Mid-Atlantic Regional Maintenance Center (MARMC) Dive Team Foxtrot divers performed leak checks to a cofferdam attached to item Number 138 on USS George H.W. Bush's (CVN 77) hull at Norfolk Naval Shipyard (NNSY), March 3.

MARMC Dive Teams Foxtrot and Echo, along with various other U.S. Navy dive teams, have installed, maintained and removed 123 cofferdams (used to create dry spaces for workers by sealing water out of the ship) to support in-hull work during Bush's Planned Incremental Availability (PIA), which began in January 2015.

"In the beginning, there was a really big push to get all the cofferdams installed," said MARMC Foxtrot Diving Foreman Thomas Gerace. "We started early at Naval Station Norfolk, to get ahead of the game, by replacing all zincs on the shafts and inside the stern tubes. We performed inspections on all shafts, propellers, main propulsion shaft bearings and rudders prior to Bush arriving in the shipyard. Once the ship arrived, we concentrated on the main patches."

According to MARMC Foxtrot Work Leader Carl Viviano, all the plant work relies on the main condenser cofferdams.

"Once we installed all main condenser cofferdams and ship service turbine generators, NNSY employees were able to start work inside the ship," said Viviano. "During these two weeks, divers worked 24 hours, in two 12-hour shifts."

Numerous single-isolation (cofferdam-to-sea) jobs required around the clock diver support including the removal and replacement of fire pump Number 20, replacing hull valves on the Number 3 air condition (A/C) sea water system, and sea chest weld repairs to item Number 28 (Number 3 A/C discharge sea chest) and item Number 138 (Main Machinery Room Number two main drain eductor overboard discharge sea chest).

"Anytime the shipyard tears into a valve, there has to be more than one barrier to sea for the safety of the ship," said Viviano. "The safety of the ship officer and the commanding officer are both involved as work is performed on a hull valve, which is the valve right before it goes out to sea. Regardless of the type of job, there has to be a cofferdam to establish double-valve isolation to sea. In some cases, we were working with double-valve isolation to sea (a cofferdam, one valve and the system that was torn apart); and in other cases, workers have torn apart the actual hull valve where the only thing stopping the ocean from getting in the ship is the cofferdam. At that point, we were standing by, monitoring that cofferdam and making sure there weren't any problems. We had to be in constant communication with the guys doing work in the ship. We've completed six of these jobs during this PIA, which last about a week depending on how long the work (inside the ship) takes."

During the PIA, 90 cofferdams were attached to the ship at the same time. These cofferdams were installed from the water line all the way down to the bilge keel (bottom of the ship) at a depth of 45 feet (four levels inside the ship).

"MARMC divers have been instrumental in performing running gear work and inspections and in supporting in-hull work ahead of schedule during the Bush PIA," said USS Bush Project Tank Zone Manager and Dive Zone Manager Lt. Cmdr. Jonathan Connelly.

"Currently, we are well ahead of schedule," said Gerace. "We have one more set of mains including the scoop cofferdam (15 feet long, 5 feet wide and weighs 2,000 pounds). NNSY workers are still repairing the ship's overboard system, so the cofferdams have to be left on the ship."

Once NNSY workers complete tests and inspections on the overboard system, divers will remove the remaining cofferdams.

"Before the ship pulls out, we have to swim by every opening of the ship to make sure they're clear," said Gerace. "Openings must be free of debris and we have to ensure there are no cofferdams left on any lines."

Divers will spend two days checking every opening on the ship. They will also swim out the running gear to look for obstructions, ensuring that when Bush leaves the shipyard her Sailors are safe to go.

"The performance of MARMC's divers has been outstanding and sets the standard of excellence in underwater ship's husbandry and first time quality, and has upheld the highest traditions of the United States naval service," said Connelly.

The Bush PIA is expected to finish later this month.

For more news from Mid-Atlantic Regional Maintenance Center, visit www.navy.mil/.