National Grid and Ørsted prep for Block Island cable repairs

In: CablesWindfarms
05/10/2020

National Grid and Ørsted have begun mobilising teams that will work throughout the autumn and winter to replace limited segments of the
Block Island offshore wind farm and sea2shore transmission cables, to achieve greater 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. After due diligence, teams from Ørsted and National Grid determined that the best approach to maintain the required burial depths of the two transmission cables is to reinstall these limited segments with new sections adjacent to where the existing cables now sit.

Over the next few weeks, teams for both National Grid and Ørsted will begin staging equipment and barges that will be used for their work. The cable landings will be constructed using a horizontal directional drill (HDD), and a conduit will be installed for the new length of onshore cable, including a new access pit. The drilling phase of the construction work at Town Beach is scheduled to begin this autumn, with the ocean-based cable installation scheduled to begin in early spring next year.  

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, with an anticipated completion date before Memorial Day (end-May) 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.

“We’re confident in the solution we’ve developed to ensure the Block Island Wind Farm transmission cable remains buried deeply below the ocean floor,”
said Mikkel Mæhlisen, Head of Operations, Ørsted North America, Offshore. “We’re working closely with the Town of New Shoreham to ensure that all of our work is completed in the offseason, with as little impact to Town Beach visitors and as minimal interruption to the energy supplied from the wind farm as possible. We are grateful to town and state leaders for their close collaboration on this important work.”

“As the first offshore wind farm in the nation, the Block Island Wind Farm remains an enormous source of pride for all of Rhode Island,”
said Terry Sobolewski, President of National Grid Rhode Island. “Both National Grid and Ørsted have been working rigorously with the town and state and federal partners on an enduring plan to address burial depth, and even amidst the pandemic, we are on track to having it completed in time for next summer.”  

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 US 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.


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