The Public Utilities Board [PUB] requires the installation of a submarine water pipeline with additional product pipelines and fibre optic cables between Jurong Island and Pulau Ular.
PUB has awarded the installation of the above services link including the procurement of the necessary materials to Van Oord Dredging and Marine Contractors [VODMC]. In order for Van Oord to do the dredging works for the laying of submarine pipes, HSL was engaged to construct the cofferdam and temporary pipe rack support. The cofferdam construction is vital to Van Oord’s pipe laying operations. A cofferdam is a type of watertight construction designed to facilitate construction projects in areas which are normally submerged, such as bridges and submarine structures. The cofferdam is installed in the work area and sea water is pumped out to expose the seabed so that HSL can construct structural support in a dry environment, in this case, the laying of submarine pipelines.
To provide the dry conditions required for construction works, the cofferdam must reliably hold water back from the work area and also withstand very high hydrostatic pressures in order to be safe. Detailed analysis of drawings and design allowed the construction team to formulate an effective way for installation and dismantling works, which contributed greatly to enhancing project delivery.
To commence the cofferdam construction, a temporary staging platform is constructed to serve as a foundation for the piling. Subsequently, a total of 168 No.s of sheet pile are driven into the seabed to form walls around the work site. To further reinforce the structure of the cofferdam, waler beams are placed on top of the installed sheet piles around the perimeter and struts were used to brace the outer circumference to withstand the outer water pressure. Drainage systems are then built to de-water the site before foundations are dug and laid. Finally once the foundation and other works are completed, the site is reinstated and the cofferdam dismantled.
The successful completion of this project supports Singapore’s endeavor in becoming a pioneer in the field of water reclamation and refinement. Till date, more than a million bottles of NEWater has been consumed. Through collaborating with one of the world’s best dredging contractors and HSL extensive experience in civil marine are we able to achieve such an engineering feat.