Part 2

One result of the determination of the Pennsylvania Railroad Company to extend its lines into New York City and thus move its principal station from Jersey City, was that the down-town local and suburban as well as through business was not provided for properly. Mr. William G. McAdoo, appreciating this opportunity, revived the scheme of an electric subway from Jersey City to New York, originally promoted by Mr. Corbin and associates, but not including the extension _via_ Maiden Lane to Brooklyn, and entered into negotiations with the Pennsylvania Railroad Company to provide for this down-town business by extensions of the tunnel lines of the New York and New Jersey Railroads to Exchange Place, Jersey City, under the Pennsylvania Railroad Station, and thence across the Hudson River to Cortlandt and Church Streets. As a result, the Hudson and Manhattan Railroad Company was organized in 1902, and contracts were made with the Pennsylvania Railroad Company for the sub-surface use of its station in Jersey City, and for the interchange of passenger business at that point between the trains of the Pennsylvania Railroad Company and the tunnel of the Hudson and Manhattan Railroad Company. Later, a further contract was made with the Pennsylvania Railroad Company providing for the construction of the tunnel of the Hudson and Manhattan Railroad Company westward under the tracks of the Pennsylvania Railroad in Jersey City to a junction with the latter at Summit Avenue, at which point can be installed a joint station, and the operation effected of a joint electric train service between Church Street, New York City, and Newark, N. J., the Pennsylvania Railroad tracks between Summit Avenue and Newark to be electrified for that purpose, with a transfer station established east of Newark, at Harrison, at which point the steam and electric locomotives will exchange. By means of this, all down-town passengers will transfer to the electric service at Harrison Station, and thus the Pennsylvania Railroad Company is expected to be relieved of maintaining a separate steam service for passenger traffic to Jersey City and a large down-town station with extensive contingent facilities at that point.

From the foregoing it will be seen that the final decision to extend the Pennsylvania Railroad into and through New York City by a system of tunnels, and erect a large station in that city on a most eligible site, was not reached in a hurried or off-hand manner, but after years of painstaking study and a full and extended investigation of all routes, projects, and schemes, whether originating with the company or suggested by others.

Plate VI is a map of New York City and vicinity on which are shown the various lines contemplated in the evolution of the New York Tunnel Extension of the Pennsylvania Railroad hereinbefore outlined.

The question of tunnels under the North River was an uncertain factor in the larger Pennsylvania Railroad scheme, owing to the nature of the ground composing the river bed in which the tunnels would be constructed.

It is well known that about 35 years ago an attempt was made to construct a tunnel under the North River by using a "Pilot" system under compressed air and forming the tunnels in brick masonry. Owing to the very soft nature of the materials through which it passed, several serious accidents occurred, and the work was abandoned after about 2,000 ft. of tunnel had been constructed. Later, this work was taken up again, when a shield was installed and an additional 1,800 ft. was built with cast-iron segmental lining, but the work was again abandoned, owing principally to financial difficulties while coincidentally before entering a rock reef which presented another serious difficulty in construction. The experience then in the construction of this tunnel led capitalists and engineers to believe that, owing to the very soft nature of the ground, a tunnel could not be built that would be sufficiently stable to withstand the vibration due to heavy traffic, and for this reason tunnels under the North River were not looked upon as practicable. The writer devised a scheme to carry within the tunnel the rolling loads on bridging supported on piers or piles extending from the tunnel invert down to hard material. These would be attached to the tunnel itself or would pass into it independently through sliding joints in the tunnel shell. This scheme gained the confidence of the management, as it was believed that, by adopting such a plan, tunnels could be built in the soft material underlying the Hudson River and remain stable under all conditions of traffic. After thus feeling assured that by this method the tunnels could be made safe beyond question, orders were given to proceed with the great work of the extension into New York of the Pennsylvania and Long Island Railroad systems.

The organization of the engineering staff is shown on the diagram, Fig. 1. In the beginning of 1902 and during the period of making studies, additional borings, and preliminary triangulations, and prior to making the contract plans and specifications, James Forgie, M. Am. Soc. C. E., was appointed Chief Assistant Engineer by the writer. To him all the Resident Engineers and other heads of the Engineering Departments reported.

The work was divided into three Residencies:

1.--The Terminal Station-West, under the charge of B. F. Cresson, Jr., M. Am. Soc. C. E., Resident Engineer, comprising the work from the east side of Ninth Avenue to the east side of Tenth Avenue, including excavation, retaining and face walls, and the extensive work of underpinning Ninth Avenue with its surface and elevated railroads and other structures.

2.--The River Tunnels, under the charge of B. H. M. Hewett, M. Am. Soc. C. E., General Resident Engineer, and Mr. H. F. D. Burke and William Lowe Brown, M. Am. Soc. C. E., Resident Engineers, including the land tunnels from the east side of Tenth Avenue, New York City, to the commencement of the iron-lined tunnels, and extending westward from there to the Weehawken Shaft, New Jersey.

3.--The Bergen Hill Tunnels, under the charge of F. Lavis, M. Am. Soc. C. E., Resident Engineer, including the rock tunnels from the Weehawken Shaft to the Hackensack Portal on the west side of the Palisades, all in New Jersey.

Paul A. Seurot, M. Am. Soc. C. E., acted as Office Engineer in charge of the drawing office, and Mr. J. Soderberg as Mechanical Engineer in charge of the mechanical drafting. Prior to the construction of the above works Mr. C. J. Crowley acted as Resident Engineer on the construction of the Weehawken Shaft, and J. F. Rodenbough, Assoc. M. Am. Soc. C. E., on that of the Manhattan Shaft.

Table 1 shows the quantities of certain materials and other statistics regarding this Division.

TABLE 1.

+---------+-----------+---------- | Bergen | River | Term. | Hill. | Tunnels. | Sta.-W. +---------+-----------+---------- | | | Excavation disposed of (or displaced), | | | in cubic yards | 263,000 | 238,995 | 517,000 Cast metal used in tunnel, including | | | cast iron and cast steel, in tons | | 64,265 | Steel bolts used, in tons | | 2,606 | Cement used (concrete and grout), | | | in barrels | 95,000 | 145,500 | 33,000 Concrete, in cubic yards | 95,000 | 75,400 | 18,500 Dynamite for blasting, in pounds | 600,000 | 100,400 | 206,000 Brickwork, in cubic yards | | 4,980 | Structural steel (including Pier 72), | | | in pounds | 50,000 | 3,141,000 | 1,475,000 ------------------------------------------+---------+-----------+----------

The number of passengers carried on the Elevated Railroad and surface lines of Ninth Avenue during the underpinning of these structures was about 125,000,000.

The Board of Engineers, organized by the Pennsylvania Railroad Company in January, 1902, immediately took up the matter of route and grade. The center line, which had been assumed as the center line of 32d Street extended westward, was slightly changed.

The grade adopted was approximately 2% descending westward from Ninth Avenue, which would place the tunnel well below the Government dredging plane of 40 ft. below mean low water at the pier head line; thence westward on a lighter grade still descending until the deepest portion of the river was reached where the top of the rail would be about 90 ft. below mean high water, this location giving sufficient cover over the tunnels to insure stability and guard against the possibility of shipwrecks settling on the tunnels. From this point to the portal an ascending grade of 1.30% was adopted, which gave the lines sufficient elevation to cross over the tracks of the New York, Susquehanna and Western and the Erie Railroads, which run along the westerly base of the Palisades. Owing to the exigencies of construction, these grades in the river were very slightly modified. Plate VII is a plan and profile of the tunnels as constructed.

The Board of Engineers early in 1902 took up the question of supports for the tunnels under the North River, and various plans and schemes were considered. It was finally decided to support the tracks on screw-piles carried through the lining of the tunnels, as originally proposed by the writer.

In order to know something of the capacity of screw-piles in the actual material to be passed through, it was resolved to test them. A caisson was sunk at the end of one of the Erie Railroad piers on the New Jersey side near the line of the tunnels, and, to obtain parallel conditions as much as possible, the excavation was carried down to the proposed grade of the tunnel. Various types of screw-piles were sunk therein and tests were made, not only of the dead load carrying capacity, but also with the addition of impact, when it was found that screw-piles could be sunk to hard ground and carry the required load. The final part of the test was the loading. The screw-pile, having a shaft 30 in. in diameter and a blade 5 ft. in diameter, was loaded with 600,000 lb., with the result that, for a month--the duration of this loaded test--there was no subsidence.

Again, and after the iron tunnel lining had been constructed across the river, tests were made of two types of supports: One a screw-pile 29-1/2 in. in diameter with a blade 4 ft. 8 in. in diameter and the other a wrought-iron pipe 16 in. in external diameter. Tests were made, not only for their carrying capacity, but also for their value as anchorages, and it was found that the screw-pile was more satisfactory in every way; it could be put down much more rapidly, it was more easily maintained in a vertical position, and it could carry satisfactorily any load which could be placed on it as a support for the track. The 16-in. pipe did not prove efficient either as a carrier or as an anchorage. These tests will be mentioned in the detailed description of the work to follow. Figs. 2 and 3 illustrate the general arrangement and details of the machine designed by the writer and used for sinking the test piles in the tunnels. This machine had been used originally on the New Jersey side on the test pile at Pier C, and the adaption was not exactly as shown on these drawings, but if the screw-piles had been placed in the tunnels, the arrangement shown would have been used.

Surveys, soundings, and borings were commenced in the latter part of 1901 on an assumed center line of tunnels which was the center line of 32d Street extended westward.

The soundings were made from a float stage fastened to a tugboat, the location being determined by transits on shore and the elevation by measuring from the surface of the water, a tide gauge being continually observed and the time of soundings and gauge readings kept.

In the river wash-borings were made from a floating pile-driver on which was installed a diamond-drill outfit of rods, pump, etc. Fourteen borings were completed in the river. Considerable difficulty was found in holding the pile-driver against the current, the material in the bottom being very soft, and several borings were lost owing to the drifting of the pile-driver. Each boring was continued, and the depth of several was more than 250 ft. below the surface of the water. The borings on land were mostly core borings, and were generally made with the chilled shot boring machine.

Base lines, about 2,250 ft. in length, were measured on each side of the river, and observation points established. It was necessary to build a triangulation tower 60 ft. high on the New Jersey side as an observation point. The base lines were measured with 100-ft. steel tapes which were tested repeatedly, and the work was done at night in order to obtain the benefit of uniform temperature and freedom from traffic interruptions. From the base line on the New Jersey side, which passed over the Weehawken Shaft, an elevated point on the assumed center line on the side of Bergen Hill was triangulated to, and from this point westward a closed polygon was measured along the streets to the top of the hill on the west side and thence along the assumed center line to the portal. The level transfer across the river was made by sighting across in opposite directions simultaneously, and also by tide gauges. The outline of the final triangulation system is shown on Plate VII.

The decision as to the locations of the shafts on both sides of the river, for construction purposes and finally for permanent use, was a comparatively simple matter, and, all circumstances considered, they are unquestionably in the most suitable places. On the New York side the shaft was as near as practicable to the line dividing the subaqueous iron-lined tunnels from the land tunnels, and on the New Jersey side the shaft was placed centrally on the line of the tunnels and on the nearest available ground to the river, while at the same time beyond the other end of the river tunnels, thus necessitating driving the subaqueous tunnels only from east and west to meet under the river. A caisson shaft on the New York side, on the line of the tunnels near the river bulkhead, was at one time considered, but was not adopted as it entailed the driving of two shields both east and west, in addition to the two from New Jersey, adding to the plant outlay while not affording any material saving in the time of construction.

It was thought desirable to construct the shafts on the two sides of the river in advance of letting the main contracts for the tunnels. The Manhattan Shaft is north of the line of the tunnels, on the north side of 32d Street, east of Eleventh Avenue. The Weehawken Shaft is on the line of the tunnels in the yards of the Erie Railroad on the New Jersey side, and the distance between the shafts is about 6,575 ft. The contracts for these shafts were let in June, 1903, to the United Engineering and Contracting Company, and they were completed and ready for use at the time of letting the main contract for the tunnels, thus saving considerable time.

_The Terminal Station-West.--Between Ninth and Tenth Avenues._--In the original design it was contemplated to have a four-track tunnel under 32d Street from Ninth to Eleventh Avenues, but owing to the necessity for having additional yard facilities, property was bought for about 100 ft. north and 100 ft. south of 32d Street, between Ninth and Tenth Avenues, and an open excavation, lined with concrete retaining walls and face walls, was made. Between Ninth and Tenth Avenues, 32d Street was closed, and the property formerly the street was bought by the Tunnel Company from the City of New York for a consideration by deed dated April 18th, 1906. The Church, Rectory, and School of St. Michael's, which was located on the west side of Ninth Avenue between 31st and 32d Streets, was acquired by the Tunnel Company after it had acquired property for and had built a similar institution on the south side of 34th Street west of Ninth Avenue.

Probably the most interesting feature of this contract was the support and maintenance of Ninth Avenue, which has a three-track elevated railway structure and a two-track surface railway structure, on which it was necessary to maintain traffic while excavation was made to a depth of about 60 ft., and a viaduct was erected to carry Ninth Avenue. The length of this viaduct is about 375 ft., and the steelwork and its erection was done apart from the North River Division work, but all excavation and underpinning was included in this division. The contract for this work on the Terminal Station-West was let to the New York Contracting Company-Pennsylvania Terminal, on April 28th, 1906, and included about 517,000 cu. yd. of excavation, about 87% being rock, the construction of about 2,000 lin. ft. of retaining and face walls containing about 18,500 cu. yd. of concrete, and a large quantity of structural steel (1,475,000 lb.) for temporary use in underpinning Ninth Avenue.

Fig. 4 shows cross-sections of the Terminal Station-West yard, and Fig. 5 shows the general method of underpinning the Ninth Avenue structures.

_River Tunnels._--In the original plan a four-track tunnel was contemplated from the east side of Tenth Avenue to the east side of Eleventh Avenue, but, owing to the extension of the Terminal Yard, previously noted, this plan was changed, and a two-track structure was built having a central wall between the tracks. This was constructed in tunnel, with the exception of 172 ft. about midway between Tenth and Eleventh Avenues, where the rock dipped below the roof of the tunnel, and there the construction was made in open cut. These tunnels were lined with concrete with brick arches, Figs. 6, 7, and 8 being typical cross-sections. This work was executed by the O'Rourke Engineering Construction Company, under a contract dated November 1st, 1904.

It was possible to excavate in full rock cover about 250 ft. of the tunnels eastward from the Weehawken Shaft and 225 ft. westward from the Manhattan Shaft. At these points the rock cover was very thin, and there shield chambers were made for the erection of two sets of shields, about 6,100 ft. apart. A typical cross-section of the Weehawken Land Tunnel is shown on Plate VIII.

The Board of Engineers decided, and it was so stated in the contract and specifications, that the river tunnels should be constructed by means of hydraulic shields, but bidders were permitted to present to the Board any scheme on which they might desire to bid, but, of course, the decision as to the practicability of such plans rested with the Board.