Foundation Installation Start

Foundation installation for Offshore Windpark Egmond aan Zee (OWEZ) commenced in April 2006 with the laying of the first scour-protection filter layers on the seabed at the offshore site, 10-18 km off the Dutch coast near Egmond aan Zee. Per the OWEZ-R-141 General Report, "Offshore works started in April 2006 when the first filter layers were laid on the seabed." Scour protection was installed prior to monopile piling because BCE's cost-comparison study had concluded that protected piles would be more cost-efficient than oversized unprotected piles (the latter would have required longer piles with larger diameter to cope with the deepest scour holes under heavy storms). Around 50,000 tons of stone was installed on the seabed around the eventual monopile locations as the OWEZ scour-protection package. Following the filter-layer phase, the Svanen heavy-lift vessel — adapted from its original bridge-construction role with an added support crane and piling frame — drove the 36 steel monopile foundations to approximately 30 m penetration depth using an IHC S-1200 hammer. Each monopile, fabricated by Bladt Industries in Denmark, weighed ~230 tons (45 m long, 4.6 m diameter, 40-60 mm wall thickness). Anode rings, J-tubes and transition pieces were installed after piling, with the TPs grouted onto the monopiles using rubber-tyre style pre-installed grout seals supplied by Densit. The Svanen continued foundation works through to autumn 2006, in parallel with A2Sea's Sea Energy installing turbines at other locations.