Assembly Starts for First U.S. Rock Installation Vessel for Offshore Wind

keel block
Keel block for the rock installation vessel lowered into the Philly Shipyard assembly dock (Great Lakes Dredge & Dock)

Published May 16, 2024 7:51 PM by The Maritime Executive


Great Lakes Dredge & Dock Corporation reports that construction has begun on its subsea rock installation vessel, the first of its kind planned for the U.S. and the first to be Joens Act complaint. The vessel is part of the company’s long-term growth strategy to enter the U.S., and possibly internationally, offshore wind market. The vessel is designed to put the company in a unique business position in the U.S. market while it also continues to pursue and tender bids both domestically and internationally.

The first section, known as the grand block, was placed into the assembly dry dock at the Philly Shipyard on May 2.  The company first announced its intentions for the vessel in December 2020 and confirmed the order with Philly Shipyard in November 2021. Work on the vessel began in the summer of 2023 with a ceremonial first steel cut attended by President Joe Biden. 

The yard reported the contract was for $197 million for the first vessel, originally scheduled for delivery in the fourth quarter of 2024, and with Great Lakes retaining a right of first refusal on a second ship possibly for the fourth quarter of 2025. The total value of the order if both vessels are built would be $382 million.

The basic design was developed by Ulstein and it will be unique in the U.S. market as the only purpose-built vessel to lay rocks and material used to protect and stabilize foundations and cables for offshore wind farms. The vessel will be 461 feet (140.5 meters) with crew accommodations for 45 people and a capacity to carry up to 20,000 MT of rock.

“Keel laying, commonly referred to as the birthday of a ship, is a big milestone in the ship construction process, said Lasse Petterson, CEO of Great Lakes. “We are so pleased to be at this stage with our new vessel, as we can see the results of years of planning and engineering coming together with Philly Shipyard.”


Rendering of the rock installation vessel (Great Lakes Dredge & Dock)


The new vessel, the Acadia, already has contracts to provide critical services to Equinor’s Empire Wind 1 wind farm in New York in 2025 and Ørsted’s Sunrise Wind project. Today, New York State granted final approval for the Empire Wind 1 project moving it a step closer to construction. Equinor has said work would begin at the onshore site in Brooklyn with a final investment decision expected before the end of this year.

Great Lakes, however, was also notified by Equinor that it was canceling a second contract that had been awarded in consortium with Van Ord. That cancellation was announced in January for the work planned in 2026 on Empire Wind II. Equinor has said it was holding the second phase of the wind farm after canceling its power purchase agreement with New York State. The company received approvals from the federal government but would need to submit the project in a future New York solicitation.

The company recently told investors during its first quarter financial report that it expects to take delivery of the Arcadia in 2025. They said they were pursuing and bidding on projects both in the U.S. and internationally for 2026 and beyond.

At the first steel cut in July 2023, President Biden highlighted that the vessel is one of 18 offshore wind shipbuilding projects as well as investments of nearly $3.5 billion across 12 manufacturing facilities and 13 ports to develop the U.S. offshore wind supply chain. The vessels are being built at shipyards ranging from Florida to Louisiana, New York, Massachusetts, Michigan, Rhode Island, Wisconsin, and Pennsylvania. A month ago, Dominion Energy announced that its wind turbine installation vessel, also the first being built in the United States, had been launched at a shipyard in Texas.