Whether constructing oversized concrete barges or gigantic tank complexes, Bouygues Travaux Publics takes on the most complex technical challenges to make energy production and storage possible. The N’Kossa barge, launched in 1995, made a lasting impression thanks to the design and construction feats required to create the largest floating hydrocarbon production unit in the world at that time. More recently, the gas tanks at the Dunkirk LNG terminal have given rise to one of the largest industrial projects in France.
Among the special features of the construction of these infrastructures is the need for safety, which is similar to that of nuclear facilities, and also the need to protect the environment, which requires exemplary practices right from the design phase. As a pioneering, rigorous and innovative company, Bouygues Travaux Publics is able to meet the many challenges involved.
Design-build of three liquefied natural gas tanks
The LNG terminal now on the Dunkirk coastline comprises three tanks measuring 90 metres in diameter and 50 metres high. The construction of these three giants was one of the largest projects in Europe, making this site a truly international and strategic gas hub. Designed and built by Bouygues Travaux Publics and Entrepose Projets, the tanks store liquefied natural gas brought in from LNG methane carrier ships at very low temperatures (- 160°C), regasify it and then inject it into the French and Belgian networks. The walls of these tanks are made of pre-stressed concrete, 80 centimetres thick and produced on site. The interior of the tanks under construction is lined with a skin of cryogenic steel plates and they are topped by gigantic 700-tonne domes that were put in place by increasing the air pressure inside the tanks. Particular attention was paid to the preservation of the coastal environment, especially during nesting periods.
Design, construction and delivery of a pre-stressed concrete barge for a hydrocarbon production unit
When it left the port of Marseille, where it was built, in the spring of 1995, the N’Kossa barge was the largest pre-stressed concrete barge in the world. A technical feat that required a year and a half of engineering studies and eight months of construction works. Custom-designed to accommodate the world’s largest floating hydrocarbon production unit, it is anchored at a depth of 170 metres off the coast of the Republic of Congo. Its design called for innovative approaches and methods never used in this context before. Some were inspired by the containment systems used in nuclear power plants, others by shipbuilding, all to ensure the safety and watertightness of the structure, particularly with regard to collisions on the outer hull, as well as its durability in the marine environment for a theoretical period of 30 years.