Groton ― The U.S. Navy has awarded Electric Boat a $967 million modification to the contract that made the company the prime contractor and lead design yard for Virginia- class submarines.

The original contract awarded four years ago and subsequent modifications add up to $2.2 billion, based on figures from the US Department of Defense. Electric Boat is a subsidiary of General Dynamics Corp.

Work is expected to be completed by next October.

The US Department of Defense in this week’s announcement said the majority of the award supports work at the Groton shipyard, including development studies and design efforts related to Virginia-class submarines. The remaining 5% will go toward work in McLeansville, North Carolina; Newport News, Virginia; and Newport and Quonset, Rhode Island.

The submarines are built jointly with the Newport News shipyard.

Electric Boat President Kevin Graney in a news release said the contract “supports critical work to further advance the capability and superiority of the Virginia-class submarine.”

Virginia-class submarines are designed for functions including anti-submarine and surface ship warfare and special operations support, the company said.

The company is also the prime contractor and lead design yard for the Columbia-class ballistic missile submarines.

Electric Boat added about 3,700 new workers in 2022, bringing its workforce to 19,500 people. With a total of 21,000 employees identified in this week’s announcement, the company continues its push to meet the demands of its contracts as local real estate developers propose and construct new apartment buildings to meet the increased demand for housing.

e.regan@theday.com