For this, the city has enlisted six deep-sea divers who are living for more than a month in a sealed 24-foot tubular pressurized tank complete with showers, a television and a Nerf basketball hoop, breathing air that is 97.5 percent helium and 2.5 percent oxygen, so their high-pitched squeals are all but unintelligible. They leave the tank only to transfer to a diving bell that is lowered 70 stories into the earth, where they work 12-hour shifts, with each man taking a four-hour turn hacking away at concrete to expose the valve.
Three divers at a time climb into the steel bell, an orb that is lowered down the shaft for 20 minutes to reach the pumping equipment in the tunnel. The bell is tethered to a bundle of cables carrying air, communication lines, electricity and water. Each diver works for four hours and rests underwater for eight before returning to the tank at the surface, where 32 more employees of Global Diving and Salvage, the Seattle company running the project, pass meals, clothes and books through an air lock.
In the saturation control room, Patrick Boyd, a life-support technician, monitors the divers’ air on a panel of screens, one of which reads 2.26 percent, for the amount of oxygen. While underwater, divers often get more oxygen in their mixture to keep them alert. John Lapeyrouse, a dive supervisor who is one of the few who can understand the helium-riddled voices, one of the side effects of what is called “saturation diving,” talked to Mr. McAfee as he worked the other day.
In a tent nearby were washers, dryers and a full kitchen. The divers can request whatever food they like, including steak and fresh salads. But the air pressure in the tank dulls the taste buds, so they use a lot of Tabasco, salsa and jalapenos; bread goes flat, more pita than challah. Once the operation is complete, the divers must remain in the tank for a week to gradually wean themselves off helium.
“They lose a lot of weight because they’re burning so many calories,” said Robert Onesti, who is running the project for Global Diving. “It’s not for everybody. It’s heavy construction work, and it’s deep.”
An Effort to Repair a New York Water Tunnel