Through two of its subsidiaries, Dragages Hong Kong and Bouygues Travaux Publics, Bouygues Construction has won a €1.15bn contract for the construction of a 4.2km undersea road tunnel in Hong Kong. It is the largest design-build contract ever awarded in Hong Kong.The project consists in constructing an undersea twin-tube tunnel, each tube with two traffic lanes and 14m in diameter.
The tunnel will link the New Territories, north of Hong Kong, to Lantau Island, where the international airport is located. It will be bored 50m below sea level, which will constitute a record depth for Bouygues Construction. Two TBMs will be used.
The two tunnel tubes will be connected every 100m by 42 cross passages. Ground-freezing technology will be used to provide a watertight environment to enable these passages to be bored.
The project will entail working in an environment in which pressure is high (over 5 bar). Maintenance operations, particularly with respect to the cutting heads of the TBMs, will be carried out by teams of divers who will live in a hyperbaric base camp for four weeks at a time to allow them to deal with any issue that may arise at any time.
The operation also includes the construction of two cut-and-cover approach tunnels of 530m and 670m respectively.
The project will be carried out in compliance with strict environmental standards with regard to marine ecology, water quality, noise impact and waste management. The two ventilation buildings powered by wind energy that will be constructed to the north and south of the tunnel have been designed to qualify for BEAM(1) Plus Gold rating.