Kvaerner Construction has beaten two of India’s monsoon seasons and some of the region’s worst sea conditions to create one of the world’s largest liquid chemical loading jetties in the Gulf of Cambay.
The £50 million ($75m) design and build scheme for a consortium of chemical, petro-chemical and fertiliser industries operating in the state of Gujarat, some 300 kilometres north of Mumbai, is now nearing completion, with the first vessels expected to unload within the next two months.
Commencing in September 1997, the project involves construction of a piled concrete jetty at Dahej reaching out 2.4 kilometres across tidal waters from the shoreline, and capable of handling up to 1.8 million tonnes of liquid cargo per year from tankers of between 6,000 and 40,000 dead weight tonnes capacity.
The contract for the Gujarat Chemical Port Terminal Company, covers design, detailed engineering, procurement, fabrication, construction, installation and commissioning of all marine structures, including berthing and mooring dolphins, with interconnecting walkways, telecommunications, gas detection and fire-alarm systems.
The scheme also includes a service platform, measuring 30 metres by 17, and control room building at the end of the jetty, together with eight marine loading and unloading arms handling a variety of liquid chemicals, including two refrigerated cryrogenic products.
To overcome very shallow inshore coastal waters, the jetty has to extend to the deep waters beyond the inter-tidal zone. Faced with the onslaught of monsoon conditions between mid-May and mid-September every year, the project team developed a largely land-based piling operation.
For the first 1,600 metres across shallow waters, over 450 concrete bored piles were installed by locally-based sister company, Kvaerner Cementation India, using a walking gantry system. A temporary steel road deck was slung between two of the pile columns to allow trucks to deliver pre-cast deck units and construction materials as work extended out to sea.
To meet stringent design and programme requirements, some 370 steel piles up to 60 metres long were driven into the seabed for the deep-water end of the project, installed by Singapore-based Antar-Koh from a floating barge - but the entire piling and construction operation was progressed from the landward end.
As Kvaerner Construction International’s projects director in India, John Bradshaw, explained: “In these coastal waters, between May and September it is normally impossible to operate floating plant. However, utilising a jack-up barge from the Middle East to support our other operations we were able to continue working through the second monsoon period of the project and maintain progress requirements.” High cost of marine plant was another factor in the drive to operate as much as possible from shore.
Three columns of piles support the jetty decking, consisting of solid precast longitudinal tie beams, with transverse pile capping beams precast as open troughs to accommodate the reinforcement and concrete which binds the structure together.
Pipe runs between the loading arms and an onshore chemical storage facility are located on one side of the jetty in steel support trestles. On the opposite side is another pipe truss to meet future requirements while between the trusses is a raised concrete roadway.
To accommodate high tidal ranges and extreme wave conditions caused by the south-west monsoon winds, the mooring point of the structure stands some 20 metres above low tide. Wrapped in extra layers of corrosion resistant plating, the driven steel piling penetrates some 24 metres into the seabed, which lies over 20 metres beneath low sea level.
Steel for the deepwater piling was shipped from Japan and Germany, but this and other offshore procurements amounted to no more than a quarter of project costs.
India’s high import and customs duties encouraged the Kvaerner team to seek out indigenous supplies wherever possible, guided by the long-established onshore experience of Cementation India as main civils sub-contractor.
In all, around 3,000 precast deck units and 400 steel trestles were fabricated onshore. The driven piling, in various thicknesses from 18 to 32 mm, was assembled and prepared from 12 metre lengths of tubular steel in a huge fabrication yard onsite.
The site also welded and fabricated 16 lines of pipework, each extending over 2.4 kilometres from the loading arms to the onshore storage facility.
With the structural work completed, the final M&E and control systems are being installed ready for contract handover before May – and the start of yet another monsoon summer...
Engineer: Engineers India Ltd
Main contractor: Kvaerner Construction International
Major sub-contractor: Kvaerner Cementation India
Contractor’s designer – Kvaerner R.J. Brown
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