Cables at beach being surveyed, again
National Grid and Deepwater Wind/Ørsted continue to collect information that will be used to design the reinstallation of sections of the electric transmission cables that became exposed in the surf zone at the Fred Benson Town Beach.
As part of that effort, simultaneous benthic surveys of both National Grid’s sea2shore cable and Deepwater Wind/Ørsted’s export cable will be conducted beginning next week. A specific start date has not yet been determined.
The surveys were scheduled to begin on Oct. 9 and run to Oct. 19 in a designated area off of Town Beach, but National Grid postponed the work due to this week’s stormy weather.
National Grid’s cable links the mainland to the island, while Deepwater Wind/Ørsted’s export cable connects the Block Island Wind Farm to the island’s electrical grid. (According to National Oceanic and Atmospheric Administration, the term benthic refers to anything associated with, or occurring at the bottom of a body of water. A benthic survey is the way that scientists assess the health or status of the marine environment.)
Assessment of the cables has involved an assortment of surveys and studies as the two companies try to determine the best method for reinstalling the exposed sections of their cables, which were discovered in August of 2018. On Oct. 5, the companies issued a joint press release outlining the upcoming survey activity that included a map.
“The purpose of the upcoming marine survey is to conduct high resolution geophysical (HRG) site investigations off Crescent Beach, along near-shore sections of the National Grid owned sea2shore and Orsted owned cable route corridors,” Ted Kresse, Director of Strategic Communications for National Grid, told The Block Island Times. “This will support the planning and design of horizontal directional drilling (HDD).”
National Grid said that horizontal directional drilling will involve a complex exercise of drilling from the parking lot at the Town Beach, under the dunes and the seabed out to a designated point offshore. A section of cable will then be spliced offshore after being threaded through a conduit from the parking lot to a vessel in the surf zone.
Kresse said National Grid will utilize the benthic survey for “gathering data that will then be put into a profile illustration that can help us understand the seabed conditions for further engineering. It will provide information on soil types, presence of vegetation, if there are any large boulders, maybe even potential shipwrecks.”
As for National Grid’s overall plans involving reinstallation of the exposed cables, Kresse said, “We are confident this plan will resolve the current challenges of sediment coverage over the cable.”
Kresse noted that National Grid intends to issue Requests for Proposal by year’s end. “We are still on track with our timeline to have the project completed by the summer of 2021.”
National Grid said it experienced hard seabed and was unable to meet its desired burial depth during installation of the sea2shore cable in June of 2016. Both companies have said that dense sediment and shifting sands were partly attributable to sections of the cables becoming exposed.
Jeffery Wright, President of the Block Island Utility District, told The Times that the survey work will not cause any power interruptions on the island. “I have not been notified of any power outages, so it’s safe to assume the cable will remain in service” during the duration of the survey activity.