Wave and current conditions
The FINO1 platform has been designed on the basis of the “100 year wave” principle, with a wave height of 17 metres. According to this theory, a wave with an height of 17 metres will only occur in this location once every 100 years. The height of the platform deck, and of the lower superstructure, above SKN level has been determined in accordance with the 100 year wave principle. Since the commissioning of the FINO1 platform in 2003, a wave of height 17 metres has yet to be measured. In recent years, a number of powerful waves have nevertheless been observed:
- On 1st November 2006, cyclone "Britta" swept through the southern region of the North Sea. On the FINO1 platform, a wave with a significant wave height of 9.77 metres was measured. Accordingly, the maximum height of this wave was some 16 metres. This wave inflicted extensive damage upon the lower gangway of the FINO1 platform, necessitating an expensive process of repair.
- On 9th November 2007, a significant wave height of 10.5 metres was measured (cyclone "Tilo"). Again, the lower part of the platform was damaged.
- On 4th October 2009, major waves with a significant wave height of 6.40 metres and a maximum height of 10.2 metres were measured.
Since the commissioning of the FINO1 platform in the summer of 2003, water currents and their direction of flow have been measured. Flow rates of up to 1.5 m/s have been recorded by this process. Underwash associated with the four supporting piles has been observed to a pile depth of 1.5 metres.
Ice motion and ice formation
Even in exceptionally icy winters, the Borkum Riffgrund site lies outside the ice limit. However, ice fragments may be encountered. However, the pressure of ice on the substructure of the platform associated with ice fragments is not critical to the dimensioning of this substructure. The entire structure of the platform, with equipment included (wind measuring mast, etc.), has been dimensioned to accommodate an additional load corresponding to a 3 cm-thick ice layer applied as a surface load to all surfaces above the waterline. A specific density of ice pIce = 700 kg/m³ has been assumed for this purpose.