Hochtief for GT1: LessonsLearned/Industrial Tripod installation

Foundation Installation for Offshore Wind Farms

Company / Unternehmen: HOCHTIEF Solutions AG – 
Civil Engineering Marine and Offshore
Speaker / Referent: Lutz Siemers

The installation of tripod foundations for the Global Tech I offshore wind farm has already entered the industrial phase. Constructing a wind farm on the high seas with 80 wind turbines at depths of 40 meters is indeed a technical challenge.
This presentation will outline which assumptions have proved correct and which adjustments had to be made to successfully turn the installation process into a safe, industrial process.

Each step of the construction process involves the most stringent occupational health and safety requirements, and these are clearly and effectively met by means of concrete measures. Ongoing inspections of the constantly changing workplace together with the immediate remedying and removal of potential risks mean safe working and thus long-term project success.

The methodical preparation of all steps of the construction process must also be undertaken in advance. Identifying and describing in detail all of the steps are basics that are carried out in- house in close collaboration with the project team responsible for technical preparation, geological surveyors, naval-architects, logistic experts and other specialists.

Sound logistics—such as the choice of the right harbour and logistics partner—also help to secure project success. The foundations and accompanying piles for anchorage in the ocean floor have been fabricated in Bremerhaven, Emden and the Netherlands. The final assembly of the tripods is partially carried out at the Bremerhaven manufacturing facilities of WeserWind and BLG. From there two foundations per rail system are pushed to a special floating BLG pontoon and towed by water to interim storage on the ABC peninsula. The loading of components onto the special jack-up crane vessel INNOVATION, owned by HGO InfraSea Solutions, a subsidiary of HOCHTIEF Solutions and DEME, takes place directly at the quayside of the Bremerhaven ABC peninsula.

With a loading capacity of 8,000 tons, the INNOVATION can transport three of the approximately 900-ton foundations and nine piles to the construction site at a time. Depending on weather conditions, the Heavy Load Installation Vessel (HLIV) can reach the wind farm area in less than ten hours, where the tripod foundations are then anchored in the ocean floor at a depth of 40 meters.

HOCHTIEF moves on successfully into the industrialisation of installation of massive foundation elements in water depths beyond 40 meters, forward on the way to stabilise their position as one of the few leading Installation Contractors in the Offshore Wind Market in Europe and globally.