Groton — Electric Boat on Friday marked the start of a major construction project — the biggest to take place in its Groton shipyard in more than 45 years — that will enable the company to build the next class of ballistic missile submarines at the same time it is churning out attack submarines.

Separately on Friday, EB issued a news release saying that company President Jeffrey Geiger will retire Sept. 30 and will be replaced by General Dynamics National Steel and Shipbuilding Company President Kevin Graney. There was no mention of Geiger's impending retirement at the earlier groundbreaking ceremony.

Geiger has served as president since 2013, overseeing a time of growth at the company due to a resurgence of submarines in U.S. national security policy. The company has hired thousands of new employees in recent years, and EB's parent company, General Dynamics, is spending more than $1.7 billion to modernize and upgrade its facilities in Connecticut and Rhode Island as a result of the increased workload. Earlier this week, the company announced the completion of a building at its Quonset Point facility that will support construction of the nation's newest attack submarines.

An $850 million expansion is planned for EB's Groton headquarters, the centerpiece of which will be a new 200,000-square foot building, where the ballistic missile submarines will be assembled.

Underscoring the scope of the project in Groton, Geiger said, "about 11,000 tons of steel will be used in construction, equivalent to the Eiffel Tower."

The project will create hundreds of construction jobs, he said, and once the building is complete, more than 1,400 EB employees will be involved in constructing and testing the Columbia-class ballistic submarines over the next 20 years.

The company, which currently has a workforce of more than 17,000, will continue to hire and train thousands of new employees and grow its supply base by more than 3,000 companies, Geiger said.

"This is clearly going to be a defining moment for Connecticut's economy for decades to come," said U.S. Rep. Joe Courtney, D-2nd District, who's chairman of a congressional subcommittee with oversight of Navy shipbuilding.

"What we're doing here is not really just about the regional economy, it's something extremely important for the country and we should all, all be proud of that," Courtney said.

This will be the first time since the early 2000s that EB will be working on two different classes of submarines at the same time, and it has not built ballistic missile submarines since the late 1990s. The Columbia submarines will be the biggest ever built and involve 2.5 times the amount of work of the Virginia-class attack submarines the company is currently building.

U.S. Sen Richard Blumenthal, D-Conn., ranking member of the Senate Armed Services Committee, said the Columbia submarines will be the "stealthiest, strongest, most versatile boat involved in nuclear deterrence, the key part of our nuclear triad, the most reliable source of deterrence that we have against nuclear attack."

j.bergman@theday.com