Groton - In the wake of the Navy's decision to scrap rather than repair the USS Miami, Navy and Electric Boat officials do not yet know how badly jobs will be affected at the shipyard.

More than 350 people were hired at EB late last year and early this year to work on the Miami (SSN 755) and to perform maintenance work on other submarines. While the figure varies daily, about 250 people are currently assigned to the Miami project. Employees at the Portsmouth Naval Shipyard in Kittery, Maine, where the Miami is in a dry dock, support their work.

The Groton-based submarine was severely damaged at the Portsmouth Naval Shipyard in May 2012 when a civilian worker set a fire on board during a planned 20-month overhaul. The Navy announced Tuesday that the cost estimate for the repairs had increased from $450 million to $700 million and, given the current fiscal constraints, top Navy leaders had decided to change course.

Rear Adm. Richard Breckenridge, director of undersea warfare, said the decision on the Miami's fate, made ultimately by the chief of naval operations and the secretary of the Navy, was "heart-wrenching," but in this "highly-pressurized environment," it was the "most prudent and responsible decision we could make."

The loss of work in Kittery will be less drastic because they will take the lead in inactivating the submarine - a $54 million project that will take about a year and a half to complete.

The Navy was planning on moving most of the repair work to EB.

Editor's note: This version corrects an earlier version.

"The surge to EB to do the repairs is what is getting canceled," Breckenridge said Wednesday in a conference call with reporters. "So we, as a navy, are looking hard at other projects we may be able to provide to EB to dampen this impact to them with their workforce."

EB won a $94 million contract in September to plan for the repairs. The repair contract also was expected to go to EB. Restoring the Miami would require 1.5 million labor hours, EB President Kevin J. Poitras told local legislators in January.

EB expects to start repairs in December on the USS Providence, a submarine that initially was scheduled to go to Kittery. But that $45 million job represents far fewer labor hours, about 240,000.

The Navy could use some EB employees in Kittery to help remove Miami from the fleet.

Poitras was traveling and could not be reached for comment Wednesday. Company spokesman Robert Hamilton said he could not yet discuss the employment outlook because the shipyard has not been told what the transition plan will be.

EB built the Miami, a Los Angeles-class submarine, for $900 million. It was commissioned at the Naval Submarine Base in Groton in 1990. The submarine had 10 years left in its 30-year service life, making it eligible for at least five more deployments.

The most important thing to do to compensate for the loss of the five deployments is to keep the production rate for Virginia-class submarines on track, Breckenridge said. EB and Newport News Shipbuilding in Virginia jointly build two attack submarines per year, and there are 53 attack submarines in the fleet.

If the shipbuilders continue to shorten the construction schedule, Breckenridge said, there will be more submarines in the fleet to deploy. The schedule for deployments could be adjusted, and some deployments could be extended if needed, he added. He said he does not believe there is any possibility of increasing the production rate to three per year.

Breckenridge was the Submarine Group Two commander in charge of the Miami at the time of the fire. He also was a government witness in the case against Casey James Fury, who was sentenced to more than 17 years in federal prison in March after he pleaded guilty to setting fire to rags aboard the Miami.

Casey, a civilian painter and sandblaster, told authorities he suffered from anxiety and wanted to leave work. Seven people were injured fighting the blaze, which burned for 12 hours.

Breckenridge said the Navy was committed to restoring the Miami to service, but cracking in steel piping and fasteners in the air, hydraulic and cooling water systems was discovered in April, and progress on the repairs was slowed by the civilian hiring freeze and overtime limits under the automatic spending cuts known as sequestration.

The Navy would have needed $390 million in fiscal 2014 to continue the work, move the work to EB and set aside funds for potential cost increases, Breckenridge said. And it would have had to delay critical maintenance on other ships and submarines, including the Groton-based USS Alexandria, he said.

About $50 million has been spent on repairs so far. The Navy would have spent some of that, in any case, on cleaning up the submarine after the fire, Breckenridge said.

The Alexandria will go to Kittery next year, as previously planned.

j.mcdermott@theday.com