Keel laid for CSL OWL’s first subsea rock installation vessel

CSL OWL Subsea Rock Installation (CSL OWL SRI) placed contracts for the construction of two subsea rock installation vessels for the offshore renewable energy sector in December 2024.

The vessels ordered by the partnership between CSL Group and Offshore Wind Logistics will have a cargo capacity of 17,500 tonnes and will be equipped with DP2 dynamic positioning. They will be able to operate on marine gas oil and/or methanol, providing a pathway to zero emission operation.

The CSL OWL SRI newbuilds are tailored to meet the demands of the rapidly growing offshore wind sector, offering optimal flexibility and performance. Purpose-built for optimal flexibility, the vessels will deliver efficient and cost-effective subsea rock installation services in water depths up to 100 m.

The vessels will be capable of installing rock of 60/300 kg grading, with the option of handling rocks weighing up to 450 kg. A Tremie pipe with active motion compensation will ensure precise placement at water depths between 30 m and 100 m. The transport belts on the vessels are designed to handle rocks weighing up to 1,500 kg, with a side chute available for larger armour gradings. Excavators will be used to handle larger amour rock.

Classed by Bureau Veritas, the new vessels will have a length overall of 166.80 m, moulded breadth of 40.00 m and design draft of 5.5 m. With a deadweight of approximately 21,000 tonnes they will have accommodation for 45 people, which can temporarily be increased to 60 if required.

With a maximum sailing speed of 12 knots and economical speed of 10 knots, they will have a maximum installation rate of 2,000 tonnes per hour.

CSL OWL SRI is based in Rotterdam, and combines OWL’s extensive experience in the offshore marine construction sector with CSL’s expertise as a provider of complex marine solutions.

The company has not publicly confirmed where the vessels are being built.