CSL OWL Subsea Rock Installation (CSL OWL SRI), a new collaboration between The CSL Group and Offshore Wind Logistics (OWL), has announced the construction of two innovative subsea rock installation vessels, designed to support the growing offshore renewable energy sector.
The vessels, each with a cargo capacity of 17,500 metric tonnes, will be equipped with dynamic positioning systems (DP2) and can operate on marine gas oil (MGO) or methanol, offering a path towards zero-emission operations. The vessels are tailored for optimal flexibility, enabling efficient and cost-effective subsea rock installation in water depths of up to 100 metres.
These vessels will play a key role in subsea rock installation services for bottom-fixed wind farms and associated cables, critical to the expansion of offshore wind energy. Capable of installing rocks ranging from 60 to 300 kg, and with the flexibility to handle larger armour rocks weighing up to 450 kg, the vessels will also feature a Tremie Pipe with active motion compensation, ensuring precise rock placement at significant depths. Transport belts on the vessels are designed to handle rocks up to 1,500 kg, with additional equipment like a side chute and excavators for handling larger materials.
CSL OWL SRI, based in Rotterdam, is an independent marine contractor, specialising in subsea rock installation services. The company combines OWL’s extensive experience in offshore marine construction with CSL’s expertise as a leading provider of marine solutions. This partnership aims to support the offshore renewable energy sector’s ambitious goals, including reducing the levelized cost of energy (LCOE) and cutting emissions.
Maarten van der Giessen, CEO of CSL OWL SRI, emphasised the company’s commitment to delivering customised services to enhance the flexibility and cost efficiency of offshore wind farm operations. “We are focused on helping green energy become more affordable and optimising offshore renewable energy logistics,” he said.
The first of the subsea rock installation vessels is expected to be delivered in August 2026, with the second vessel set to follow in November 2026. This new fleet will help accelerate the development of offshore wind energy projects by providing reliable, sustainable, and cost-effective installation services.
CSL, headquartered in Montreal, is the largest owner and operator of self-unloading ships globally, providing a range of marine solutions across the Americas, Europe, Australia, and Africa. OWL, known for its logistics expertise in the offshore wind sector, will contribute its operational capabilities to this joint venture, supporting the ongoing push for more sustainable energy sources.
