Two methanol-ready subsea rock installation vessels to enter offshore wind market in 2026

Rotterdam-based CSL OWL Subsea Rock Installation (CSL OWL SRI), a newly formed partnership between The CSL Group and Offshore Wind Logistics (OWL), has placed an order for the construction of two subsea rock installation vessels that will service the offshore wind sector.

The DP2 vessels will each have a cargo capacity of 17,500 metric tonnes and will be able to operate on marine gas oil (MGO) and/or methanol.

According to CSL OWL SRI, they are purpose-built for optimal flexibility and will feature a Tremie Pipe with active motion compensation that ensures precise placement at water depths between 30 and 100 meters.

The vessels will be capable of installing rock material up to the 60/300 kg grading, with the option of handling rocks weighing up to 450 kg. The transport belts are designed to handle rocks weighing up to 1,500 kg, with a side chute available for larger armour gradings.

“We are committed to providing tailormade capacity to the fast-growing offshore renewable sector. This will support the sectors’ ambitions of ramping up installed capacity, reducing the levelized cost of energy (LCOE) and minimizing emissions,” said Maarten van der Giessen, CEO of CSL OWL SRI.

“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 optimizing offshore renewable energy logistics.”

The first subsea rock installation vessel is scheduled for delivery from the shipyard in August 2026, followed by the second in November 2026.