Video: Dewatering the Brooklyn Battery Tunnel
Video by Mary Cochran
BROOKLYN, New York -- A diverse partnership of government, military and private industry professionals have joined forces to remove floodwater caused by Hurricane Sandy's record-level storm surge from the Brooklyn Battery Tunnel, which connects Brooklyn with the island of Manhattan. The Federal Emergency Management Agency (FEMA) is overseeing the unified federal response. At 9,117 feet the Brooklyn Battery Tunnel is the longest continuous underwater vehicular tunnel in North America. The U.S. Army Corps of Engineers (USACE) dewatering team, based in Rock Island, Ill., is working closely with the Metropolitan Transit Authority (MTA) to get this vital transportation conduit back in service. The U.S. Coast Guard, U.S. Navy and private contractors are all contributing innovative solutions to speed the effort. Initial efforts focused on pumping water from the Brooklyn end of the tunnel and from Governors Island, where a large ventilation shaft, which exists to remove vehicle exhaust fumes, provides a unique angle from which to drain the tunnel. Working from the Brooklyn side, MTA commercial contractor Restani Construction Corp., pumped water from that side into an intermediate sump area. The U.S. Coast Guard then pumped the water from the intermediate sump to the surface at the Brooklyn tunnel entrance. As water levels have dropped, engineers have repositioned the pumping equipment and extended discharge pipes to follow the receding water level lower and lower into the tunnel approximately 150' below the surface and totaling nearly half the distance of the tunnel with discharge piping. At Governors Island, the U.S. Coast Guard brought specialized maritime dewatering technology to speed the effort. Coast Guardsmen used submersible hydraulic pumps normally used aboard ship to remove water from flooded compartments, and lowered them down the ventilation shafts to remove water from the lowest part of the tunnel. Restani also installed submersible electric pumps through the ventilation shafts. The pumps, attached to 6-inch diameter hoses, drew water the 150 foot vertical distance to the surface. On the Manhattan side, commercial contractor Donjon Marine Co., Inc., working under an existing U.S. Navy contract, began pumping at the Manhattan Cellular Structure Plaza. The cellular structure is a sump at the entrance to the tunnel designed to collect stormwater and prevent it from entering the tunnel. The first priority has been to remove water from the roadway section of the tunnel, then from ventilation sections of the same tunnel. "Everyone has done an excellent job," said USACE dewatering team engineer John Behrens. "I'm especially pleased with the work the Coast Guard has done. They came prepared to execute and have done a great job. The MTA and commercial contractors have all done a truly professional job bringing great ideas and hard work to the effort." At its peak the combined effort removed about 11,000 gallons of water from the tunnel each minute. Initial estimates were that as much as 86 million gallons of water had flooded the tunnel. The Coast Guardsmen have completed the majority of their portion of the pumping effort. "The U.S. Coast Guard National Strike Force is proud to be part of the combined effort that is working day and night to help the people of New York restore their transportation infrastructure," Coast Guard on scene commander Lt. Joel Ferguson said. Available in high definition.