Hudson Yards is the largest private development project in U.S. history, and it’s being built without footings or foundations.

Instead, the project is going to sit atop 300 concrete-sleeved, steel caissons inserted down into the underlying bedrock.

Borrowed from the concept behind bridge building, the caissons technology will involve engineers meticulously arranging the steel deep underground to line up with the narrow spaces between the train tracks.

Above, they will connect to deep-girdle trusses – some up to 8 stories tall – that control and redirect the towering weight overhead. 

Finally, an elevated platform made from approximately 35,000 tons of steel and 50,000 cubic yards of concrete will be built over the active train line.

Work on the platform broke ground last week, and is expected to take nearly two and a half years to complete.

Image: tktkt creditA timeline of the construction. Image: Related Companies

Courtesy Wired