The South Yard assembly building at General Dynamics Electric Boat in Groton, Conn. — dubbed Building 600 — has been assigned an appraised value of nearly $640 million. (General Dymanics Electric Boat)

(Tribune News Service) — The USS District of Columbia will be among the most expensive ships in U.S. history, when the nuclear submarine launches years from now into the Thames River at a projected cost of $16 billion, at last report.

As for the riverfront Groton “shed” that houses the sub under construction today? That catapulted to become one of Connecticut’s most valuable buildings — with Groton taxpayers the possible beneficiaries.

The South Yard assembly building at General Dynamics Electric Boat — dubbed Building 600 — has been assigned an appraised value of nearly $640 million for the October 2023 grand list, according to the town of Groton’s tax assessor. That increases the value of the 75-acre shipyard campus by roughly 60% on paper, to more than $1.6 billion.

“Electric Boat ... became our top taxpayer in 2023 for the first time since the 1980s,” said Mary Gardner, Groton’s town assessor. “EB ruled in the ‘80s and then Pfizer took over.”

General Dynamics built the “shed” facility for assembly of the Columbia-class ballistic missile submarine, which the U.S. Navy plans to phase in as the replacement for its existing, Ohio-class subs nearing the end of their planned lifecycles. As construction in Groton ramped up between 2019 and 2020, the company reported a $155 million increase in capital expenditures supporting its marine systems segment, which includes Electric Boat and shipyards in Maine and California.

Under former president Joe Biden’s administration, Department of Defense officials routinely cited the Columbia-class sub program as the nation’s top military priority. As of November 2024, the first sub was just over half complete according to the most recent estimates the Navy provided the Congressional Research Service, with General Dynamics stating in its recent 2024 annual report it aims to complete the sub by 2028.

Columbia-class subs will be launched over 20 years as sections are barged to Groton from an Electric Boat shipyard in Rhode Island and from Newport News Shipbuilding in Virginia operated by Huntington Ingalls Industries.

Including development costs, the total program is currently projected to cost $130 billion. Once complete, the South Yard assembly building at Electric Boat would likely take on assembly work for a planned attack submarine fleet that, over time, would replace today’s Virginia-class subs.

The South Yard assembly building is among a few new additions to Electric Boat’s Groton campus, along with a new building for engineer offices and an emergency response center; and one to house and train the Navy sailors who will be on board.

The state Department of Economic and Community Development awarded General Dynamics property tax abatements under the Connecticut Enterprise Zones program, which resulted in the value of state investments under the program rocketing to nearly $684 million covering the grand-list year of 2023. That was about equal to the combined value of Enterprise Zone certificates over the preceding five years, with DECD spokesperson Jim Watson confirming that the Electric Boat investment drove the spike.

Groton Mayor Rachael Franco could not be immediately reached for comment on how the expanded Electric Boat campus might affect taxes for property owners in that town, once the incentives run their course.

More than 45 cities and towns in Connecticut participate in the Enterprise Zones program, which allows them to select projects for tax incentives in qualifying neighborhoods based on certain economic criteria, including employment, income trends or an older stock of existing housing.

Companies can receive an 80% abatement on local property taxes for five years, including the cost of machinery and equipment. The incentives can cover investments in existing structures, if those dollars increase the facility’s value by at least half, or if it brings a dormant property back into economic activity that had gone dark.

The incentive can be applied as well to companies that lease facilities, if the lease runs five years with an option to renew or a deal otherwise to purchase the property.

General Dynamics is already looking ahead to additional facilities, stating in its recent annual report it will work with the Navy “on any additional construction needs that could develop in light of increased submarine demand.” In January, it purchased land in North Stonington for a future warehouse facility, while continuing to invest as well in its auxiliary shipyard in Quonset Point, Rhode Island, and an Austal USA shipyard in Mobile, Alabama, which is building a new facility to make components for Columbia- and Virginia-class subs.

Includes prior reporting by Paul Schott and Luther Turmelle.

©2025 the New Haven Register (New Haven, Conn.).

Visit www.nhregister.com.

Distributed by Tribune Content Agency, LLC.