Source :- NAKHEEL
The Palm Jumeirah: the creation of an artificial reef
In the creation of the island, a primary goal was to ensure that construction not only had the smallest possible negative impact on the environment in which it was being created, but that it actually enhanced the environment above the original, pre-development status.
Two independent oceanographic experts from California, Professor Joseph Valencic and Jim Miller, spent several years documenting the sea life around the location of The Palm Jumeirah, before, during and after reclamation. Their work on monitoring the temperature and salinity of the water, as well as the bottom conditions and the health of the marine animals, involved numerous dives in and around the site to establish base-line parameters and verify how the reclamation work has affected them.
Before reclamation commenced, the area was almost barren with virtually no signs of marine life; in studies conducted, 95% of the area was bare sand or mud. The impact of the project has been simply to create a foundation for a variety of landscapes and seascapes, which give way to the existence of marine life.
The importance of using natural material in the creation of the island was key to encouraging the development of marine life in the area. In creating the breakwater only natural rock was used, despite it being difficult to find in the region, expensive and requiring a higher level of engineering to place. Using natural rock has meant the creation of a 550 hectare reef on which corals and a biodiversified eco-system has grown, resulting in a dramatic increase of fish in the area.
As soon as the placement of rocks began, algae started to grow, offering some hard substrate for colonization. Urchins, barnacles, sponges, clams, crabs and fish soon followed. As the island was reclaimed, the fine sediments that were created by the reclamation eventually paved the way for a biologically and organically fertile soil on the sea bed, on which turtles and a variety of fish are living. This will lead to a highly oxygenated water, with excellent visibility for divers and snorkelers.
In fact, it is not only the natural reef on the breakwater that will attract divers – and fish. Two passenger aircraft – an Airbus A 340 and an Illushyn 76 (a huge Russian cargo plane) have been salvaged, environmentally sanitized and sunk into the nearby shallow waters. Entirely environmentally friendly, the same process of colonization that happened on the breakwater, has happened on the planes. This will provide a visually fascinating dive site just off the breakwater of The Palm Jumeirah
Nakheel is currently employing a ground improvement technique at The Palm Jebel Ali known as vibrocompaction. The process, which is performed with specially designed vibrating probes, significantly increases the bearing capacity of the soil making it ready for construction and ensures that no subsidence of land can take place in the future.
Currently 18 vibroprobes are being used at The Palm Jebel Ali, each weighing approximately 2,600 kilograms and capable of up to 1,800 revolutions per minute, resulting in a force of 30 to 50 tonnes. The long, hollow probes go through the entire depth of reclamation until they penetrate the seabed’s hard layers at average depths of 15 metres. During this process, the combined action of vibration and the jetting of water rearrange loose sand grains into a compact state. Sand is then added from the ground surface to fill the void space created by the vibrator and to ensure that any soft layers on the sea bed are densified
Vibrocompaction increases the soil bearing capacity of reclaimed land by around 80% to create a land mass that is similar in strength to mainland Dubai. The average area being compacted at The Palm Jebel Ali on a daily basis is approximately 13,000 m2 per day, with the entire 7.5km by 7.5km island to be treated. The entire process is expected to be completed at the end of March 2008.
Marwan Al Qamzi, Managing Director, The Palm Jebel Ali, said:
“What would normally take nature a period of more than 20 years to achieve can be accomplished in just a few months using vibrocompaction. The process ensures that the reclaimed land mass of The Palm Jebel Ali is strong enough to build buildings of significant height; it also ensures that the island will not move - there’s absolutely no chance that the island can sink despite the rumours that seem to circulate in Dubai!”
The Palm Jebel Ali is a landmark commercial, residential and tourism development for Dubai, which, along with the Waterfront project, will transform an area of empty desert and sea into a bustling international community, with an estimated population of 1.7 million people by 2020. With the majority of land reclamation on The Palm Jebel Ali complete, Nakheel has already begun putting in place an infrastructure which will eventually support a population of more than 250,000 people.