Subsea rock installation vessels ordered

Based in Rotterdam the new partnership, named CSL OWL SRI, has set itself up as an independent marine contractor specialising in subsea rock installations.

CSL’s bulker experience added to OWL’s offshore construction know-how make the partnership ideal, the firms say.

The vessels will each have a Tremie Pipe to ensure they can install rocks in a controlled, accurate way to a maximum depth of 100 metres. They will have a cargo capacity of 17,500 tonnes and each will have dynamic positioning.

Transport belts will be able to handle rocks weighing up to 1,500kg with a side chute for larger armour gradings, and excavators can also be used to cope with larger armour rock.

In line with the drive towards new fuels in shipping, the vessels will both be able to use methanol as a fuel as well as marine gas oil.

“We are committed to providing tailor-made capacity to the fast-growing offshore renewable sector,” said Maarten van der Giessen, CEO of CSL OWL SRI. “This will support the sector’s ambitions of ramping up installed capacity, reducing the levelised cost of energy and minimising emissions.

“Our subsea rock installation solutions are specifically designed to enhance flexibility and cost efficiency for operations in and around bottom-fixed wind farms and associated cables. We believe in making green energy affordable and are committed to doing our part by optimising offshore renewable energy logistics.”

The first vessel is due to be delivered in August 2026, with the second coming three months later, in November.