General Dynamics Electric Boat (GDEB) has received a contract worth $9.474bn from the US Navy for the construction and testing of the lead and second ships of its Columbia-class submarines.

The contract also includes related design and engineering support for the two submarines, SSBN 826 and SSBN 827.

Previously called the SSBN-X Future Follow-on Submarine, a class of 12 new Columbia-class submarines will replace the US Navy’s existing force of 14 ageing Ohio-class ballistic missile submarines.

The prime contractor of the Columbia programme is Electric Boat.

As per the contract, the company will be responsible for the complete construction of SSBN 826, Columbia.

For the second vessel, SSBN 827, Wisconsin, the contract includes the advance procurement, advance construction, and associated engineering efforts. The construction of the vessel will commence in FY2024 following Congressional authorisation and appropriation.

Around 78% of the construction of the vessel will be carried out by Electric Boat, which transferred the programme to full-scale construction at its Quonset Point manufacturing complex.

Four of the six ‘supermodules’ will be constructed at the Quonset Point facility.

Following the construction, the supermodules will be shifted to the Final Test and Assembly yard in Groton in Connecticut.

The assembly will take place in a new facility, spread over 200,000ft², which is being constructed for the Columbia class.

The submarines will be 560ft-long and will have a displacement of 21,000t. They are claimed to be the largest submarines being constructed by the US.

Assistant secretary of the navy for research development and acquisition James Geurts said: “I applaud the efforts of the navy and industry team who worked aggressively on this contract.

“Columbia is the navy’s number one acquisition priority programme. Awarding this contract on time is vital to keeping the programme on track.”

Last month, the US Navy named its second Columbia-class ballistic missile submarine as Wisconsin and bear SSBN-827 as the hull number.