UPDATED: New York City's downtown areas hit hardest by Hurricane Sandy's storm surge were getting pumped out through the weekend  as city and federal officials worked to get more tunnels and subway systems back into operation.

For the U.S. Army Corps of Engineers, which has been upgraded to a $20-million mission assignment since the storm struck the Northeast U.S. region Monday, unwatering is the main focus of that mission. Rene Poche, public affairs specialist for the USACE, says the Corps expects to pump an estimated 600 million gallons of water out of its entire mission area—which includes pumping some 10 million gallons alone from the flooded Battery Park underpass in lower Manhattan.

City and state officials expect all of lower Manhattan to be pumped out or in the midst of a unwatering operation through the weekend of Nov. 3rd, 4th and beyond, with particular focus on pumping water out of key infrastructure to help get more vehicles and transit moving in and out of all the boroughs.

In addition, New York Gov. Andrew M. Cuomo said on Nov. 3 that crews working at the World Trade Center site had successfully completed pumping the storm surge from the vehicle security center (VSC) where the storm surge entered during Hurricane Sandy. Approximately 11 million gallons or roughly 28 feet flooded the VSC during the brunt of the storm Monday night. (See the image in this slide show.)

Officials also said 14 pumps were in place at the Sept. 11 Museum as of the weekend, working to remove the water at the bedrock and across other parts of the site. They say more than 90% of the artifacts are currently being stored offsite, but for those that are at bedrock in the museum space, artifact conservators are providing guidance for caring for the artifacts once the pumping is complete.

As the pumping operations ramped up downtown, and parts of Manhattan south of 34th Street started to came back to life, construction crews were clearing debris in the New York, New Jersey metro areas hit hardest by Sandy's force.  Late Friday and into Saturday, Nov. 3rd, power had returned to many residents in the lower regions of Manhattan and more subways were opening.

In Midtown, city officials continued working out a rescue plan about how to get a 1,000-ft-tall tower crane, dangling off the side of the One57 tower in Midtown since Monday's hurricane damaged it, off the building safely.

But for the USACE, unwatering is a key mission among many since Sandy struck. "Our priority right now is support to the NYC unwatering mission," said Curry Graham of the USACE, in a statement. Prior to the arrival of Sandy, the Corps shipped 12 eight-inch pumps and 13 six-inch pumps from New Orleans in order to support the Corps' unwatering mission assignment from FEMA.

This story was corrected on Nov. 4th to clarify how much storm water the USACE expects to pump across its entire mission area.