Main contractor Eiffage and foundations contractor MT Højgaard are to use a new gravity foundation system for the met mast on the Fécamp offshore wind development for Dong Energy and EDF Energies Nouvelles off the coast of Normandy, France.
The Seatower system does not require cranes to lift and position the foundation and the Fécamp project is the first time the design has been used.
The Fécamp concrete foundation will be taken to the construction site 13km offshore by a towing vessel before being positioned and subsequently sunk in a controlled manner by gradually letting in seawater.
“Our technology will ease and speed up the construction of offshore wind farms at a time when cutting costs and risks is necessary to help the sector progress to more challenging project sites,” said Seatower CEO Petter Karal.“Cranefree gravity foundations are generally more cost-efficient, quicker to install and less risky than current methods that use steel foundation designs. They also allow for local construction, which provides welcome economic activities to the coastal communities close to the wind farms.”
According to Karal, the technology is game changing because it gives offshore wind farm constructors more overall control of the installation process. ”Construction management can run foundation installation programmes all year round, uninterrupted by poor weather,” he said. ”The process can easily be sped up if necessary by increasing the number of towing vessels. Furthermore, crane-free installation does not involve noisy underwater piling, which is subject to restrictions in several jurisdictions, including “no-build” seasons when installation is prohibited for fear of noise interference with mammals.”
The 1,420t foundation is currently being fabricated at Le Harve harbour and will be positioned in 26.8m to 31m water depth this spring.