Onne Port Complex: dredging and reclamation

Challenge

Rich in oil and gas, the east-Nigerian region of the Niger river delta is the treasure vault of the largest state of West-Africa and the most populous of the black continent. The focal point of oil- & gas export is the island of Bonny, some 60 km south of the regional capital Port Harcourt. Oil & gas export accounts for 50 percent of GNP and 95 percent of exports in Nigeria. The ‘Bonny Light’ is a reference for one of the purest crude oil brands. Furthermore, since a presidential decree was issued which banned natural gas flaring, the island of Bonny has been developed into a huge complex of major installations, including the second largest Gas Export Terminal in the world.

In these clammy and moisty marshlands of the Niger delta, the port of Onne is a fast growing service centre for the entire region. The land-based port is located in a side creek of the Bonny river, almost half way between Port Harcourt and Bonny island. The port operates a container terminal, handles cargo-ships of up to 60.000 tonnes, and has become a main support base for offshore activities in the region.   

Working in the delta is challenging in its own right. It is an area intersected by creeks and swamps full of dense tropical vegetation of bush and mangrove. Moreover, the local population enjoys traditional rights and executing major infrastructure projects requires intensive consultation with many stakeholders. For more than twenty years, DEME companies have been involved in creating the oil- & gas infrastructure in this region. In 1995 Dredging International Services (Nigeria) (DISN) reclaimed land and prepared the pre-loads for the first tank farm on Bonny Island. Various capital dredging and reclamation phases followed. As the technical partner of the Bonny Channel Company, a DEME partner company was awarded the long-term management and maintenance of the 85 km access channel. The Group has also a stake in a ten-year concession for port towage services.  And now there is the dredging and land reclamation at Onne, part of the Phase 4B of Onne Port Development.

Our solution

 

Dredging and reclamation at Onne was awarded by Prodeco International Ltd and Bellsea Ltd, the client. No less than 600 ha will be added to the existing port, with a contract deadline of eighteen months for the first section. Over time, a variation order has somewhat changed the global scope of work.

The 4B project is executed in three consecutive sections, with an initial assignment of trailing suction hopper dredger (TSHD) ‘Reynaert’, the cutter suction dredger (CSD) ‘Rubens’, and an excavator CAT 385 mounted on a spud barge as main plant. The contract calls for dredging a dock at minus 8 m (minus 12 m in a future campaign), reclamation of the platform, and removing unsuitable material behind the quay wall.  

The sand material for the reclamation works     are being dredged in designated medium to coarse sand borrow areas in the Bonny River, within 10 km from the project site. The soft material from the soil improvement and the  “Dock Area” dredging works is being disposed in the “empty” sand borrow areas or alternatively onshore adjacent to the reclamation area.

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