Challenge

The Revolution Wind offshore wind farm, in US federal waters 30 km to 45 km off the coast of Rhode Island, covers an area of approximately 500 km2 of challenging ground conditions. Revolution Wind will deliver 400 MW of power to Rhode Island and 304 MW to Connecticut, and will consist of around up to 100 wind turbine generators, up to 2 offshore substations (OSS), inter-array cables, and export cables.

Revolution Wind contracted Fugro to deliver geophysical surveys, geotechnical site investigations, and soil data and analysis. We provided near-real-time soil Geo-data to inform project decisions and allow early decision-making, including rerouting export and inter-array cables around geohazards and obstructions; siting wind turbine generator locations; and making foundation design considerations.

Solution

Initial site framework

In 2017, Fugro conducted a reconnaissance survey with a 900 m by 900 m survey grid to provide Revolution Wind with an initial site framework and geological model of the wind farm.

Fugro continued supporting Ørsted and Eversource throughout 2018 and 2019 by completing preliminary export cable route geophysical and geotechnical surveys.

In 2019 and 2020, Fugro completed offshore site investigations to capture the full complexity of the site.

We conducted a series of tests to determine which seismic source power settings were the best balance between imaging the deep geology and overworking the power source. Seismic processors developed a workflow for processing and reviewing the Geo-data on board the survey vessel, which meant Fugro did not need to send the data back to shore.

Tricky terminal moraine

The project site is located on the terminal moraine of a former glacier and consequently the seafloor contains many boulders. In response to this challenge, our office in Norfolk, Virginia, developed a GIS-based customised machine-learning algorithm for locating and dimensioning the boulders on the seafloor. The algorithm picked boulders from the side scan sonar imagery, which allowed Fugro to provide a product which could not have been manually produced. We provided Ørsted and Eversource with boulder hazard polygons for the entire site in advance of the final boulder point delivery based on the side scan sonar data, which exceeded client expectations and reduced the overall project development risk.

To ensure the project was completed within the required time frame, Fugro conducted the fieldwork from several vessels simultaneously. Two vessels were deployed for the geotechnical investigations (a seabed vessel and a drilling vessel) and four vessels were deployed for the geophysical scope (offshore survey operations and shallow water operations).

We also used our office assisted remote services (OARS®) for navigation, positioning and PCPT processing during the survey, which eliminated the need for onboard surveyors and engineers, therefore optimising project crewing, safety and efficiency.

Sampling success

The project team achieved excellent sample and core recoveries from challenging ground conditions, and our automated logging system guaranteed retrieval of the highest-quality data.

The offshore campaign was followed by a large in-house laboratory programme that included advanced testing to determine soil strength and strain properties, soil dynamic properties, and detailed ground layering, for thorough characterisation of the ground conditions.

Our project management team, coupled with clear lines of communication with Revolution Wind, ensured the safe and on time completion of this extensive project.

Innovative highlight

Fugro’s VirGeo® platform, accessible to all project stakeholders, helped accelerate data delivery through near-real-time updates, customised modules and 24-hour access to all project Geo-data.

The seabed CPTs were performed using the 20-tonne SEACALF® PCPT system with a seabed reaction frame and continuous drive system.

Special clamping blocks improved the force transmission to the PCPT rod, resulting in an efficient system with a push and pull capacity of 200 kN and a constant penetration rate aligned with industry best practices. This rate of penetration was maintained even through hard layers, such as those encountered on the Atlantic OCS, resulting in a higher quality of PCPT data. The continuous drive system consists of simple components, making it reliable and easy to maintain.

Impact

The project was delivered on time and fulfilled Revolution Wind’s defined scope of work. The Geo-data Fugro acquired will help Revolution Wind navigate challenging ground conditions at the design stage to optimise foundation design and will also mitigate future risks to the structures and during the installation phase of the wind farm.