BLOCK ISLAND, R.I. – Orsted offshore wind development company and National Grid have agreed to bury their offshore transmission cables to new and required depths after the cables became exposed in shallow water last spring at a popular beach, according to New Shoreham facilities manager Sam Bird.
“We need it buried to the depth that it should be buried,” Bird said of the two cables that land at Crescent Beach about 100 feet apart.
The town of New Shoreham, which includes all of Block Island, and the Rhode Island Coastal Resources Management Council have jurisdiction over aspects of the two cables. The Orsted cable runs from a five-turbine offshore wind farm to the island, and the National Grid cable runs from the island to the mainland.
“Both cables are not buried to their designed burial depths,” Bird said. But what appears to be an unexpected rocky and boulder-filled ocean floor combined with a beach with dynamic accretion and erosion, led to the mainland cable becoming exposed last summer in shallow water, he said. Likewise, the wind farm cable was exposed briefly later last summer, and company officials came immediately to dump sand on it, Bird said.
Currently, neither cable is visible in the water, but in a depth profile in early May, the mainland cable was still not nearly deep enough, he said. “A foot of sand on an easterly-facing beach can disappear in 12 hours in one good storm,” Bird said. “Our sand is extraordinarily fine. We could lose a foot of beach in a heartbeat.”
National Grid intends to protect its mainland cable through the summer by installing buoys and monitoring a no-anchor zone mandated by the Rhode Island council, company spokesman John Lamontagne said. There are no safety concerns through direct or indirect contact, such as swimming, Lamontagne said. Another order from the state council would likely lead to reburial of that portion of the cable via horizontal directional drilling once engineering and design plans are complete, with a late 2020 or early 2021 construction schedule, he said.
Likewise, Orsted is currently designing a plan to reinstall part of its wind farm cable, and is exploring whether there are other methods to ensure the cable is maintained at a proper depth in the long run, company spokeswoman Meaghan Wims said. “We are working closely with the town, the Rhode Island Coastal Resources Management Council, and National Grid to deliver the solution expeditiously,” Wims said.
On Monday afternoon, a petition raising issues about Vineyard Wind’s cables that are set to land at Covell Beach in Centerville had 392 signatures. The petition expresses concern about radiation exposure, the health of marine and land life and protection of drinking water. The Vineyard Wind project has in May received approvals from both the Cape Cod Commission and the Barnstable Conservation Commission.
Vineyard Wind intends to bury its cables with the horizontal directional drilling technique, starting at the Covell Beach parking lot and then drilling out to about 1,000 feet offshore, company spokesman Scott Farmelant said. At the beach’s low-water mark, the cables would be buried at about 30 feet, and farther out, where a land-based cable would connect to the main wind farm cable, the depth would be about 5 to 8 feet, Farmelant said.
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