Dodging rocks: a new coastal road in the Indian Ocean
A safer connection between La Réunion’s main cities
On La Réunion, a French island in the Indian Ocean, the New Coastal Road is being built - and it's an impressive project. When technical director Stéphane Magné tells us about the existing road, there is a strong sense of urgency: “The road is right next to a cliff, and rocks keep falling off along the older parts.”
“The main reason we’re building this road is to make travel safer between La Possession, the economic capital, and Saint-Denis, the administrative capital,” says Magné, who works for Colas GTOI (Grands Travaux de l’Océan Indien), one of the companies involved in this project.
Assistant project manager François Verriaux, who works for SBTPC, elaborates: “Every time there was a storm, the swells would wash over the road, so it was closed frequently. The region needs a new road that is high enough to not be flooded, and far enough from the cliffs.”
The New Coastal Road may help the island avoid serious setbacks, as Stéphane Magné illustrates: “There was a large landslide in 2006, which took out the road and kneecapped the local economy.”
And so it’s time for action. “The road is being built on the sea, at a distance of 50 to 200 meters from the cliffs,” says Verriaux. “It is 12 kilometers long. We are building embankments that are about 6 kilometers long. The other parts consist of a 5.5 kilometer viaduct and a small viaduct near La Grande Chaloupe that connects two embankments.”
]"There was a large landslide in 2006, which took out the road and kneecapped the local economy. The New Coastal Road will be safer.”
A 19 million tonne challenge
We met with Verriaux in the embankments section of the New Coastal Road offices. “The project is managed from here by the support staff. All the teams are coordinated from here. The construction teams and the teams that dig up all the required materials. Others provide support for topography, because all the machines are equipped with GPS devices, and so all the construction work is tracked using geographic coordinates.”
On the D3 embankment near La Grande Chaloupe, we met with Magné. “We are approximately halfway between La Possession and Saint-Denis. We started building this dike around six months ago. Right now we’re preparing everything for the storm season.”
“The project’s key aspect is planning, because it is relatively tight,” he continues. “Our goal is to build everything as best as we can, as fast as we can. We started in 2014 and the target is to have our part of the project done by 2019.”
Within the limited time frame, 19 million tonnes of material had to be sourced to build the embankments. This had to be done on the island itself. It's one of the biggest challenges, Magné and Verriaux agree, but it’s being met. "The island measures 2500 square meters and these materials are not easy to find," says Verriaux.
“And on top of everything,” says Verriaux, “Réunion has a unique environment, with marine mammals and rare bird species that must be protected, and there’s the Indian Ocean with all its beautiful coral reefs.” In other words: handle with care. “It's challenging to place the blocks that protect the embankment against the sea. We had to know where to put them. We know that the Indian Ocean isn’t always very clear, and so you need to be able to find the right position underwater.”
”This new solution permitted us to gain production time, and reduce the underwater teams which are quite costly and weren’t the safest option.”
Accurate positioning in unclear waters
“All our machines are equipped with GPS devices from Topcon. This has enabled us to deal with all kinds of challenges,” says Verriaux. “The advantage of these devices is that you can accurately position all the materials in the right place. This also solves the problem with the divers. The Topcon equipment allowed us to gain production time, and reduce the underwater teams which are quite costly and were not the safest option. These blocks can weigh up to 32 tonnes... We wanted the whole process to be safe.”
“Once we’re underwater, we can’t see anything, but thanks to the Topcon equipment, we can,” Magné agrees. “The georeferenced positioning of our equipment is very useful, especially on the long-reach excavators. We also use the GPS system on our lattice boom cranes, in particular the 300 tonne cranes, to position accropodes that are placed along the dike for protection.”
“It benefits the construction process,” he concludes. “We use it every day, and without it, our process would come to a standstill.”
Among the machines that are guided by GPS are two large excavators from a Dutch company called Snijder. Operator John Hock: “Machine control tells us the position of the bucket, the height, and our design. This GPS system gives us everything we need to know to do our job. Without it, it would be difficult.”
“It’s a very impressive construction site as well. It’s the first time I’ve ever helped build a road in the sea. I’m quite proud of that.”
He has every right to be – as does the rest of the crew. Efficiently working towards 2019, the companies are doing an excellent job in providing La Réunion with a faster and safer connection. No more dodging rocks!