National Geographic : 1918 Jul
Photograph byPaul Thompson A PROSPECTIVE GOLD MINE BENEATH BROADWAY The problem of building new subway lines in New York is a tremendous one. For instance, Broadway, atCanal street, isonly tenfeet above sealevel, and the excavation had to be carried down forty-seven feet. Great quantities of water were encountered and atone time twenty million gallons a day, enough to supply a city of 150,000 inhabitants, had to be pumped out with great care, sothat nosand was carried along. Because of the head of water, large masses of concrete had to be introduced to keep the subway from floating. Where itcrosses theHudson tubes the two systems had to be linked together with a concrete saddle.