The daily morning journal and courier., 1903-12-17
BUILDING HARLEM TUNNEL
AN IMPROVEMENT ON THE CON-
 TRACTORS

orieinaI Msthod of UBder-yVater cOn- | struetIon-Ths Great Advantages He
 claims for Is.
 Much has been written of the novel method employed by the contractor, D. | D. Mclean, in building the east half Of the Harlem River tunnel for the Rapid Transit railroad, which consisted, roughly speaking, in building huge box under the water, pumping out the water, and then building the tunnel in side of it. The contractor, however, has developed the idea much more pro- fitably, he thinks, for the west half of inc tunnel, and he declares that his new method will make underwater tunnell- ing easier than sub-street tunnelling, and tunnel for teams under the Har- lem, for instance, cheaper than bridge. He says, also, that with his new meth cd the tunnel now being built under the East river could be raised thirty-five feet higher than it's present lever, with a consequent elimination of grade. His plans, more in detail, may be given in his own words. for he writes orf them I
 For the construction of the east half of the river portion of the Harlem river tunnel in this city for the Rapid Tran sit railroad, am prepared to say that the method have adopted and am now carrying out will be a great improve ment on the novel method under which ! successfully constructed the west half of the river portion of the same tunnel.
 Briefly stated: The first method was to dredge channel across the river bottom to within a few feet of the full depth of excavation required to build the tunnel. In this channel foundation piles and row of. specially prepared heavy timber sheeting, along each side and across the ends, were driven and cut off to true plane about twenty five feet below the surface of the water, this sheeting forming the sides and ends of a pneumatic working chamber. ; For the roof of this chamber a platform of timber, forty inches ill thickness and extending the full width and length of the tunnel section, was built and sunk, I and rested on the cutoff sheeting, which formed the sides and ends as above described. Simultaneously with pumping the water from under this roof, compressed air was forced into the chamber under a pressure correspond ing to the pressure of the water above the roof Inside this chamber the west half of the tunnel was built, and then the timber roof was removed. .,,
 'sThe new method for the east half of the river will be to prepare the sides of < the pneumatic working chamber, as above described, but the sheeting and piles will be cut off about twelve feet lower down than was done in the for mer case, or exactly on the grade of the spring line of the arch of the tunnel. The top half of he tunnel will be built at the surface on pontoons, then launched and foated over the tunnel site and sum- into it's final and true position, the outward fianges of it rest ing on the cutoff sheeting above de- scribed. then the top half of the tunnel X will be used to form the roof of the pneumatic working chamber. In this chamber the foundation and bottom half of the tunnel will be constructed, with the use of compressed air, thus dis i pensing with the timber roof, as used in the first method, and greatly decreasing the cost of the construction of the tun- ! netl in many ways.
 "This method is bringing the con- struction of sub-aqueous tunnels to a fine point. It provides for preparing a foundation where the material under the bed of the river is not sufficient in Itself. The sheeting which forms the sides of the working chamber is driven deep enough to penetrate and conffne the earths material under the tunnel for several feet below sub-grade. The foundation piles driven into this con- fined material compact it. .s :.
 This method enables tunnel to be constructed under a nayigable river with the minimum depth of water over 4 it that the United States government requires for navigation. For illustra- ton. take the tunnel now being con- strueted across the East river from Bat tery Place, Manhattan, to Joralemon < street, Brooklyn. By this method that tunnel may be raised thirty-five feet higher than it is now located and still be below the United States government dredging line; by thus raising it there would be three thousand feet, or 31 per cent, of the grade eliminated.
 With regard to safety and surety, tiiiS luctlUu IS JO Suu-dQueUuS Cullll6l work what. pneumatic caisson work is to deep excavation work, viz, absolute Iy safe and sure. The pneumatic work ing chamber is built in place immedf- ately encompassing the work to be ' done; the pressure of the water on the outside of 1t is counterbalanced by the pressure of compressed air forced with in it. Consequently, it is not subject to the heavy ordeal that a working cham Der under a pneumatic cassson sunk from surface would have to undergo, and, therefore, is much cheaper to con- struct. :.-.
 My new method enables the con- struction of a tunnel any desired shape or dimension. Tunnels where two CT s more railroad tracks are required may be built under the one roof and with partitions and inter communicating openings where desired, whereas with the shield process they are limited to single track tunnels and a circular form. A double-tracl tunnel can be built un- der this method at much less cost than twice the cost of a single-track tunnel, four-tracls tunnel at much less than twice the cost of double-track tunnel.