Engineering Wonders of the World
Volume I

THE RIVER TUNNELS OF NEW YORK CITY. 119 To complete the sketch picture of the Pennsylvania East River work, we should mention that the four tubes were also con- tinued by shield work under the land east- ward from the Long Island caissons for a distance of 2,000 feet to another caisson, at which the shield tunnelling ended. The land The Battery Tunnels. tip of Manhattan Island eastward to Brooklyn, carrying the two tracks of the Rapid Transit Subway extension. Beginning in rock at the New York shore, the tubes strike fine sand after going half - way across, and thereafter remain in sand except Fig. 21.—AIR-BLOW ABOVE SHIELD AT BROOKLYN END OF BATTERY TUNNEL. This is a mild case of blow. Sometimes a fountain of water 5 to 10 feet high is formed. work was, of course, easier than progress directly under the river, but still was difficult, since it lay in fin© sand, and was well below the saturation level of the soil. Now, however, these tunnels are all com- pleted, and but for the finishing of some of the associated work, as station, yards, electric equipment, they are ready for trains. The two Battery tubes run from the very for passing through a narrow reef of rock that juts up above the tunnels. They are about 4,200 feet long, bank to bank, and, like the other tunnels, reach a greatest depth of some 90 feet. They are cast-iron tubes, of course, and were driven by. the shield method. Their diameter is 15| feet inside and 16 feet 8 inches outside. The shields used were somewhat like those of the old Gas Tunnel, but of a much heavier pattern. Fig. 20 shows the