track single-level structure to the south. At the Jay Street-Borough Hall station the tracks are spread for two island platforms which are 28 feet wide and 660 feet long. Along the southerly portion of this station the tracks are on a 2-per-cent grade which is unusual at platforms, but was necessary in this instance because within 200 feet the subway passes first over the BMT tunnels in Willoughby street and then under the IRT subway in Fulton Street. This subway connects at Schermerhorn and Smith Streets with the Fulton Street (Brooklyn) subway, which extends easterly from this junction to Rockaway Avenue and Fulton Street.
Crossing under existing IRT structure at Fulton Street. (Click to enlarge.)
South of Schermerhorn Street the subway becomes a double-deck structure with two tracks on each level. The double-deck profile is maintained through the Bergen Street station and for half a mile beyond, as Smith Street is only 60 feet wide. At the approach to the Carroll Street station, property was acquired and the upper-level tracks are spread out so that the two lower-level tracks can rise on a 3-per-cent grade until all four tracks are on the same level. From the junction of the grades, the four tracks continue through an open cut and on an embankment to the abutment of the only elevated structure along the Independent System. This elevated structure forms the approach to a bridge crossing over the Gowanus canal.
Station at Carroll and Smith Streets. Buildings to rest on roof of subway. (Click to enlarge.)
Structural Features of the Jay-Smith Street Subway
The profile necessary to connect with the river tunnels, combined with high street elevations, resulted in the excavation for the subway having a maximum depth of 65 feet at Concord and Jay Streets. Due to this great depth, there are roof loads up to 3,600 pounds per square foot and pressures on the sidewalks up to 1,500 pounds per square foot.
At three locations along the Jay-Smith Street subway, property was acquired because the subway extends beyond the street line. At the High Street-Jay Street curve and at the Carroll Street station the subway structure within the property lines was designed to support building loads of 3,500 pounds per square foot on the roof. Within property acquired at the Jay Street station, the design of the subway provides for the support of 140 columns for future buildings having loads varying from 400 to 500 tons per column. Grillages to carry the bases of the building columns were incorporated in the subway roof.
Plan and profile of the Jay-Smith Street Subway. (Click to enlarge.)
At the southwest corner of Fulton and Smith Streets the subway passes under a 6-story building which is used for a high-grade retail store and fur storage plant. The building is unusual in that, although it is 50 feet wide, it has no interior columns on the ground floor, resulting in heavy loads along the building and lot lines. In order to reduce real estate damages, an agreement for an easement was made with the owners of this property, which provided that the building be retained in place and maintained in operation above the street level while the subway was being constructed under it. The subway plans provided for the maintenance of this building during construction, for the permanent support of the building on the subway roof, and also for loads which will permit the erection of a higher building in the future.
Four track subway constructed under six-story Balch Price Building. (Click to enlarge.)
A portion of the Jay Street station is immediately above the two cast-iron tunnels in Willoughby street, previously mentioned, in which trains of the BMT system are being operated. In order to protect the tunnels against any possible settlement of the Jay Street subway, 276 14-inch sectional steel shell piles, each designed for a load of 40 tons, were provided adjacent to these tunnels, to support the Jay Street subway.
The four tracks and two station entrance passageways of the subway are under the four-track IRT subway in Fulton Street. The IRT subway, in which trains are operating, supports the street surface with trolley cars and an elevated railroad structure. At this crossing, the Jay Street subway is 120 feet wide and the structure was so designed that it could be built in narrow drifts. This reduced the construction hazard due to the already existing subway in Fulton Street.
The double-deck Bergen Street station, although planned to be as close to the street as subsurface utilities permitted, has a depth of 45 feet, of which 25 feet is in ground water. Because Smith Street is only 60 feet wide, the station structure occupies the entire width of the street and the station entrances, as well as the stairways connecting the upper and lower platforms, were located in the three cross streets along this station.
At Degraw street, the Smith Street subway crosses over a 12-foot circular brick-lined tunnel which supplies water for flushing the Gowanus Canal. At this location the double-deck subway structure is supported on spread footings adjacent to and encasing the upper half of the tunnel. The portal of the subway is at Second Place, south of the Carroll Street station. The earth alongside the open cut beyond the portal is retained by L-shaped reinforced-concrete walls and similar walls hold the embankment in place where the tracks are above ground.
Fulton Street Subway
The four tracks of the Fulton Street subway spread out east of Lewis Avenue for the two 28-foot wide and 660-foot long island platforms of the Utica Avenue station. At Utica Avenue the base of rail is 44 feet below the street surface in order to provide room above for a future subway. Between the Utica Avenue and Ralph Avenue stations the subway had to be at a depth sufficient to allow room for sewers above the subway. This depth resulted in roof loads up to 21,800 pounds per square foot and correspondingly heavy pressures on the sidewalls of the subway. From east of Ralph Avenue to Rockaway Avenue, grades of two and three per cent are used to follow the rising street surface of Fulton Street.
The future Utica Avenue subway will cross diagonally over the Fulton Street subway and the portion of the future line located above the Utica Avenue station was built together with the Fulton Street line. The depth required on account of the future subway in Utica Avenue increased the normal vertical distances of 10 feet from the mezzanine floor to the platforms to 25 feet and ramps were built instead of stairs for the more convenient access from the mezzanine to the platforms.
Station at Utica Avenue and Fulton Street. (Click to enlarge.)
The Fulton Street elevated railroad is supported on columns spaced 45 feet apart alongside the curb. The maximum load on an elevated column is 375 tons, the average being 200 tons per column. Three hundred of these elevated railroad columns had to be supported on the subway structure described.
In excavating pits for the temporary support of the elevated railroad columns east of Ralph Avenue water was encountered. In some of the pits the water was as high as Elevation 192, ninety-two feet above tide level, while others were entirely dry. The water frequently disappeared as the excavation of a pit progressed. Chemical analysis showed that ground water and not leakage from water mains or sewers was being encountered. Plans to meet this situation were prepared on the theory, verified during the subsequent excavation for the subway, that the ground water was retained by strata of clay which formed water-tight bottoms for pools of water. The sidewalls were strengthened by placing additional I-beam columns midway in the normal 5-foot bays, and for the track floor a reinforced-concrete slab was designed to resist upward water pressure. Where wet ground of low bearing power was encountered, piles were used at the footings of the subway columns supporting the elevated railroad.
At the Ralph Avenue station the bottom of the subway excavation was in a stratum of clay which extended only a few feet below the subgrade to coarse sand capable of draining off water. By excavating longitudinal ditches through the clay to the underlying sand and backfilling with coarse sand, drainage was provided for the ground water and the possibility of building up a head of water at the track floor was eliminated. The reinforcing of the track floor for water pressure was dispensed with, where drainage by stripping the clay as described was more economical.
Draining clay subsoil to underlying sand stratum, Fulton Street subway. (Click to enlarge.)
The Jay-Smith Street subway and the Fulton Street subway are part of the 55-mile long Independent System, which was built and 30 miles of which are now being operated by the Board of Transportation of the City of New York. Chairman John H. Delaney and Commissioners Daniel L. Ryan and Francis X. Sullivan comprised the Board of Transportation up to December 1933 when Commissioner Ryan retired and was succeeded by Mr. Charles V. Halley. Mr. Robert Ridgway, M.M.E.N.Y., was Chief Engineer of the Board of Transportation until his recent retirement, when he was succeeded by Mr. Jesse B. Snow. The plans were prepared under the direction of Mr. Aaron I. Raisman, M.M.E.N.Y. Chief Designing Engineer. The several divisions of the Engineering Department engaged in the planning and construction of these subways were in charge of Division Engineers Charles E. Conover, John H. Myers, Jesse O. Shipman, and George L. Lucas, Members of The Municipal Engineers of The City of New York.
[Photographs accompanying this article were not of high enough quality after photocopying and were omitted.]