General Dynamics Electric Boat Corp., Groton, Connecticut, is awarded a $475,002,626 cost-plus-fixed-fee and cost-plus-incentive-fee modification to previously awarded contract N00024-17-C-2117 for lead yard support efforts serving the entire Columbia-class fleet ballistic missile submarines (SSBNs) through 2028. The contract modification also provide continued support for class continuous production of shipyard components, shipyard labor in support of fully outfitted missile tubes, and submarine industrial base development and expansion as part of the integrated enterprise plan (IEP) and multi-program material procurement supporting Columbia SSBNs and the nuclear shipbuilding enterprise (Virginia-class and Ford-class). The industrial base development work is for the furtherance of the fiscal 2021 National Defense Authorization Act (Public Law 116-283) which authorized, and the Department of Defense Appropriations Act, 2021 (Public Law 116-133) which appropriated, additional funds for submarine industrial base development and expansion to ensure second- and third-tier contractors are able to meet increased production requirements. Additionally, this modification includes additional IEP investments in production backup units (PBUs) and continuous outfitting of missile tubes. Work will be performed in Groton, Connecticut (97.3%); and Newport News, Virginia (2.7%), and is expected to complete December 2031. No funding will be obligated at the time of award. This contract was not competitively procured. This is a sole source award in accordance with Defense Federal Acquisition Regulation 6.302-1(a)(2)(iii) — only one responsible source and no other supplies or services will satisfy agency requirements. The Naval Sea Systems Command, Washington, D.C., is the contracting activity.