VESSEL REVIEW | Modular pontoon takes on River Thames infrastructure maintenance work

A self-propelled pontoon workboat made entirely from standard scaffold components and fitted with a crane has been used for a project on the River Thames in the UK to install ladders, chains, and wooden fendering.

For the project on the Thames, local boatbuilder Scafffloat mobilised an eight- by 6.4-metre pontoon fitted with two 44kW high-thrust outboard engines giving 0.8 tonnes of bollard pull and a service speed of five knots. Thirty of the company's small 0.5-cubic-metre patented plastic floats provided 15 cubic metres of buoyancy, giving the pontoon a comfortable five-tonne payload on the large open 50-square-metre wood deck. The deck is also fire-rated, making it suitable for hot works including cutting and welding.

A 2.8-tonne knuckle boom crane that can lift 600 kg at five metres was fitted to a custom-made steel crane base. This was designed in accordance with Lloyd's Register Code for Lifting Appliances in a Marine Environment, July 2021 (CLAME, 2021). After non-destructive testing it was then LOLER tested once fitted to the pontoon, and a full stability assessment was provided in line with relevant IMO standards.

The pontoon was also surveyed and licensed by the Port of London Authority (PLA) as a commercial vessel prior to commencing works.

Other added features include spud legs and deck winches.

The pontoon was on hire for almost two months to GPS MACS, a specialist marine contractor on the Thames. The vessel also had the benefit of a low draught of only 0.3 metres. The pontoon itself could be dried out on steep mud banks, giving the operator a much larger tidal working window compared to traditional workboats that would not have been able to ground out.