PORT 2000 AND ENVIRONMENT

A – THE RESTORATION OF THE MUDFLATS, A MAJOR ELEMENT IN THE ENVIRONMENTAL PART OF PORT 2000

Begun in the summer of 2003 after simulations on models (carried out by SOGREAH with DIREN as the contracting party and under supervision of a committee of experts), the works for the restoration of the mudflats is due to be completed in late 2005. Several stages have indeed been thought necessary in order to give time to nature to take its course again.

The first step consisted in creating the substructure of the groin, in the summer of 2003, in the northern part of the estuary at right angles with the radar tower in Honfleur. The changes noted in situ (reduction in bottom depth and beginning of a mudflat) confirmed the studies, which permitted to launch the second phase of work. From September to December 2004, the groin was raised on almost all the length (500 metres) and the lower Northern breakwater on a length of 2,000 metres (downstream the Normandy bridge, between the opening and the groin).

The third and last stage of this programme aims at improving the water circulation and creating additional mudflats upstream the Normandy Bridge to protect fish nurseries. Begun in late 2004, it includes the digging of an environmental channel and the creation of an opening at the upstream outlet of the channel while raising the present opening. The invitations to tender for this last stage were launched during the summer of 2003, and the tenders were addressed for this contract of design/completion in December of the same year. In early 2004, a selection committee made up of PAH, PAR, DIREN, the ‘Maison de l’Estuaire’ and the Le Havre Chamber of Commerce and industry (CCIH) met to study the tenders. The SODRANORD Company, a subsidiary of the Dutch group VAN OORT, expert in studies and completion of dredging works, was selected, as its technical solution was the most respectful for the environment especially because putting dredged materials ashore is carried out by pipes and the placing and removing of the pipes takes place before the nesting period and after the young birds have left the nest.

SODRANORD made the most of the summer of 2004 to complete the studies of the project and the specifications, on the basis of the guidelines provided by the Port Autonome du Havre. As prime contractor and work contractor for this work site, SODRANORD began the works end of 2004 by the development of a deposit area, north of the Estuary Highway. Connected to the dredger by 2.5 km of pipes (including a shore part and a floating one), this deposit area receives the materials collected by the stationary suction dredger “AEGYR”. After settling of the sediments dredged from the docks, the water received in the deposit area is pumped towards the Seine estuary, thus re-supplying the existing ‘filandres’ (local name for the drainage channels of the slikke) to guarantee their long-term existence in a better way. Prior to the dredging of the environmental channel, additional protection of the northern access piles of the Normandy bridge was carried out. This meant digging an underwater excavation, between February and mid-March 2005, at the foot of the piles and, afterwards, a pontoon brought rock-fills there, to get a protection against erosion. Dredging works have then begun : they involve 1.8 million cubic metres of sediments on-site (mixed materials made up of sand and mud), corresponding to the dredging of a channel 100 metres wide (from north to south) and on a length of 2,800 metres (from west to east). Positioned owing to its GPS, the dredger is maintained by a rear pile and two anchors on each side. It is said that it ‘moves like a butterfly’, because it carries out circle movements with several goes. It is equipped with a cutter (or cutterhead) with a suction head connected to a pump whose output is 4m/s and the pressure 6 bars : 900 m3 of sediments are thus pumped in every hour. The last stage of this work site, scheduled for the autumn of 2005, involves the creation of a new opening at the upstream outlet of the environmental channel and raising of the downstream opening in order to facilitate the free flow. All the works are due to be completed by the 3rd quarter of 2005.

B – CREATION OF A REST PLACE FOR BIRDS IN THE SEINE ESTUARY After 165 days of work and some 600 trips with nautical craft, the rest place for birds located in the southern part of the estuary (in front of Villerville) has just been completed. Constructed by “ATLANTIQUE DRAGAGE” – a subsidiary of the Dutch group BOSKALIS – on the basis of the studies and survey on model previously carried out, this unique site is 320 m long and 200 m wide.

Its main characteristics (shape, level of the grounds) have been decided first of all in very close cooperation with the Upper and Lower-Normandy “DIREN” and the ‘GON’ (Groupe Ornithologique Normand : Normandy Ornithological Society). Designed to receive sea birds and diversify the reception and rest places for the various species, this 5-hectare sanctuary which is unbroken at low tide, is divided into 3 separate emerging islets at high tide, with a total surface of 1.5 hectare.

Being a true technical achievement owing to the complex shape of the sanctuary and its situation in the estuary, the works began in early October 2004 and were completed in mid-April 2005. On-site, 4 craft (1 self-propelling barge, 1 barge, 1 dredger and 1 discharging barge and 5 shore machines (2 bulls, 2 shovels and 1 loader) have worked simultaneously to carry out the deposit of 57 000 tonnes of rock-fills from the Cotentin and 610 000 tonnes of sand and gravel materials coming from the dredging operations performed in the future channel of Port 2000.

The personnel of the Maison de l’estuaire excepted, as they will control the coming of birds and the possible settling of fauna and flora species, any presence of human beings is forbidden, in compliance with the decree of the Nature Reserve in order to preserve the tranquillity of the place.

C – ADDITIONAL DEVELOPMENT FOR THE DUNE SANCTUARY FOR BIRDS As the first environmental measure to be implemented, the works for the creation of the dune sanctuary for birds were completed as early as February 2002. Since then, a follow-up survey of how it works and how often it is used is carried out in connection with the DIREN and the ‘Maison de l’Estuaire’, the manager of the Nature Reserve of the Seine Estuary. The observations made are very encouraging and have made it possible to define a few additional measures to improve the functioning even further, as regards especially the management of the water levels of the dune sanctuary.

In order to improve the reception capacity of the dune sanctuary, additional development was made in mid-July and August 2003 in the North-Eastern part of the sanctuary. This arrangement aims at receiving the avocets for nesting. The reshaping works included the digging of a network of always submerged ditches around five islets with gentle slopes. This system is kept apart from the rest of the sanctuary by earthworks, a duct equipped with a non return valve makes it possible to manage precisely water levels (in and out) and to remain independent of the water management of the rest of the sanctuary. This management requires setting up a structure of water level management for the sanctuary. Two places to set up the structure were studied by an external project management within the scope of the preliminary design study (to have a look at both sites, click on the photograph below). After study of all advantages and drawbacks of each of the two sites, the ‘A’ site was selected by the steering committee (DIREN, MDE, PAH) as it favourably meets the requirements of the structure and the environmental conditions. The aim is to be able to set water levels which can vary according to the period.

The water analysis and the feasibility study have made it possible to define a mobile structure (see 3-D diagram) whose main characteristics are as follows :