National Grid and Ørsted have begun mobilizing teams that will work throughout this fall and winter to replace limited segments of the Block Island Wind Farm and sea2shore transmission cables to achieve proper burial depths beneath the ocean floor. The effort includes replacing approximately 1,700 feet of National Grid’s sea2shore submarine cable that carries electricity between Block Island and mainland Rhode Island, and approximately 3,100 feet of Ørsted’s submarine cable that carries electricity from the Block Island Wind Farm to Block Island.
The submarine cables were installed in the spring/summer of 2016 and subsequently experienced challenges with sediment coverage over the cables. After extensive due diligence, teams from Ørsted and National Grid determined the best approach to maintain proper burial depths of the two transmission cables is to reinstall these limited segments of the cables with new sections adjacent to where the existing cables now sit.
Through the end of October teams for both National Grid and Ørsted will be staging equipment and barges that will be used to replace the cables’ shore landings. The cable landings will be constructed using a horizontal directional drill (HDD), a common procedure for submarine cables such as these. The land-based phase of the construction work at Town Beach is scheduled to begin Fall 2020, with the HDD and ocean-based cable installation scheduled to begin in late winter or early spring.
The HDD will bury the cables at a depth of between 25 to 50 feet below the seafloor, as compared with the current 4 to 6 feet. This is deep enough to withstand changing ocean floor conditions and provide a continued reliable interconnection for Block Island and the Block Island Wind Farm for years to come. The new cables will be spliced onto the existing cable that connects the Island, the wind project and the mainland. The existing portions of the exposed cables are scheduled to be removed at the end of construction.
Construction related activities will be ongoing throughout the fall and winter, with an anticipated completion date before Memorial Day 2021.
Block Island and Rhode Island will continue to receive electricity from the wind farm during the construction, except for a brief outage in the spring, when the new cable will be spliced with the existing cable. During the National Grid cable and Block Island Wind Farm outage, Block Island Power Company (BIPCo) will provide the needed electrical power to the Island utilizing its on-island diesel generation.
National Grid and Ørsted have worked in close collaboration with the Town of New Shoreham, the Rhode Island Coastal Resources Management Council, Rhode Island Department of Environmental Management, the U.S. Army Corps of Engineers, and other key agencies to receive the necessary work permits and to keep stakeholders informed of the plans.
All work crews will follow CDC COVID-19 guidelines regarding social distancing, masks and hygiene.