Blue Ring is a patented process developed by Damien Grimont, an experienced sailor and entrepreneurial engineer who has spent two years researching and developing his solution for berth shortages. The viability of Blue Ring has convinced two local authorities to rethink marina concepts, and pre-construction work on the first project could start at the end of this year.

Concrete concept
Blue Ring is essentially a tried and tested underground car park technology with a twist. It takes up land space not water space, can be built adjacent to existing landside structures and facilities (shops, restaurants and cafés) and is self-contained requiring no sea wall.

It thus escapes seabed dredging and environmental embargoes that are often placed on waterbed sites. It can, in fact, be constructed on polluted land without the attendant cost of polluted spoil disposal. As the excavation for the cylindrical concrete shafts is undertaken, the clean deeper spoil can be removed and the polluted top layers dropped and buried.

Curves are essential to the design of the concept as they give the necessary stability but basins need not, strictly speaking, be circular. Concepts using circles and elliptical shapes, in single and multiple configurations and sizes, have been developed emphasising the aesthetic appeal of the design.

The maximum diameter of the cylinder is, however, 90m with 75m probably the ideal. The reinforced concrete diaphragm wall is 1.5m thick and cylinders can be sunk to depths of 150m using specialist machinery.

Quality control is strict at each stage of the construction process. During excavation, the quality of the slurry, the dimensions of the trench and the accuracy of positioning of the steel reinforcement cages is checked. The quality of the concrete and its volume versus depth is assessed and checks are undertaken to ensure there is proper interlocking between primary and secondary concrete panels.

Clean and green
In addition to being less intrusive of the waterbed, a Blue Ring marina offers several environmental and water quality control benefits, and is claimed to be the first self-cleaning port. Its circular shape permits sufficient energy flow to create a permanent current that prevents mud from settling.

By its very nature, it encourages better landscaping. In freeing up surface space by stacking a marina basin, drystack and/or car park on the same footprint of land, the surrounding area (which could have been the car park site) can be green and landscaped. It can also be located in unsightly areas where little else could be profitably developed.

Multiple options
Blue Ring can accommodate boats and cars in different configurations, for exampls above ground car park, below ground drystack; water basin with car or boat park (or both) below.

It can also incorporate commercial buildings, which may help fund the project. Different marina basins can be used for different types of boat storage and water depth can be sufficient to accommodate large boats. This is beneficial for the marina operator as different basins may require different services. In a superyacht basin, for example, a high level of security and/or more private shoreside access may be required.

If the marina is to include an underground drystack, Damien Grimont estimates that around 40 boats can be stored on each level. Each can be launched/retrieved in around three minutes using an automated stacker system. The drystack is completely hidden from view.

This is a benefit as, despite major successes in creating architecturally pleasing buildings, the visual impact of a traditional drystack still remains a stumbling block with some civic planners. It is also perfect for use in cyclone or hurricane prone areas as the boats are totally protected.

From an economic perspective, construction costs are in line with underground car parks. 'Initial projects can be self-financing if you add up all aspects such as underground car parks, underground drystack, storage of polluted spoil, stormwater basin and dry docks,' Grimont explains. 'All of these free up the land for new buildings, such as houses, offices or related services and the circular impact of the port should also be highlighted. It creates great "nautical theatre".'

Blue Ring, based in Nantes, France, works in association with the SCE consultancy group, which undertakes design and environmental studies, and Soletanche Bachy, a leader in foundations and earthworks with an impressive international portfolio.

The first project, in the Pays de la Loire, should enter its construction phase by the middle of 2009. A second project, in Aquitaine, is also mooted. Both will incorporate underground drystack systems.

Contact Damien Grimont in France on email: damien.grimont@bluering.fr

Reproduced with kind permission from Marina World magazine