La Cotinière port, a high-precision project in tune with the tides

28 October 2021 - Projects update and handover - France

Multiple VINCI subsidiaries have expanded and renovated La Cotinière fishing port on the island of Île d’Oléron in Charente-Maritime, southwest France. In a three-year project, they created a third basin for the port as well as a landing quayside and a 40,000 m2 platform – large enough for a fish market twice the size of the previous one that will open to the general public. The project was carried out in an environmentally friendly way, following the tides and currents around the island, giving VINCI teams an opportunity to demonstrate their maritime expertise.

The port of La Cotinière, located in Saint-Pierre-d’Oléron on Île d’Oléron, is one of the largest ports for small-scale fishing in Charente-Maritime; two thirds of the fish caught in the department come in to this port alone.
However, the port infrastructure was last renovated in 1987 and had since become too small to keep up with growing local production. What’s more, as access to the launch area and landing quayside was only possible at high tide, fishermen’s safety was at risk as they were unable to enter the port for shelter from sudden dramatic weather events. Meanwhile, the sales infrastructure – i.e., the fish market building – was too small for the 6,000 tonnes of fish sold there every year.

The Charente-Maritime Departmental Council therefore launched a consultation in 2013 for a public-private partnership, covering the design, construction, funding and major maintenance and renovation of the fishing port.
A public-private partnership was signed in 2016 with a joint venture made up of several VINCI Construction* subsidiaries as well as a project management consortium led by Artelia, along with architects BPG + Associés and two VINCI Energies** companies for building equipment.

Key elements of La Cotinière project

Carrying out earthworks in a protected area

Two years later, after a pre-operational study, the project – in a protected area and in tune with the tides – was able to begin. The main challenge was building a new 4.3 ha port basin using only diggers kitted out with ground engaging tools, such as rock breakers, rather than explosives. “Given that mining operations were not allowed, we decided to fracture and mechanically extract the material,” explained Antoine Blandin, Construction Services Manager at VINCI Construction Terrassement.
A total of 250,000 m³ was therefore excavated 1 to 5 m underwater during the earthworks phase. To make a port that would be accessible in all conditions and not just at high tide, a new channel also needed to be dug.

Creation of a basin during the earthworks phase

Divers carrying out meticulous tasks

The key element of the project is the new landing quayside, which is optimised for fishing boats. Measuring 250 m long and 11 m high, it is made up of 500 prefabricated concrete components. Divers were required to help install it in particularly murky waters. Their tasks included upgrading and cleaning the port’s seabed and ensuring the metallic frames for laying the concrete foundations of the quayside underwater were in the right place.
“The divers played a crucial part, because the concrete components had to be assembled with 10 mm thick joints and with a tolerance of around 3 mm over the 11 m high quayside,” said Nicolas Marsaud, Works Director at VINCI Construction Maritime et Fluvial.

A new fish market adapted to the local maritime environment

In addition to port infrastructure, the project to modernise the La Cotinière port included the creation of a new fish market. The 11,000 m², two‑story building will enable users to process, package, store, sell and export fish. Although the fish market meets the requirements for a conventional industrial building, the teams went even further by installing appropriate materials and solutions for the seaside environment such as anti-corrosion protection for technical equipment, reinforced coatings, marine grade stainless alloys, etc.
Far less conventional is the frame of the structure, which was designed to host the public and features a walkway accessible via an immense stairway spanning its entire length.

These unique features will make La Cotinière a major port for both industry and tourism when it opens to the public in March 2022.

Teams at La Cotinière worksite

^* Lead company GTM Bâtiment Aquitaine (VINCI Construction France), along with VINCI Construction Terrassement and VINCI Construction Maritime et Fluviale
^** Cegelec and Thomas Froid