This $600 million project involved the construction of a 53-mile undersea high voltage direct current (HVDC) transmission link between San Francisco's City Center electrical power grid and a Pacific Gas & Electric substation near Pittsburg, California. With minimal impacts on the bay's ecology, the HVDC Plus system will transmit up to 400 megawatts at a direct current (DC) voltage of 200 kV and is the first order for Siemens' innovative HVDC Plus technology.

Carlton Engineering provided structural engineering, civil engineering, architecture, and site landscaping design of the converter buildings at each end of this transmission link. Site plans, engineering design and construction drawings and were Carlton's responsibility. Specific challenges included an 18-month fast-track schedule and numerous changes in equipment during design, as the latest evolution of Siemens' technology concluded test trials and incorporation into the design. Carlton's team met the challenges of producing efficient designs based on stringent California building code requirement for seismic design, and ensuring that designs met the requirements of IEEE 693, which governs the seismic design of electrical substations.

Carlton provided Resident Engineer services during the construction of both converter stations.