115 kV submarine cable Boston Harbor crossing

The Massachusetts Water Resource Authority (MWRA) is constructing a major sewage treatment facility at Deer Island located in Boston Harbor. A new 115 kV submarine cable fed from the Boston Edison Company (BECo) substation across the Harbor was chosen to provide one of the required offsite power sources for the facility. The cable had to be installed five years prior to the treatment facility startup to provide construction power. This required an extremely fast track schedule for licensing and construction because the power supply had to be in service in less than two years from the time of conception. Authorization to proceed was given in August 1988. The submarine cable installation was completed in March 1990. The cable design consists of three single-conductor, 115 kV self-contained fluid-filled (SCFF) armored cables. The three cables were simultaneously embedded as deep as 7.6 m (25 ft) into the Harbor bottom using the hydrojet installation method. Approximate length of this Harbor crossing is 6 km (20000 ft). The route selection, permitting effort, cable design, and installation method are discussed