"If you get above a 12-inch discharge [size], then you have a rigid pipe application that requires heavy equipment and takes days to stage and mobilize," says Roger Less, design branch chief with the Corps' Rock Island district, which had answered the call for help with Hurricane Katrina and gained a Corps-wide reputation as unwatering experts. "At 10 inches or smaller, you're portable. You can move in hours rather than days."

In the subway tunnels, "there were no access points to pump out low areas," says Roger Perk, assistant manager of projects and programs with the Rock Island district. "We would access the shaft, pump out as deep as we could, then start lateral pumping. At the access point, we pumped the water up vertically."

The Corps also worked with the New York Metropolitan Transportation Authority (MTA) to make sure that pumping operations—on average 10,000 to 20,000 gallons a minute—would not compromise the tunnels' structural stability.

Triple Approach

Portability and flexibility were crucial for pumping out the 9,117-ft-long Brooklyn-Battery Tunnel, recently named the Hugh L. Carey Tunnel, between Manhattan and Brooklyn. Crews with the MTA, the Coast Guard and Donjon pumped out water from the Brooklyn portal, the midpoint and the Manhattan portal of the tunnel, respectively, with the Corps coordinating.

"Each side of the tunnel was a bit different," says the Corps' Owen. "We ran flexible pumps from the Brooklyn side, a vertical hose in the center and fused, bigger pipes at the Manhattan side."

Crews used a ventilation shaft in a building on Governors Island right at the tunnel's midpoint, says Ronald Pinzon, Corps project manager for the effort there. "From water level to the bottom of the shaft, it's about 180 feet. We cut through the shaft and ran pumps in tandem."

The Coast Guard combined two pumps, each with a capacity to pump water up to a height of 90 ft, to create a capacity of 170 ft, says Coast Guard Chief Petty Officer Broko Boland. "We had trained and talked about it but never had occasion to do it." The Coast Guard called on colleagues from California and Alabama, he says, adding, "We had 100 people and 15 boatloads of equipment."

By Nov. 10, crews pumped out 60 million gallons from the tunnel. In all, the Corps and its collaborators pumped out 470 million gallons of water from 14 locations, using Battery Park City as an emergency staging area to run hose, off-load barged equipment and fuel, house and feed workers, and provide information to the public.