Grieg Seafood – salvage fish farm barge
To assist Grieg Seafood and salvage a concrete feed barge that had sunk in 43 metres of exposed waters off the coast of Skye.
The salvage was particularly challenging given that the structure was partially buried, by several metres, into the soft, silty seabed and had no suitable lifting points. The estimated weight of around 400 tonnes made it even more challenging. A total of almost 750 tonnes of lift was required to release the wreck from the seabed.
Our salvage master and veteran diver, Roger Goudie, quickly mobilised on site with his dive team, ROV equipment and a decompression chamber to ensure diver safety. Our design team set out to find a solution on how we could attach secure lifting points.
All lifting options were explored, including threading heavy chains under the barge, using hawse pipes, and even a giant grab. The best solution was to fabricate four x 200 tonne SWL lifting brackets which would be bolted into the wreck using 250mm diameter pins. This would then allow heavy duty, three-inch chains to be secured to the barge.
Our tradesmen quickly manufactured and tested the lifting lugs, each was tested to 200 tonnes before being shipped to site. Using our purpose-built hydraulic core drill, our dive team set up and drilled the 300mm diameter holes through the 250mm thick reinforced concrete walls of the barge.
The chains were fitted to the structure, as were parachute lifting bags to provide extra buoyancy.
After applying 750 tonnes of lift pressure, the barge began to emerge from the seabed and was slowly moved into shallow water. The structure was cleaned, de-ballasted and was then approved for safe towage up to Shetland to help form a new pier.