Groton - Repairing a severely damaged 17-year-old submarine with the technology Electric Boat uses to build modern subs was like reconstructing a Ford Model T in a Lexus shop.

The Navy contracted with EB for about $120 million worth of repairs to the USS Hartford after the Los Angeles-class submarine collided with a Navy amphibious ship in the Strait of Hormuz in 2009.

The Navy wanted the submarine back at sea as soon as possible - ideally, in one year.

The repair team at EB knew the Hartford (SSN 768) had rolled about 85 degrees and damaged its sail, hull and port bow plane. But the destruction turned out to be far worse than expected.

The sail leaned 15 to 20 degrees to the starboard side. Seventy-five percent of it was torn off. It would have to be removed to patch the hull.

There would be no saving the sub if the Hartford did not keep its shape when welders cut into the hull to remove the damaged section, or after they patched it.

And the team discovered after the submarine was taken out of the water that the bow plane had caved in to the ballast tank. The masts and antennas weren't working because hydraulic fluid had shot through the system after the collision and damaged many valves.

"In my 38 years here, we have never worked on something of this magnitude, repairwise," said Stanley J. Gwudz, the director of ship's management who likened the repairs to reconstructing a Model T.

This type of repair is "about as complex as they come," said Rear Adm. David M. Duryea, deputy commander for undersea warfare.

Retirees share knowledge

Because EB and its relatively young work force are set up for building today's Virginia-class submarines- not for major repairs to the aging Los Angeles class - some former employees came out of retirement to share their knowledge.

The trick was figuring out how to combine today's technology with yesterday's hand-drawn designs, some of which didn't match up. Daniel Vieira, the ship's manager for the repair project, laughed when asked how such a feat was accomplished.

"I lived it, and I'm not sure," Vieira said. "It was through a lot of pain. You know, you depend on a lot of people with a lot of experience and training to come back to you and say, 'This is right. This isn't. We need to fix this.'"

The biggest problem was that the sail had crushed into the pressure hull. It had been 20 years since anyone in the shipyard had performed a major cut into a submarine's hull, the pressure-tight shell of a submarine, while maintaining the circularity of the ship.

"The pressure hull is sacred ground," Vieira said. "It keeps water out. Anytime you have anything that penetrates the pressure hull, it's a big deal."

The half-moon shaped patch to fix the hull measured more than 150 square feet.

"It's very easy to get warping or misalignment or change the geometry with all the welding, which would have significant effects," Vieira said. "The ship is shaped that way for a reason."

Welders and shipfitters at EB's Quonset Point facility built a new sail using the modular construction techniques developed for the Virginia class. Years ago they would have had to fix the hull, then build the sail piece by piece on the submarine.

The repairs could have taken years if each step were done in sequence, instead of at the same time, Gwudz said.

Useful lessons learned

Few vendors still make parts for Los Angeles-class submarines.

In the crash, the bow plane was forced back into its locking mechanism, caving the structure into the ballast tank. A 16-inch diameter shaft bent 4 inches, but a new shaft wasn't available. So EB engineers incorporated the 4-inch bend into the design. A new, fully functional bow plane was built around the bent shaft to dive the sub.

The damaged valves were replaced.

Testing at sea in January showed the repairs to be successful.

Gwudz could only recall one other repair job at EB where the level of damage on a submarine came close to the severity of the Hartford's. In the early 1980s, he said, a Los Angeles-class submarine needed its masts fixed and a patch underneath. The graving dock was secured for this confidential job and Gwudz said he was never told how the submarine sustained its damage.

EB can now use what it learned working on the Hartford to repair other Los Angeles-class submarines more effectively, Gwudz said. The USS Alexandria (SSN 757) is at EB for routine maintenance.

Instead of taking a ventilation valve apart to see which of the older parts are corroded, for example, Gwudz said they will know to get new flappers or linkages because these parts were corroded on the Hartford. That gives vendors more time to make the parts so they are ready when EB needs them.

Robert Hamilton, an EB spokesman, said the Hartford repair job "used 50 Connecticut suppliers with a total spend of $3.5 million."

The project took more than one million man-hours and the efforts of 450 people at its peak.

The $120 million price tag is less than 5 percent of what it would have cost to replace the Hartford with a new Virginia-class submarine.

"Everybody in the Navy had a lot of confidence in EB and the NAVSEA team to execute the repairs," Duryea said, referring to the Navy command responsible for overseeing the construction and maintenance of the Navy's ships. "Certainly we knew it would be a challenge, but EB does a very good job at executing complex work. This was just another example of the fine work they were able to do.

"We needed this capability out in the fleet," Duryea said. "Hartford has a lot of good life left in her, and we wanted to get her back to sea."

Hartford at fault

EB originally built the Hartford at a cost of about $900 million.

The submarine returned to the Naval Submarine Base in February, nearly two years after the March 2009 crash and 18 months after arriving at EB.

The submerged submarine and the USS New Orleans (LPD 18), a San Diego-based amphibious ship, had both been heading into port when the collision occurred.

The fuel tank ruptured on the New Orleans, creating a 16-by-18-foot hole and spilling about 25,000 gallons of diesel fuel. Two ballast tanks were damaged.

Navy investigators concluded the crew of the Hartford was at fault. The sub's leadership was called "ineffective and negligent" and sailors were accused of falling asleep on the job, spending too much time away from their stations and chatting informally while working.

Vieira could see a silver lining in the task of repairing the Hartford. He said the repairs were an opportunity for senior employees to impart their knowledge to the younger ones so these newer employees will be able to help with work on the Los Angeles class in the future.

Duryea agreed that there were technical lessons learned but, he said, "my only hope is we don't have to do these types of repairs again."

j.mcdermott@theday.com