Earth-Shattering Developments At East Side Access Project.

Literally.  The MTA states, via Gothamist:

Since March 7, 2007, nearly 1,000 employees working 24 hours a day, five days a week, have completed more than 2,400 controlled blasts - all without affecting the nearby operations of MTA Metro-North Railroad or the New York City Subway. Approximately 857,000 cubic yards of rocky muck were excavated and removed, enough to cover the entirety of Central Park one foot deep.
“This is a very significant milestone for the East Side Access project,” said Dr. Michael Horodniceanu, President of MTA Capital Construction. “The caverns are essentially now fully excavated. Much work remains to be done to build the platforms and tracks, and finish what is currently raw, cave-like space. But we now have a fully built shell in which all future work will take place.”

What's also cool is that a lot of this fill is finding it's way into the new parts of Brooklyn Bridge Park, building up the uplands and forming the bulk of the coming "sound-attenuating berm" that is intended to cut down on highway noise pollution.