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In France, the nautical sector faces a major environmental challenge: the lack of careening areas that comply with ecological standards. Careening, essential for the maintenance of boat hulls, generates significant pollution due to the paints and toxic residues released. These practices, if not supported by adequate facilities, can seriously damage marine ecosystems. This is why it is now forbidden to careen on a slipway. You have to be in an area that recovers wastewater.
At the Port des Sablons in Saint-Malo, Bretagne Plaisance is committed to a virtuous environmental approach, certified Ports Propres. Since 2014, an initiative has been in place with the installation of a submersible careening area aimed at reducing the ecological impact on marine ecosystems. A model that could serve as a model for other French ports. Dominique Bonnel, deputy director of Société Bretagne Plaisance, and Stéphane Horvais, technical manager of the Port des Sablons in Saint-Malo, tell us how it works.
A submersible careening dock
Covering a surface area of 20 hectares, the Port des Sablons, located to the southwest of the city of Saint-Malo, near the mouth of the Rance river, can accommodate 1,200 boats. In addition to being a marina, it is also an economic zone incorporating various technical areas, including both a land-based technical area and a submersible careening dock. The latter, established in 2014 with the support of the Loire-Brittany Water Agency, represents an innovative response to the needs of yachtsmen.
'' Careening is a key issue for marinas: you can't careen just anywhere. There are dedicated areas it's an essential step in the maintenance of boats, but it can also be a source of environmental problems if it isn't carried out properly. While boat careening is an essential stage in maintenance, it can also be a source of environmental problems if not carried out properly. This is where initiatives like the one set up at the Port des Sablons come in, with the aim of limiting pollution linked to underwater paintwork on both professional and pleasure boats.
"T ll ports are involved in virtuous initiatives, in particular environmental certifications. At Les Sablons, we have the Port Propre active in biodiversity theme. Among the subjects covered by the certification issued by AFNOR, the issue of careening is essential, as it is a major source of pollution if there are no spaces dedicated to careening "she adds. Despite these advances, a gap persists between the number of boats requiring careening and the number of operations actually carried out. Understanding careening practices, as well as the needs and expectations of users, therefore remains a major challenge for marinas.
Operation of the submersible careening dock
The principle of the submersible careening area is ingenious, but simple. Boats arrive at high tide and run aground against the quay or esplanade.
The process starts when the sea recedes. Stéphane Horvais, technical manager at the Port des Sablons, describes it in detail: '' There are two identical sections on the slipway, the upper and lower, separated by a gutter. As the tide goes out, a pumping system will first empty the gutters and the lifting chamber, which are logically full of seawater. We don't mix seawater with freshwater and careening effluent. Once all the seawater has been pumped out, an alarm sounds to enable careening. The idea is that the yachtsman should not be able to start a careening operation at all until the conditions are right to avoid polluting the environment. An automatic system will then activate the high-pressure cleaners available to boaters for careening. All wastewater is collected in the gutters that enter the lift chamber. This wastewater is treated by a reprocessing unit which is identical for the slipway and the technical area. This treated water is used at the end of the cycle. When the tide comes in, before it reaches the slipway, a second bell sounds and the high-pressure cleaners are switched off. It is then forbidden to continue careening. ''
The last essential stage in this closed circuit: the rinsing vents complete the rinsing of the slipway with the recycled water, which is then returned to the treatment tanks. When the tide comes back in, the slipway is clean and free of pollutants.
Free access without reservation
Dominique Bonnel adds the importance of making the system accessible to all for environmental reasons. The submersible area is free and self-service. Only the use of high-pressure cleaners is subject to a charge.
This approach sets them apart from other ports, which charge for beaching. At Les Sablons, an evaluation was carried out, revealing an average of 1,000 careenings per year. Boaters, so to speak, are convinced and frequent the slipway.
As a result, Stéphane recounts their difficulties last year in finding the right time to carry out the major cleaning of the submersible hold, as moss and sediment accumulated there: " Throughout the summer of 2023, until mid-September, we had a large influx of careeners, whereas the area usually operates from May to the end of June ".
Modernize by drawing inspiration from other initiatives
The success of the submersible careening area at the Port des Sablons demonstrates that it is possible to combine boat maintenance with respect for the environment. However, the deputy director of Bretagne Plaisance reminds us: " We need to think about modernizing and extending our marina to make it more eco-responsible. Technologies must be increasingly virtuous in terms of water consumption ."
This new awareness is in response to the fact that the installations at the Port des Sablons have been in place for several years now, and are in the process of becoming obsolete on the market. '' Budget-wise, it costs several thousand euros. This system was the best ten years ago. In 2024, things have changed. Everything is a closed circuit, meaning that there are large water recovery tanks and everything runs on rainwater and reprocessed water. A In Port-la-Forêt, for example, they should start using such a system shortly says Stéphane.
Although the Bas Sablons submersible careening area in Saint-Malo operates in a closed circuit, it's important to understand that in reality it's not totally closed, since it uses drinking water from the public network to operate the high-pressure cleaners. '' A real mess s", agree Dominique and Stéphane, even though once the water has been soiled, it is treated locally to rinse the hold. Water restrictions, meanwhile, are rightly imposed when drought decrees are issued. The activity is indeed not vital, but this constitutes a real problem for the needs of yachtsmen. " A system such as the one envisaged by Port-la-Forêt with water recycling is therefore ideal "says Stéphane, highlighting a promising solution, albeit a demanding one in terms of infrastructure.
Dominique insists: '' It's a challenge for the harbors of tomorrow, or even today. That's why we're thinking about modernizing and extending our marina. How can we achieve a more eco-responsible facility in the near future? How can we encourage yachtsmen not to opt for the illegal careening prohibited by the regulations? As long as boaters use antifouling to careen or chemical products to protect their hulls, the subject will always be topical. The other option is to work on alternative practices. Even if this is a heavy budget for other yards, they have to comply with standards .''
