AMERICAN SOCIETY OF CIVIL ENGINEERS

INSTITUTED 1852

TRANSACTIONS

Paper No. 1152

THE NEW YORK TUNNEL EXTENSION OFTHE PENNSYLVANIA RAILROAD. 

THE EAST RIVER DIVISION. 

BY ALFRED NOBLE, PAST-PRESIDENT, AM. SOC. C. E. 

A general outline of the work included in this Division has been givenby General C. W. Raymond, M. Am. Soc. C. E. , in the first paper of theseries. The few pages following are intended only as a note to connecthis paper with the more detailed descriptions of the execution of thework, which will be supplied by the Resident Engineers in immediatecharge. 

Soon after the Company's project was made public, in the latter part of1901, borings were begun in the East River, and a few weeks later inManhattan and Long Island City. A preliminary base line was measured onthe Manhattan side, and temporary transit stations were established onbuildings from which all borings in the river were located. The riverborings were all wash-borings made from a pile-driver boat. After theresults were plotted on the map, contour lines were drawn to indicatethe rock surface, and profiles along the tunnel lines were plotted fromthe contours; as the borings were preliminary to the final location ofthe tunnels, and in many cases at some distance from the tunnel lines, considerable divergence from the actual rock surface was expected, andrealized in a few places, yet on the whole the agreement was very good. The borings revealed two depressions or channels where the rock surfacepassed below the grade of the projected tunnels, these depressions beingseparated by a rock reef which extends down stream from Blackwell'sIsland. In 32d and 33d Streets in Manhattan, borings were made from theriver to the station site at intervals of about 100 ft. , wash-boringsand core-borings alternating. In Long Island City, where the tunnellines were to pass diagonally under the passenger station building andpassenger yard of the Long Island Railroad and under streets and privateproperty, the arrangement of borings was less regular, although thealternation of wash-borings and core-borings was carried out as far aspracticable. After the final location of the work, additional boringswere made, particularly on shaft sites and also along the approaches andin the Sunnyside Yard, Long Island City. 

A triangulation was carried across the river with a measured base oneach side. It was impossible to measure directly between the extremitiesof either base. The bases were measured with 100-ft. Steel tapes, supported every 20 ft. , stretched with a uniform pull, and frequentlycompared with standardized tapes. On account of the crowded condition ofthe streets during the hours of daylight and evening, most of the workwas done between 10 P. M. And 5 A. M. Similar measurements were made inthe streets along the tunnel lines. Angle readings were repeated manytimes, as is usual in such work. Fig. 1 shows the triangulation, thestreet measurements being omitted. 

Levels were first transmitted across the river by simultaneousobservations of the river surface; then by several repetitions, acrossBlackwell's Island and the narrow channels on each side, where thelongest sights were about 1100 ft. ; and, finally, by several linesthrough the tunnel of the East River Gas Company at 71st Street. 

The franchise granted by the City of New York provided for the sale tothe Railroad Company of the portions of 32d Street between Seventh andEighth Avenues, and between Eighth and Ninth Avenues. Later, the Companyacquired by purchase the portion of 32d Street between Ninth and TenthAvenues. The franchise granted sub-surface rights under streets aroundthe station site to within 19 ft. Of the street surface under Seventh, Eighth, and Ninth Avenues; to within 30 in. Of the street surface under31st and 33d Streets, except that, under the sidewalks opposite thestation, that is to say, the south sidewalk in 31st Street and the northsidewalk in 33d Street, the construction must be at least 5 ft. Belowthe street surface. In carrying out the work, full use of these rightswas made under Eighth Avenue, but only under such portions of Seventhand Ninth Avenues as were indispensable for access by trains to thestation area. It was not practicable to make full use of the rightsgranted under 31st and 33d Streets without incurring great expense forsupporting adjacent buildings or for injuries to them, and, aftercareful consideration, the arrangement shown in the plans was decidedon, making about 45% of the sub-surface area under these streetsavailable at track level. 

[Illustration: FIG. 1. --Triangulation System East River Tunnel]

The work of the East River Division at this site embraced the excavationto the depth necessary for railroad tracks, and the building of aretaining wall extending in 31st Street from the east side of NinthAvenue to the west side of Seventh Avenue, thence northward alongSeventh Avenue for a distance of 155. 5 ft. ; also a retaining wall in 33dStreet from the west side of Seventh Avenue to the east side of NinthAvenue, and thence southward along Ninth Avenue for a distance of 136. 3ft. This work was placed under contract June 21st, 1904, with the NewYork Contracting and Trucking Company, and later assigned by thatcompany to the New York Contracting Company-Pennsylvania Terminal, andwas carried out under the direction of George C. Clarke, M. Am. Soc. C. E. , as Resident Engineer, by whom it will be described in detail. 

[Illustration: PLATE IX. --Map of Portion of Manhattan Island from 23d to40th Streets, Showing Former Topography From Map Made by Gen. Egbert L. Viele in 1865]

The station tracks leading eastward from the station will converge underSeventh Avenue and for some distance farther east, and pass into twothree-track tunnels, one under 32d Street and the other under 33dStreet, at the respective distances of 192 and 402 ft. From SeventhAvenue. A typical cross-section of the three-track tunnel is shown onPlate XII. The converging sections were considered as easterlyextensions of the station, and were not included in the East RiverDivision. Within a few hundred feet (Plate XIV), the tracks are reducedto two, each passing into a single tube, the two tunnels under eachstreet being formed in one excavation, the distance between center linesof tunnels being 20 ft. 4 in. This construction has been termed a twintunnel, and a typical cross-section is shown on Plate XII. The tunnelscontinue on tangents under the streets to Second Avenue where they curveto the left by 1° 30' curves, passing under private property, graduallydiverging and passing through shafts just east of First Avenue. About350 ft. West of the shaft, the divergence of the two lines from eachstreet becomes sufficient to leave a rock dividing wall between them, and thence eastward each tunnel is formed in a separate excavation. Atypical cross-section of the two separated tunnels is shown on PlateXII. 

It thus appears that eastward from the station the lines constitute afour-track railroad, each track being in a separate tunnel; forconvenience of the work these lines were designated _A_, _B_, _C_, and_D_, from north to south. 

[Illustration: PLATE X. --Manhattan Shaft, Lines _A_ and _B_]

At an early date, when the organization of the engineering staff wastaken up, Charles L. Harrison, M. Am. Soc. C. E. , was appointedPrincipal Assistant Engineer. He was directly in charge of all parts ofthe work, and all Resident Engineers reported to him. George Leighton, M. Am. Soc. C. E. , was placed in charge as Resident Engineer of the 33dStreet lines from the west end of the three-track tunnel to the shaftand also eastward from the shaft under East River. As he was not thenable to endure the effects of compressed air, the work under the riverwas transferred to James H. Brace, M. Am. Soc. C. E. , as ResidentEngineer. Before the completion of the land tunnels under 33d Street, Mr. Leighton accepted more responsible employment elsewhere, and Mr. Brace assumed charge of them also. Francis Mason, M. Am. Soc. C. E. , wasin charge as Resident Engineer of the 32d Street lines during theirentire construction, and also of the tunnels extending these lineseastward from the First Avenue shaft under the river. 

The work just described as the 32d and 33d Street lines, terminating atthe easterly end at the First Avenue shafts, was placed under contracton May 29th, 1905, with the United Engineering and Contracting Company. The plans then provided for three-track tunnels from the west end of thework under the contract eastward 1, 628 ft. In 32d Street and 1, 418 ft. In 33d Street to the west line of Fifth Avenue, with a descending gradeof 0. 4%; this was to constitute, in a degree, an extension of thestation, where trains could stand without brakes while awaiting signalsto proceed to or from the station. From Fifth Avenue eastward to thelowest point under the river, the grade was to be 1. 5% on all lines. Later, during construction, when excavating westward under 33d Streetfrom Fifth Avenue, the surface of the rock was broken through, disclosing quicksand; within the next few days trial drill holes throughthe tunnel roof at 32d Street and Fifth Avenue showed a thin cover withquicksand above it. The conditions had been indicated in a general wayby borings made before construction was begun, but they proved to berather worse than anticipated. On the topographical map of ManhattanIsland, made by General Egbert L. Viele in 1865, is shown a watercoursewhich had its source near what is now Broadway and 44th Street, flowingthence along the west side and south end of Murray Hill, passing underthe present site of the Waldorf-Astoria Hotel, crossing 33d Street atthe point where the rock surface was broken through in the tunnelexcavation, as above stated, crossing 32d Street at its intersectionwith Fifth Avenue, where trial drilling showed thin rock cover over thetunnel excavation, passing thence eastward a short distance south of 32dStreet, which it recrossed near Third Avenue, and finally discharginginto the East River near 34th Street, and a little west of the presentFirst Avenue. The ancient creek apparently followed the course of avalley in the rock, the valley having become filled to a considerabledepth with very fine quicksand. This concurrence of depressions in therock surface with the watercourse shown on Viele's map was noted in somany places and the difficulties of construction were so serious atthese places, that a section of the map showing the old topography alongand adjacent to the station and tunnel lines is reproduced in Plate IX. 

[Illustration: PLATE XI. --Long Island Shaft. Lines _A_ and _B_]

The unfavorable conditions developed at Fifth Avenue affected both theconstruction of the tunnels and the maintenance of adjacent buildings. It would be necessary to construct the tunnels in open cut for a largepart of the way westward, causing serious inconvenience to the public;the buildings were mostly of the older class, founded in earth, butthere were several modern high buildings with foundations in the samematerial; some of these had been built since the tunnels were planned. In view of these added risks and the increased cost of construction, thevalue of the three-track construction was reconsidered, and twoimportant changes were made in the plans. The first of these was tocontinue the twin tunnel westward to Sixth Avenue in 32d Street, and toa point 180 ft. West of Sixth Avenue in 33d Street; the twin tunnelbeing 9-1/2 ft. Less in height than the three-track tunnel and 9 ft. Narrower, the change reduced the difficulties considerably. Where thethree-track tunnel was thus eliminated, there was no longer objection toa steeper grade, so that, going eastward from the station, a grade of0. 8% in 33d Street and 0. 9% in 32d Street was substituted for theoriginal 0. 4% grade. From the west line of Fifth Avenue eastward shortsections with descending grades of 0. 3% connect with the original 1. 5%grade near Madison Avenue. The effect of these two changes--type oftunnel and grade--was to lower the roof of the tunnels at Fifth Avenueabout 15 ft. , which made it practicable to avoid open cutting east ofSixth Avenue. 

A full account of the construction of the cross-town tunnels will begiven by the Resident Engineers. 

Permanent shafts were made on both sides of the East River, those inManhattan being located a few feet east of First Avenue, and those inLong Island City being located, one in the so-called Annex Slip, theother in the pier just south of it. The two railroad lines coming from32d Street in Manhattan, and curving to the left at Second Avenue, areabout 34 ft. Apart between centers at First Avenue, and it wasconvenient to make the shaft large enough to cover both lines. Boringshad shown that the excavation for the tunnels would break out of therock about 200 ft. East of First Avenue. It was desirable to carry thetunnel excavation eastward from the shaft in normal air far enough topermit of building at least 50 ft. Of tunnel and installing air-locks, so that compressed air might be available when the rock surface wasbroken through. The location adopted, and shown on Plate XIII, had thefurther advantages that the rock surface was several feet above thelevel of the top of the tunnels, and access to the river for receivingand discharging materials could be had without crossing any street. Similar reasons governed the location of the north shaft for the linesfrom 33d Street. On the Long Island side of the river there were onlytwo feasible locations meeting these conditions, particularly in respectto a safe thickness of rock above the tunnels, one near the pierheadline, the other just outside the bulkhead line, and for many minorreasons the latter was preferable. The center lines of each pair oftunnels were 37 ft. Apart, and each shaft, therefore, was made to crossboth lines of a pair, the same as on Manhattan side of the river. It wasnot expected, however, that the Long Island shafts could be builtconveniently or the tunnels begun from them in normal air. 

The decision to make the shafts of permanent construction was based notonly on the desirability of having access to and egress from the tunnelsnear the banks of the river for convenience of the workmen or exit forpassengers in case of accident, but to facilitate ventilation; theselocations divide the entire lengths of tunnels east of the station intothree parts, two of which were approximately 4, 000 ft. Each, and theother about 5, 500 ft. The accident risk was believed to be very small, while much weight was given to the feature of facilitating ventilation. Further studies have enhanced the importance attached to ventilation, and it is now intended to provide appliances for mechanical ventilationat all shafts. The plans of the shafts are shown on Plates X and XI. Thecaissons for the shafts are of structural steel, with double walls, filled between with concrete, including a cross-wall between andparallel to the tunnels. All these structures were fitted for sinkingwith compressed air, if that should prove necessary. 

Although borings had shown that rock would be found at all the shaftsites several feet above the tunnel level, it could not be determined inadvance of excavation whether the caissons would have to be sunk to fulldepth; if sound, unfissured rock were found, the sinking could bestopped above the tunnel level; but, if not, the caissons, in any case, would have to be sunk far enough to permit placing a water-tight floorbelow the tunnels, and the tunnels themselves begun through openings inthe side-walls of the caisson; such openings, therefore, closed byremovable bulkheads, were provided in all caissons. 

[Illustration: PLATE XII. --Typical Tunnel Sections]

As already stated, the grade of 1. 5% from Fifth Avenue eastward wasfixed with reference to the lowest point of the river bed in order togive the requisite cover over the tunnels at the deepest point of thechannel on the west side of the reef, where the river bottom was about60 ft. Below mean high tide for a short distance. On the other hand, asthe use of compressed air in building the tunnels was anticipated, anexcessive depth below the water surface was to be avoided as far aspossible; it was necessary, however, to continue the descending gradesome further distance until the tunnels were mostly in rock, so thatdrainage sumps under the tunnels could be made readily. Eastward fromthe sumps the tunnels had a rising grade of 0. 7% to the establishedbulkhead line on the Long Island side, giving a cover at the pointswhere the tunnels enter rock, a short distance westward, of about 10 ft. (if the dredging plane should be fixed at some future time at 40 ft. Below mean low tide, as may be reasonably anticipated). Eastward fromthe bulkhead line, Tunnels _A_, _B_, and _D_ have ascending grades ofabout 1. 25%, while Tunnel _C_ rises at the rate of 1. 9% in order toeffect a crossing over Tunnel _B_ west of the portals. This feature wasintroduced in order to place the two west-bound tracks together throughthe Sunnyside Yard, and the heavier grade, being downward with thetraffic, was not objectionable. 

The arrangement of grades and tracks in the approaches and in SunnysideYard would require the introduction of too much detail to be taken uphere, but will be dealt with in the paper on the Sunnyside Yard. 

It was recognized from the inception of the project that the tunnelsunder the East River would be the most difficult and expensive sectionof the East River Division. The borings had shown a great variety ofmaterials to be passed through, embracing quicksand, coarse sand, gravel, boulders, and bed-rock, as well as some clayey materials. (SeePlate XIII. ) The rock was usually covered by a few feet of sand, gravel, and boulders intermixed, but, in some places, where the rock surface wasat some distance below the tunnel grade, the material met in tunnelingwas all quicksand; the nearest parallels in work previously done weresome of the tunnels under the Thames, particularly the Blackwall tunnel, where open gravel was passed through. Before the plans for the EastRiver tunnels were completed, work had been resumed, after many years'interruption, in the old Hudson River tunnels between 15th Street, Jersey City, and Morton Street, Manhattan, and sand materials werepassed through for a short distance. These experiences satisfied nearlyall the engineers in any way connected with the work that the shieldmethod was the most suitable for the East River tunnels, and the plansfor the work were based on its adoption. (See Plate XII forcross-sections, etc. ) Other methods, as stated by General Raymond in theintroductory paper, were advocated, particularly caisson constructionsand the freezing process, the latter being urged very strongly, and, when proposals were invited, in October, 1903, bidders were informedthat alternative methods would be taken into consideration. 

Bids were received and opened on December 15th, 1903. Only one bidderproposed to carry out the work on the basis of unit prices, but theprices were so low that the acceptance of the proposal was deemedinadmissible; no bid based on caisson methods was received; severaloffers were made to perform the work by the shield method, in accordancewith the plans, for a percentage of its cost, and one was submitted, ona similar basis, covering the use of the freezing method. The firm of S. Pearson and Son, Limited, of London, England, submitted a proposal forbuilding the tunnels by the shield method, on a modification of thepercentage basis, and as this firm had built the Blackwall tunnel withinthe estimates of cost and was the only bidder having such an experienceand record in work in any way similar to the East River tunnels, negotiations were continued between that firm and the railroad company. 

The original plans and specifications contemplated that all tunnelsbetween the First Avenue shafts in Manhattan and East Avenue in LongIsland City would be shield-driven, and that work would proceedsimultaneously eastward from the First Avenue shafts and both eastwardand westward from the Long Island City shafts located west of FrontStreet at the river, requiring twelve shields. When making theirproposal, S. Pearson and Son, Limited, suggested that shields might bestarted from the east end of the work and arrive at the Front Streetshafts as soon as these shafts could be completed, and proposed sinkinga temporary shaft transversely across all four lines near the east endof the work just west of East Avenue, from which, within a short time, to drive toward Front Street by the use of shields. The railroad companyaccepted the suggestion for the additional shaft, although the greaterpart of the tunnels east of Front Street was built without shields. After several months of negotiation, a contract was entered into on July7th, 1904, with S. Pearson and Son, Incorporated, a corporation of theState of New York organized by the English firm for the purpose ofentering into and carrying out this contract. The main features had beenagreed upon, and work had begun about two months before. The contractembraced the permanent shafts in Manhattan and Long Island City, thetunnels between these shafts, and their extension eastward in LongIsland City to East Avenue, including in all about 23, 600 ft. Ofsingle-track tunnels. The contract had novel features, and seemed to bepeculiarly suitable for the unknown risks and the unusual magnitude ofthe work. A fixed amount was named as contractor's profit. If the actualcost of the work when completed, including this sum named ascontractor's profit, should be less than a certain estimated amountnamed in the contract, the contractor should have one-half of thesaving. If, on the other hand, the actual cost of the completed work, including the fixed sum for contractor's profit, should exceed theestimated cost named in the contract, the contractor should pay one-halfthe excess and the railroad company the other half; the contractor'sliability was limited, however, to the amount named for profit plus$1, 000, 000; or, in other words, his maximum money loss would be$1, 000, 000. Any further excess of cost was to be borne wholly by therailroad company. The management of the work, with some unimportantrestrictions, was placed with the contractor; the relations of theengineer, as to plans, inspection, etc. , were the same as in ordinarywork, and the interest of the contractor to reduce cost was the same inkind as in ordinary work. 

[Illustration: PLATE XIII. --Plan and Profile. East River Tunnels]

On account of the extent of the work embraced in this contract, and thedangerous exposure to compressed air required in most of it, it wasdivided into three residencies; two of these, including also thecross-town tunnels, have been described; the third, with S. H. Woodard, M. Am. Soc. C. E. , as Resident Engineer, embraced all tunnels from theeasterly end of the work near East Avenue in Long Island City to themeeting points under the river and also the permanent shafts in LongIsland City. A few months after the execution of the principal contract, the work to be done was extended eastward 107. 5 ft. , across East Avenue. The extensions of the tunnels were built without cast-iron linings andwith an interior cross-section of the same height as the tube tunnels, but somewhat narrower. The work was also extended westward from theFirst Avenue shafts to include the excavation of top headings in eachtunnel for a distance of 100 ft. And an enlargement to full size for 50ft. The borings having shown that soft earth existed below the grade ofthe tops of the tunnel under the passenger station building of the LongIsland Railroad on the east side of Front Street, and that earth ofvarying character would be met in places beyond the station buildingunder the railroad tracks in the passenger yard and the street cartracks in Borden Avenue, it had been decided, before proposals wereinvited, to extend the metal lining eastward to East Avenue, at the eastend of the work embraced in the original contract, where the risingtunnel grades approached the surface of the ground so closely that theirfurther extension would be in open cut. In places where the tunnels werewholly in rock, the weight of the cast-iron tunnel lining was reduced43%; where the surface of the rock was below the top of the tunnel, butabove the axis, the reduction of weight was somewhat less, about 25%;notwithstanding these savings, the cost of the tunnels was probablyincreased by the use of the cast-iron lining; on the other hand, whenpassing through bad ground, a section of tunnel could be made absolutelysafe more quickly by erecting the lining as soon as a length of a fewfeet of tunnel was ready; under a crowded passenger yard, this featurehad great value. 

The execution of the work under this contract will be described fully bythe Resident Engineers. 

The plant assembled by the contractors is believed to be the mostextensive ever placed on a single piece of work, and will be describedin detail by their Managing Engineer, Henry Japp, M. Am. Soc. C. E. 

For convenience in receiving materials to be used in construction, andto facilitate the disposal of excavated materials, one pier was leasedon the east side of the Hudson River, two on the west side of the EastRiver and three on the east side. Excavated materials from the station, the cross-town tunnels, and the river tunnels, were placed on bargesfurnished by Mr. Henry Steers under several contracts embracing alsothe disposal of the materials. In the earlier part of the work, theywere used as fill in the freight terminal of the Pennsylvania Railroadat Greenville on the west side of the Upper Bay; when the fill at thisplace was completed, the materials were sent to the tunnel company'syard on the Passaic, at Harrison, N. J. , and a small part to theembankment in the Meadows Division. On account of the occasional closingof the Passaic by ice, this involved the possibility of, and to someextent resulted in, interruptions to the work of excavation. Thecontract for the cross-town tunnels carried an option in favor of thecompany to require the contractor for those tunnels to dispose ofmaterials at a stated price, and in the latter part of 1907, when theexcavation in these tunnels was being pushed rapidly, the railroadcompany, unwilling to incur the responsibility for delays during thewinter, availed itself of this option. The disposal of materials was animportant part of the work, and will be dealt with more fully by theResident Engineers. 

[Illustration: PLATE XIV. --Map and Profile, Cross-Town Tunnels]

At the time the contract was made with S. Pearson and Son, Incorporated, it had not been determined whether mechanical ventilation would beprovided for the tunnels, and therefore the contract with that firm didnot include the final concrete lining at the shafts, above the invertsof the tunnels. After the adoption of plans for mechanical ventilation, in the latter part of 1908, the plans for lining the shafts withconcrete, including flues for conducting air to the tunnels, andstairways for ingress and egress, were completed, and the work wasplaced under contract; it will be described in detail by F. M. Green, Assoc. M. Am. Soc. C. E. 

At the east end of the work under the Pearson contract, the rising gradeof the tunnels brought them so near the surface of the ground that theirextension eastward could be carried out more readily in open cut than bytunneling. The locations of the portals could be varied somewhat, andthey were built on rock which was found in rather narrow ridges atconvenient places. Tunnels _B_ and _D_ have a common portal; Tunnels _A_and _C_ have separate ones, the portal for Tunnel _C_ being locatedabout 800 ft, west of the others as a result of its crossing over Tunnel_B_, as already explained. Eastward from the portals, the track systemexpands, in order to provide connections with the tracks of the LongIsland Railroad to and from Long Island City, with the New YorkConnecting Railroad and New England lines, and with the storage andcleaning yard known as the Sunnyside Yard extending to the west side ofWoodside Avenue, 2-3/4 miles east of the East River. (Plate XV. ) Theyard and approaches are designed to avoid grade crossings by opposingtrains. The various general features of the yard and tunnel approaches, bridge crossings, and street closings, have been described in sufficientdetail by General Raymond in the introductory paper. 

[Illustration: PLATE XV. --Plan and Profile of Lines _A_ and _B_, andSunnyside Yards]

For convenience in placing the work under contract, a line was drawn 10ft. West of Thomson Avenue, dividing the work east of that embraced inthe Pearson contract into two parts. The work west of the line wasplaced under the immediate direction of George C. Clarke, M. Am. Soc. C. E. , as Resident Engineer, with Naughton Company and Arthur McMullen, Contractors; Mr. Louis H. Barker was Resident Engineer of the part eastof the dividing line, with the Degnon Realty and Terminal ImprovementCompany as the principal contractors. The substructures of the severalbridges in or across the yard were included in these contracts, but thesuperstructures were carried out by various bridge companies, and otherminor features were executed by other contractors. More completedescriptions of the plans and of the execution of the work will be givenby the Resident Engineers.