Both of the towers of the Brooklyn Bridge are in the water of the East River. Ever wonder how you dig a big hole in the bottom of a river bed? In the late 1800s? It’s called a caisson, which is a huge, watertight wooden box half the size of a city block. This monstrosity was constructed on the river, sealed with pine tar, and carefully floated to a specific location on the river. It was then slowly sunk to the riverbed by placing stone on top that would eventually become the foundation.
Wrong. With the caisson on the riverbed, it’s time to push it another 45 feet into the riverbed in search of bedrock. Workers did this through the continued application of stone to the top while workers in the caisson dug out the riverbed with shovels, buckets, and, when necessary, dynamite. There was nothing resembling an electrical grid, so there was nothing resembling modern lighting in this watertight pine-tarred box, which was slowly descending through the floor of the East River. There were no jack hammers, so when they hit rock, they used small amounts of dynamite to crack these rocks. In a pine-tarred box, at the bottom of a river, mostly in a very wet dark.
As he says, it was a time without power tools, heavy machinery or even a proper understanding of steel. The whole thing is worth a look.
- talking about bridges feels worryingly Jeremy Clarkson. Am a little concerned. [↩]