De Mist recovered


Ingenuity, tenacity and the sweat equity in the form of hard work were major contributing factors in bringing the Tug de Mist to the surface this week just on four weeks after she sank in the Still Water Basin of Simon’s town harbour.

The SA Navy decided to utilise own resources to bring the out of service tug to surface without employing extras or special equipment. It also provided invaluable practical salvage experience for Navy divers Commander Greyling van den Berg said.

Following a comprehensive assessment by the Naval Engineering department and the Navy divers, operations commenced to bring De Mist out of the water using a limited array of lifting bags and submersible pumps. The salvage entailed raising the tug off the seabed and towing her to the synchrolift facility about 50m away,” he said adding “shallow water salvages are known to be difficult because of the lack of air expansion and buoyancy at this depth”.
“The main challenge experienced was making the 39-year old tug airtight – and buoyant. Divers used underwater welding equipment to seal off holes to pump her full of air, but as soon as leaks were sealed other leaks appeared. Armscor Dockyard personnel were constantly on hand providing bungs and other mechanisms for leak stopping and shoring.
“Wednesday, November 28 saw Navy divers concentrate all lifting efforts to the aft of the tug, managing to raise her and bring her 2m from the quay, with her keel resting on the bedrock. The same was achieved on the forward side.
“The mooring lighter, built by dockyard apprentices more than 100 years ago, was used to create further lift. Because of her age, the mooring lighter does not have a generator and cannot operate her capstan. To mitigate the winch of Tug Umalusi was used to create lift through the mooring lighter’s fair leads. The docking plate under the tug kept getting stuck in the sand during the lifting process, adding complications. Throughout the lifting process, divers continued sealing off leaks and filling fuel, freshwater and ballast tanks with air.
“Monday, December 3, saw Navy riggers in conjunction with the Navy Harbour Master, devise a way of using ‘snatch blocks’ to create further buoyancy. The aim was to raise the tug high enough to clear the synchrolift platform. This was achieved on Wednesday but prevailing airlocks in the tug created balance issues, finally overcome around midnight.
“Floating, but still listing slightly, she was finally pulled to the synchrolift,” Van den Berg said.

The salvage operation and obstacles overcome is seen by the maritime service of the national defence force as an “amazing display of teamwork and resourcefulness by a dedicated team of professionals who worked tirelessly to solve numerous mathematical, physical and engineering problems”.

A floating barrier was put in place to contain the oil spill in the still water basin, with a second barrier between the still water basin and outer basin to further prevent the possibility of pollution.