Water supply tunnel between Gravelines and Dunkirk - 8 February 2016

For the past three years, Girus has been assisting EDF in the construction of a water supply tunnel connecting the nuclear power plant in Gravelines to the new thermal power plant in Dunkirk.

This 5-kilometre long, 3-metre diameter tunnel excavated partly underneath the seabed is designed to transfer warm water from the nuclear power plant to the thermal power plant to be used to heat liquefied gas. The pumping station at the tunnel outlet has a capacity of up to 12 m3 per second.

As a member of the RAZEL-BEC-CSM-BESSAC consortium, Girus’ Water team performed all the hydraulic studies, from the preliminary and working design phases through to the definition of the acceptance and performance testing protocol.

The tunnel was commissioned in the autumn of 2015. The tests, in particular the overall pressure drop performance test, delivered their verdict: the design calculations performed by Girus proved to be extremely accurate and made it possible to comply with EDF’s extremely precise requirements. Girus rose to the challenge of this underground concrete structure, which required developing a 3D model and conducting complex probabilistic calculations in view of the number of different components used to create the tunnel.


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