Installation Subsea Jacket for Baltic II Offshore Substation

Market: Renewables and Environmental
Scope of Work: Installation subsea jacket for Baltic II offshore substation 
Location: Baltic Sea
Client: Weserwind GmbH
Period: August 2014
HLV: Rambiz

In August 2014 Scaldis installed the subsea jacket for the Baltic II offshore substation. The jacket was manufactured by Weserwind in Bremerhaven and towed to the offshore location in the Baltic Sea.

The jacket is a four legged structure weighing 1500 tons. After installation, the top of the jacket is approximately 5 m below sea level. This clearance is needed to allow the installation of the float-over substation. A pile (80.3 m long with a diameter of 5m) was installed in each of the four jacket sleeves.

As the pile diameter was much bigger than standard for jacket foundation piles, a custom-made upending frame was designed to assist the Rambiz with this task. Once in a vertical position, the piles were stabbed into the jacket sleeve. Due to limited self-penetration and the height of the piles, the Rambiz was equipped with a newly designed pile frame on the bow of the vessel. Once the pile was secured in the frame, it was hammered 65m into the seabed in order to have enough holding capacity for the jacket. All four piles were grouted to the jacket to make the rigid structure safe for the substation installation. After the grouting was completed, the submerged rigging platform was removed with ROV assistance and the Rambiz left the site.