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Boskalis jaarverslagen 2012

Eco-engineering in Gabon

In 2013 Boskalis worked on the construction of a new industrial area in Gabon.
Protecting the marine environment was a major challenge on this project. An important consideration was to mitigate noise and other factors affecting whales, because Cap Lopez Bay is home to large numbers of humpback whales in the winter.

In Port Gentil, Gabon’s second port city, the government has designated an area of 1,500 hectares as an industrial free-trade area. The first activity is the development of the Gabon Fertilizer Company (GFC), for which 80 hectares of land is being reclaimed. As the main financier for GFC, the International Finance Corporation (IFC), part of the World Bank, sets tough environmental requirements.

Eighteen months of preparation

“The project was preceded by 18 months of preparation, studies and environmental impact analyses,” says Annemiek Hermans, an environmental engineer with Hydronamic, the Boskalis engineering consultancy. Together with her colleagues Stefanie Ross and James Brocklehurst she supervised the environmental aspects of the project. “There was hardly any documentation about this region, but there was considerable concern about the impact of the dredging works. The humpback whales were a particular focus of interest,” says Stefanie.

The ecological challenge

Since the international ban on whaling came into force the global population of humpbacks has risen to around 60,000. They spend part of the year within the Arctic Circles, where they build up their food reserves. When the temperature starts to drop, they swim thousands of miles to various tropical locations where they spend the winter mating and giving birth. “Cap Lopez Bay near Port Gentil is visited every year by what we call ‘subpopulation B1’ of the humpback whales,” explains James. “Because this site is so important to the humpbacks, steps were needed to make sure they weren’t disturbed. There were two main points in this respect. The first was to prevent any possible underwater noise nuisance by the dredging equipment. Secondly, the whales use the underwater slopes of the bay to protect and feed their young. That meant that the original shape of the bay had to be preserved.”

The eco-engineering solution

During the preparation phase, a creative solution was devised that would keep the noise level to a minimum and barely affect the shape of the bay. “The solution was an ‘underwater noise barrier’,” says Annemiek. “And instead of taking the sand from a large area of the seabed we opted to dredge an underwater lagoon. As a result, the slopes of the bay remained virtually unaffected.”

The environmental engineers took various initiatives to determine whether the approach would reduce underwater noise levels adequately. “Measurements were taken at various times and at various locations and the predictions turned out to be right: our noise barrier muffled the noise even better than we had expected. The sound of the dredging activities turned out to have no visible impact on the sea mammals’ behavior,” says James. The employees of the fleet and the support vessels also followed the ‘Marine Mammal Observer’ training course, which taught them how to spot and avoid whales and other marine animals such as dolphins and turtles.

Stakeholder appreciation

Representatives of the IFC expressed their appreciation during a visit to the project. Josefina Doumbia, Principal Environmental and Social Specialist at the IFC: “We were impressed by the way in which the stated environmental requirements had been met, and particularly by the commitment of the crew and the project team, and the cooperation with the Liambissi Foundation NGO.”The Liambissi Foundation is a local NGO that monitors the turtle population on this stretch of coast. The project team asked them to handle the monitoring of the turtle population. Philippe Du Plessis, the head of the foundation, says: “At the outset, we were quite skeptical. But the final result was very satisfactory. We were able to make a contribution thanks to our knowledge of the marine life in the region and the monitoring has revealed that there has been no impact on the turtle population.”

Annemiek concludes: “The data we gathered during this project has given us a lot of new insights into ways of protecting the marine environment. This knowledge will be very valuable on future projects.”


The project in Gabon has been nominated for the British Expertise Awards 2013/14 - Outstanding International Environmental Project. The winner will be picked from the three names on the shortlist and announced in April 2014.

For more instances of eco-engineering, please see pages 40-41 of this report.

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