ALASTAIR IV

ALASTAIR IV

The 1200t Alastair IV Jackup barge broke her tow during positioning operations of the coast of the Congo in early 2010. The barge was outfitted with extensive pumping equipment to supply water to inland oil fields. The tow could not be reconnected as the barge had crossed a shallow sand bar which the tug could not cross due to her deeper draft. Small boats could not be deployed to reconnect the tow due to the heavy swell inshore of the sand bar.  

The barge became logged 50m of the beach with severe damage to the jacking legs. A causeway was constructed to the barge and the pumping equipment recovered before adverse weather prevented recovery operations being carried out. The barge was subject to storm conditions on the beach during January and February of 2010 causing further damage to the jacking system and hull plating.

 With further salvage operations being outside the capabilities of local contractors Norfolk Marine Ltd was tasked with recovering the barge to the port of Pointe-Noire some 18km north of the wreck site.

 Work commenced with a full survey of the vessel to establish the extent of the damage after three months on the beach with constant battering by the heavy swell. Emergency repairs were carried out to patch the damaged hull and the jacking legs were secured in position to prevent them dropping during refloating operations. A de-ballasting system was designed, procured, flown to site and install inside the hull by the dive team. The system was designed to take advantage of the 1 hour low water window when the deck of the barge dried and so was capable of removing 1000tons of water per hour.    

With the pumps fitted and tested a tow line was attached to a tug stationed outside the shallow sand bar and pumping operations commenced. Calculations proved correct and after forty five minutes of pumping the barge clear the bottom and was towed back across the shallow sand bar. The salvage crew remained on the barge standing by with the pumps during the slow tow back to Point-Noire.

With the barge alongside the quay wall a second survey was carried and further repairs made. Patches to the hull were reinforced with concrete and the barge was ballasted to lay on an even keel before being handed back to the owners