3. Remnants in the Boiler Room
The Woolworth Building’s basement was filled with numerous relics of Woolworth’s attempt to have the building be self-sufficient. An attempt was made to drill through the foundations (which are made up of caissons since the building is located on mud and not bedrock) to reach a fresh water source.
After drilling over 1,500 feet, the drill still had not exited the Manhattan schist, Manhattan’s bedrock. The secondary source of water sought was never found. It is the deepest anyone has ever attempted to drill through the bedrock and it is still used as the minimum depth that the schist reaches.