More at 15 Broad Street, this time the foundation construction. In case the fact that they are building caissons isn’t obvious – and I’ll discuss why it is next paragraph – the big wood box on the sidewalk bridge, to the left of the Little-House-On-The-Prairie construction shack, is labelled “The Foundation Company.” The Foundation Company is a perfect example of a subcontractor that did only one thing but did it very well: they built foundations for large and complex buildings.
Bedrock is fairly high downtown, but irregular and there are old streams and waterways. Broad Street, for example, was dug out by the Dutch colonists as a canal in part because there was a natural inlet and a line of low and soft ground there. So a number of downtown skyscrapers have caisson or pile foundations. In this case, we can see the steel shell of a caisson sticking up in the center of the photo, more shell sections sitting on the far left and far right ends of the bridge, and another shell in progress in shadow on the far right. I’d argue the presence of six derricks when the work is not yet out of the ground argues for caissons as well: it’s hard to see what kind of shallow foundation would need so much lifting equipment. Finally, the third derrick from the left is carrying a bucket that is most likely concrete to fill a caisson shell that’s in place.
My favorite detail: the wood ladder to the left of the shack. Is it broken, or did they remove two rungs to keep people from accessing the bridge?
