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From the removal of shipwrecks, the dismantling of subsea infrastructures, assistance with the installation of offshore wind farms and relevant repair and maintenance works of these offshore structures to the realization of subsea construction structures. A conversation with Didier De Graaff, Managing Director of DISA International, about the four divisions and the specialist techniques and systems developed.
DISA International has its roots in shipwreck removal. "Over the years, we have established ourselves as a strong and widely recognized contractor for innovative, safe, time-saving removal solutions with the least environmental impact," begins De Graaff. "With an impressive track record and years of experience in the complex marine and subsea environment, our professional team can master projects and manage the entire process. We deliver to the highest safety and quality standards. For example, we assisted in the salvage operation of the passenger ship Costa Concordia, to date the largest salvage operation of its kind in maritime history."
The removal of shipwrecks is a complex operation and requires creative and innovative solutions, De Graaff knows. "After all, every project is unique and so are the underwater conditions. The 'in house' knowledge we have built up in the fascinating underwater world and the unique solutions devised for it also proved very applicable in civil underwater construction. Reason enough to establish the Civil Construction Division in 2005. This division specializes in underwater services for the construction, repair and maintenance of a wide variety of infrastructure projects. Over the years, we have built a reputation as a leading underwater contractor among international civil engineering, construction and contracting companies. We are involved as a 'wet subcontractor' in major infrastructure works, such as the Blankenburg connection and the sea lock in IJmuiden. Every year we realize between 90,000 m3 and 120,000 m3 of underwater concrete floors in the Netherlands, Belgium and Germany."
"Our established civil construction teams have developed innovative tools and methodologies to overcome the obstacles of working underwater in a very challenging environment," continued De Graaff. He cites a few example projects. "For example, for the parking basement under the gardens of Paleis Het Loo, we performed the necessary work underwater and poured the floor. We also made our contribution to the S-Bahn connecting tunnel in Berlin. The tunnel was built completely underwater. The work involved specialized diving work, including excavation by a tracked ROV underwater robot, removal of reinforced concrete slabs, bottom dredging, sidewall cleaning, and accurate pile inspections and measurements until finally pouring the concrete floor, which was a very unique challenge in itself. In addition, our Civil Construction Division is closely involved in the IJmuiden Sea Lock. We assist in all subsea operations, including the sinking of two caissons to install the two lock gates, structural welding, dredging, underwater concrete pouring, construction and installation of large underwater structures and lifting operations, all underwater."
Since 2008, DISA International has also contributed substantially to the installation, repair and maintenance (O&M) as well as decommissioning of offshore wind farms. "We quickly noticed that this market was different from our traditional divisions within DISA International," says De Graaff. "That is also the reason we established a separate offshore branch for this purpose called C-Ventus Offshore Windfarm Services (C-Ventus). C-Ventus has since become a well-known name and a dedicated service provider with specialist knowledge in the field of offshore wind farms. State-of-the-art equipment and highly skilled personnel have enabled us to assist in the safe and timely completion of work for some of the world's leading energy suppliers. For example, C-Ventus was contracted to assist in the completion of the Borkum Offshore Wind Farm, consisting of forty wind turbines 45 kilometers off the coast of the German island of Borkum. C-Ventus is busy with objects at sea 365 days a year."
"We also provide a full range of subsea services and support to offshore oil and gas companies and major installation companies around the world. We are mainly called in for special projects," De Graaff says. "Whether it is the installation of single-point buoys, pipeline inspection or the decommissioning of subsea infrastructures, we always know how to come up with the right project solution. This is actually true of all our divisions. If necessary, we develop new concepts and techniques to find better solutions to the labyrinth that is the underwater world. For example, we have 25 diving systems, ROV underwater robots and a whole arsenal of special techniques and tools. Think of a specialized remotely operated underwater drilling unit, which we developed together with our partner VL Specials -part of Van Leeuwen Sleufloze Technieken (VLST)-. Or our Deep Sea Oil Recovery unit for recovering hydrocarbons and other hazardous liquids in subsea structures at depth. In addition, together with VLST, in the joint venture VLCV BV, we have applied a revolutionary technique for trenchless laying of cables in the ground. A technique that was awarded the NSTT No-Dig Award."
In addition to developing new techniques, we at DISA are able to transfer proven concepts, techniques and specialized personnel from one division to solve various operational challenges in another. This efficient, economical and sustainable approach to subsea projects is what sets us apart and gives us a competitive advantage," De Graaff concluded.
