(Bloomberg) -- A delay of as much as 16 months in delivering the first of the US’s first Columbia-class nuclear-missile submarines — the Navy’s top weapons priority — stems from contractor delays in delivering the vessel’s bow section and power generators, according to an internal assessment by the service.

The lead vessel, the USS District of Columbia, was scheduled to be delivered in October 2027 so that it could go on its first deployment in 2031. 

The House Armed Service’s seapower subcommittee is holding a hearing Wednesday to review the Navy’s fiscal 2025 shipbuilding request as well as this month’s review by the service of its ship programs, which disclosed the Columbia delay of as much as 16 months but not the reasons in detail.

Contractors General Dynamics Corp. and HII are designing and constructing the 12-boat class, a roughly $130 billion program, with each sub assembled from six large hull segments. During construction, these “super modules” are outfitted with systems and connections before final assembly by General Dynamics.

The Navy calls the bow section that’s under contract with HII “Super Module No. 1,” reflecting its significance.

HII was to ship the bow in May 2025 from its Newport News, Virginia, yard to the General Dynamics facility in Groton, Connecticut. That’s now estimated for June 2026, or 13 months late, according to internal service figures. The service declined to discuss the reasons.

HII said in a statement that “we experienced first-in-class challenges on a complex welding sequence” that required revising the plan for “the largest submarines ever built in the US.” A revised plan “was successfully executed and is now incorporated on follow-on ships,” it said.

In addition, Northrop Grumman Corp. was contracted by the Navy to deliver the first ship’s turbine generators by November 2021, which would have provided months of margin before they’d be needed.

Instead, the turbine generators are projected to be delivered in early 2025, according to a Navy statement. Each sub has two of the generators that provide the vessel’s propulsion and electrical power requirements. 

‘Lagging’ Performance

The Government Accountability Office said in a January 2023 assessment that delays on the first submarine were looming in part because of “lagging shipbuilder performance on design products.”

Navy Secretary Carlos Del Toro said in a brief interview that he’s sure the delay of the power generators “has something to do with the amount of labor” required and the inexperience “of the labor force there at Northrop Grumman — questions that the leadership will have to answer.”

Northrop spokesman Lindsey Borg said in statement that the company “is fully committed to the program, and is fully supportive of General Dynamics and the US Navy as we work to together to deliver this program.” He referred questions to General Dynamics, which in turn referred questions to the Navy.

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