With view on future expansion of maritime container traffic, the Port Autonome du Havre (PAH) decided to build a completely new port in the mouths of the river Seine. The new container port had to triple existing container handling capacity, and feature twelve container berths.
The construction of a new port at such an exposed location experienced specific challenges important currents in the work zone; the very shallow character of the work zone, allowing access only at high tide; the extreme tidal range; the dominant swell, waves, and wind direction; and erosion of the
sub-basements for the breakwaters. In addition, the sensitive environment in the Seine estuary called for particular care and compensatory measures.
The contract was awarded to a consortium of DEME companies, in joint-venture with civil contractors. DEME had two competitive advantages: its deep knowledge and experience of the port, as the company has been involved in all maritime works in Le Havre for the past century, and on the other hand its innovative approach modifying the initial design in full agreement with the client and leading to considerable cost savings.
In the course of four years, all major vessels of DEME were assigned to Port 2000 as well as hundreds of staff and crew. The variety, complexity and the mere figures are astonishing: construction of 10 km of sub-basements for the breakwaters on an exposed leeshore (6.2 million m³); demolition of the existing seawall; 25 km of slope profiling; reclamation of two areas totaling 78 ha and a fill of 7.7 million m³; construction and later demolition of a temporary causeway; realisation of two beaches with pebbles and sand; dredging of two 30 m x 65 m trenches to a depth of up to minus 22 m and installation of protective layers in the foundation pits; construction, transport and high-precision submersion of two enormous concrete quoin caissons; dredging of a total of 45 million m³; deepening to minus 16 m of the outer access channel, the inner channel and the turning circle.
On the dikes, the conventional rock embankment was replaced by Accropode concrete blocks to provide protection.
Combining mathematics and physical modelling with site experience, the expected heavy erosion of the sub-basement during winter was turned into an opportunity by enabling the controlled settlement of the sub-structure basement.
Two particular elements attracted world-wide interest. In the first place, the innovative design of a dynamically positioned and automatically guided gravel spraying pontoon; linked by telemetry to a cutter suction dredger, the pontoon works at least five times faster than the traditional dipper technique.
Secondly, the construction and high-precision positioning of two enormous quoin caissons on the head of the breakwaters was a spectacular achievement. With a weight of 13.000 tonnes each (!), they measure 55 m in length, are 28 m high, and 20 m wide.