VESSEL REVIEW | Acadia – Large-capacity rock installation vessel to support US offshore wind projects
Great Lakes Dredge and Dock (GLDD) has taken delivery of a new subsea rock installation vessel (SRIV) built by Hanwha Philly Shipyard in Pennsylvania.
Acadia has been engineered to transport and precisely install up to 20,000 tonnes of rock on the seabed.
GLDD said this rock would provide critical scour protection for subsea infrastructure including subsea cables for power transmission, telecommunications cables, oil and gas pipelines and subsea structures and offshore wind turbine foundations, preventing erosion caused by waves and currents and mechanical impacts from equipment and vessels.
First vessel of her kind to be built and operated in the US
Acadia was designed by naval architecture firm Ulstein Design and Solutions. The SRIV has a steel hull, an LOA of 140.5 metres (461 feet), a moulded beam of 34.1 metres (112 feet), a maximum draught of seven metres (23 feet), a depth of 10.7 metres (35.1 feet), and accommodation for up to 45 personnel.
GLDD said Acadia is the first US-flagged, Jones Act-compliant SRIV. The vessel will install protective rock layers at offshore wind turbine foundations using an inclined fall pipe system deployed over the side and down to the seabed, thus ensuring precise subsea rock installation.
Ulstein helped design the fall pipe and the rock transport mechanism, which uses excavators and conveyors to deliver rocks from the SRIV’s onboard storage to the seabed.
A large and robust aft deck area will meanwhile enable specialised subsea operations, making it an essential tool for offshore wind projects.
Configured for generating reduced emissions
The SRI is fitted with two 3,150kW (4,220hp) and two 2,250kW (3,000hp) US EPA Tier IV engines that drive two 2,500kW thrusters to deliver a service speed of 12 knots. The vessel is also able to run on biofuel to reduce its CO2 footprint and is equipped with active emission control technology to minimise NOx emissions.
The propulsion arrangement also includes a plug-in shore power connection for loading in ports, battery packs for peak shaving, two 1,200kW retractable side thrusters, and two 900kW bow tunnel thrusters. A DP2 system will work in conjunction with the thrusters to ensure accurate positioning during installation operations.
Slated for domestic and overseas deployments
Acadia will soon mobilise to begin work on Equinor’s Empire Wind I project offshore New York. Upon completion, the vessel is expected to proceed directly to Ørsted’s Sunrise Wind project, also located offshore New York.
In addition to supporting the US domestic market, GLDD has expanded its focus for the SRIV to work in the international offshore energy development markets. Thus, upon completion of the two US projects, the vessel will mobilise to Europe to begin rock installation for an undisclosed offshore wind developer, keeping her utilised for the majority of 2027.
Acadia was designed and built in compliance with American Bureau of Shipping class requirements.
