From the New York Times:
The flooding in subways and tunnels in Lower Manhattan was so severe that the Federal Emergency Management Agency has asked a team of specialists skilled at draining flooded areas from the Army Corps of Engineers to help New York City officials. The team plans to first assess the severity of the flooding, and over the next few days more personnel would most likely be sent to New York, said Rodney Delp, the chief of the team, which is based in Rock Island, Ill. The deployment of the team marks the first time it has been asked to help clear water outside of New Orleans since it was was created after Hurricane Katrina. “They are overwhelmed by the magnitude of the flooding,” Mr. Delp said of the officials in New York. He said the State of New York had asked the federal agency for assistance and that the agency had then reached out to his team. “What they typically do is look at engineering drawings to look at the natural low points and what the natural drainage may be, and how long it will take to drain,” Mr. Delp said of his team. “They then look for areas to breach, figure out what size of pumps to use for the water,” and begin the process of removing the water.
Aside from electricity itself, nothing is more vital to NYC commerce than the subway system.