The New England Clean Power Link (NECPL) developed by TDI New England (TDI-NE) is a proposed high voltage direct current (HVDC) transmission line from the Canadian border at Alburgh, Vermont to Ludlow, Vermont along underwater and underground routes. The project includes the installation of approximately 97 circuit miles of marine cable along the bottom of Lake Champlain, requiring transition into and out of the Lake by Horizontal Directional Drilling (HDD). The southern exit from the Lake is located in Benson, Vermont where the transmission system will follow town roads eastward. Approximately 54 miles of transmission system will be installed four feet underground along existing highway and town road rights-of- way with an additional three miles along state railroad property. The HVDC line will terminate at a converter station in Ludlow that will change the power from direct current to alternating current power which will be transferred to VELCO’s existing Coolidge substation via an underground 345kV transmission system.
When complete, the system will deliver 1,000 MW of clean, affordable electricity from Canada to the New England power grid.
As lead engineer, TRC supported project design from inception through permitting, contributing to activities including routing, resource assessment, agency consultation, and application development. TRC staff provided testimony for public hearings conducted by the Vermont Public Utilities Commission and participated in mitigation negotiations with Federal and State agency staff.
TRC also led the project’s geotechnical investigation activities that consisted of drilling test borings through soil and rock at over 194 locations along the 57 mile overland portion of the project including the proposed converter station. Since the proposed transmission cables will be installed utilizing various methods that will included trenching, horizontal directional drilling (HDD), and jack and bore, the depth of the test borings varied from as shallow as 12 feet for the trenching portion to nearly 100 feet in depth for the HDD locations. Services included engineering oversight and logging of the test borings, laboratory testing of soil and rock, field and laboratory testing of the thermal resistivity properties of the soil and rock, and preparation of a geotechnical data report. These pre-construction geotechnical activities are important to complete the final design and refine the cable construction techniques.
You can learn more about the geotechnical aspects of the project, including TRC’s process, equipment used, and subsurface findings in this video from TDI-NE.
As the project continues to progress, TRC is also supporting the transmission system. During project implementation, TRC expects to provide detailed design and engineering of the entire terrestrial route, including cable installation, ductbank design, HDD design, stream crossings, manholes, 320 kV DC and 345 kV AC riser structures, municipal road improvements, state highway repairs, related infrastructure improvements and facilities. In addition, we will provide on-site monitoring of environmental compliance, consulting, liaison with state officials, and permitting support. Finally, TRC will provide on-site construction monitoring and QA inspections and coordination. (This work will be performed by others and not directly to TDI-NE.)