Dredging boats: Construction of “The World Islands”, Dubai

A whole fleet of dredgers is currently working in the Persian Gulf, involved in one of the many maritime projects being undertaken at the moment in this area. Because of its size and complexity, the construction of these projects requires a large number of dredgers of various sizes and systems.

A fascinating example of a dredging project in this area is known as “The World Islands”. The project is an initiative of a group from Dubai called Nakheel, and it consists on the construction of 300 small islands located 4 kilometers from the coast.

The islands are grouped to form the shape of the continents, resulting in a huge world map. The size of these islands varies between 1.1 and 4.5 hectares. The islands will be sold individually, making it possible to build them in hotels, apartments or private villas, depending the desires of the owner.

Additionally, the islands will be surrounded by a ring of sand and rocks of 25 miles of length that will protect the islands of the vagaries of the sea, while it will also be used to two marinas. The contract for the execution of this project has been given to the Dutch company Van Oord, equipped with a large fleet of dredgers manufactured mainly by IHC Holland Merwede Group.

To complete the formation of these islands it will be required to deposit 300 million cubic meters of sand, in an area where the seabed is between 10 and 17 meters. The sand needed for the project is dredged from the open sea and transported from an average distance of 10 kilometers from the location of the artificial archipelago, an activity that requires the deployment of a large number of dredgers TSHD (tow dredgers and hopper suction). In order to achieve the greatest efficiency possible, Van Oord is using dredges TSHD of different sizes, as well as using different methods of emptying. At first is used the emptying by dump hopper, that is faster and cheaper. Later, to the upper layers of the islands and the process of giving the desired shape, they use the projection method consisting in blasting the sand.

In the project of “The world islands”, the sequence of operations for the formation of the islands is the next one:

1. Forming the base of the island, using large dredges TSHD, with hoppers with a minimum of 18,000 m3, reaching a level of -10 meters. The material is deposited by the method of emptying.

2. Since the height -10 to -7, the emptying job is carried out by dredges something smaller, with hopper capacities of between 8,000 and 12,000 m3.

3. By the use of small dredges they use the most of the amount of material that can be deposited by emptying normally until the -5 meters.

4. Above the -5 meters, emptying it is not possible, and the rest of the work, to reach a level of +3 meters, is made by the projection by blasting the sand, resorting again to the large dredges.

Since the seabed up to the level -5, the material is deposited evenly for complete sets of islands (the continents). Only from that level they begin to form the body of each island separately.

For the realization of this project, the company Van Oord has deployed its entire fleet of dredgers TSHD. One of the largest is the Volvox Terranova, with a capacity of 20,000 m3 hopper. This dredge is equipped with a trawling suction pipe of 1.2 meters of diameter, where is mounted a submerged suction pump. The pump is moved by two submerged motors of 2500 kW of power. Each part of the dredge Volvox Terranova has been designed to work in the hardest conditions, so that the dredger can be used easily with the rocks layers that cover the depth of the sea in the coastal waters of Dubai.

Making use of its great power of pumping and its powerful head of suction, the dredge breaks the layer of rocks with ease, a task that a few years ago was only possible through the use of large dredges that shredded the rocks. Removing the surface layer of rocks, the dredge Volvox Terranova allows the access to smaller dredges to the sand layer existing under them. In the project “The World Islands”, this dredge performs a critical work, and it has been proved highly efficient.

The other two large dredgers deployed by Van Oord in this project include the Rotterdam, (21,500 m3) and the Amsterdam (18,000 m3). The fleet is completed by other dredgers of medium and small sizes. The use of small dredges has allowed the contractor to use the method of emptying as much as possible. By this method it is realized the downloading of the sand in less time than if it’s done by projecting it, saving large amounts of time and money.

The project “The World Islands” is not only about the formation of islands with sand, it is also a huge breakwater perimeter of 25 kilometers of length around these, using stones and rocks. This breakwater, because of its complexity and magnitude, carries a time of realization of 3 years. The need for the islands to be completed in 2007 forced the implementation of this plan perimeter at the same time as the rest of the islands.

The prior existence of such a protective barrier would have greatly facilitated the formation of the islands, because it could have protected the work of the vagaries of the sea.

The fact that each of the islands has a complex shape is one of the most laborious things to do. To minimize the task of having to make the shape of the islands and moving the deposited sand by dredges, they tried to deposit these materials as precisely as possible. For this reason the task of monitoring and inspection is crucial, in order to guide operators to work properly. For that, during the construction, the islands are continuously monitored in order to detect possible movement of materials because of the water so they can indicate specifically which need emptying sand at each point. For this task they use small inspections boats, which are continuously collecting information of the ground. These ships are also equipped with small guided amphibian teams for more precise inspection under the water. These inspection boats are continuously connected to a data processing centre, which organizes the information and distributes the information to the dredgers in active for its use.

“The World Islands” is not the only project of artificial emerged lands in Dubai. The remaining projects like Palm Deira, Palm Jumeirah, Palm Jebel Ali, Deira Corniche, etc.… follow a similar operational implementation of the project “The World Islands, with their respective peculiarities, of course. The following links are available more information about projects in Dubai.

Fuentes: IHC Holland Merwede / Van Oord

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