A/Z was engaged by Electric Boat to provide specialty construction services for the T105 Substation Transformer Project. The project team was responsible for removing an existing 1,500 kVA unit substation, which consisted of two 15 kV disconnect switches, one 1,500 kVA dry-type transformer, and one secondary switchgear lineup consisting of a 480 V, 3,000 A main circuit breaker and twenty 480 V, 600 A feeder circuit breakers. The unit substation was replaced by the team with a three-way 15 kV fault-interrupting vacuum switch, a 1,500 kVA Uniclad enclosed transformer, and a walk-in switchgear house.New cables were connected from the secondary switchgear to the existing circuits. Additionally, the project team was responsible for the necessary high voltage switching, disconnecting, and relocating and reconnection of both high and low voltage cables as well as general demolition, cable testing, structural steel, and cast-in-place concrete work. Upon the successful completion of these construction activities, A/Z was responsible for re-energizing the switchgear.