Press

The Bay of Mont Saint Michel is a place of rare beauty. And with 3 million visitors every year, it is one of France’s biggest tourist attractions. But there is a problem: the silting-up of the bay and the gradual seaward advance of the salt pastures are threatening the unique character of what locals call “The Rock”. “These days, it takes the sort of tide we get only one-third of the time for the Rock to be surrounded by water,” explains Bruno Legendre of the Bay of Mont Saint Michel Committee, the organisation having the work done. “Once the job is finished, the site will be surrounded by water three times more often than at present, from early autumn to the end of spring.” A new life will begin!

The programme for returning the Bay of Mont Saint Michel to its original maritime splendour involves several phases and a number of structures, but Bruno Legendre is quick to describe the dam as “the cornerstone of the project”. And rightly so. The solution adopted for keeping sand out of the bay for good entails harnessing two naturally occurring forces: the Couesnon River which, as it flows into the bay, flushes out some of the accumulated sediment; and tides which, once they have reached their high point, will be held back by the dam and then released at low tide to flush out even more sand. While this might seem simple, “implementing the project is a real engineering challenge,” confides site manager Julien Froment. “We’re caught in a pincer movement by the Couesnon inland – which flows out to the sea – and by the tide from offshore, which sweeps right up to the dam and beyond. What makes things difficult is that we can’t predict river floods, only the tides, whose variation is the highest in Europe.” To overcome these complications, the dam is being built in two phases, behind cofferdams in each case. “This involves driving sheet piles in the middle of the river to hold back the water temporarily and create a dry area where the engineering work, which by definition has to be done in the dry, can proceed,” explains Froment. “This stage requires good engineering skill, for the sheetpile wall must be strong enough to withstand the pressures of the high water levels, which can attain 9 metres. That sort of head exerts tremendous pressure on the structure and can accentuate the deformation of all parts of the cofferdam,” he adds, pointing to a freshly sprung leak.

Fortunately a large part of the enabling works was done early on. A 2-kilometre-long haulage road was built so heavy construction plant could get to the site. The old dam has been strengthened and converted into a bridge to provide access from one bank to the other. And earthmoving and dewatering of the actual construction site – which required a system of pipework to be laid – is also now complete. On the western bank, the first cofferdam is practically finished. Working on it is welder and boilermaker Sébastien Vasseur, a member of the Order of the Trident, the Quille division of the Minorange Guild. He has been on site from the start, and makes no secret of his satisfaction about participating in such a prestigious project which “leaves a visible mark on the landscape”. Once the cofferdam is complete, civil works on the first part of the dam can start. Then, after construction of the abutment and construction of the first half of the piers, the same operation will be repeated on the right bank: removal and reinstallation of the cofferdam, dewatering of the construction site, and construction of the second half of the dam. Before the dam comes into operation, however, the Quille workforce will have one last job to do: demolish the old dam which prevents water flowing in from the sea. This will be done in June 2008, some two years after the start of work on the project.

Their prolonged presence on the site means the Quille workforce has to pay a great deal of attention to minimising disturbance. “We have to take two types of people into consideration,” explains deputy works manager David Compte. “On one hand, the tourists visiting Mont Saint Michel, for whom we must be as discreet as possible so as not to diminish their enjoyment. And on the other hand, people in the immediate vicinity of the site: there are houses and, above all, hotels less than 200 metres away which have to live with us on their doorsteps for two years!” A committee of site workers has surveyed the reactions of local residents who, despite the disruption to their lives, perfectly understand that the project is vital for preserving the exceptional landscape and the economic lifeblood of the region. Similarly, meetings are organised regularly with different counterparts in order to pinpoint any sources of tension which might arise out of mutual incomprehension, and to nip them in the bud. A sound level meter has been set up to monitor the level of noise generated by the site, and a fenced track has been specially built to allow flocks of sheep to access their salt pastures. Things even went as far as painting the site huts beige so they would blend into the background...

All these undertakings are aspects of the QSE, or “blue”, approach the project team is striving to implement. “Our objective is to meet all the criteria of the environmental specification so that we can fly the symbolic blue flag over the site as soon as possible,” enthuses David Compte. “Through everyone’s commitment we’ve already achieved a lot, and we’re expecting to meet all the criteria very soon,” he adds, referring to his management indicators. The QSE approach calls for everyone’s expectations to be taken into account – those of clients, local residents, subcontractors, suppliers and workers – for a high level of cleanliness to be maintained at site entrances and exits, and for the job site to be kept perfect in every respect, with neatly organised storage of equipment and materials, and stringent control of the project’s environmental impacts.

All this is a major component of Quille’s integration into the backdrop of Mont Saint Michel, something the company is hoping to prolong by winning the upcoming contract for construction of the light bridge that will replace the existing causeway to the Mount. So that the magic of the place can be enjoyed a little longer...

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There are several reasons why we won this contract. Undoubtedly our level of expertise and our many references in civil engineering and river and maritime works were in our favour. Add to that the quality of our two-part commercial proposal which was also decisive: in addition to the basic solution comprising a highly tailored work method integrating most of the parameters, we proposed a variant which demonstrated to the people in charge that we really knew what we were dealing with. As a result they had the utmost confidence in us.

Yes! Since the 1990s maritime work has been coming up repeatedly for Quille. It is currently a growth sector that in 2006 represented close to onethird of the company’s sales in civil works... A job like the Mont Saint Michel project is an extraordinary opportunity to bring our expertise to bear, hopefully with the long-term result of developing business in the sector through new contracts and investment in equipment.

The initiative is based on respect: respect for our clients, local residents, suppliers and subcontractors, and of course all our employees. Alongside this “human” aspect lie environmental concerns such as sorting of waste or implementation of innovative means of saving energy and raw materials. All these factors are a priority for the company and generate legitimately high expectations from all those involved. From this point of view, everything Quille has been doing for the La Caserne Dam project fits perfectly into Actitudes, Bouygues Construction’s sustainable development policy.