Keel laid for first US subsea rock installation vessel

The keel for the first Jones Act-compliant subsea rock installation vessel (SRIV) for the U.S. offshore wind industry, Acadia, was laid on May 2 at the Philly Shipyard in Philadelphia, Pennsylvania.

The vessel was ordered by Great Lakes Dredge & Dock Corporation (GLDD) in 2021 and the first steel for the SRIV was cut in July 2023.

With Acadia set to become the only Jones Act-compliant rock placement vessel in the U.S. commercial fleet, the SRIV is a critical vessel needed to develop the offshore wind projects the U.S. has planned and permitted, GLDD said in a social media post on May 16.

The vessel is of an Ulstein design and has an overall length of 140.5 metres (461 feet), a breadth of 34.1 metres (112 feet), and crew accommodations for 45 people.

Acadia can carry up to 20,000 tonnes of rock and deposit it on the seabed at monopile foundation locations within an offshore wind project site.

In May 2022, Equinor and BP selected a consortium comprising Van Oord and GLDD for subsea rock installation work at their Empire Wind offshore wind farms in New York, now owned solely by Equinor.

At the beginning of this year, BP and Equinor notified Van Oord and GLDD of the termination of the rock installation contract for the Empire Wind 2 project, which was set to commence in 2026, following the developers terminating their power purchase agreement with the state.

The Empire Wind 1 project has officially entered construction and is on track for rock installation next year.

In July last year, Great Lakes Dredge & Dock signed the first-ever subcontract for the procurement of rock for an offshore wind farm with Carver Sand & Gravel, under which GLDD will use rock produced in New York to provide scour protection for Empire Wind offshore wind turbine foundations and substations.

In December 2023, the Texas-based company announced it was awarded its third subsea rock installation contract for an offshore wind farm off the U.S. East Coast, leaving the project and the client unnamed.

All the contracts in GLDD’s pipeline so far will be executed using the Acadia subsea rock installation vessel.

GLDD signed an agreement for two vessels with Philly Shipyard, with GLDD retaining the right of first refusal on a second vessel.