Since 2015, an LNG terminal with an annual regasification capacity of 13 billion cu. metres is open in the Port of Dunkirk. The project includes the construction of a platform and marine structures, the LNG terminal itself and connecting structures. Soletanche Bachy was involved in various phases of the project between 2011 and 2013.
Bessac and Soletanche Bachy France, in joint-venture with Razel, carried out the “Sea Water Tunnel”, 5 km long and with a 3 m inner diameter. Its purpose is to transport warm wastewater from the Gravelines nuclear power plant to the LNG terminal, where it is used in the regasification process.
Before starting the operation, the tunnel boring machine spent several months at the Bessac workshops, where it underwent the required adaptations. A new cutting wheel was designed to bore through Flanders clay and installed on the earth pressure balance TBM. Also prior to tunnelling operations, Soletanche Bachy France built the launching shaft (diaphragm walls at a depth of 65 metres) and the pumping station.
The consortium proposed an original alternative solution, combining the pumping station shaft (29 m) with the fallout shaft (16 m), equipped with a flexible slab at the bottom.
The 50 m deep shaft was excavated with a KS hydraulic rig. The CWS joints were lowered 55 m deep, which represented a world record at the time. The pumping station had a 29 m inner diameter and foundation barrettes.
The consortium then carried out the earth works and civil engineering works, consisting of:
- The 2 m high capping beam
- The junction beams forming 3 struts recovering the compression results between the shaft wall and the pumping station wall
- The pumping station slab, 1 m thick, stabilised with barrettes
- The shaft draining slab