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HOW TO MAKE THE POST-INDUSTRIAL WORLD GREENER
When the Port of Le Havre made plans for expansion in 2000, it also made plans for Ilot Reposoir, a bird sanctuary. When Hong Kong’s Chek Lap Kok was being built, the corner of Lantau Island where the turtles nest was carefully preserved. These environmental stories are not the exception. For the private dredging and maritime construction industry, they are the rule.
Restoration of the Gorai River, Bangladesh
For several decades, the Gorai River, a branch of the Ganges in Bangladesh, was drying up, causing difficulties for the people living along its banks. Sand deposits were increasing as was the water’s salinity. This led to harmful environmental conditions, including the destruction of a mangrove forest at the river’s mouth and the lengthening of the dry season. Because the drought was having catastrophic consequences, a dredging project was instituted to try to reverse the situation. As a direct result of this intervention, water is flowing once again through the Gorai, even in the dry season. Villagers use the waters of the Gorai to wash clothes and bathe, and children are playing in its streams. Fish are plentiful as the salinity has been reduced. Boats can be sailed all year round and so goods can be brought from village to village. The restoration of low-water discharge has established the prerequisites for an enduring development. The certainty of sweet surface water all year round creates the basic condition for future irrigation development for agriculture. Surface water also means that with the installation of water purification facilities the river can be used as a source of drinking water. Since the groundwater in Bangladesh is contaminated with arsenic, while the surface water is not, this could be a great boon to general public health. Efforts are ongoing to find alternatives for disposal and to utilise clean dredged material for environmental enhancement, habitats and flood defence. In recent years the emphasis has shifted from direct disposal to managing relocation to creating safe confinement areas and dewatering lagoons. As a result, many beneficial use options have evolved where dredged material is regarded as a potential resource for landscaping. Where it can be used to recharge or recreate inter-tidal habitats such as mangroves, estuaries, coastal areas and wetlands. A look at the projects that follow shows how dredging and maritime construction projects are an essential tool for creating a positive synergy between ecology and economy, for achieving sustainable development, for making the world greener and cleaner.
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| A cutter suction dredger moving sand to improve the flow of the Gorai River. |
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| The Gorai River provides water for washing and fishing. In the background dredgers continue their work. |
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Restoration of the precious Ria habitat in Avilès, Spain
An environmental clean-up operation in the old heavily industrialised Asturias region of Spain, has turned a contaminated sedimentation basin of a river mouth into an inviting urban green space for the Spanish coastal town of Avilès. The project has restored sound ecological conditions in the sensitive Ría Avilès habitat. The rías of northern Spain are protected tidal inlets, very much like the abers in Brittany or some parts of the big estuary systems along the North Atlantic coast of France and the Low Countries. Some ría’s support very productive ecosystems, which have led to major economic activities such as mussel farming. However, since they provide very good shelter from the ocean as well, important harbour facilities have developed which in turn caused massive pollution. Over the past decades, the Ría Avilès has degraded into an open sewer in between the 90,000 people city of Avilès on the left bank, and a cokes and steel factory and a power plant on the opposite bank. The rehabilitation of this industrial area, required intensive study of the chemical composition and careful treatment and disposal, but it was an important step in converting a brownfield into a clean safe area
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| The Avilès area before the clean-up. |
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| The Avilès area after the clean-up. |
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The greening of Belgium’s waterways
With the passage of time, society’s pursuit of industrial advancement has been brought into balance with its need for a cleaner environment. And the private dredging and maritime construction industry has embraced this attitude, applying their skills to an innumerable number of projects. In Belgium, as else where, new techniques for cleaning dredged slurry from canals and ports are continually being sought. This slurry is often contaminated with heavy metals from urban, industrial and agricultural waste. Sometimes this has meant the development of innovative dredge heads. Sometimes this has meant extensive laboratory studies and modelling. Several ongoing projects are related to the maintenance and clean-up of the River Scheldt and other Belgian water ways. Artificial lagoons and dewatering sites have proven to be an excellent way of disposing of contaminated sediments and, for the material that can be cleaned, re-using it for beneficial land enhancement projects. For instance, the Kallo Lock connects the Scheldt with the Left Bank of Antwerp Harbour and is a place of accumulating sediment. Recycled soil from the access channel at the Kallo Lock and the adjacent harbour area is now being used for landscaping. Also part of environmental management programmes is the lagooning field at the Ruisbroek site near Brussels, used to process sediment from Brussels port. Other Belgian sites for lagunation, dewatering and sediment treat - ment facilities are located at Krankeloon, Couillet and Tubize, to name a few. Another area for the disposal of dredged material which was developed in the 1990s, is Fasiver, near Ghent. Here a 42-ha deserted black-point site that was already severely contaminated from industrial overuse was first sanitised, then a confined disposal area was built, and finally a sludge treatment centre with dewatering lagoons will be used to create a greenbelt. An example of ecological and dredging ingenuity: remediating this industrial wasteland into a new useable industrial zone surrounded by a beautified greenbelt.
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| Test site for landscaping at Kallo Lock, for the disposal of fine-grained contaminated sediment from the River Scheldt. |
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| Disposal site for contaminated sediment from Belgian waterways at Fasiver near Ghent. |
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Habitat restoration, waste disposal and how to solve two problems with one…
Under the name “Port 2000” the Port of Le Havre (France) has realised a major port extension, including the construction of a new container terminal. Part of the “environmental compensation package” of the project is the creation of a bird sanctuary on a newly reclaimed island Ilot Reposoir, at the site of the sandbank Banc du Ratier. Le Havre is at the mouth of the River Seine. Upstream, but still influenced by the tidal movements, there are many silt banks in the river – a great habitat for all types of special fauna, as long as the banks are under water at high tide, and above water at low tide. But because of the steady accrual of sediments over many years the silt banks had risen above the high water line, and no longer became immersed. This resulted in the dying off of many of the rarest species. In order to save the vitality of the silt banks a number of measures were taken: new dams were built to guide the river currents, a storage depot for dredged silt was constructed, and the pillars of the nearby bridge Pont de Normandie were strengthened to withstand the force of the new currents.
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| Bird sanctuary Ilot Reposoir at the mouth of the Seine. |
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| Silt banks at the Pont de Normandie in the River Seine. (Port Autonome du Havre) |
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