Divers defy tide in seabed challenge

One recent project meant dealing with the fitting of a 12 metre concrete case weighing in at 450 tons for a nuclear project about a kilometre off the coast of France.

The block, a diffuser for a nuclear reactor, had to be installed near Cherbourg where the tidal flow was the biggest difficulty.

The depth varied between 20m and 28m with the current running at around 7 knots. This left Seawork Marine Services with a window of operations which was around 40 minutes, with time travelling to and from the seabed carved out of it. Even so, the installation went smoothly.

The first dive was used to ensure the socket, previously bored into the seabed, was clear of all debris that would otherwise have caused an obstruction. The next dive operation was for the actual diffuser installation. The diver remained on the seabed whilst giving instructions to the crane operators so that the whole unit could be sat accurately in its socket, ensuring that the inflatable seal and all 22 grout hoses were kept clear of entrapment. The final part of the project was completed with an ROV which was passed inside the diffuser through a narrow opening to check the seal internally. All in all, the whole operation was cleared within ten days rather than the allotted three weeks.

The company also recently removed and refitted eight lock gates on the Gloucester/Sharpness canal in preparation for an engineering inspection. These gates individually measured 6m by 7m and weighed 13 tons. This operation was carried out on remote sites making the logistics of craneage particularly challenging.

The company is currently busy working with Associated British Ports, British Waterways and Exxon Mobil.