Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 The Site of the Terminal Station. Paper No. 1157
The larger illustrations are shown as thumbnails linked to thefull-size version.
AMERICAN SOCIETY OF CIVIL ENGINEERS
Paper No. 1157
THE NEW YORK TUNNEL EXTENSION OF THE
THE SITE OF THE TERMINALSTATION.1
By George C. Clarke, M. Am. Soc. C. E.
The purpose of this paper is to describe the preliminary work for andthe preparation of that portion of the site for the Terminal Station inManhattan, of the New York Tunnel Extension of the PennsylvaniaRailroad, which was constructed under the direction of the ChiefEngineer of the East River Division, including the disposal of materialexcavated from all parts of the Terminal construction and the tunnels onthe East River Division.
As outlined in the paper by Brigadier-General Charles W. Raymond,M. Am. Soc. C. E., Chairman of the Board of Engineers,the track yard ofthe station, Plate LIII, extends fromthe east line of Tenth Avenue eastward to points in 32d and 33d Streets,respectively, 292 and 502 ft. east of the west line of Seventh Avenue.The width of the available area at track level at Tenth Avenue is 213ft., continuing at this width to within 182 ft. of the west line ofNinth Avenue, where, by an offset toward the south, it is increased to355 ft. This width is held to a point 5 ft. east of the east line ofNinth Avenue, where, by an offset toward the north, it is increased to509 ft., which width continues to the west line of Seventh Avenue, whereit divides into two fan-shaped areas. The north area has a width ofabout 170341 ft. and the south one, 160 ft., at the house line, each area taperinggradually to the width of the standard three-track tunnel at the eastends, noted above in 33d and 32d Streets. Additional track room for fourtail-tracks is gained by the construction of two double-track tunnelsunder Ninth Avenue at 33d Street, their center lines being parallel tothe street and 45.5 and 84.5 ft. distant, respectively, from the northhouse line. An additional width of 24.5 ft. is occupied on the northfrom 277.5 ft. to 543.5 ft. west of the west line of Seventh Avenue,where the buildings on the north side of 33d Street have been torn downand the enclosing wall set back in anticipation of a future outlet to34th Street; and on the south, from 459 ft. to 597 ft. west of the westline of Seventh Avenue a rectangular offset of 124 ft. encloses the areaoccupied by the Service Building. The total area above outlined is thespace occupied at track level, and amounts to 28 acres, of which theportion west of the east house line of Ninth Avenue and south of a line107.3 ft. south of the south line of 33d Street is a part of the NorthRiver Division, and was constructed under the direction of the engineersof that Division; the fan-shaped areas east of the west house line ofSeventh Avenue were constructed under the direction of the ChiefEngineer of Electric Traction and Terminal Station Construction.
In June, 1903, when the writer's connection with the work began, thepreliminary surveys had been completed and the location and extent ofthe Terminal track area had been fixed, in so far as the city blocks tobe occupied were concerned. This contemplated area, however, did notinclude the portion between Ninth and Tenth Avenues, that being addedsubsequently. The elevation of the track level had also been fixed bythe requirement in the agreement with the City that no part of thepermanent structure should approach within 19 ft. of the surface underany avenue or under any street except within the Terminal area. Thenearest approach of the tracks to the surface is at a point 320 ft. eastof Eighth Avenue, where the top of the rail is 40 ft. below the 31stStreet curb line.
The general plan of enclosing the area in retaining walls having beenadopted, wash-borings were taken, for the purpose of determining thebest location for the walls, the depth of rock, and the nature of342 the material overlying it. These borings were made along both curb linesof Seventh Avenue, the east curb line of Ninth Avenue, the north curbline of 33d Street, and the south curb line of 31st Street. The borings,as a rule, were taken at intervals of approximately 100 ft., somedeviation in these intervals being made in order to prevent injury towater, gas, and sewer connections, and, if the elevation of the surfaceof the rock, as determined by one of these borings, corresponded fairlywell with the borings on either side of it, no intermediate borings weretaken. When a discrepancy appeared, a boring was taken midway betweenthe two non-corresponding ones, and if the information obtained from theintermediate boring failed to account for the discrepancy, others weretaken at the quarter points of the original 100-ft. interval.
The dotted lines on Fig. 1 show theprofiles of the surface of the rock underlying 31st and 33d Streets, onthe line of the borings, constructed from the elevations obtained bythem; the solid lines show the profiles of the actual surface of therock as found when uncovered. It will be noted that, except in threecases, Borings 313, 328, and 333, the two profiles correspond veryclosely at the points where the borings were made, but they differwidely between those points, a variation of 5 ft. being common; there isa variation of 14 ft. between Borings 324 and 327, and between Nos. 337and 340; and of 12 ft. between Nos. 333 and 335, and between Nos. 312and 313, while an extreme variation of 17 ft. is shown between Nos. 303and 305. At each of the points where the variation is great the intervalbetween borings is the full 100 ft., and it is quite apparent that, if adefinite idea is to be obtained of the elevation of the surface of therock in Manhattan, borings must be taken at shorter intervals.
The necessary width of trench for the construction of the retainingwalls was determined by the elevation of the rock, as shown by theborings, and only in the case of the dip between Borings 303 and 305 didthe variation lead to any difficulty. The trench at that point had to bewidened after rock was reached. This depression corresponded veryclosely in location to that of one arm of the creek shown on GeneralViele's map of 1865,2the bed of that stream, or one in approximately344 the same location, being clearly marked across the excavation bysmoothly-worn rock and well-rounded boulders. The original stream,however, seemed to have turned in a westerly direction under 31st Streetto Eighth Avenue instead of crossing, as shown on GeneralViele's map.
 Fig. 1.
The arrangement of the sewers in the streets in the vicinity of theTerminal Site, previous to the beginning of the construction, and thedrainage area tributary to those sewers, is shown by Fig. 2. The main sewer for this district was in EighthAvenue, and was a 6-ft. circular brick conduit within the Terminal area.The sewers leading to it from the west, in 31st, 32d, and 33d Streets,were elliptical, 3 by 2 ft., and egg-shaped, 4 ft. by 2 ft. 8 in.,although in no case did they drain more than one block, and they were ona heavy grade. Draining into Eighth Avenue from the east, the one on31st Street was 4 ft. by 2 ft. 8 in., egg-shaped, and drained a lengthof two blocks, and those on 32d and 33d Streets were circular, 4 ft. indiameter, and drained the territory for three blocks, or as far east asFifth Avenue. There were no sewers in Seventh Avenue within the Terminalarea, except small vitrified pipes, each less than 200 ft. inlength.
It was desirable that the size and number of the sewers in thestreets and avenues surrounding the Terminal should be reduced to aminimum, on account of the difficulty of caring for them duringconstruction and also to reduce the probability of sewage leaking intothe underground portion of the work after its completion. With this inview, the plan was adopted of building an intercepting sewer downSeventh Avenue from north of 33d Street to the 30th Street sewer, which,being a 4-ft. circular conduit, was sufficiently large to carry all thesewage coming from east of Seventh Avenue and south of 34th Street. Itwas decided to build this sewer of cast iron where it crossed theproposed construction work, and also to replace with cast iron the bricksewers on 31st, 32d, and 33d Streets from Seventh Avenue to a point eastof the west end of the standard tunnel section, and also the sewer onEighth Avenue from the north side of 33d Street to the south side of31st Street. This arrangement permitted: first, the removal of the sewerin 32d Street between Seventh and Eighth Avenues, which was necessary,as that street was to be excavated; second, the reduction of the sewerin Eighth Avenue from a346 6-ft. to a 5-ft. circular conduit; and, third, assuming that the sewageand drainage from the Terminal would be pumped directly to the sewers inthe avenues, the reduction of the sewers in 31st and 33d Streets, fromSeventh to Ninth Avenue, to 15-in. vitrified pipes, except west of theService Building in 31st Street, to accommodate which section, a largersewer was required. The sewer in 32d Street, from Ninth to EighthAvenue, of course, could be dispensed with in any arrangement, as allthe area tributary to it was to be excavated.
 Fig. 2.
Gas and Water Mains.
A rearrangement of the gas pipes in the three streets crossing theTerminal site was necessary. These pipes were of two classes: trunkmains and service mains. Fortunately, there were but two trunk mains inthe three streets, one a 20-in. in 31st Street from east of SeventhAvenue to Ninth Avenue, the other a 16-in. in 32d Street from east ofSeventh Avenue to Eighth Avenue. The 20-in. main was relaid from SeventhAvenue and 31st Street down Seventh Avenue to 30th Street and throughthat street to Ninth Avenue. The 16-in. main was relaid from SeventhAvenue and 32d Street north to 34th Street and through that street toEighth Avenue. The service mains in 32d Street were no longer required,and were taken up and not replaced. The houses on 31st and 33d Streetswere provided with service by two 6-in. wrought-iron mains back of theretaining walls in each street, that location being chosen to avoiddamage by gas drip to the water-proofing of the street bridges. As thepermanent structures under the avenues were not to approach the surfacenearer than 19 ft., only slight rearrangements, sufficient to permit thenew sewers and water lines to be laid, were necessary.
There were no large water mains to be cared for, in fact, those inthe streets were too small for ample fire protection, being only 6 in.in diameter. The main in 32d Street was taken up and not replaced, andthose on 31st and 33d Streets were replaced by 12-in. pipes laid back ofthe retaining walls. No changes were necessary in the mains in theavenues, but, before approving the